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9 Alphabet Patterns and Oblique Muscle Dysfunctions Kenneth W. Wright I n this chapter, A- and V-pattern strabismus and oblique dysfunction are discussed, including management strategies. Under the category of A- and V-patterns, special subtypes are described. The section on oblique dysfunction includes the following: head tilt test, inferior oblique paresis and inferior oblique overaction, superior oblique paresis and superior oblique overaction, and Brown’s syndrome. A- AND V-PATTERNS A significant difference in the horizontal deviation from upgaze to downgaze is described as an A- or V-pattern. An A-pattern is described as more divergence in downgaze versus upgaze of at least 10 prism diopters (PD), whereas a V-pattern is increasing divergence in upgaze versus downgaze by 15 PD or more. A- and V-patterns are often a result of oblique muscle overaction or oblique muscle paresis. Other less common causes include nerve misdirection such as Duane’s syndrome, ectopic muscle course with ectopic muscle pulleys, and a rotated orbit associated with craniofacial abnormalities.5,6,29 Examples of strabismus patterns (1 through 5) follow. Example 1. A-pattern ET A-pattern XT V-pattern ET V-pattern XT 10 XT 20 XT 30 ET 30 ET 20 ET 10 XT 30 XT 20 XT 10 ET 10 ET 20 ET 30 Upgaze Primary position Downgaze XT, exotropia; ET, esotropia. 284 V-pattern XT A-pattern chapter 9: alphabet patterns and oblique muscle dysfunctions 285 A- and V-Pattern Subtypes Look critically at the type of pattern: is it symmetrical or does the change in horizontal deviation occur more in upgaze or downgaze? This is important to know, as the configuration or subtype of the A- or V-pattern can indicate an identifying etiology and can influence the surgical plan. For example, a V-pattern consisting of convergence in downgaze without significant change in horizontal deviation from primary position to upgaze is highly suggestive of a bilateral superior oblique palsy. Listed below are subtypes of A- and V-patterns in which the change in horizontal deviation is asymmetrical. V-PATTERN SUBTYPES Y-PATTERN The Y-pattern is a V-pattern subtype with divergence occurring in upgaze and little change in the horizontal deviation between primary position and downgaze. This pattern is highly suggestive of bilateral inferior oblique overaction, which is often associated with infantile esotropia and may also be seen with intermittent exotropia. Y-pattern can also be seen in patients with Brown’s syndrome, Duane’s syndrome with upshoot, and rarely congenital aberrant innervation of the lateral rectus muscle with the superior rectus nerve (see Example 2). Example 2. Upgaze Primary position Downgaze ET Y-pattern XT Y-pattern ET 10 ET 25 ET 30 XT 30 XT 15 XT 10 ARROW PATTERN Another V-pattern subtype is convergence that largely occurs between primary position and downgaze. This author has termed this pattern “arrow” pattern. The presence of an arrow pattern and extorsion in downgaze is virtually diagnostic for bilateral superior oblique muscle palsy. The lack of abduction and intorsion in downgaze because of weak superior oblique muscles allows unopposed adduction and extorsion by the inferior recti muscles (see Example 3). 286 handbook of pediatric strabismus and amblyopia Example 3. ET Arrow Pattern Upgaze Primary Position Downgaze Ortho ET 5 ET 20 A-PATTERN SUBTYPE LAMBDA PATTERN The lambda pattern, an A-pattern subtype, is characterized by a divergence in downgaze without much change in the horizontal deviation from primary position to upgaze. A lambda pattern is most frequently associated with bilateral superior oblique overaction. Overrecessed or slipped inferior rectus muscles will also cause an A-pattern lambda subtype with apparent superior oblique muscle overaction. In contrast, inferior oblique muscle underaction causes an A-pattern with most of the horizontal change as convergence in upgaze (see Example 4). Example 4. XT lambda pattern Lambda pattern Upgaze Primary Position Downgaze XT 15 XT 20 XT 35 X-PATTERN An X-pattern occurs when there is divergence in upgaze and divergence in downgaze, which can occur without a specific cause. Patients with long-standing large-angle exotropia will frequently show an X-pattern, presumably caused by a tight contracted lateral rectus muscle. As the eye adducts against the tight lateral rectus muscle, it acts as a leash and produces lateral forces. If the eye then rotates up or down the tight lateral rectus slips above or below the eye and pulls the eye up and out, or down and out, respectively. This leash effect of the lateral rectus is also seen in Duane’s syndrome, usually type III, with both an upshoot and downshoot present on attempted adduction. Lateral rectus recessions reduce the X-pattern associated with exotropia, and an ipsilateral lateral rectus recession with a Ysplit works well to reduce the vertical overshoot and X-pattern associated with Duane’s syndrome type III29 (see Example 5). chapter 9: alphabet patterns and oblique muscle dysfunctions 287 Example 5. XT X-Pattern Upgaze Primary position Downgaze XT40 XT30 XT40 Treatment of A- and V-Patterns A- and V-patterns with minimal or no oblique overaction can be managed by offsetting, or transposing, the horizontal rectus muscles superiorly or inferiorly. Transpose the medial recti insertions toward the apex of the pattern (up for an A-pattern and down for a V-pattern) and the lateral recti insertions to the wide part of the pattern (down for an A-pattern and up for a Vpattern) (Fig. 9-1). An A-pattern exotropia, for example, can be treated by recessing both lateral rectus muscles and transposing them inferiorly (Fig. 9-2). Vertical transposition of horizontal muscles in the treatment of A- or V-patterns changes vector forces and muscle tension as the eyes rotate up and down. For example, when the medial recti are infraplaced for a V-pattern, they gain increased function as the eyes rotate up, thus collapsing the V-pattern. Conversely, when the eyes rotate down, the infraplaced medial rectus muscles slacken, resulting in divergence of the apex of the V-pattern. One-half-tendon-width FIGURE 9-1. Direction to transpose the rectus muscles to correct for Aand V-patterns. Left diagram: transposition for a V-pattern, with the lateral rectus muscles moved up and medial rectus muscles moved down. Right diagram: transposition for an A-pattern, with the medial rectus muscles moved up and the lateral rectus muscles moved down. The medial rectus is moved toward the apex of the A or V and the lateral rectus is moved away from the apex of the A or V. This transposition holds true whether the muscles are recessed or resected. 288 handbook of pediatric strabismus and amblyopia FIGURE 9-2. Drawing of a one-half-tendon-width inferior transposition of the lateral rectus muscle with recession for an A-pattern associated with an intermittent exotropia. A Insertion to limbus distance. B Recession measured from the insertion. (5 mm) of vertical displacement results in approximately 15 PD of pattern correction. A full-tendon-width vertical displacement results in approximately 25 PD of correction and is reserved for extremely large A- or V-patterns. Vertical transposition of a horizontal rectus muscle by one full-tendon-width reduces the vector forces at the horizontal plane and, in this author’s opinion, often results in unpredictable horizontal alignment. For example, a full-tendon-width infra-placement of the lateral rectus muscles for an A-pattern would predispose to an overcorrection (esotropia) in primary position. This author rarely performs a horizontal rectus muscle transposition more than one-half tendon-width (5 mm) except in cases of a large A- or Vpattern associated with craniofacial disorders or absent muscles. Monocular supraplacement of one rectus muscle and infraplacement of the partner antagonist muscle can be used to correct an A- or V-pattern in a patient with amblyopia to avoid surgery on the only good eye. Monocular A- or V-pattern horizontal muscle offsets can cause significant torsional changes and should be done only on amblyopic eyes in patients with poor binocular fusion to avoid inducing torsional diplopia. Thus, monocular horizontal offsets can be used to correct torsional diplopia. In cases with significant inferior or superior oblique overaction and an A- or V-pattern, the appropriate oblique muscles should be weakened rather than performing a horizontal rectus muscle transposition. An exception exists for patients with chapter 9: alphabet patterns and oblique muscle dysfunctions 289 superior oblique overaction and binocular fusion. These patients are at risk for developing cyclovertical diplopia after superior oblique tenotomy.23 Patients with binocular fusion and mild superior oblique overaction are best treated with transposition of the horizontal recti rather than a superior oblique tenotomy. Another surgical option for the fusing patient is a controlled tendon elongation procedure, such as the Wright superior oblique tendon expander or a split-tendon elongation. For large A- and V-patterns (25 PD) with 3 or more oblique overaction, consider combining oblique weakening with a half-tendonwidth horizontal rectus muscle transposition. OBLIQUE DYSFUNCTION Clinical Evaluation of Oblique Dysfunction When an oblique muscle overacts or underacts, all three functions of the muscle are involved: torsional, vertical, and horizontal. Clinical quantification of oblique dysfunction, however, is primarily based on the vertical hyper- or hypofunction seen on version testing. To assess oblique function, move the eye under examination into adduction and make an observation. Then move the eye into the field of action of the muscle: adduction and elevation for the inferior oblique muscle, and adduction and