Download 95 - Cranial Nerve Disorders

95 Cranial Nerve Disorders
Ernest E. Wang
KEY POINTS
• The 12 cranial nerves supply motor and sensory
innervation to the head and neck.
• Cranial nerve disorders generally cause visual
disturbances, facial weakness, or facial pain or
paresthesias, depending on the nerve or nerves
involved.
• Trigeminal neuralgia and Bell palsy are common cranial
nerve disorders.
• A thorough history and physical examination should
focus on assessing the potential for trauma (skull
fracture), tumor, cerebrovascular accidents, vascular
derangements (aneurysm, dissection, thrombosis), and
infection (meningitis, abscess).
• The presence of concomitant focal neurologic or
systemic signs should heighten suspicion for a central
rather than a peripheral cause of the neurologic
dysfunction.
PERSPECTIVE
The 12 cranial nerves provide motor and sensory innervation
to the head and neck. Some nerves serve purely motor functions (cranial nerves III, IV, VI, XI, and XII), some serve
purely sensory functions (cranial nerves I, II, and VIII), and
the remainder serve mixed motor and sensory functions
(cranial nerves V, VII, IX, and X).
In addition to somatic and visceral sensory components, the
cranial nerves provide the special sensory functions of sight,
smell, hearing, taste, and balance. Understanding the functions of individual cranial nerves aids in recognition of patterns of the clinical syndromes classically associated with
disorders of specific cranial nerves.
EPIDEMIOLOGY
Cranial neuropathies are a heterogeneous group of disorders
with a variety of causes. Trauma is a common cause, and
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diabetes and hypertension are common comorbid conditions.
Cranial nerves I, VI, and VII are the most frequently affected
after minor head trauma.1 Trigeminal neuralgia is a common
cause of facial pain that affects approximately 4.5 per 100,000
individuals; women are affected twice as often as men, and it
is more common in those older than 60 years.2 Trigeminal
neuralgia can be severely debilitating and has been termed the
“suicide disease.”3 Bell palsy is the most common cause of
acute facial paralysis worldwide. The peak age at incidence
has been reported to be between 15 and 45 years,4 but other
investigators have noted an increased incidence in individuals
older than 70.5,6 Pregnant women and patients with diabetes
have an associated increased incidence of the disease. A
familial association of Bell palsy is noted in 4% of cases,4
and it can cause both significant psychologic and physical
morbidity.
PATHOPHYSIOLOGY
CRANIAL NERVE I (OLFACTORY NERVE)
Anatomy
Cranial nerve I is a special sensory nerve that provides the
sense of smell. Inhaled scents are detected by the olfactory
epithelium lining the nasal cavity and transmitted to the olfactory bulb, which lies adjacent to the cribriform plate of the
ethmoid bone. Olfactory sensations are relayed from the
olfactory bulb to the brain via the olfactory tract.
Presenting Signs and Symptoms
The patient should be questioned about a history of head
trauma. An anteroposterior skull fracture parallel to the sagittal suture or an anteroposterior shearing injury can tear the
olfactory fibers traversing the cribriform plate and lead to
disruption of the synapses from the olfactory epithelium to
the olfactory bulb.
A frontal lobe mass such as a tumor, meningioma, or
abscess can compress the olfactory bulb as well, but the signs
and symptoms associated with such masses tend to be more
subacute.
Treatment
Treatment depends on the presence of concomitant injury.
Basilar skull fracture and cerebrospinal fluid rhinorrhea associated with trauma require immediate neurosurgical consultation. A subacute mass or abscess should be managed in
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consultation with neurosurgery, depending on the acuity of
the findings. Patients with anosmia secondary to trauma and
normal findings on head computed tomography (CT) can
referred to neurology or neurosurgery for outpatient follow-up.
CRANIAL NERVE II (OPTIC NERVE)
Anatomy
Visual stimuli are transmitted from the retina to the optic
nerve through the optic chiasm to the lateral geniculate
nucleus in the thalamus, where they synapse. From there,
impulses are transmitted along the optic radiations (geniculocalcarine tracts, including the Meyer loop) to the primary
visual cortex in the occipital lobes.
Presenting Signs and Symptoms
Unilateral loss of vision is most common with injuries to the
optic nerve. Patients with bilateral visual loss may not be
aware of any such injury until an examination is performed.
Acute visual loss is often of vascular origin, including central
retinal arterial or venous occlusion and cerebrovascular
disease. Neurologic causes, such as multiple sclerosis, may be
suggested by progression of the visual loss over a period of
hours or days, pain, and a history of additional neurologic
complaints with a recurrent waxing and waning pattern.
Inflammatory processes such as optic neuritis may be the
initial symptom of multiple sclerosis.
Neuropathy from temporal arteritis usually occurs in elderly
patients and is associated with progressive loss of vision (unilaterally or bilaterally), constitutional symptoms, jaw claudication, and headache.
Idiopathic intracranial hypertension should be considered
in patients with a history of headache, visual scotomata, and
visual changes. The typical patient is a young, heavy-set
woman who is taking oral contraceptives. The headache and
visual changes are typically worsened by coughing, bend­
ing over, or performing techniques such as the Valsalva
maneuver.
Orbital compressive tumors or aneurysms cause mass
effects that compromise optic nerve function.
Differential Diagnosis
The differential patterns of visual loss are described in
Box 95.1.
Treatment
Treatment depends on the cause. Emergency ophthalmologic
consultation is essential for vascular causes. Treatment of
central retinal artery occlusion should focus on lowering intraocular pressure. Inpatient evaluation for neurologic causes is
warranted depending on the clinical findings. Temporal arteritis requires high-dose steroid therapy. Idiopathic intracranial
hypertension requires urgent diagnostic and therapeutic
lumbar puncture.
