Download Chapter 105 - Brain and Cranial Nerve Disorders

CHAPTER 105 Brain and Cranial Nerve
Disorders
Brian A. Stettler
This chapter discusses cranial nerve problems, cerebral venous
thrombosis, and multiple sclerosis—neurologic disorders that
often provide significant diagnostic and therapeutic challenges in
the emergency department (ED) setting (Table 105-1).
TRIGEMINAL NEURALGIA
Perspective
Trigeminal neuralgia, or tic douloureux, is a syndrome featuring
painful paroxysms in one or more distributions of the trigeminal
nerve. Trigeminal neuralgia is relatively uncommon, with an
annual incidence of 4 to 13 cases per 100,000 population.1,2 It is
more common in women than in men, with a female-to-male
ratio of 1.7 : 1. Affected persons typically are between 50 and 69
years of age, and symptoms occur more frequently on the right
side of the face.3
Pathophysiology
Trigeminal neuralgia is an idiopathic disorder, although significant evidence points to vascular compression of the trigeminal
nerve root in many cases. This compression commonly is caused
by a tortuous arterial or venous loop in the posterior fossa, an
arteriovenous malformation, or rarely a tumor. In surgical case
series, vascular compression of the trigeminal nerve root is found
in 80 to 90% of cases.4,5 Of note, however, structural lesions are
not found in all patients with trigeminal neuralgia.6
Clinical Features
Trigeminal neuralgia is manifested with unilateral facial pain,
typically characterized as lancinating paroxysms of pain in the lips,
teeth, gums, or chin. The pain of trigeminal neuralgia is commonly associated with physical triggers such as chewing, brushing
the teeth, shaving, washing or touching the affected area of the
face, swallowing, or exposure to hot or cold temperature in the
affected area. The maxillary and mandibular divisions of the trigeminal nerve are most commonly involved; rarely, the ophthalmic division alone is involved. Patients tend to experience the pain
in clustered episodes that last a few seconds to several minutes.
The attacks can occur during the day or night but rarely arise
during sleep.6,7
Diagnostic Strategies
A careful history and physical examination should be performed
to rule out other painful facial conditions, including odontogenic
infections, sinus disease, otitis media, acute glaucoma, temporomandibular joint disease, and herpes zoster. Patients who lack
local pathologic findings to explain the painful syndrome require
a careful neurologic examination. The presence of a neurologic
deficit should prompt suspicion of a structural lesion, such as
aneurysm, tumor, or other intracranial lesion (e.g., from multiple
sclerosis). Of note, 2 to 4% of patients with trigeminal neuralgia
also have multiple sclerosis.8 Patients with normal findings on the
head and neck examination and no neurologic deficits who have
episodic, unilateral facial pain associated with nonpainful triggers
are likely to have trigeminal neuralgia.
Management
Since the 1960s the treatment of choice for trigeminal neuralgia
has been the anticonvulsant medication carbamazepine. The purported effectiveness of this treatment, however, is based on uncontrolled studies, and the mechanism of action of anticonvulsant
therapy for trigeminal neuralgia is unclear. The true efficacy of
medical therapy is difficult to assess owing to a high rate of spontaneous remission. Nonetheless, carbamazepine appears to be an
effective and well-tolerated agent for treatment of trigeminal neuralgia. The initial dosage of carbamazepine is 100 mg twice daily;
this dose is then increased to three times daily after 1 week. The
dose may be increased by 100 mg/day, up to a maximum of
1200 mg/day. A complete blood count and liver function studies
are performed periodically in patients who are taking carbamazepine to monitor for hematologic and hepatic side effects. Additional agents that have been used for treatment of trigeminal
neuralgia include phenytoin, baclofen, valproate sodium, lamotrigine, gabapentin, and levetiracetam. None of these drugs has been
shown to be more effective than carbamazepine.7
Surgical management has been a therapeutic option since the
1950s. Surgical procedures include both peripheral and central
procedures. Peripheral strategies include medication injection and
cryotherapy techniques designed to temporarily block or permanently ablate branches of the peripheral trigeminal nerve. Although
these procedures are relatively effective initially, recurrence is
common. Repeated nerve blocks are not recommended because of
a high risk of permanent facial anesthesia.