depression for the superior oblique muscle. The amount of overaction or underaction can be graded on a scale of 1 to 4 for overaction and 1 to 4 for underaction. A measurement of 1 overaction is recorded if there is no hypertropia with horizontal versions, but there is slight overaction when the eye is moved into the field of action of the oblique muscle vertically. With 2 overaction, there is a slight hypertropia in horizontal gaze, and with 3 overaction, there is obvious hypertropia on direct horizontal gaze. In 4 overaction, there is a large hypertropia in horizontal gaze with an abduction movement as the eye moves vertically into its field of action. Figure 5-3 in Chapter 5 shows degrees of inferior oblique overaction on version testing. The amount of A- or V-pattern and amount of fundus torsion are additional parameters to help quantitate the amount of oblique dysfunction. When evaluating oblique dysfunction, the abducting eye should be fixing so the adducting eye is free to manifest oblique dysfunction. For example, when the right inferior oblique is 290 handbook of pediatric strabismus and amblyopia being evaluated, a version movement to the left is directed, the right eye is partially covered, and the right eye is observed behind the cover for an upshoot (see Chapter 5, Fig. 5-4). Discussion of the characteristics of individual oblique muscle dysfunctions follows. Primary Oblique Overaction Versus Paresis Overaction of an oblique muscle can be primary (i.e., unknown etiology) or can be secondary to a muscle paresis. Primary oblique muscle overaction is commonly found in association with A- and V-pattern horizontal strabismus. One possible etiology for what appears to be primary oblique muscle overaction is ectopic location of rectus muscles and their pulleys.5,6 A transient congenital oblique muscle paresis could also cause secondary overaction of its antagonist muscle. A congenital superior oblique paresis, for example, produces ipsilateral inferior oblique overaction. Oblique overaction can also be caused by paresis of its yoke vertical rectus muscle of the contralateral eye (Hering’s law of yoke muscles). For example, a left inferior rectus paresis causes apparent overaction of the right superior oblique muscle and is best observed when the patient fixes with the paretic left eye, down and in abduction. In general, acquired oblique muscle paresis is associated with underaction of the agonist and with relatively mild overaction of the antagonist oblique muscle. Congenital and longstanding oblique muscle paresis are usually associated with minimal superior oblique underaction and significant overaction of the antagonist oblique muscle. The head tilt test, described below, is used to distinguish primary oblique dysfunction from oblique dysfunction secondary to a vertical or oblique muscle paresis. A positive head tilt test is a strong indication that there is a vertical rectus or oblique muscle paresis whereas a negative head tilt usually indicates a primary oblique overaction. If the vertical deviation changes by more than 5 PD on right tilt versus left tilt, then the head tilt test is said to be positive. If there is no significant difference in the deviation (5 PD or less) from right tilt to left tilt, then the head tilt test is said to be negative. BIELSCHOWSKY HEAD TILT TEST Tilting the head stimulates the utricular reflex and invokes torsional eye movements to correct and maintain the appropriate chapter 9: alphabet patterns and oblique muscle dysfunctions 291 retinal orientation. A tilt right, for example, invokes intorsion of the right eye and extorsion of the left eye. The intortors are the superior oblique and the superior rectus muscles, and the extortors are the inferior oblique and the inferior rectus muscles. This arrangement keeps vertical forces balanced during the head tilt. If one of the torsional muscles is paretic, then there will be an imbalance of vertical forces and a vertical deviation will occur on head tilt testing. Figure 9-3 demonstrates this concept for a right superior oblique paresis. As the head tilts to the right, the right superior oblique and right superior rectus contract to intort the right eye. Because the superior oblique is paretic, the superior rectus has unopposed vertical force and elevates the eye, creating an increasing right hyperdeviation on head tilt to the right. The head tilt test is used in patients with a vertical deviation to determine if either a vertical rectus or oblique muscle is paretic. When a patient presents with a vertical deviation, first perform the head tilt test to see if a paretic muscle is present. If the head tilt test is positive (5 PD difference in right tilt vs. left tilt), then it is likely there is a vertical rectus or oblique muscle paresis. To determine which muscle is paretic, measure the deviation in sidegaze and use the three-step test as described next. FIGURE 9-3. Diagram of a right superior oblique paresis with a positive head tilt in tilt right. As the head tilts to the right, the left eye extorts and the right eye intorts. The extorters of the left eye are the inferior rectus and the inferior oblique. Their vertical functions cancel each other, so there is no vertical overshoot. The intortors of the right eye are the superior rectus (SR) and superior oblique (SO) muscles. Because the right superior oblique is paretic, the elevation effect of the superior rectus is unopposed, and a right hypertropia occurs on tilt to the right. 292 handbook of pediatric strabismus and amblyopia PARKS THREE-STEP TEST Marshall Parks in 1958 published the “Three-Step Test” for the diagnosis of cyclovertical muscle palsies.23 This test identifies which muscle is paretic in patients with a hypertropia caused by an isolated vertical rectus muscle or oblique muscle palsy. The three steps are to determine (1) which paretic muscle might be causing the hyperdeviation in primary position, (2) where the hypertropia is greatest, in rightgaze or leftgaze, and (3) on head tilt, which side the hypertropia is greatest: tilt right or tilt left. See Table 9-1 for results of the three-step test for both vertical and oblique muscle palsy. The first step is to determine which paretic muscle could be causing a hyperdeviation in primary position. A right hyperdeviation, for example, might be caused by a weak depressor muscle of the right eye (i.e., right inferior rectus or right superior oblique) or a weak elevator muscle of the left eye (i.e., left superior rectus or left inferior oblique). The second step is to determine in which horizontal field of gaze the hypertropia increases. If the hypertropia increases on gaze away from the hypertropic eye, the paretic muscle is the TABLE 9-1. Responses to the Three-Step Test for All Vertical and Oblique Muscle Palsies. First step: hyper in primary Second step: hyper increases in gaze Third step: hyper increases with head tilt (hyper ⬎ ipsilateral tilt ⫽ oblique hyper ⬎ contralateral tilt ⫽ vertical rectus) RIR R LIO LIO L RIR RSO R RSO LSR L LSR RSR R RSR LSO L LSO RIO R LIR LIR L RIO RSO RIR RHT vs. R LSR LIO L RSR RIO LHT vs. R LSO LIR L chapter 9: alphabet patterns and oblique muscle dysfunctions 293 ipsilateral oblique or contralateral vertical rectus. A hypertropia that increases to the side of the hypertropia is caused by a paretic vertical muscle on the side of the hypertropia or the contralateral vertical rectus muscle, that is, the paretic muscle is a vertical rectus muscle of the abducting eye or an oblique muscle of the adducting eye. For example, a right hyperdeviation that increases in leftgaze could only be caused by a paretic left superior rectus muscle or a paretic right superior oblique muscle. The third step is based on the Bielschowsky head tilt test as previously described. This last step can be difficult to calculate, so this author uses a trick that he shamelessly calls Wright’s rule. The author states, “I am sure others have used the same trick to simplify the head tilt test, but I like the way it sounds: Wright’s Rule.” Wright’s rule states that if the hyperdeviation increases on head tilt to the same side of the hyperdeviation, then an oblique muscle is paretic. If the hyperdeviation increases to the opposite side of the hyperdeviation, then a vertical rectus muscle is paretic. For example, if the right hyper increases on head tilt to the right (same side as the hyper), then the oblique muscle is paretic; namely, the right superior oblique (SO) or left inferior oblique (IO) muscle. If the right hyper increases on left head tilt (opposite side of the hyper), then it is the vertical rectus muscle that is weak; namely, the left superior rectus (SR) muscle or right inferior rectus (IR) muscle. Example 6 describes characteristics of a right superior oblique paresis. Example 6. Right Superior Oblique Paresis Rightgaze RHT10 Leftgaze RHT 15 RHT 25 Head tilt test: right, RHT 15 PD; left, RHT 4 PD. PARKS THREE-STEP TEST FOR EXAMPLE 6 Step 1: Right hypertropia Right IR or SO versus left SR or IO (underacting muscles, right eye vs. left eye). Step 2: Right hypertropia increases in leftgaze Left SR or right SO (the muscles with field of action in leftgaze). Step 3: Right hypertropia increases in head tilt to the right Right tilt induces intorsion of the right eye and extorsion of left eye. Both the muscles in contention (RSO and LSR) are 294 handbook of pediatric strabismus and amblyopia intortors, but only the RSO intorts on right tilt. Therefore, the diagnosis is right superior oblique paresis. or, by Wright’s rule: Right hyperdeviation increases on right head tilt (same side as the hyper); therefore, it has to be an oblique muscle paresis. As we are down to two choices from step 2, RSO and LSR, the paretic muscle is the right superior oblique. SHORTCUT TO THE THREE-STEP TEST Classically, the