CRANIAL NERVE III (OCULOMOTOR NERVE)
Anatomy
The oculomotor nerve is a pure motor nerve that works in
conjunction with cranial nerves IV and VI to coordinate extraocular movements. The oculomotor nerve controls the superior rectus (globe elevator), medial rectus (globe adductor),
inferior rectus (globe depressor), and inferior oblique (globe
elevator) muscles. It also controls the levator palpebrae
Cranial Nerve Disorders
BOX 95.1 Differential Patterns of Visual Loss
A central retinal etiology of the fovea or optic disk compromises visual acuity or causes central loss of vision in the
affected eye only.
Unilateral blindness is usually associated with an optic nerve
lesion, and only the affected eye has complete visual field
loss.
Unilateral nasal visual field loss can be caused by an internal
carotid artery aneurysm compressing the lateral optic
chiasm.
Bitemporal hemianopia can be caused by a midchiasmatic
lesion.
Homonymous hemianopia from an optic tract lesion causes
full contralateral visual field loss in both eyes.
Homonymous quadrantanopia secondary to a Meyer loop
lesion causes contralateral one-quarter visual field loss in
both eyes.
Fig. 95.1 This 60-year-old man had diabetes mellitus,
hypertension, coronary artery disease, chronic renal failure, and
multiple myeloma. He sought medical care because of double
vision (he described the images as “a little side by side but mostly
up and down”), diplopia, ptosis, and papillary sparing. Findings on laboratory tests, magnetic resonance imaging, and magnetic
resonance angiography were negative. The patient was evaluated
by a neurologist and an ophthalmologist, and diabetic cranial nerve
palsy was ultimately diagnosed. He was given an eye patch and
scheduled for ophthalmologic follow-up.
superioris muscle (upper eyelid elevator) and the intrinsic
visceral motor function of the sphincter pupillae muscles and
the ciliary muscles, which perform pupillary constriction and
accommodation, respectively.
Presenting Signs and Symptoms
The patient typically complains of double vision or difficulty
seeing out of the affected eye. There may be mild photophobia
in bright light. The patient may also complain of an inability
to raise the eyelid (ptosis).
Cranial nerve III palsy is more common in patients older
than 60 years and in those with diabetes or hypertension
(Fig. 95.1).
Patients with herniation syndromes will have a history of
trauma (Fig. 95.2), tumor, or other neurologic findings.7
Pain associated with unilateral mydriasis should alert the
emergency physician (EP) to look for an aneurysm involving
the terminal internal carotid artery. Computed tomographic
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angiography is more reliable than magnetic resonance
angiography.8
Patients with an abscess or cavernous sinus thrombosis may
have headaches, altered mental status, and seizures. This diagnosis should be considered in patients with signs and symptoms in the contralateral eye, previous sinus or midface
infection, fever, chemosis, eyelid or periorbital edema, and
exophthalmos. Extension of internal carotid artery dissection
intracranially into the cavernous sinus can result in third,
fourth, and sixth cranial nerve palsies.9
Treatment
Treatment is dependent on the cause. CT should be performed
to exclude a herniating mass. Admission for magnetic resonance imaging (MRI) and neurology or neurosurgical consultation is indicated for acute-onset deficits.
CRANIAL NERVE IV (TROCHLEAR NERVE)
Anatomy
The trochlear nerve innervates the superior oblique muscle of
the eye and causes inward rotation and downward and lateral
movement of the globe. It is the smallest cranial nerve but has
the longest intracranial course.
Fig. 95.2 Ptosis and mydriasis suggest a cranial nerve III
palsy. The appearance of these signs after a crush injury indicates
that a skull fracture is impinging on the nerve canal. (Reproduced
with permission from Baker C, Cannon J. Images in clinical
medicine. Traumatic cranial nerve palsy. N Engl J Med
2005;353:1955.)
A
Presenting Signs and Symptoms
Patients with a fourth cranial nerve palsy have double vision
exacerbated by looking downward. The classic complaint is
difficulty going down stairs. Most commonly, a history of
trauma is reported. On physical examination the patient may
unconsciously tilt the head away from the affected side (Fig.
95.3). Etiologic mechanisms are similar to those for the third
cranial nerve and include inflammatory processes, trauma,
and vascular causes.10
Treatment
Treatment of isolated fourth nerve palsy is generally conservative, and the patient should be referred to neurology or
neurosurgery as appropriate.10 CT, MRI, and neurology consultation are warranted if multiple cranial nerves are involved.
CRANIAL NERVE V (TRIGEMINAL NERVE)
Anatomy
The trigeminal nerve is a mixed motor and sensory nerve. It
provides motor innervation to the muscles of mastication, as
well as sensation from the face, scalp, conjunctiva, globe,
mucous membranes of the sinuses, tongue, teeth, and part of
the external tympanic membrane.
The trigeminal sensory ganglion is located in the middle
cranial fossa and branches into three divisions: the ophthalmic
nerve (V1), the maxillary nerve (V2), and the mandibular
nerve (V3).
Presenting Signs and Symptoms
Patients with trigeminal nerve dysfunction have either sensory
or motor deficits. Sensory dysfunctions include paroxysmal
pain, paresthesias (abnormal sensations such as burning,
pricking, tickling, or tingling), dysesthesias (disagreeable,
unpleasant, or painful sensations produced by ordinary
stimuli), and anesthesia (loss of sensation). The motor dysfunction is usually described as difficulty chewing and difficulty swallowing.
Peripheral lesions cause loss of sensation or pain in only
one division. Positive findings in two or more divisions (e.g.,
loss of light touch in one division and loss of sensitivity to
pain, temperature, or pinprick in another division) should
raise suspicion for a central cause.
B
Normal eye rotation
When the head tilts to the left, both eyes rotate
in the opposite direction (right eye extorts, left
eye intorts)
Cranial nerve IV palsy (right eye)
Right eye extorted and slightly elevated, causing
double vision. To compensate, the patient tilts her
head to the left
Fig. 95.3 A, Normal eye rotation. When the head tilts, both eyes rotate in the opposite direction. B, Cranial nerve IV palsy (right eye). The
right eye is extorted and slightly elevated, which is causing double vision. The patient compensates by tilting the head to the left.