Central procedures can be divided into percutaneous approaches
and open approaches. Percutaneous destruction of the trigeminal
ganglion can be done by means of radiofrequency ablation,
thermal ablation, glycerol injection, or balloon microcompression.
These procedures carry the risk of corneal anesthesia, oculomotor
paresis, or masticatory weakness.9
Open surgical management is the surgical option of choice
in many treatment centers. Open surgical procedures include
1409
1410 PART III ◆ Medicine and Surgery / Section Seven • Neurology
Table 105-1 The Cranial Nerves: Normal Function and Pathologic Considerations
CLINICAL FUNCTION RELEVANT TO
EMERGENCY MEDICINE
PATHOLOGIC FEATURES
POSSIBLE CAUSES
Cranial nerve I:
Olfactory nerve
Sense of smell
Unilateral anosmia
Trauma: Skull fracture or shear injury
interrupting olfactory fibers traversing
the cribriform plate
Tumor: Frontal lobe masses compressing
the nerve
Cranial nerve II:
Optic nerve
Vision
Unilateral vision loss
Trauma: Traumatic optic neuropathy
Tumor: Orbital compressive lesion
Inflammatory: Optic neuritis (MS)
Ischemic: Ischemic optic neuropathy
Cranial nerve III:
Oculomotor nerve
Extraoculomotor function via motor
fibers to levator palpebrae, superior
rectus, medial rectus, inferior rectus,
inferior oblique muscles
Pupillary constriction via
parasympathetic fibers to constrictor
pupillae and ciliary muscles
Ptosis caused by loss of levator
palpebrae function
Eye deviated laterally and down
Diplopia
Dilated, nonreactive pupil
Loss of accommodation
Trauma: Herniation of the temporal lobe
through the tentorial opening, causing
compression and stretch injury to the
nerve
Ischemic: Especially in diabetes
Microvascular ischemic injury to nerve
causes extraocular muscle paralysis
but usually is papillary sparing (often
painful)
Vascular: Intracranial aneurysms
may press on the nerve, leading to
dysfunction
Myasthenia gravis can lead to atraumatic
ocular muscle palsy
Cranial nerve IV:
Trochlear nerve
Motor supply to the superior oblique
muscle
Inability to move eye downward and
laterally
Diplopia
Patients tilt head toward unaffected
eye to overcome inward rotation of
affected eye
Trauma is the most common cause of
nerve dysfunction
Cranial nerve V:
Trigeminal nerve
Motor supply to muscles of mastication
and to tensor tympani
Sensory to face, scalp, oral cavity
(including tongue and teeth)
Partial facial anesthesia
Episodic, lancinating facial pain
associated with benign triggers such
as chewing, brushing teeth, light
touch
Trauma: Facial bone fracture may injure
one section, leading to area of facial
anesthesia
Tic douloureux
Cranial nerve VI:
Abducens nerve
Motor supply to the lateral rectus muscle
Inability to move affected eye laterally
Diplopia on attempting lateral gaze
Tumor: Lesions in the cerebellopontine
angle
Any lesion, vascular or otherwise, in the
cavernous sinus may compress nerve
Elevated intracranial pressure (ICP):
Because of its position and long
intracranial length, increased ICP
from any cause may lead to injury and
dysfunction of the nerve
Cranial nerve VII:
Facial nerve
Motor supply to muscles of facial
expression
Parasympathetic stimulation of the
lacrimal, submandibular, and
sublingual glands
Sensation to the ear canal and tympanic
membrane
Hemifacial paresis:
Lower motor neuron lesion leaves
entire side of face paralyzed
Upper motor neuron lesion leaves
forehead musculature functioning
Abnormal taste
Sensory deficit around ear
Intolerance to sudden loud noises
Lower motor neuron:
Infection (viral): The likely cause of
Bell’s palsy
Lyme disease: The most common cause
of bilateral cranial nerve VII palsy in
areas where Lyme disease is endemic
Bacterial infection extending from
otitis media
Upper motor neuron: Stroke, tumor
Cranial nerve VIII:
Vestibulocochlear
nerve
Hearing and balance
Unilateral hearing loss
Tinnitus
Vertigo, unsteadiness
Tumor: Acoustic neuroma
Mimics Ménière’s disease, perilymphatic
fistula
Cranial nerve IX:
Glossopharyngeal
nerve
General sensation to posterior third of
tongue
Taste for posterior third of tongue
Motor supply to the stylopharyngeus
Clinical pathology referable to the
nerve in isolation is very rare
Occasionally painful paroxysms
beginning in the throat and radiating
down the side of the neck in front of