paretic muscle is determined by the Parks threestep test as just described. In 1967, Helveston13 described combining steps 1 and 2 to make a two-step test. This author prefers to start with the head tilt test and use Wright’s rule. To know which vertical rectus or oblique muscle is weak, determine in which horizontal gaze the vertical deviation increases, right or left. As an example, a right hypertropia that increases on head tilt to the right and increases on rightgaze has to be caused by an oblique muscle paresis because the tilt is positive to the same side as the hypertropia. Because the right hypertropia increases on rightgaze, in the field of action of the left inferior oblique muscle (not in the field of action of the right superior oblique muscle), the paretic muscle is the left inferior oblique. Using Wright’s rule alone narrows the choices to two muscles: either an oblique or a vertical rectus muscle of each eye. Determining the horizontal gaze where the hypertropia is greatest tells us which eye, the right eye or the left eye. PROBLEMS WITH THE HEAD TILT TEST A positive head tilt test is not infallible when diagnosing cyclovertical muscle paresis. Patients with dissociated vertical deviations, as well as some patients with intermittent exotropia, show a positive head tilt. In addition, the head tilt test is designed to diagnose an isolated paretic muscle, and it may not be reliable when multiple muscles are paretic or if an ocular restriction is present. Superior Oblique Paresis A superior oblique paresis is the most common cause for an isolated vertical deviation. The typical findings of a unilateral superior oblique paresis include an ipsilateral hypertropia that increases on contralateral side-gaze and a positive head tilt test with the hyperdeviation increasing on head tilt to the ipsilateral chapter 9: alphabet patterns and oblique muscle dysfunctions 295 shoulder (see Example 6). There may be relatively little superior oblique underaction and mostly inferior oblique overaction (Fig. 9-4A,B). Mild extorsion is recorded if less than 10°. To reduce the hypertropia and fuse, patients with a unilateral superior oblique paresis adopt a compensatory head tilt to the side, opposite the paresis, combined with a face turn away from the side of the palsy. Long-standing unilateral superior oblique paresis with a large hypertropia may show pseudosuperior oblique overaction of the contralateral eye, as a result of contraction of the ipsilateral superior rectus muscle because of the long-standing hypertropia and Hering’s Law of yoke muscles. As the ipsilateral eye has restricted depression in abduction, the yoke muscle overacts (i.e., contralateral superior rectus muscle). FIGURE 9-4A,B. Composite nine-gaze photograph of patient with a congenital right superior oblique palsy. Note the large RHT in primary position that increases in leftgaze. There is 3 right inferior oblique overaction and 2 superior oblique underaction. In straight rightgaze, it appears that the left superior oblique is overacting, but the right superior oblique is slightly tight because of secondary contracture. (B) Positive head tilt test with large RHT on tilt right. 296 handbook of pediatric strabismus and amblyopia FIGURE 9-5. Composite nine-gaze photograph of patient with bilateral traumatic superior oblique palsy. Patient has a small esotropia and extorsion in primary position that increases in downgaze. Note the V-pattern (arrow pattern subtype) with a large esotropia in downgaze. There is also severe underaction of both superior oblique muscles associated with relatively mild inferior oblique overaction. Bilateral superior oblique paresis is associated with bilateral superior oblique underaction, a V-pattern (arrow subtype), little or no hypertropia, and a right hypertropia in leftgaze and a left hypertropia in rightgaze (Fig. 9-5). Other signs include a bilateral extorsion (total greater than 10°), a reversing head tilt test with a right hypertropia in tilt right, and a left hypertropia in tilt left. The presence of an arrow pattern with extorsion increasing in downgaze (Example 7) is diagnostic for an acute bilateral superior oblique palsy and is often seen with traumatic superior oblique palsies. Clinical signs of unilateral versus bilateral superior oblique paresis are shown in Table 9-2. Example 7. Bilateral Superior Oblique Paresis Rightgaze LHT10 Leftgaze RHT 2, ET4 RHT 5, ET 20 Bilateral Maddox Rod—15° Extorsion. Bilateral extorsion on fundus exam. Head tilt test: right, RHT 10 PD; left, LHT 10 PD. ET on downgaze RHT 10 297 chapter 9: alphabet patterns and oblique muscle dysfunctions TABLE 9-2. Unilateral Versus Bilateral Superior Oblique Paresis. Clinical sign Unilateral Bilateral Superior oblique underaction Inferior oblique overaction V-pattern Ipsilateral underaction Ipsilateral overaction Less than 10 PD Hypertropia Greater than 5 PD Head tilt test Increasing hyper on ipsilateral head tilt (Rt SOP RH tilt right) Less than 10° Bilateral underaction Bilateral overaction Greater than 10 PD with arrow pattern (convergence in downgaze) Less than 5 PD (except asymmetrical paresis) Positive head tilt to both sides (RHT on right tilt and LHT on left tilt) Extorsion Greater than 10° A bilateral asymmetrical superior oblique paresis can look like a unilateral superior oblique paresis; this is termed masked bilateral superior oblique paresis.16,17 Suspect a masked bilateral paresis if the hypertropia precipitously diminishes in lateral gaze toward the side of the obvious paretic superior oblique muscle and if there is even slight inferior oblique overaction of the fellow eye (see Example 8). Example 8. Masked Bilateral Superior Oblique Paresis Rightgaze RHT5 Leftgaze RHT 20 RHT 30 Head tilt test: right, RHT 25 PD; left, RHT 3 PD. The presence of a V-pattern and bilateral extorsion on fundus examination also suggest bilateral involvement in patients with a presumed unilateral paresis. In these cases of masked bilateral superior oblique paresis, if surgery is performed only for a unilateral superior oblique palsy, the contralateral superior oblique paresis will become evident postoperatively. FALLEN EYE Significant underaction of the superior oblique muscle and fixation with the paretic eye will produce the classic finding called the fallen eye. When a patient with a superior oblique paresis fixes with the paretic eye and tries to look into the field of action of the paretic superior oblique muscle, the weak superior oblique muscle requires a large amount of innervation to make the eye 298 handbook of pediatric strabismus and amblyopia FIGURE 9-6. Photograph of a traumatic right superior oblique palsy, showing the fallen eye, left eye. The right eye is fixing in the field of action of its paretic superior oblique muscle (i.e., down and in adduction), requiring a great deal of innervation. Because of Hering’s law of equal innervation of yoke muscles, the left inferior rectus muscle (yoke muscle to the paretic right superior oblique muscle) also receives a great deal of innervation. Because the left inferior rectus is at full strength, it overacts and pulls the left eye down, thus causing the appearance of a left fallen eye. move down and nasally. Because of Hering’s law, the yoke muscle (contralateral inferior rectus muscle) receives an equally large amount of innervation. Because the contralateral inferior rectus muscle has normal function, this increased innervation produces a large secondary hypotropia, or the fallen eye (Fig. 9-6). INHIBITIONAL PALSY ANTAGONIST OF THE CONTRALATERAL Chavasse, in 1939, described the term inhibitional palsy of the contralateral antagonist. This term relates to a patient who chronically fixates with the paretic eye, resulting in an apparent weakness on version testing of the yoke muscle to the antagonist of the paretic eye. That is, the paretic eye moves easily into the field of its antagonist with little innervation because the agonist is weak. The yoke muscle to the antagonist of the paretic muscle receives the same small innervation (Hering’s law), so it chapter 9: alphabet patterns and oblique muscle dysfunctions 299 will appear paretic on versions because its antagonist is innervated. Clinically, this is seen in association with a congenital fourth nerve palsy and ipsilateral inferior oblique overaction when the patient fixates with the paretic eye. For example, a left fourth nerve palsy with left inferior oblique overaction will produce a left hypertropia increasing in rightgaze. If the patient fixates with the left eye, the innervation required for the left eye to look up and right is minimal, as it is in the field of the overacting left inferior oblique muscle. The yoke muscle to the left inferior oblique muscle is the right superior rectus muscle, and it too will receive little innervation. The right superior rectus will appear to underact or be paretic because its antagonist, the right inferior rectus, is normally innervated and holds the eye down. Inhibitional palsy of the contralateral antagonist is only seen on version testing when the paretic eye is fixing. PRIMARY INFERIOR OBLIQUE OVERACTION VERSUS SUPERIOR OBLIQUE PALSY Primary inferior oblique overaction can be differentiated from superior oblique palsy by the head tilt test and type of V-pattern (Table 9-3). Traumatic Superior Oblique Paresis Traumatic superior oblique paresis is usually associated with severe closed head trauma, loss of consciousness, and cerebral concussion; however, even very mild head trauma without loss of consciousness can cause a superior oblique paresis. Traumatic superior oblique paresis occurs when the tentorium traumatizes TABLE 9-3. Primary Inferior Oblique Overaction Versus Superior Oblique Paresis. Clinical sign Primary overaction Superior oblique paresis Inferior oblique overaction