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The presence of associated cranial nerve deficits (III, IV,
IV, or any combination of these nerves) suggests cavernous
sinus involvement. In the setting of trauma, if a bruit over the
orbit can be detected, a carotid–cavernous sinus fistula may
be present. Associated involvement of cranial nerve VII or
VIII or gait ataxia should raise suspicion for a cerebellopontine angle or lateral pontine tumor (Table 95.1).
Associated Horner syndrome may indicate a cervical or
lateral brainstem lesion.
The main categories of trigeminal nerve dysfunction are
trigeminal neuralgia and trigeminal neuropathy. A sudden
Cranial Nerve Disorders
onset of symptoms should raise suspicion for a vascular, traumatic, or demyelinating cause, whereas a more indolent course
suggests tumor or inflammation (Table 95.2).
TRIGEMINAL NEUROPATHY Causes include compression
by an extrinsic mass, trauma, and vascular, inflammatory, or
demyelinating disorders.
Symptoms include neuralgia or paresthesia (or both) involving half of the face. Unlike trigeminal neuralgia, the pain with
trigeminal neuropathy is more constant. Loss of the corneal
reflex is evident. The patient’s mouth may become more oval
Table 95.1 Clinicoanatomic Correlation of Localization of Lesions of Cranial Nerve V
ANATOMIC SITE
OF DAMAGE
CLINICAL FINDINGS
OTHER NEUROLOGIC
AND MEDICAL FINDINGS
COMMON CAUSES
Sensory cortex
Facial numbness, paresthesias
Neglect, apraxia, aphasia
Stroke, tumor, hemorrhage
Internal capsule
Hemifacial sensory loss
Hemiparesis of the arm
Stroke, tumor, hemorrhage, MS
Supranuclear
Corona radiata
Central seventh cranial nerve paresis
VPM thalamus
Facial numbness, paresthesias,
pain; cheirooral syndrome
Anosmia, hemisensory deficit
Stroke, tumor, hemorrhage
Midbrain
Facial numbness, paresthesias, pain
Ophthalmoparesis
Stroke, MS, tumor, aneurysm
Pons
Facial numbness and weakness,
paresthesias, pain; trigeminal
neuralgia
Ophthalmoparesis; CN VI, CN VII, CN
VIII palsies; Horner syndrome
Stroke, tumor, hemorrhage;
MS, syringobulbia, abscess,
trauma
Medulla
Facial numbness, paresthesias,
pain; trigeminal neuralgia
Ataxia, CN X palsy, ophthalmoparesis,
nystagmus, Horner syndrome,
Wallenberg syndrome
Stroke, MS, tumor, aneurysm,
abscess, vasculopathy
Facial numbness
CN VII, CN VIII palsies; headache,
cerebellar dysergia
Neuroma, meningioma,
meningitis (bacterial, TB,
cancer), aneurysm, trauma
Gasserian
ganglion
Facial numbness and weakness
Gradenigo syndrome; CN VI, CN VII
palsies
Tumor, infection, trauma
Skull base
Facial numbness and weakness
Headache, meningismus
Meningitis (bacterial, TB,
cancer, sarcoid)
Nuclear
Preganglionic
Cerebellopontine
angle
Middle cranial fossa
Trigeminal Nerve Branches
V1: Cavernous sinus
Facial numbness, pain
Headache, ophthalmoparesis; Horner
syndrome
Tumor, thrombosis, infection,
trauma
V1: Carotidcavernous fistula
Facial numbness
Proptosis, bruit, ophthalmoparesis
Trauma
V2: Maxillary region
Facial numbness; numb cheek
syndrome
Tumor, infarct, vasculopathy,
trauma
V3: Mandibular
region
Weakness of mastication; numb
chin syndrome
Tumor, trauma, infarct
CN, Cranial nerve; MS, multiple sclerosis; TB, tuberculosis; VPM, ventroposteromedial.
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Table 95.2 Selected Specific Causes Associated with Trigeminal Nerve Disorders
ETIOLOGIC CATEGORY
SELECTED SPECIFIC CAUSES
Structural Disorders
Developmental
Brainstem vascular loop, syringobulbia
Degenerative and compressive
Paget disease
Hereditary and Degenerative Disorders
Chromosomal abnormalities, neurocutaneous disorders
Hereditary sensorimotor neuropathy type I, neurofibromatosis
(schwannoma)
Degenerative motor, sensory, and autonomic disorders
Amyotrophic lateral sclerosis
Acquired Metabolic and Nutritional Disorders
Endogenous metabolic disorders
Diabetes
Exogenous disorders (toxins, illicit drugs)
Trichloroethylene, trichloroacetic acid
Nutritional deficiencies, syndromes associated with alcoholism
Thiamine, folate, vitamin B12, pyridoxine, pantothenic acid, vitamin A
deficiencies
Infectious Disorders
Viral infections
Herpes zoster, unknown
Nonviral infections
Bacteria, tuberculous meningitis, brain abscess, Gradenigo
syndrome, leprosy, cavernous sinus thrombosis
HIV infection, AIDS
Opportunistic infection; abscess, herpes zoster
Stroke, hemorrhage, aneurysm
Neurovascular Disorders
Neoplastic Disorders
Primary neurologic tumors
Glial tumors, meningioma, schwannoma
Metastatic neoplasms, paraneoplastic syndromes
Lung, breast; lymphoma, carcinomatous meningitis
Demyelinating Disorders
Central nervous system disorders
Multiple sclerosis, acute demyelinating encephalomyelitis
Peripheral nervous system disorders
Guillain-Barré syndrome, chronic inflammatory demyelinating
polyneuropathy
Tolosa-Hunt syndrome, sarcoidosis, lupus, orbital pseudotumor
Autoimmune and Inflammatory Disorders
Traumatic Disorders
Carotid-cavernous fistula, cavernous sinus thrombosis, maxillary/
mandibular injury
Epilepsy
Focal seizures
Headache and Facial Pain
Raeder neuralgia, cluster headache
Drug-Induced and Iatrogenic Neurologic Disorders
Orbital, facial, dental surgery
From Goetz CG, editor. Textbook of clinical neurology. 2nd ed. Philadelphia: Saunders; 2003.