the ear but behind the mandible
Brainstem lesion
Glossopharyngeal neuralgia
CRANIAL NERVE
Chapter 105 / Brain and Cranial Nerve Disorders 1411
Table 105-1 The Cranial Nerves: Normal Function and Pathologic Considerations—cont’d
CRANIAL NERVE
CLINICAL FUNCTION RELEVANT TO
EMERGENCY MEDICINE
PATHOLOGIC FEATURES
POSSIBLE CAUSES
Cranial nerve X:
Vagus nerve
Motor to striated muscles and muscles of
the pharynx, larynx, and tensor (veli)
palatini
Motor to smooth muscles and glands
of the pharynx, larynx, thoracic and
abdominal viscera
Sensory from larynx, trachea, esophagus,
thoracic and abdominal viscera
Unilateral loss of palatal elevation:
Patients complain that on drinking
liquids, the fluid refluxes through
the nose
Unilateral vocal cord paralysis: Hoarse
voice
Brainstem lesion
Injury to the recurrent laryngeal nerve
during surgery
Cranial nerve XI:
Spinal accessory
nerve
Motor supply to the sternocleidomastoid
and trapezius muscles
Downward and lateral rotation of the
scapula and shoulder drop
Trauma to the nerve
Cranial nerve XII:
Hypoglossal nerve
Motor supply to the intrinsic and
extrinsic muscles of the tongue
Tongue deviations:
Upper motor neuron lesion causes
the tongue to deviate toward the
opposite side
Lower motor neuron lesion causes the
tongue to deviate toward the side
of the lesion, and the affected side
atrophies over time
Stroke or tumor can cause upper motor
neuron lesion
Amyotrophic lateral sclerosis can cause
bilateral lower motor neuron lesion
with atrophy
Metastatic disease to the skull base may
involve the nerve
microvascular decompression of the nerve with or without partial
ablation. Although the open microvascular decompression procedure has proved to be effective, with pain relief achieved in 80
to 95% of patients, the surgery is associated with the risk of significant complications, including hearing loss, facial anesthesia,
cerebrospinal fluid (CSF) leak, brainstem or cerebellar injury,
headaches, meningitis, and death.10,11 Gamma Knife radiosurgery,
a minimally invasive, precision-directed stereotactic radiosurgery,
also has been associated with good outcomes. This highly specialized technique requires extremely sophisticated stereotactic radiofrequency equipment and is available only in specialized centers,
but in many cases it has similar results for pain relief without the
morbidity associated with open procedures in patients who might
otherwise be a surgical risk.12-14
Disposition
Patients with suspected trigeminal neuralgia should be referred
for specialty evaluation. Patients with a neurologic deficit require
urgent imaging studies, typically magnetic resonance imaging
(MRI), to rule out a mass or vascular abnormality.
FACIAL NERVE PARALYSIS
Perspective
The acute onset of facial nerve paralysis often will prompt an ED
visit. Fortunately, early diagnosis and therapy may improve the
patient’s chance for recovery of function of the facial nerve. Facial
nerve paralysis of acute onset affects approximately 20 to 25
persons per 100,000 population per year, without geographic,
gender, or race predilection.15,16
Principles of Disease
The facial nerve innervates the muscles of facial expression and
the muscles of the scalp and external ear in addition to the buccinator, platysma, stapedius, stylohyoid, and posterior belly of the
digastric muscles. The sensory portion of the nerve supplies the
anterior two thirds of the tongue with taste and sensation to portions of the external auditory meatus, soft palate, and adjacent
pharynx. The parasympathetic portion supplies secretomotor
fibers for the submandibular, sublingual, lacrimal, nasal, and palatine glands.17
The nerve originates from the pontomedullary junction of the
brainstem and enters the internal auditory meatus with cranial
nerve VIII. Within the temporal bone, the facial nerve has four
major branches: the greater and lesser superficial petrosal nerves,
the nerve to the stapedius muscle, and the chorda tympani. The
facial nerve exits the temporal bone at the stylomastoid foramen
and then enters the parotid gland, where it divides to supply the
muscles of facial expression.17,18
Pathophysiology
The three main causes of facial nerve paralysis that are relevant to
emergency medicine are grouped into infectious, traumatic, and
neoplastic.
