Download Alphabet Patterns and Oblique Muscle Dysfunctions

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
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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).
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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).
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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.
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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
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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
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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
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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.
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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
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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
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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
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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.
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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
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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
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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
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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
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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.
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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.
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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
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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)
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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
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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
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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).
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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.
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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
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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.
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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).
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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,
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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
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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.
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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,
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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).
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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
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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
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