AIDS, Acquired immunodeficiency syndrome; HIV, human immunodeficiency virus.
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and oblique in appearance, and because of loss of masseter
muscle strength, the chin may be deviated toward the affected
side.
Until proved otherwise, neuropathies of cranial nerve V, the
chin (numb chin; V3), and the suborbital region (numb cheek)
should be presumed to be due to malignancies.11
TIC DOULOUREUX The term tic douloureux was coined by
Nicolaus André, a French surgeon, in 1756. Its mechanism is
probably compression of the trigeminal nerve root within millimeters of entry into the pons.12 The maxillary and mandibular divisions are most commonly affected, either alone or in
combination. In one longitudinal case series, no cases of trigeminal neuralgia affecting both the ophthalmic and mandibular divisions were reported.2 Causes of tic douloureux are
listed in Box 95.2.
The International Association for the Study of Pain defines
tic douloureux as “a sudden usually unilateral, severe, brief,
stabbing, recurrent pain in the distribution of one or more
branches of the fifth cranial nerve.” The pain is classically
precipitated by normal activities such as eating, talking,
washing the face, or cleaning the teeth.
Diagnostic Testing
The presence or absence of a corneal reflex should be checked.
An intact reflex indicates normal function of the afferent V1
division, as well as normal cranial nerve VII motor efferent
function. Absence of a corneal reflex can be caused by tumors
in the posterior fossa or cerebellopontine angle, multiple sclerosis, brainstem strokes (Wallenberg or lateral medullary syndrome), and Parkinson disease.
Motor function is evaluated by having the patient open and
close the mouth and laterally deviate the jaw against resistance. Loss of muscle bulk or the presence of fasciculations
in the temporalis or masseter musculature indicates a lower
motor neuron lesion.
The jaw jerk reflex test determines the integrity of the V3
division. The examiner places a thumb on the patient’s chin,
after which the patient is instructed to relax the jaw completely with the mouth closed, and the examiner then taps the
chin to elicit the jaw jerk reflex. The reflex will be diminished
BOX 95.2 Causes of Tic Douloureux
Vascular compression by an artery or vein
Saccular aneurysm
Arteriovenous malformation
Vestibular schwannomas
Meningioma
Epidermoid cyst
Tumor
Primary demyelinating disorders
• Multiple sclerosis
• Charcot-Marie-Tooth disease (rare)
Infiltrative disorders
• Trigeminal amyloidoma
Nondemyelinating lesions
• Small infarct or angioma in the brainstem
Familial
Cranial Nerve Disorders
in patients with a lower motor neuron lesion and accentuated
in patients with a supranuclear lesion.
Treatment
A trial of carbamazepine can be therapeutic as well as diagnostic because failure to improve with carbamazepine suggests some other cause. Treatment options are listed in Box
95.3.3 Surgical approaches are considered when medication
cannot control the pain or pain medication is not tolerated.13
CRANIAL NERVE VI (ABDUCENS NERVE)
Anatomy
The abducens nerve is a pure motor nerve that supplies the
ipsilateral lateral rectus muscle of the eye and controls globe
abduction.
PRESENTING SIGNS AND SYMPTOMS
Patients with an abducens nerve palsy usually complain of
double vision. The head may be turned away from the affected
side to maintain binocularity. Diabetes and hypertension are
common risk factors. Another common sign is “crossed eyes”
(esotropia or strabismus) (Fig. 95.4).14
Differential Diagnosis
Children are more likely to have a tumor as the principal
cause, and older individuals are more likely to have an ischemic cause such as temporal arteritis.
An abducens nerve palsy occurring in isolation is rare.
Usually, the seventh and eighth cranial nerves are also
involved, which signals a central cause. Causes of abducens
nerve palsy are listed in Box 95.4.
BOX 95.3 Treatment of Trigeminal Neuralgia
First-Line Agent
Carbamazepine (Tegretol)—Start at 150 mg daily and
increase by 100 mg every 3 days as needed to a total
daily dose of 800 to 1600 mg divided into three doses.
Second-Line Agents
Oxcarbazepine (Trileptal)—Start at 300 mg daily and increase
by 300 mg every 3 days as needed to a total daily dose
of 1200 to 1800 mg divided into two doses.
Gabapentin (Neurontin)—Start at 300 mg three times daily
and increase as needed to a total daily dose of 3600 mg
divided into three doses. Also commonly used as first-line
therapy.
Phenytoin (Dilantin)—Start at 300 mg daily and increase as
needed, divided into two or three doses.
Third-Line Agents (Add-On Therapy or Monotherapy)
Lamotrigine (Lamictal)—Start at 25 mg daily and increase by
25 mg every 7 days as needed to a total daily dose of 200
to 400 mg divided into two doses.
Baclofen (Lioresal)—Start at 15 mg daily and increase by
5 mg every 3 days as needed to a total daily dose of 60
to 80 mg divided into three doses.
Reprinted with permission from Prasad S, Galetta S. Trigeminal neuralgia:
historical notes and current concepts. Neurologist 2009;15:87-94.