Infection
Bell’s Palsy. Bell’s palsy, also commonly called idiopathic facial
paralysis, has long been postulated to have a viral cause. This
disease entity is characterized by an abrupt onset of a lower motor
neuron paresis that can progress during 1 to 7 days to complete
paralysis. A prodromal illness is described by 60% of patients.
Symptoms and signs frequently associated with the facial paresis
include ear pain, perception of sensory change on the involved
side of the face, decreased tearing, overflow of tears on the cheek
(epiphora), abnormally acute hearing (hyperacusis), and impairment or perversion of taste (dysgeusia).19
Treatment approaches can be medical or surgical. The primary
medical therapies for Bell’s palsy center on reducing inflammatory
changes to the nerve with corticosteroids and treating the presumed viral cause. If these therapies are unsuccessful, surgical
decompression may be considered.
Available evidence now strongly favors the use of corticosteroids for the treatment of Bell’s palsy, and earlier treatment is
associated with better efficacy and outcomes.20-24 The rationale for
this application of steroid therapy is that edema of the nerve,
confined within the facial canal, is thought to cause or contribute
to the nerve injury. On the basis of this theory, most experts currently recommend a course of prednisone with an initial dose of
1 mg/kg per day for 7 to 10 days, with or without a short
1412 PART III ◆ Medicine and Surgery / Section Seven • Neurology
taper.15,18,25,26 The most definitive randomized, double-blind,
placebo-controlled trial involving 496 patients showed an improvement in complete recovery of facial nerve function at 3 months
from 64% with placebo to 83% with the use of prednisolone in a
dose of 25 mg by mouth twice daily.27 Therapy should be started
as soon as possible, ideally within the first 24 hours, but it is still
recommended for patients without contraindications who seek
treatment within 1 week of symptom onset.25
A number of studies have supported the contention that Bell’s
palsy may be caused by herpes virus infection. One study demonstrated herpes simplex virus type 1 DNA in the endoneurial tissue
of 11 of 14 patients with Bell’s palsy but not in control subjects.28
In a trial of prednisone and acyclovir in 99 patients, patients
treated with prednisone and acyclovir had a more favorable recovery than that observed in patients receiving prednisone alone.29 A
study of 296 patients with Bell’s palsy treated with valacyclovir or
placebo in addition to a fixed dose of prednisolone found significant benefit to the addition of valacyclovir, particularly in the
setting of severe palsy or in those treated within 24 hours of
symptom onset.30 Other studies have found conflicting results.
Despite a lack of overwhelming evidence, the addition of an antiviral agent should be considered in the treatment of Bell’s palsy,
especially with severe loss of function. The most commonly recommended antiviral regimen is valacyclovir, 1000 mg orally two
times daily for 10 days. Valacyclovir and famciclovir have better
oral absorption, are better tolerated, and are dosed less frequently,
resulting in higher compliance than with acyclovir treatment.18,25,26,28,31 As with steroid therapy, although earlier treatment
is preferred, treatment should be considered for patients presenting within 1 week of symptom onset.
Ramsay Hunt Syndrome. Ramsay Hunt syndrome (herpes zoster
oticus) is characterized by unilateral facial paralysis, a herpetiform
vesicular eruption, and vestibulocochlear dysfunction. The vesicular eruption may occur on the pinna, external auditory canal,
tympanic membrane, soft palate, oral cavity, face, and neck as far
down as the shoulder. The pain is considerably more severe than
that associated with Bell’s palsy, and it frequently is out of proportion to physical findings. In addition, outcomes are worse than
with Bell’s palsy, with a lower incidence of complete facial recovery
and the possibility of sensorineural hearing loss. Therapy is similar
to that for Bell’s palsy. Both prednisone and antiviral therapy for
7 to 10 days are advocated.18,32,33
Lyme Disease. Lyme disease is the most frequent vector-borne
infection in the United States. It is caused by the spirochete Borrelia burgdorferi and is spread by the bite of Ixodes genus ticks.