V-pattern Head tilt test Subjective torsion Yes Yes, Y-pattern Negative No Objective extorsion (fundus examination) Underaction of ipsilateral superior oblique muscle Yes Yes Yes, “arrow” pattern Positive Yes (except in congenital superior oblique paresis) Yes No (minimal if any) Yes 300 handbook of pediatric strabismus and amblyopia the trochlear nerves as they exit the posterior midbrain posteriorly. Since the two trochlear nerves exit the midbrain together, only a few millimeters apart, the nerve trauma is almost always bilateral. Thus, most cases of traumatic superior oblique paresis are bilateral, although the paresis may be asymmetrical. The pattern of strabismus is classically, minimal or no hypertropia in primary position, a left hypertropia in rightgaze, a right hypertropia in leftgaze, underaction of both superior oblique muscles, and an esotropia in downgaze (Figs. 9-5, 9-6). There is a positive head tilt with a right hypertropia on right tilt and a left hypertropia on left tilt. Extorsion increasing in downgaze can be demonstrated by Maddox rod and indirect ophthalmoscopy. Patients complain of horizontal or vertical torsional diplopia that is worse in downgaze (Fig. 9-5). In most cases, there is not much ipsilateral inferior oblique muscle overaction, usually 1 or less. Because the strabismus is acquired, patients complain of diplopia—torsional, vertical, and horizontal—that increases in downgaze. The management of traumatic superior oblique paresis is discussed later in this chapter under Treatment of Superior Oblique Paresis. Congenital Superior Oblique Paresis The cause of congenital superior oblique paresis is usually unknown. The paresis may be associated with a lax superior oblique tendon or rarely an absent tendon.12 Most cases present as a unilateral paresis or an asymmetrical masked bilateral paresis. Typically, there is a large hypertropia in primary position and significant inferior oblique overaction, usually with relatively little superior oblique underaction (see Fig. 9-4). The most common presenting sign is a head tilt opposite to the side of the palsy. Even though the paresis is present at birth, symptoms often occur in late childhood or even adulthood. It is common for patients to be diagnosed for the first time in middle age. Normally vertical fusional amplitudes are weak and even small acquired hyperdeviations of 3 to 5 PD cannot be fused and result in constant diplopia. Patients with congenital superior oblique paresis, however, develop large vertical fusional amplitudes, and fuse large hypertropias up to 35 PD. The presence of large vertical fusion amplitudes is an important clinical sign that the hyperdeviation is long-standing, rather than acutely acquired, and is suggestive of a congenital superior oblique palsy. chapter 9: alphabet patterns and oblique muscle dysfunctions 301 Over time, the fusional control weakens, resulting in a deviation that becomes manifest in later life. In addition to large fusional vergence amplitudes, patients with congenital superior oblique paresis adopt a compensatory head tilt opposite to the palsy to minimize the deviation and establish binocular fusion. Patients with congenital superior oblique paresis typically have good stereopsis and manifest the hyperdeviation intermittently, usually when fatigued. Even though patients with congenital superior oblique paresis have high-grade stereopsis, most also have the ability to suppress when tropic so that they usually do not experience diplopia. This sensory adaptation is similar to the adaptation of patients with intermittent exotropia. Typically these patients also do not demonstrate extorsion by Maddox rod testing as they adapt to the retinal extorsion. Facial asymmetry is seen in approximately 75% of patients with congenital superior oblique palsy, with one side of the face being hypoplastic and smaller.26 The hypoplastic side of the face is on the side of the head tilt (i.e., the dependent side of the face) (Fig. 9-7). One theory for the facial asymmetry is that gravita- FIGURE 9-7. Photograph of patient with a compensatory right head tilt and right face turn associated with a left congenital superior oblique palsy. Note the facial asymmetry, as the right side of the face is hypoplastic. Hypoplasia is ipsilateral to the head tilt and contralateral to the superior oblique palsy. 302 handbook of pediatric strabismus and amblyopia tional pull on the dependent side of the face causes changes in size of facial structures. Another theory is that facial asymmetry represents a mild form of congenital plagiocephaly associated with the superior oblique palsy. In summary, signs that a superior oblique palsy is congenital and not acquired include childhood photographs showing a long-standing head tilt, facial asymmetry, lack of extorsional diplopia, lack of extorsion by Maddox rod, and large vertical fusion amplitudes. In most cases, the diagnosis of congenital superior oblique muscle palsy can be made on the basis of clinical evaluation. Other Causes of Superior Oblique Paresis The majority of superior oblique pareses are either congenital or traumatic, but other causes include vascular disease with brainstem lacunar infarcts, multiple sclerosis, intracranial neoplasm, herpes zoster ophthalmicus, diabetes and associated mononeuropathy, and iatrogenic after superior oblique tenotomy. An acquired idiopathic superior oblique paresis requires a neurological workup including neuroimaging. Patients with craniosynostosis may have bilateral superior oblique palsies caused by absent superior oblique tendons. Treatment of Superior Oblique Paresis The treatment of superior oblique paresis depends on the pattern of the strabismus. Cardinal position of gaze measurements and evaluation for inferior oblique overaction and superior oblique underaction are needed to determine the pattern of strabismus and where the deviation is greatest. Subjective torsion should be assessed by double Maddox rod testing in acquired cases; however, patients with a congenital superior oblique palsy will not have subjective torsion. Objective torsion evaluated by indirect ophthalmoscopy can be useful for verifying torsional abnormalities but is usually not the major clinical sign that directs the treatment plan. Most treatment strategies require identifying where the hypertropia is greatest, and surgery is then designed to correct the deviation in primary position while reducing the incomitance.15 For example, a right unilateral superior oblique paresis with a hypertropia less than 10 PD in primary position, inferior oblique overaction, and minimal superior oblique underaction chapter 9: alphabet patterns and oblique muscle dysfunctions 303 can be treated with a simple ipsilateral inferior oblique weakening procedure (e.g., inferior oblique muscle graded anteriorization). If the hypertropia in primary position is greater than 15 PD, then an isolated inferior oblique recession may not be enough to correct the hypertropia. In this case, especially if there is a significant hypertropia in downgaze, one should add a contralateral inferior rectus recession to an ipsilateral inferior oblique recession (Table 9-4). Late overcorrections have been known to occur after inferior rectus recessions. This author has changed to a nonabsorbable suture or a long lasting absorbable suture for inferior rectus muscle recessions, and this choice seems to have solved the late overcorrection problem. In cases of congenital superior oblique palsies, be conservative in regard to recessing the contralateral inferior rectus muscle. A small undercorrection is usually well tolerated, but an overcorrection and a reverse hypertropia is difficult for these patients to fuse. Tightening the entire width of the superior oblique tendon by performing a superior oblique tuck has theoretical utility for improving superior oblique function. A superior oblique tuck, however, usually results in minimal to no improvement of superior oblique function, and the tight tendon creates a restrictive leash of elevation in adduction (i.e., iatrogenic Brown’s syndrome). The tuck has been suggested for patients with congenital superior oblique paresis secondary to a lax superior oblique tendon.12,27 Plager27 suggests performing exaggerated forced duction testing of the superior oblique tendon at the beginning of surgery to see if the tendon is lax or absent. Caution should TABLE 9-4. Treatment of Unilateral Superior Oblique Paresis. Clinical manifestation Procedure Inferior oblique overaction: small hypertropia Hyperdeviation in primary position 15 PD; deviation is greater in upgaze Inferior oblique overaction: large hypertropia Hyperdeviation in primary position 15 PD Lax superior oblique tendon with superior oblique underaction Hyperdeviation in primary position 15 PD; minimal inferior oblique overaction; deviation is greatest in downgaze Inferior oblique weakening (author prefers graded anteriorization) (common) Ipsilateral inferior oblique weakening (author prefers graded anteriorization), with contralateral inferior rectus recession (common) Small superior oblique tuck (rare) 304 handbook of pediatric strabismus and amblyopia be used when tucking the superior oblique, as iatrogenic Brown’s syndrome is a frequent complication of a superior oblique tendon tuck. Most surgeons avoid the superior oblique tuck unless there is significant superior oblique underaction and an extremely lax tendon or, in cases of bilateral superior oblique paresis, where there is severe superior oblique underaction. Traumatic superior oblique palsies should be observed for 6 months following recovery of muscle function. Patients who have partial recovery of superior oblique muscle function will often be left with extorsional diplopia worse in downgaze, without significant oblique dysfunction, V-pattern, or