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BOX 95.4 Causes of Abducens Nerve Palsy
A
B
Trauma—a blowout fracture of the orbit may result in a
trapped medial rectus muscle and mimic a sixth nerve
palsy
Subarachnoid disorders—hemorrhage, infection (meningitis),
tumor
Vascular—intracavernous aneurysms; sixth nerve palsies are
almost always the first clinical feature because of this
nerve’s close relationship to the carotid artery and the fact
that it is unsupported by a fibrous covering
Giant cell arteritis
Pontine glioma (in children)
Pseudotumor cerebri—may be manifested as an isolated
abducens nerve palsy in 30% of cases
Inflammatory (postviral or demyelinating) leptomeningeal
involvement secondary to carcinomatous meningitis;
inflammatory or infiltrating lesions of the cavernous sinus
Metabolic—vitamin B deficiency, Wernicke-Korsakoff
syndrome
Congenital absence of cranial nerve VI (Duane syndrome)
C
Fig. 95.4 This 62-year-old man reported acute left retroorbital
pain of 1 week’s duration. Double vision developed, a rash
appeared on his forehead, and he had restricted abduction in his left eye; this finding is diagnostic of a left sixth cranial nerve
palsy (right, center, and left gaze seen in panels A, B, and C,
respectively) and binocular horizontal diplopia. A diagnosis of
herpes zoster ophthalmicus was made. The patient was treated
with gabapentin and acyclovir for 1 week. Six weeks later, he had minimal residual diplopia with no postherpetic neuralgia.
(Reproduced with permission from Jude E, Chakraborty A. Images
in clinical medicine. Left sixth cranial nerve palsy with herpes zoster
ophthalmicus. N Engl J Med 2005;353:e14.)
Treatment
Truly isolated sixth nerve palsies are often caused by microvascular ischemia secondary to hypertension or diabetes. A
thorough work-up must be performed to rule out a central,
inflammatory, infectious, or neoplastic cause. Close follow-up
by a neurologist over a 6-month period is indicated; most
cases resolve within 3 to 6 months.
CRANIAL NERVE VII (FACIAL NERVE)—
BELL PALSY
Mechanisms
The pathophysiology of Bell palsy has not been clearly established. Several theories have been proposed, including infectious or ischemic inflammation leading to nerve compression
within the narrow canal as the nerve exits the stylomastoid
foramen. Because the nerve is encased in a tight dural sheath
within the temporal bone, this edema then causes additional
compression of the vascular supply to the nerve.15
The cause of Bell palsy is most commonly idiopathic
(66%).4 Numerous observed associations have been described
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in the literature. The palsy is often preceded by a viral syndrome, and a correlation has been noted with herpes simplex
virus (HSV). Its association with shingles and the characteristic blistering (from varicella-zoster virus [VZV]) is given
the designation Ramsay Hunt syndrome. Reactivation of VZV
has also been theorized as a cause. In addition, Bell palsy may
be seen in patients with Lyme disease in places where the
disease is endemic.
Diabetes, hypertension, human immunodeficiency virus
infection, sarcoidosis, Sjögren syndrome, parotid nerve
tumors, eclampsia, amyloidosis, and the intranasal influenza
vaccine have been associated with the development of Bell
palsy.5,16 Other common triggers include stress, trauma, fever,
tooth extraction, and a chilling episode from exposure to
drafts and cold.
Complete facial weakness, severe non–ear-related pain
(e.g., retroauricular, cheek), late onset of recovery or no recovery by 3 weeks, diabetes, pregnancy, age older than 60 years,
hypertension, and Ramsay Hunt syndrome are risk factors for
incomplete recovery.17,18
Electroneurographic studies demonstrate a steady decline
in electrical activity on days 4 to 10. When excitability
is retained, 90% of patients recover fully, but when
excitability diminishes to absence, only 20% of patients
recover completely.5
Anatomy
Cranial nerve VII is a mixed motor and sensory cranial nerve,
which accounts for the varied symptoms. It travels adjacent
to cranial nerves V, VI, and VIII as it traverses the cerebellopontine angle, the internal auditory meatus, and the temporal bone.
Motor function involves the muscles of facial expression,
the posterior digastric muscle, the stylohyoid muscle, and the
stapedius muscle of the inner ear.
CHAPTER 95
Fig. 95.5 “Raise your eyebrows.” A patient with a peripheral
seventh nerve palsy (i.e., Bell palsy) will have loss of forehead
wrinkles at rest and an inability to wrinkle the forehead and raise
the eyebrow on the affected side (right side in this patient).
Parasympathetic innervation includes the lacrimal glands,
the mucous membranes of the nose, the hard and soft palate,
and the submandibular and sublingual glands.
The geniculate ganglion contains the nerve cell bodies of
the sensory taste fibers of the anterior two thirds of the
tongue.19
Presenting Signs and Symptoms
To the patient, the most alarming symptom of Bell palsy is
the abrupt onset of unilateral facial paralysis. Approximately
50% of patients believe that they have suffered a stroke, 25%
think that they have an intracranial tumor, and the remaining
25% have no clear conception of what is wrong but are
extremely anxious.4
The EP may note drooping of the eyebrow or the corner of
the mouth (or both) and loss of wrinkles on the forehead or
the nasolabial folds (or both). Inability to raise the eyebrow
and furrow the forehead is a cardinal sign of Bell palsy (Fig.
95.5). Preservation of forehead motor neuron innervation
should raise suspicion for a central cause.17 Because the forehead receives bilateral upper motor neuron innervation, a
central stroke will spare the forehead and allow the patient to
raise the eyebrow. If the patient can do this, it is not Bell palsy.
Loss of nasolabial fold and nasal flaring is common. Loss
of buccinator strength causes an inability to blow out the
cheeks. An inability to close the eye on the affected side is a
hallmark of Bell palsy. Speech is affected and may sound
slurred or garbled, similar to dysarthria from a stroke. An
asymmetric smile is often noted on examination (Fig. 95.6).
The signs and symptoms vary depending on the site of the
affected nerve. They are listed in Box 95.5.
Cranial Nerve Disorders
Fig. 95.6 “Show me your teeth”; “wrinkle your nose.” The
risorius and orbicularis oris muscles are denervated. Notice the
inability to corrugate the nose on the affected right side because of
loss of function of the nasal and buccal musculature.
BOX 95.5 Signs and Symptoms of Bell Palsy
Ipsilateral tongue numbness
Loss of taste or a dull taste
Overt paralysis preceded by a sensation of subjective numbness or weakness on the affected side
Ear pain in the external auditory canal
Retroauricular pain
Occipital headache
Hyperacusis
Fullness or snapping sound in the affected ear
Tinnitus
Drooling
Inability to keep liquids in the mouth or chew
Noticeable dryness of the oral and nasal mucous membranes
on the affected side
Anxiety
Diagnostic Testing and Differential Diagnosis
The “blow out your cheeks” test (Fig. 95.7) demonstrates loss
of buccinator function. A sensitive variation of this test is to
ask patients to hold water in their mouth and contract the
buccal muscles. The water will either dribble out of the corner
of the mouth or shoot across the room.
On testing of hearing, hyperacusis may be observed on the
affected side because of denervation of the stapedius. The
patient should have no hearing loss.
825
SECTION IX
NERVOUS SYSTEM DISORDERS
Fig. 95.7 “Blow out your cheeks.” Loss of buccinator function
prevents pursing of the lips and allows air (and food and liquids) to
escape.
Fig. 95.9 Characteristic auricular rash of Ramsay Hunt
syndrome.
Fig. 95.8 Buccal herpetic lesions in an individual with
Ramsay Hunt syndrome.
To evaluate taste sensation, a few granules of sugar are
placed on the tip of the patient’s tongue on the affected side.
Decreased taste sensation may be noted.
Other cranial nerves should be normal. The abducens
nucleus lies at the level of the genu of cranial nerve VII;
infarction in the area can cause concomitant palsy of cranial
nerve VI, which signals an upper motor neuron lesion rather
than Bell palsy. No evidence of expressive or receptive aphasia
should be present.
The presence of vesicles on the tympanic membrane or in
the oropharynx (Fig. 95.8) or the presence of grouped vesicular lesions on the face or around the ear (Fig. 95.9) suggests
a diagnosis of Ramsay Hunt syndrome.
Residual synkinesis can result from abnormal regeneration
of nerve fibers. This can be manifested as abnormal motor
function (e.g., blinking causes involuntary contracture of the
risorius); as abnormal parasympathetic function, which is
classically accompanied by “crocodile tears”—lacrimation
after a salivary stimulus; or as hemifacial spasm, which can
be bothersome, especially when the patient is tired.
826
Treatment
The algorithm shown in Figure 95.10 outlines the treatment
of patients with Bell palsy.
Patients can be discharged home with oral medication,
instructions for eye care, and expedited follow-up with a neurologist. Additional investigation for Lyme disease may be
indicated for patients at risk.
The evidence available indicates that steroids are safe and
effective in shortening the course of the neurologic deficit and
improving facial function.5,20-24 Patients receiving steroid
therapy are up to 1.2 times more likely to attain good functional outcomes than untreated patients are.25 Corticosteroids
reduce the risk for unsatisfactory recovery by 9%, with the
number needed to benefit (NNTB) being 11.21 Corticosteroids
were also associated with a 14% absolute reduction in risk for
synkinesis and autonomic dysfunction, with an NNTB of 7.22
No studies have demonstrated significantly worse facial
functional outcomes in patients treated with steroids.21,22,25
The most commonly reported treatment regimen is oral
prednisone, 1 mg/kg up to 70 mg/day for a 10-day course.
Dosing can be once daily or split into twice daily. The starting
dose is continued for 6 days and tapered over the next 4
days.22,25 Alternatively, prednisone, 1 mg/kg/day, may be given
for 7 days without a taper.4
Recent studies and metaanalyses have questioned the
benefit of using antivirals for the treatment of Bell palsy.20-24,26
Antiviral agents used alone did not provide any benefit over
placebo, and their use as the sole therapeutic agent is not
recommended.20 When combined with corticosteroid therapy,
antiviral therapy may have incremental benefit,21 but this
remains to be shown conclusively. Therefore, until definitive
studies are performed, clinical judgment will probably guide
the use of antiviral therapy in cases in which a viral cause is
strongly suspected (i.e., patients in whom HSV or VZV is
CHAPTER 95
more significant than the physical disability. Patients report
self-consciousness about the facial disfigurement, fear of
permanent disfigurement, loss of self-esteem, and social
ostracism.
Acute facial
weakness
Central or
peripheral?
Peripheral
Central
Herpes
zoster
oticus
No
Bell palsy
Ramsay Hunt
syndrome
Cranial Nerve Disorders
1) MRI to evaluate for
ischemia and for
infectious and
inflammatory
diseases
2) Consider:
a. CSF
b. ESR
c. Serologic studies
for syphilis, HIV,
and vasculitis
3) Admit patient
1) Prednisone (started within 2-14
days of onset), 1 mg/kg/day for
7-14 days. Taper to 10 mg/day
if more than 7 days
2) Valacyclovir 1000 mg three times
daily for 7 days as clinically
indicated and only in conjunction
with corticosteroids
Fig. 95.10 Algorithm outlining the treatment of patients with
Bell palsy. CSF, Cerebrospinal fluid; ESR, erythrocyte
sedimentation rate; HIV, human immunodeficiency virus; MRI,
magnetic resonance imaging.
contributory). Valacyclovir, 1 g three times daily for 7 days,
can be prescribed in conjunction with corticosteroids.
An eye shield or an eye patch should be worn during the
night to prevent drying of the cornea. Liberal use of artificial
tears during the day and an ophthalmic ointment such as
Lacri-Lube at night should be prescribed to prevent drying of
the cornea. Pain medication should be prescribed because the
otalgia and cephalgia can be debilitatingly painful.