hypertropia. In these cases, extorsion can be improved by the Harada–Ito procedure, which consists of selectively tightening the anterior one-fourth to one-third of the superior oblique tendon fibers.11 Patients with a bilateral superior oblique palsy and poor recovery of muscle function show a large esotropia in downgaze (arrow subtype V-pattern), extorsion greater in downgaze, left hypertropia in rightgaze, and a right hypertropia in leftgaze, but minimal or no hypertropia in primary position. In these cases, consider either bilateral Harada–Ito procedures and bilateral medial rectus muscle recessions with infraplacement one-half-tendon-width or bilateral superior oblique tendon tucks and bilateral medial rectus muscle recessions with infraplacement one-half-tendon-width. This is a difficult strabismus to correct; however, surgery can often improve diplopic symptoms. The superior oblique tucks will create a bilateral iatrogenic Brown’s syndrome, but this may be an acceptable trade-off for improved single binocular vision in downgaze. Table 9-4 lists treatment strategies for unilateral superior oblique paresis, and Table 9-5 lists treatments for bilateral superior oblique paresis. Inferior Oblique Paresis An isolated inferior oblique paresis is extremely rare and, when it does occur, it is usually idiopathic. Pollard28 reported on 25 patients having an isolated inferior oblique palsy, with 23 being unilateral and 2 bilateral. All cases were idiopathic and benign without an identifiable neurological cause. Rarely, inferior oblique palsy has been reported after head trauma20 or attributed to a microvascular occlusive event. Patients with isolated inferior oblique paresis show ipsilateral superior oblique overaction, but they can be distinguished from those with primary superior chapter 9: alphabet patterns and oblique muscle dysfunctions 305 TABLE 9-5. Treatment of Bilateral Superior Oblique Paresis. Clinical manifestation Procedure Extorsional diplopia (partially recovered traumatic SOP) Extorsional diplopia (5°), minimal hypertropia, 8 PD, small or no V-pattern (10 PD), and minimal inferior oblique overaction and superior oblique underaction Bilateral Harada–Ito Bilateral superior oblique underaction or (often traumatic SOP, rarely congenital lax SO tendon) Bilateral superior oblique tendon tuck with bilateral medial rectus recessions with inferior transposition one-half tendon width Hypertropia 8 PD and big arrow pattern (15 PD increase in esotropia from primary to downgaze), 10° extorsion in primary position increasing in downgaze, and reversing hypertropias in sidegaze Masked bilateral or asymmetrical bilateral superior oblique palsy (usually congenital SOP) Hyperdeviation in primary position 10 PD, asymmetrical inferior oblique overaction Bilateral inferior oblique graded anteriorization (more anteriorized on the side of the obvious SOP) and recession of inferior rectus contralateral to the obvious SOP or If associated with a large head tilt, bilateral inferior oblique graded anteriorization (more anteriorized on the side of the obvious SOP) and Harada–Ito on the side of the obvious SOP oblique overaction. Unlike primary superior oblique overaction, inferior oblique paresis is associated with a positive head tilt test and a hyperdeviation that is greatest when the patient looks up and in a horizontal gaze away from the affected eye. For example, a left inferior oblique paresis results in a right hypertropia that increases in rightgaze and upgaze, and the hyperdeviation increases on head tilt to the right. Note that, on versions, inferior oblique paresis looks similar to Brown’s syndrome with limited elevation in adduction; however, there is an A-pattern and superior oblique overaction with an inferior oblique palsy, and forced ductions are negative (Table 9-6). The treatment of a unilateral inferior oblique paresis is an ipsilateral superior oblique weakening procedure (e.g., Wright 306 handbook of pediatric strabismus and amblyopia TABLE 9-6. Differential Diagnoses of Elevation Deficit in Adduction. Bilateral involvement Pattern Superior oblique overaction Inferior oblique underaction Standard forced ductions Head tilt test Torsion Greatest vertical deviation Brown’s syndrome Primary superior oblique overaction Inferior oblique paresis Unusual Common Unusual “Y” (divergence in upgaze) No Lambda (divergence in downgaze) Yes “A” (convergence in upgaze) Yes Yes Minimal to moderate Negative Yes Positive Negative None to slight intorsion in upgaze Upgaze Negative Intorsion (increasing in downgaze) Downgaze Negative Positive Intorsion (increasing in upgaze) Upgaze superior oblique tendon expander) if the hypotropia is less than 10 PD, or add a recession of the contralateral superior rectus recession if the hypotropia is greater than 10 PD.30 Superior Oblique Overaction The cause of superior oblique overaction (SOOA) is unknown. It may be related to an associated paresis of the contralateral inferior rectus muscle, thus producing a secondary overaction of the yoke superior oblique muscle. The author has noted several patients with superior oblique overaction who also have an underacting contralateral inferior rectus muscle. CLINICAL FEATURES OF SUPERIOR OBLIQUE OVERACTION Superior oblique overaction is an exaggeration of the normal function of the superior oblique muscle that includes intorsion, depression, and abduction. Patients with superior oblique overaction show a downshoot of the adducting eye in lateral gaze, abduction in downgaze causing an A-pattern, and intorsion that is seen on indirect ophthalmoscopy. The A-pattern is not symmetrical, but shows more divergence from primary position to downgaze than from upgaze to primary position. This type of Apattern is termed a lambda pattern (Fig. 9-8). chapter 9: alphabet patterns and oblique muscle dysfunctions 307 Superior oblique overaction often occurs in association with horizontal strabismus such as intermittent exotropia. Most patients with superior oblique overaction do not show subjective incyclotorsion with Maddox rod testing, even though indirect ophthalmoscopy reveals intorsion, because sensory adaptation of the superior oblique overaction has been present since early infancy. Like inferior oblique overaction, superior oblique overaction is usually bilateral. Another characteristic of superior oblique overaction is limited elevation in adduction, which is secondary to a contracted tight superior oblique muscle. DIFFERENTIAL DIAGNOSIS OF SUPERIOR OBLIQUE OVERACTION The differential diagnosis of limited elevation in adduction includes superior oblique overaction, Brown’s syndrome, and inferior oblique paresis (Table 9-6). Brown’s syndrome is caused by a tight superior oblique muscle–tendon complex. In Brown’s syndrome, there is no superior oblique overaction, and forced ductions are positive to elevation in adduction. In addition, the syndrome is often associated with an exodeviation when the eyes move from primary position to upgaze (Y-pattern), whereas superior oblique overaction is associated with a lambda Apattern. FIGURE 9-8. Composite nine-gaze photograph of a patient with intermittent exotropia and bilateral superior oblique overaction (3 OU) with typical A-pattern (lambda subtype) with increasing divergence in downgaze. 308 handbook of pediatric strabismus and amblyopia TREATMENT OF SUPERIOR OBLIQUE OVERACTION The ideal superior oblique weakening procedure produces a measured slackening of the muscle–tendon complex without disrupting the functional mechanics of the insertion. Many surgical approaches to weaken the superior oblique have been tried.3,31 Presently, the two procedures most commonly used are the superior oblique tenotomy and the Wright silicone tendon expander.38,41 The tenotomy technique involves cutting the tendon in two, while the silicone tendon expander consists of inserting a segment of a 240 retinal silicone band (4–6 mm) between the cut ends of a nasal tenotomy to elongate the tendon.42 Other superior oblique weakening procedures include tenectomy, recession, and posterior tenotomy.3,31 In a comparative study, this author found the silicone tendon expander procedure to be superior to a tenotomy, especially in patients with preoperative fusion.40 Performing a superior oblique tenotomy on patients with high-grade stereopsis and fusion carries a significant risk for creating a secondary superior oblique paresis and causing postoperative diplopia.25 In these cases, the silicone tendon expander is preferred. Another situation where superior oblique weakening procedures can cause problems is in patients with preexisting dissociated vertical deviation (DVD); weakening the superior obliques will exacerbate DVD. In these cases, options are to treat the A-pattern with horizontal rectus muscle transpositions rather than weakening the superior obliques, or to plan an undercorrection of the superior oblique overaction with the silicone tendon expander. The advantage of the superior oblique silicone tendon expander is that it lengthens the superior oblique tendon in a controlled manner and holds the cut tendon ends apart at a fixed distance. This technique reduces postoperative superior oblique paresis, allows for controlled weakening, and makes it possible to find cut tendon ends if a reoperation is necessary. Inferior Oblique Overaction Primary inferior oblique overaction is most commonly associated with a horizontal strabismus such as congenital esotropia or intermittent exotropia. Isolated primary inferior oblique overaction can also occur without associated horizontal strabismus. Although primary inferior oblique overaction is bilateral, in chapter 9: alphabet patterns and oblique muscle dysfunctions 309 most cases it can be quite asymmetrical, with the lesser overacting inferior oblique muscle difficult to