Prognosis
In a prospective study describing the spontaneous untreated
course of idiopathic peripheral nerve palsy in patients with
diabetes, 38% of patients had complete palsies, and only 25%
regained normal facial muscle function.4 This is significantly
worse than the observed rate of spontaneous full recovery in
nondiabetic patients.27 Recurrence is rare (6.3%28) and should
prompt a work-up for other causes such as myasthenia gravis,
lymphoma, sarcoidosis, Lyme disease, and rarely, GuillainBarré syndrome.5,29,30
Although the prognosis for recovery is good, the psychologic consequences can be long-lasting and are perhaps
CRANIAL NERVE VIII (VESTIBULOCOCHLEAR
NERVE)
Anatomy
The vestibulocochlear nerve is a special sensory nerve that
transmits auditory signals from the cochlea (hearing) and
signals from the semicircular canals (balance). The vestibular
apparatus also sits in the petrous temporal bone and is composed of a body consisting of the saccule and utricle and three
semicircular canals aligned in three different planes. Hair cells
within the endolymph of the canals detect angular movement
and transmit the impulses to the vestibular nuclear complex
in the floor of the fourth ventricle. The hair cells collectively
combine to form the vestibular ganglion.
Presenting Signs and Symptoms
Patients with vestibulocochlear nerve dysfunction usually
exhibit various degrees of hearing loss, tinnitus, vertigo,
falling, and imbalance. The mechanism is asymmetric integration of vestibular input to the central nervous system or asymmetric disruption of sensory input from the vestibular organs.31
If the vertigo is severe, nausea and vomiting also occur.
Symptoms may be constant or episodic. Vestibular neuronitis
causes vertigo that lasts for weeks, and central vertigo may
persist for years.32
Patients should be asked about triggers, particularly positional triggers because this may indicate benign paroxysmal
positional vertigo. Recent viral and upper respiratory tract
infections may be significant because they predispose to vestibular neuronitis. The history should also include the use of
medications such as anticonvulsants, antihypertensives, sedatives, and ototoxic drugs.
The examination should be focused on determining reproducibility of the symptoms, gait, balance, and ataxia; on
evaluation of possible acute stroke symptoms; and on the
character of the nystagmus and severity of the ataxia. The
presence or absence of associated cerebellar signs such as
lateralizing dysmetria, motor weakness, sensory loss, and
abnormal reflexes should be noted, as well as the Babinski
reflex and cranial nerve abnormalities such as ophthalmoplegia, dysarthria, and Horner syndrome.31 Abnormalities in cerebellar function should prompt consideration of a central
cause. Patients should also be examined for vertical and rotatory nystagmus, which are not typically present in patients
with peripheral vertigo; their presence warrants imaging and
neurologic evaluation.
Diagnostic Testing and Differential Diagnosis
The Dix-Hallpike maneuver is commonly used to elicit positional nystagmus (see Fig. 96.1), which is associated with
benign paroxysmal positional vertigo and usually lasts 5 to 60
seconds. Prolonged nystagmus is unlikely to be a result of this
disorder. Gait and balance can be assessed with tandem
walking and the Romberg test. Ataxia and lateralizing dysmetria can be assessed with finger-to-nose and heel-knee-shin
testing. Hearing can be evaluated with the finger rub or finger
snap, the Weber test, and the Rinne test. The ear and external
auditory canal should be examined for evidence of cerumen,
827
SECTION IX
NERVOUS SYSTEM DISORDERS
otitis media, perforation of the tympanic membrane, and mass
lesions.
CT lacks sensitivity in the evaluation of cranial nerve VIII
disorders but may be useful in evaluating the bony temporal
region. MRI with gadolinium enhancement is useful in identifying acoustic neuroma.
When a central cause is suspected because of abnormalities
on cerebellar testing or clinical suspicion, MRI or magnetic
resonance angiography (or both) should be performed to rule
out a posterior circulation stroke as a central cause of the
vertigo.
The differential diagnosis should include other cranial
nerve deficits that are not typically present in benign causes
of cranial nerve VIII dysfunction. Acoustic neuromas may
compress the trigeminal nerve when they attain a size of 3 cm
or greater; patients with complaints of facial numbness should
therefore be evaluated for trigeminal neuropathy, as well for
a mass lesion. Because large tumors can affect cranial nerves
IX, X, and XI, these nerves should also be tested.
Treatment
Some patients who come to the emergency department with
sudden or severe symptoms may not be able to comply with
testing because the severity of the symptoms limits the ability
to open their eyes and turn their head without experiencing
nausea and vomiting or exacerbating the symptoms. In these
cases it is appropriate to treat the patient symptomatically,
initiate a work-up, and reassess clinically for improvement
before attempting to move the patient or perform provocative
testing.
CRANIAL NERVE IX (GLOSSOPHARYNGEAL
NERVE)
Anatomy
The glossopharyngeal nerve provides branchial motor function to the stylopharyngeus muscle; visceral motor function
to the otic ganglion and parotid gland; visceral sensory function from the carotid body; somatic sensory function to the
posterior third of the tongue, the skin of the external ear, and
the internal surface of the tympanic membrane; and the
special sensory function of taste sensation from the posterior
third of the tongue.
Presenting Signs and Symptoms
Patients with glossopharyngeal nerve palsy usually have associated symptoms involving other cranial nerves, most commonly cranial nerves X and XI. The most common symptoms
are dysphagia and choking. If the vagus nerve is involved, the
patient complains of hoarseness and demonstrates ipsilateral
paralysis of the soft palate. Head, neck, and oral trauma or
surgery can cause acute dysfunction of cranial nerve IX. Glossopharyngeal nerve palsy is a known complication of tonsillectomy surgery.33
Glossopharyngeal neuralgia is a rare disorder consisting of
paroxysms of pain in the back of the throat and tongue. The
pain is similar to that of trigeminal neuralgia in that the attacks
are brief, lasting seconds to minutes. It is unilateral and usually
triggered by chewing, swallowing, coughing, or sneezing.
Treatment
CT scanning is warranted to evaluate for a cerebrovascular
event or tumor. Rarely, vasovagal syncope can result from
828
bradycardia or asystole caused by vagus nerve cardioinhibitory input. Medical management is similar to that for trigeminal neuralgia. If involvement of other cranial nerves is evident
on examination, the patient should be admitted for further
evaluation and neurologic consultation.
CRANIAL NERVE X (VAGUS NERVE)
Anatomy
The vagus nerve is a mixed motor and sensory nerve
that provides motor function to striated muscle of the pharynx,
tongue, larynx, and tensor veli palatini, as well as motor
function to smooth muscle and glands of the pharynx, larynx,
and thoracic and abdominal viscera. Cranial nerve X provides
general sensation from the skin at the back of the ear,
the external auditory meatus, the pharynx, and part of the
external surface of the tympanic membrane, as well as visceral sensation from the larynx, trachea, esophagus, and
thoracic and abdominal viscera; from chemoreceptors in the
aortic bodies; and from stretch receptors in the walls of the
aortic arch.
Presenting Signs and Symptoms
Patients with palsies of the vagus nerve generally have
hoarseness or difficulty swallowing. A history of recent
carotid or thyroid surgery should prompt suspicion for
a recurrent laryngeal nerve injury. The patient may also
complain of regurgitation of food and liquid into the
nose. Oropharyngeal examination usually reveals a drooped
arch of the soft palate and uvular deviation away from
the affected side.
Treatment
A CT scan of the head without contrast enhancement should
be performed to evaluate for a cerebrovascular accident (hemorrhagic or ischemic) or skull-based lesions. Further inpatient
evaluation may include MRI of the head and neck and workups for metabolic, infectious, or inflammatory disorders as
warranted.
CRANIAL NERVE XI (ACCESSORY NERVE)
Anatomy
The accessory nerve provides motor function to the sternocleidomastoid and trapezius muscles.
Presenting Signs and Symptoms
Patients with accessory nerve palsies have neck and
shoulder weakness on the affected side. Inspection may reveal
a “dropped” shoulder—that is, the affected shoulder lying
downward and in lateral rotation. Testing of the sterno­­
cleidomastoid reveals weakness when turning the head
against resistance to the contralateral side. Because of the
proximity of cranial nerves IX and X, particular attention
should be paid to these nerve functions on examination.
The most common causes are postoperative trauma (e.g.,
from cervical lymph node dissection) and a cerebrovascular
accident.
Treatment
Treatment and disposition are similar to that for cranial nerves
IX and X.
CHAPTER 95
CRANIAL NERVE XII (HYPOGLOSSAL NERVE)
Anatomy
The hypoglossal nerve provides motor function to all the
intrinsic tongue muscles and three of the four extrinsic tongue
muscles: the genioglossus, styloglossus, and hypoglossus.
Presenting Signs and Symptoms
Patients with hypoglossal nerve palsies usually have unilateral
tongue weakness.
Differential Diagnosis
The primary diagnostic consideration is distinguishing an
upper from a lower motor neuron lesion. An upper motor
TIPS AND TRICKS
Patients with palsies of any of the 12 cranial nerves have
heterogeneous symptoms reflecting the intrinsic function
of each nerve.
Patients with cranial nerve disorders generally have visual
disturbances, facial weakness or pain, or paresthesias,
depending on the nerve or nerves involved.
Knowledge of the function of each of the cranial nerves helps
the emergency physician recognize the classic signs and
symptoms of cranial nerve palsies.
Trigeminal neuralgia and Bell palsy are common cranial
nerve disorders encountered in the emergency
department.
Corticosteroids are beneficial in the treatment of Bell palsy.
Additional benefit of antiviral therapy is unclear.
The majority of patients with an acute onset of facial weakness are concerned about a stroke.
A thorough history and physical examination should be
focused on assessing the potential for trauma (skull fracture), tumor, cerebrovascular accident, vascular derangements (aneurysm, dissection, thrombosis), and infection
(meningitis, abscess). Morbidity primary results from
these entities.
The diagnostic work-up and disposition depend on the clinical findings.
The presence of concomitant focal neurologic or systemic
signs should heighten suspicion for a central rather than
a peripheral cause of the neurologic dysfunction.
Cranial Nerve Disorders
neuron lesion causes contralateral tongue deviation and fasciculations, and tongue atrophy is absent. A lower motor
neuron lesion causes ipsilateral tongue deviation and fasciculations, and tongue atrophy is present. A 26-year review of
100 cases of hypoglossal nerve palsy revealed that tumors,
predominantly malignant ones, produced nearly half of the
palsies. Only 15% of patients made a complete or nearly
complete recovery.34 External lesions that cause compression
or stretching of the nerve include internal carotid artery dissection or aneurysm, intracranial tumor, abscess, and other
pharyngeal space tumors.
Treatment
Treatment and disposition are similar to that for cranial nerves
IX, X, and XI. If there is concern for a cerebrovascular accident or space-occupying lesion, the patient should be admitted
for evaluation.
SUGGESTED READINGS
de Almeida JR, Al Khabori M, Guyatt GH, et al. Combined corticosteroid and
antiviral treatment for Bell palsy: a systematic review and meta-analysis. JAMA
2009;302:985-93.
Engström M, Berg T, Stjernquist-Desatnik A, et al. Prednisolone and valaciclovir in
Bell’s palsy: a randomised, double-blind, placebo-controlled, multicentre trial.
Lancet Neurol 2008;7:993-1000.
Gilden DH. Clinical practice. Bell’s palsy. N Engl J Med 2004;351:1323-31.
Gilden D. Treatment of Bell’s palsy—the pendulum has swung back to steroids alone.
Lancet Neurol 2008;7:976–7.
Salinas RA, Alvarez G, Daly F, et al. Corticosteroids for Bell’s palsy (idiopathic facial
paralysis). Cochrane Database Syst Rev 2010;3:CD001942.
Sherbino J. Evidence-based emergency medicine: clinical synopsis. Do antiviral
medications improve recovery in patients with Bell’s palsy? Ann Emerg Med
2010;55:475-6.
Worster A, Keim SM, Sahsi R, et al; Best Evidence in Emergency Medicine (BEEM)
Group. Do either corticosteroids or antiviral agents reduce the risk of long-term
facial paresis in patients with new-onset Bell’s palsy? J Emerg Med
2010;38:518-23.
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on
Expert
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