detect.24 When inferior oblique overaction is identified, it is important to differentiate primary inferior oblique overaction from a secondary inferior oblique overaction (i.e., superior oblique paresis). It can be difficult to differentiate primary inferior oblique overaction from secondary overaction, as patients with marked inferior oblique overaction may have significant superior oblique underaction secondary to the tight inferior oblique muscle. On the other hand, patients with a superior oblique paresis often have inferior oblique overaction. In addition, indirect ophthalmoscopy will show significant objective extorsion in both primary and secondary inferior oblique overaction. The key to distinguishing primary from secondary inferior oblique overaction is the head tilt test. The head tilt test is negative in primary inferior oblique overaction and is positive with secondary inferior oblique overaction. In both groups, there is the typical upshoot of the adducting eye, and both types usually manifest a significant V-pattern, especially if there is bilateral inferior oblique overaction. The type of V-pattern, however, can help differentiate primary versus secondary inferior oblique overaction. Patients with primary inferior oblique overaction have a Y-pattern with a significant exotropia shift occurring from primary position to upgaze but relatively little change between primary position and downgaze (Fig. 9-9). The Y-pattern FIGURE 9-9. Composite nine-gaze photograph of patient with bilateral primary inferior oblique overaction. There is a large V-pattern (Y-subtype) with divergence in upgaze. The inferior oblique overaction is 3 OU with no significant superior oblique underaction. 310 handbook of pediatric strabismus and amblyopia occurs because the inferior oblique muscles act as abductors in upgaze. In contradistinction, a V-pattern associated with superior oblique paresis (especially bilateral) shows an arrow pattern with an esotropic shift that occurs when moving from primary position to downgaze. Because the inferior oblique muscle is an extortor, elevator, and abductor, these elements are exaggerated in direct proportion to the overaction. When quantitating inferior oblique overaction, look at the entire function of the muscle, including the upshoot, amount of V-pattern, and fundus extorsion.10,37 See Table 9-3 for a comparison of the clinical signs of primary inferior oblique overaction with secondary inferior oblique overaction caused by superior oblique paresis. MIMICKERS OF INFERIOR OBLIQUE OVERACTION Inferior oblique overaction is the most common cause of an ocular upshoot in adduction. Dissociated vertical deviation (DVD) can look just like inferior oblique overaction, because DVD will become manifest in sidegaze as the adducted eye is occluded by the nasal bridge (see Chapter 10); this results in a hyperdeviation in sidegaze that mimics inferior oblique overaction. DVD can be differentiated from inferior oblique overaction by occluding the affected eye in abduction as well as adduction and evaluating for a change in the vertical deviation. If the elevation is the same in adduction and abduction, then this is DVD, whereas an increasing hyperdeviation in adduction suggests inferior oblique overaction. Because DVD commonly coexists with inferior oblique overaction in patients with infantile esotropia, the distinction can be extremely difficult to see. Distinguishing clinical features such as the presence of a Vpattern (Y-subtype), a true hyperdeviation in lateral gaze with a hypotropia of the contralateral eye, and objective extorsion on indirect ophthalmoscopy will help to identify inferior oblique overaction rather than DVD. An upshoot in adduction can be caused by a tight lateral rectus muscle. As the eye adducts and slightly elevates, the tight lateral rectus pulls the eye up, causing pseudo-overaction of the inferior oblique. Aberrant innervation of the inferior oblique and superior rectus muscles has been documented as causing an upshoot associated with Duane’s syndrome (see Chapter 10). chapter 9: alphabet patterns and oblique muscle dysfunctions 311 TREATMENT OF INFERIOR OBLIQUE OVERACTION Surgery is indicated when the inferior oblique overaction and V-pattern interfere with fusion, or if it becomes a cosmetic problem. In general, 2 or more inferior oblique overaction should be considered surgically significant whereas 1 or less overaction usually does not require treatment. There are, however, two important exceptions to this rule. The first exception is in patients with bilateral asymmetrical inferior oblique overaction in which one eye shows minimal overaction. In these cases, both inferior oblique muscles should be weakened, even if one only shows trace overaction. Unilateral inferior oblique weakening surgery in an asymmetrical bilateral case unmasks the inferior oblique overaction of the nonoperated eye. Inferior oblique surgery should also be considered for bilateral overaction associated with a significant V-pattern (Y-subtype), even if there is minimal upshoot on sidegaze. Patients who have a significant divergence when the eyes move from primary position to upgaze should have inferior oblique weakening surgery, despite the minimal overaction observed with versions. In most cases, inferior oblique overaction is bilateral and bilateral surgery should be performed. Patients with amblyopia of two lines or greater difference in visual acuity, however, should have monocular surgery, which should be limited to the amblyopic eye to avoid the risk (although slight) of surgical complications to the nonamblyopic eye. When inferior oblique overaction coexists with horizontal strabismus, both should be corrected in the same operation. Staged planning of two separate operations does not improve surgical results and requires a second round of anesthesia. When planning simultaneous horizontal and inferior oblique surgery, the horizontal surgical numbers are not altered. Even though the inferior oblique muscles have an abduction function, weakening the inferior oblique muscles does not significantly alter the horizontal alignment unless there is an extremely large V-pattern and severe inferior oblique overaction. SURGICAL TECHNIQUES FOR WEAKENING THE INFERIOR OBLIQUE MUSCLES (SEE ALSO CHAPTER 11) Surgical techniques for correcting inferior oblique overaction include myectomy, recession, and anteriorization.1,7,19 Recently, 312 handbook of pediatric strabismus and amblyopia the anteriorization procedure has become popular, as results have been good even in cases of severe overaction. Anteriorization works by transposing the inferior oblique insertion from its normal position posterior to the equator of the eye to a position anterior to the equator. When the inferior oblique insertion is anterior to the equator, the inferior oblique muscle no longer acts as an elevator but, instead, pulls the front of the eye down; now, it is actually a depressor. This change is why anteriorization procedures that place the inferior oblique muscle anterior to the inferior rectus insertion can cause the complication of an ipsilateral hypodeviation and limited elevation.4,33 This complication can be avoided by keeping the anterior inferior oblique muscle fibers posterior to the inferior rectus insertion. Keeping the posterior fibers of the inferior oblique muscle at least 3 mm posterior to the inferior rectus insertion is especially important because of the inferior oblique neurovascular bundle.34,35 The neurovascular bundle is a relatively inelastic structure inserting in the posterior aspect of the inferior oblique muscle. If the posterior fibers are anteriorized to the level of the inferior rectus insertion, the neurovascular bundle will tighten and act as a tether holding the eye down. Anteriorizing the posterior fibers produces a J-deformity of the inferior oblique insertion. This author prefers avoiding the J-deformity and has developed a graded anterior transposition procedure that keeps the posterior fibers posterior to the anterior fibers. The graded anterior transposition procedure yields excellent results, even in severe cases, without the complication of limited elevation.9 Because the full anteriorization procedure with a J-deformity causes limited elevation, it is rarely indicated. However, it can be considered if performed bilaterally for severe bilateral inferior oblique overaction with a large DVD. Brown’s Syndrome ETIOLOGY Brown’s syndrome is a restrictive strabismus characterized by limitation of elevation that is worse when the eye is in adduction (Fig. 9-10A). It can be congenital or acquired, with a variety of causes for the restriction of elevation in adduction (see Table 9-7). The term congenital Brown’s syndrome or “true” Brown’s syndrome, is used to refer to Brown’s syndrome caused by a congenitally inelastic superior oblique muscle–tendon complex.36 chapter 9: alphabet patterns and oblique muscle dysfunctions 313 FIGURE 9-10A,B. (A) Preoperative composite nine-gaze photograph of patient with congenital Brown’s syndrome, right eye, with limited elevation in adduction and minimal to no superior oblique overaction. Note Y-pattern with exodeviation in upgaze. Also note there is some limitation of the right eye even in abduction, but the limitation is greatest in adduction. Despite the severe limitation of elevation, there is only trace hypotropia in primary position. (B) Postoperative photograph after a Wright’s superior oblique tendon silicone expander, right eye, for Brown’s syndrome. Note the versions are almost normal with only a trace limitation to elevation, which is the optimal result, with a slight residual limitation of elevation in adduction right eye. This was the author’s first silicone expander patient, and the results have remained excellent over 11 years of follow-up. 314 handbook of pediatric strabismus and amblyopia TABLE 15-7. Classification of Brown’s Syndrome. I. Congenital onset A. True congenital Brown’s syndrome (superior oblique etiology) i. Unknown: probable inelastic muscle–tendon complex B. Congenital pseudo-Brown’s syndrome (nonsuperior oblique cause) i. Anomalous inferior orbital adhesions ii. Posterior orbital bands iii. Anomalous insertion of rectus muscle and pulley (e.g., inferior displacement of lateral rectus pulley or insertion) II. Acquired onset A. Superior pblique or trochlear etiology i. Peritrochlear scarring and adhesions 1. Chronic sinusitis 2. Trauma: superior temporal orbit 3. Blepharoplasty and fat removal 4. Lichen sclerosus et atrophicus and morphea ii. Tendon–trochlear inflammation and edema 1. Idiopathic inflammatory (pain and click) 2. Trochleitis with superior oblique myocytis 3. Acute sinusitis 4. Adult rheumatoid arthritis 5. Juvenile rheumatoid arthritis 6. Systemic lupus erythematous 7. Possibly distant trauma (CPR and long bone fractures) 8. Possibly hormonal changes postpartum iii. Superior nasal orbital mass 1. Glaucoma implant 2. Neoplasm iv. Tight or inelastic superior oblique muscle 1. Thyroid disease (inelastic muscle) 2. Peribulbar anesthesia (inelastic tendon) 3. Hurler–Scheie’s syndrome (inelastic tendon) 4. Superior oblique tuck (short tendon) v. Idiopathic B. Nonsuperior oblique or trochlear causes i. Floor fracture ii. Retinal band around inferior oblique muscle iii. Inferior temporal adhesions Source: From Ref. 32, with permission. There are nonsuperior oblique causes for congenital Brown’s syndrome, including inferior orbital mechanical restriction, superior nasal orbital mass, and inferior displaced lateral rectus muscle and pulley.22,36 CLINICAL FEATURES OF BROWN’S SYNDROME The hallmark of Brown’s syndrome, regardless of the cause, is limited elevation in adduction. In congenital Brown’s syndrome, chapter 9: alphabet patterns and oblique muscle dysfunctions 315 this occurs because the tight posterior tendon fibers prevent the back of the eye from rotating down; therefore, the front of the eye cannot elevate.36 This restriction is a constant limitation and does not improve or resolve on its own. Typically, on clinical examination, there is minimal to no hypotropia in primary position, minimal to no superior oblique overaction, limited elevation in adduction, and divergence (Y-pattern) in upgaze (Fig. 9-10A).36 There is often some limitation of elevation in abduction, but the key is that the limitation is much worse in adduction.36 Limited elevation in abduction can produce pseudoinferior oblique overaction of the fellow eye because of Hering’s law.36 Intorsion on attempted upgaze has been reported.36 Patients with Brown’s syndrome usually have excellent binocular fusion, as they adopt a compensatory chin elevation and a face turn away from the Brown’s eye to maintain fusion. A patient with a right Brown’s syndrome will have a chin elevation and a face turn to the left. Standard forced-duction testing shows a restriction to elevation in adduction. If the Brown’s syndrome is caused by a tight superior oblique tendon, then Guyton’s exaggerated forcedduction testing of the superior oblique muscle will reveal a restriction to the eye moving up and in. ACQUIRED BROWN’S SYNDROME Causes of acquired Brown’s syndrome include pathology of the superior oblique tendon and trochlea and nonsuperior oblique pathology.36 Causes for trochlear or tendon abnormalities include repeat upper eyelid blepharoplasty, sinusitis with peritrochlear inflammation, rheumatoid arthritis, and a superior nasal mass deflecting the course of the superior oblique tendon (e.g., superior nasal glaucoma implant or superior nasal orbital tumor). Inflammatory Brown’s syndrome may be idiopathic primary trochleitis or secondary to sinusitis. Acquired nonsuperior oblique or trochlear causes of limited elevation in adduction include floor fracture, inferior scarring of the globe, fat adherence after inferior oblique muscle surgery, and strabismus surgery with inferior transposition of horizontal rectus muscles (e.g., infraplacement of a lateral rectus resection and medial rectus recession). Furthermore, many patients will develop an acquired Brown’s syndrome of unknown etiology (Table 9-6). 316 handbook of pediatric strabismus and amblyopia Idiopathic acquired Brown’s syndrome is often intermittent and sometimes associated with a “click” that is felt by the patient in the superior nasal quadrant when the patient looks up and in. In some cases, the click can be heard with a stethoscope placed in the superior nasal quadrant. The cause of the click and limited elevation is not known, but it may represent inflammation or an abnormality of fascial tissue around the superior oblique tendon. If the cause of an acquired Brown’s syndrome is in question, then orbital imaging studies are indicated. In many cases, acquired Brown’s syndrome will spontaneously resolve over several months to even several years. Surgery should only be considered after the patient has been observed for at least 6 months to 1 year. Another form of acquired Brown’s syndrome is inflammatory Brown’s syndrome, which is associated with superonasal orbital pain and tenderness. It is hypothesized that trochlear or peritrochlear inflammation is the cause. In some cases, inflammatory Brown’s syndrome is associated with a concurrent sinusitis36 or rheumatoid arthritis (rarely). In the majority of cases, however, the cause of the inflammation is unknown. The treatment of inflammatory Brown’s syndrome includes a trial of systemic nonsteroidal antiinflammatory agents (e.g., indomethacin 25–50 mg TID) or a local steroid injection in the area of the trochlea. A patient diagnosed with acquired Brown’s syndrome of unknown etiology should undergo workup with orbital imaging, as a variety of local or systemic diseases involving the trochlea may cause a Brown’s syndrome. Medical therapy, not surgery, is the treatment of choice for most cases of inflammatory Brown’s syndrome. CONGENITAL ELEVATION DEFICIT: DIFFERENTIAL DIAGNOSIS Congenital causes for limited elevation include double elevator palsy (see Chapter 10), Brown’s syndrome, inferior oblique paresis, and superior oblique overaction. Double elevator palsy can be distinguished by the presence of similar limitation in abduction and adduction, while primary superior oblique overaction and inferior oblique paresis may be more difficult to differentiate because they have a greater elevation deficit in adduction. See Table 10-6 for a comparison of the clinical findings of superior oblique overaction, Brown’s syndrome, and inferior oblique paresis. chapter 9: alphabet patterns and oblique muscle dysfunctions 317 SURGICAL INDICATIONS FOR CONGENITAL BROWN’S SYNDROME In general, surgery should be considered for Brown’s syndrome if there is a hypodeviation in primary position that causes a significant chin elevation. Patients with a minimal restriction and no significant face turn can be managed conservatively. Except for a few exceptions, surgery should be reserved for children older than 4 years of age; older children are less likely to develop postoperative suppression and amblyopia. Rarely, one may be forced to operate on a child under 4 years of age if the hypodeviation is large enough to disrupt fusion. SURGERY FOR CONGENITAL BROWN’S SYNDROME Management of congenital Brown’s syndrome is based on lengthening the superior oblique tendon.39 Procedures such as tenotomy and tenectomy release the restriction but are not controlled, as the cut ends of the tendon can separate widely and result in a superior oblique paresis. In Brown’s syndrome, the superior oblique muscle is not overacting and, therefore, procedures such as tenotomy or tenectomy often result in a secondary superior oblique paresis. In a study by Eustis et al., 85% of Brown’s patients demonstrated some degree of posttenotomy superior oblique paresis, with one-third requiring a second operation.8 Sprunger et al. reported that 50% of their study patients required further surgery caused by an ipsilateral superior oblique paresis after superior oblique tenotomy.32 To address this problem, Parks has previously suggested performing an ipsilateral inferior oblique recession at the same time as the superior oblique tenotomy. This approach, however, results in prolonged underaction of the inferior oblique and a persistence of Brown’s syndrome. To achieve a controlled elongation of the superior oblique tendon, this author has developed a procedure called the Wright superior oblique tendon expander (see Chapter 11). A segment of retinal silicone band (usually 6.0 mm long) is carefully sutured between the cut ends of the superior oblique tendon, 3 mm nasal to the superior rectus muscle. The initial conjunctival incision, however, is made temporal to the superior rectus muscle. The temporal incision is stretched nasally to expose the nasal aspect of the superior rectus muscle. This maneuver preserves nasal intermuscular septum so the silicone segment does not scar to 318 handbook of pediatric strabismus and amblyopia sclera. With the capsule floor intact, the silicone is actually placed within the superior oblique tendon capsule. Parks, this author, and others have obtained excellent results using the superior oblique tendon expander. The expander allows for controlled and reversible elongation of the tendon while maintaining the functional integrity of the superior oblique muscle–tendon complex. In trained hands, complications of the procedure are rare, but these include extrusion of silicone and scarring of the silicone to the sclera, causing postoperative limitation of depression. These complications can be limited by meticulous technique and limiting the maximum length of the silicone segment to 7.0 mm. Many now consider the superior oblique silicone tendon expander the procedure of choice for Brown’s syndrome. RESULTS OF THE SILICONE TENDON EXPANDER This author has reported his long-term results using the Wright superior oblique silicone tendon expander on patients with severe Brown’s syndrome (see Fig. 9-10A,B).41 Of 15 patients operated on by the author, preoperative limitation of elevation in adduction measured 3 in 1 patient and 4 in 14 patients. Postoperatively, 14 of the 15 patients showed improved motility with 10 patients demonstrating essentially normal versions. The 1 patient who did not improve after the silicone expander had a nonsuperior oblique tendon cause of Brown’s syndrome. The average final result graded on a scale of 1 to 10 (10 being best) was 8.3. Thirteen (13) of 15 patients (87%) achieved a final result score of 7 or better with a single surgery, and an additional patient was corrected with a second surgery providing an overall success rate of 93%. Ten of the 15 patients had at least 11 months follow-up, with 6 of the 10 patients showing a delayed improvement over a 4- to 6-month period. Five patients had more than 5 years follow-up and 4 (80%) had an excellent long-term outcome (final result, 9–10) with a single operation. All 5 patients had a good outcome (final result, 7–10; mean, 9.2) with 1 patient requiring a second surgery. There were no long-term complications, including no extrusions, no restriction of ocular rotations, and no infections. Stager et al.34 also reported good long-term results; however, in both papers, Wright and Stager emphasized the importance of surgical technique.34,41 Keep the nasal intermuscular septum and the floor of the superior oblique tendon capsule intact. Also, chapter 9: alphabet patterns and oblique muscle dysfunctions 319 perform the tenotomy at least 3 mm nasal to the superior rectus muscle to avoid adhesions to the superior rectus muscle. Finally, use 5 to 6 mm of silicone band segment for Brown’s syndrome. Both papers also commented on late improvement after surgery. Some patients showed a significant undercorrection immediately after surgery, but then improved to have excellent result by weeks, to even months, after surgery. The Wright silicone tendon expander is an effective option for correcting Brown’s syndrome, caused by a stiff or inelastic superior oblique tendon, with excellent long-term outcomes. Proper technique with maintenance of the tendon capsule is critical to the successful outcome of the procedure.43 CANINE TOOTH SYNDROME Scarring in the area of the superior oblique tendon and trochlea will limit movement of the tendon in both directions, resulting in a Brown’s syndrome with a superior oblique paresis. This disorder has been called “Canine tooth syndrome” or Knapp type 7 classification.2,14,15,18,21,43 In this author’s thesis43 on Brown’s syndrome, three patients were diagnosed as having Canine tooth syndrome with both restrictive elevation in adduction and a superior oblique palsy. All three cases presented with penetrating trauma to the trochlear area, two by metal hooks and one from a dog bite. Management of these cases is difficult, as surgery in the area of the trochlea can lead to further scarring and worsening of the condition. In the acute phase immediately after trauma, local corticosteroid injection might help reduce secondary fibrosis.2 Initial management is conservative observation because spontaneous improvement may occur.18 If the deviation persists after 4 to 6 months, then surgical correction can be considered. In these cases, it is best to correct the strabismus by operating on the extraocular muscles rather than trying to remove fibrosis in the trochlear area.43 References 1. Apt L, Call NB. Inferior oblique muscle recession. Am J Ophthalmol 1978;95:95. 2. Bachynski BN, Flynn JT. Direct trauma to the superior oblique tendon following penetrating injuries of the upper eyelid. Arch Ophthalmol 1985;103:1510–1514. 3. Berke RN. Tenotomy of the superior oblique for hypertropia. Trans Am Ophthalmol Soc 1946;44:304–342. 320 handbook of pediatric strabismus and amblyopia 4. Bremer DL, Rogers GL, Quick LD. Primary position hypotropia after anterior transposition of the inferior oblique. Arch Ophthalmol 1986; 104:229–232. 5. Cheng H, Burdon MA, Shun GA, Czypionka S. Dissociated eye movements in craniosynostosis: a hypothesis revived. Br J Ophthalmol 1993;77:563–568. 6. Demer JL. Orbital connective tissue in binocular alignment and strabismus. In: Lennerstrand G (ed) Advances in strabismus research: basic and clinical aspects. London: Portland Press, 2000:17–31. 7. Elliot L, Nankin J. Anterior transposition of the inferior oblique. J Pediatr Ophthalmol Strabismus 1981;18:35. 8. Eustis HS, O’Reily C, Crawford JS. Management of superior oblique palsy after surgery for true Brown’s syndrome. J Pediatr Ophthalmol Strabismus 1987;24:10–16. 9. Guemes A, Wright KW. Effect of graded anterior transposition of the inferior oblique muscle on versions and vertical deviation in primary position. J Am Assoc Pediatr Ophthalmol Strabismus 1998:2:201– 206. 10. Guyton DL. Clinical assessment of ocular torsion. Am Orthopt J 1983;33:7. 11. Harada M, Ito Y. Visual correction of cyclotropia. Jpn J Ophthalmol 1964;8:88. 12. Helveston EM. Classification of superior oblique muscle palsy. Ophthalmology 1992;99:1609–1615. 13. Helveston EM. A two-step test for diagnosing paresis of a single vertically acting extraocular muscle. Am J Ophthalmol 1967;64(5): 914–915. 14. Helveston EM, Birchler C. Class VII superior oblique palsy: subclassification and treatment suggestions. Am Orthopt J 1982;32:104– 110. 15. Knapp RP. Classification and treatment of superior oblique palsy. Am Orthopt J 1974;24:18–22. 16. Kraft SP, Scott WE. Masked bilateral superior oblique palsy: clinical features and diagnosis. J Pediatr Ophthalmol Strabismus 1986;23(6): 264–272. 17. Kushner BJ. The diagnosis and treatment of bilateral masked superior oblique palsy. Am J Ophthalmol 1988;105(2):186–194. 18. Legge RH, Hedges TR III, Anderson M, et al. Hypertropia following trochlear trauma. J Pediatr Ophthalmol Strabismus 1992;29(3):163– 166. 19. Mims JL, Wood RC. Bilateral anterior transposition of the inferior obliques. Arch Ophthalmol 1989;107:41. 20. Muchnick RS, Stoj M, Hornblass A. Traumatic inferior oblique muscle paresis. J Pediatr Ophthalmol Strabismus 1985;22(4):143– 146. 21. Neely KA, Ernest JT, Mottier M. Combined superior oblique paresis and Brown’s syndrome after blepharoplasty. Am J Ophthalmol 1990; 109(3):347–349. chapter 9: alphabet patterns and oblique muscle dysfunctions 321 22. Oh SY, Clark RA, Velez F, Demer JL. Magnetic resonance imaging (MRI) demonstration of instability of rectus pulleys as cause of incomitant strabismus. Investig Ophthalmol Vis Sci 2001;42(4):167. 23. Parks M. Isolated cyclovertical muscle palsy. Arch Ophthalmol 1958;60:1027. 24. Parks MM. The overacting inferior oblique muscle. Am J Ophthalmol 1974;77:787. 25. Parks MM. Bilateral superior oblique tenotomy for A-pattern strabismus in patients with fusion (commentary). Binoc Vis 1988; 3:39. 26. Paysee EA, Coats DK, Plager DA. Facial asymmetry and tendon laxity in superior oblique palsy. J Pediatr Ophthalmol Strabismus 1995;32(3):158–161. 27. Plager DA. Traction testing and superior oblique palsy. J Pediatr Ophthalmol Strabismus 1990;27:136–140. 28. Pollard ZF. Diagnosis and treatment of inferior oblique palsy. J Pediatr Ophthalmol Strabismus 1993;30(1):15–18. 29. Raina J, Wright KW, Lin MM, McVey JH. Effectiveness of lateral rectus Y-split surgery for correcting the upshoot and downshoot in Duane’s retraction syndrome, type III. Binoc Vis Strabismus 1997; 12(4):233–238. 30. Reese PD, Scott WE. Superior oblique tenotomy in the treatment of isolated inferior oblique paresis. J Pediatr Ophthalmol Strabismus 1987;24(1):4–9. 31. Romano P, Roholt P. Measured graduated recession of the superior oblique muscle. J Pediatr Ophthalmol Strabismus 1983;20:134–140. 32. Sprunger DT, von Noorden GK, Helveston EM. Surgical results in Brown’s syndrome. J Pediatr Ophthalmol Strabismus 1991;28(3):164– 167. 33. Stager DR, Weakley DR, Stager D. Anterior transposition of the inferior oblique: anatomic assessment of the neurovascular bundle. Arch Ophthalmol 1992;110:360. 34. Stager DR, Stager D, Parks MM. Long-term results of silicone expander for moderate and severe Brown’s syndrome. J Am Assoc Pediatr Ophthalmol Strabismus 1999;3:328–332. 35. Stager DR. The neurofibrovascular bundle of the inferior oblique muscle as its ancillary origin. Trans Am Ophthalmol Soc 1996;94: 1073–1094. 36. Wright KW. Color atlas of strabismus surgery: strategies and techniques. Torrance, CA: Wright 2000:184–203. 37. Wright KW. Current approaches to inferior oblique muscle surgery. In: Hoyt CS (ed) Focal points 1986: clinical modules for ophthalmologists. Am Acad Ophthalmol 1986;1. 38. Wright KW. Superior oblique silicone expander for Brown’s syndrome and superior oblique overaction. J Pediatr Ophthalmol Strabismus 1991;28:101–107. 39. Wright KW. Surgical procedure for lengthening the superior oblique tendon. Investig Ophthalmol Vis Sci 1989;30(suppl):377. 322 handbook of pediatric strabismus and amblyopia 40. Wright KW, Min BM, Park C. Comparison of superior oblique tendon expander to superior oblique tenotomy for the management of superior oblique overaction and Brown’s syndrome. J Pediatr Ophthalmol Strabismus 1992;29:92–99. 41. Wright KW. Results of the superior oblique tendon elongation procedure for severe Brown’s syndrome. Trans Am Ophthalmol Soc 2000;98:41–50. 42. Wright KW. Superior oblique silicone expander for Brown’s syndrome and superior oblique overaction. J Pediatr Ophthalmol Strabismus 1991;28:101–107. 43. Wright KW. Brown’s syndrome: diagnosis and management. Trans Am Ophthalmol Soc 1999;97:1023–1109.