Neurologic manifestations can arise in any phase of the disease,
and the incidence of facial palsy in patients with neurologic
involvement is 35 to 51%. In regions in which Lyme disease is
endemic, it has been shown to be the leading cause of facial paralysis in children, responsible for half of all pediatric cases of facial
nerve paralysis.34,35
Bilateral facial nerve paralysis is rare but can occur with systemic infections. The two diseases most commonly associated with
bilateral simultaneous onset of facial paralysis are Lyme disease
and infectious mononucleosis. Bilateral facial paralysis should be
considered to be a manifestation of Lyme disease until further
testing excludes this diagnosis.26,34-36 The evaluation and treatment
of Lyme disease are discussed in Chapter 134.
Bacterial Infections. Facial paralysis can be caused by acute bacterial infections of the middle ear, mastoid, or external auditory
canal. In the pre-antibiotic era, facial paralysis was associated with
acute otitis media in approximately 2% of cases; today, however,
it occurs in only 0.2% of cases. Treatment consists of intravenous
antibiotics and myringotomy for decompression. Malignant otitis
externa can be associated with facial paralysis. This disease entity
is most commonly seen in immunocompromised patients and
usually is caused by Pseudomonas infection. Treatment involves
prolonged intravenous antipseudomonal antibiotic therapy and
may require surgical débridement.26,37
Trauma
In patients with head trauma, the facial nerve is the most commonly injured cranial nerve. The cause generally is a temporal
bone fracture with nerve transection. Surgical exploration is warranted if there is firm evidence that the nerve has been transected,
indicated by a sudden onset of complete unilateral facial paralysis,
loss of electrical activity, and evidence of a displaced fracture
involving the facial canal.
Neoplasm
Tumors of the facial nerve itself or tumors anywhere along
the course of the facial nerve that invade or compress the nerve
may lead to facial paralysis. The course is typically progressive
for at least 3 weeks. A sudden onset of paralysis, however, does
not rule out an underlying tumor because facial paralysis secondary to a neoplasm is of sudden onset in approximately 25% of
cases.38 A neoplastic cause should be suspected in patients who
suffer from recurrent ipsilateral facial paralysis, significant pain,
prolonged symptoms, or any other concomitant cranial nerve
abnormality.
Clinical Features and Differential
Considerations
The medical history in patients with facial paralysis focuses on
onset of the paralysis, concentrating on timing and rapidity of
onset and associated signs and symptoms. A rapid onset of facial
paralysis with dysgeusia and hyperacusis preceded by a viral prodrome is suggestive of Bell’s palsy. A history of recurrent ipsilateral
paralysis or slow progression of symptoms is more characteristic
of a tumor. Associated cranial nerve abnormalities, although occasionally seen with Bell’s palsy, also point to the possibility of a
tumor or ischemic insult. The Ramsay Hunt syndrome causes
significant pain and a vesicular rash, although the rash may follow
the facial paresis by a few days. Significant anatomic abnormalities
on visual or otoscopic inspection of the ipsilateral ear will be
found with bacterial otitis media and otitis externa. Finally, systemic symptoms or bilateral facial paresis, especially in endemic
areas, should raise the possibility of Lyme disease.
Diagnostic Strategies
The diagnostic workup of acute facial nerve paresis is based on
whether the clinical picture is suggestive of a disease process other
than Bell’s palsy. If the clinical history is classic for Bell’s palsy, no
imaging or laboratory studies are required. Of note, any history
of possible exposure warrants serologic evaluation for Lyme
disease. Although outpatient testing including electroneurography
may ultimately be performed, this usually is not part of the initial
evaluation.
The presence of a “central” seventh nerve paralysis (upper face
sparing) should prompt imaging with computed tomography
(CT) or MRI, and consideration should be given to the possibility
of an acute stroke or other hemispheric lesion. History or physical
examination findings suggestive of a possible tumor require
imaging to rule out a neoplasm. The study of choice will depend
on the institution and preferences of the consultant.
Disposition
Most patients who have a seventh nerve paralysis will have a clinical diagnosis of Bell’s palsy and may be discharged with referral
Chapter 105 / Brain and Cranial Nerve Disorders 1413
for short-term follow-up. Patients with a possible hemispheric
process, such as stroke or tumor, require further evaluation and
usually hospitalization. Patients thought to have Lyme disease
require immediate initiation of appropriate antibiotic therapy.
In patients with a peripheral facial nerve paralysis, the ipsilateral
eye should be patched, and consideration should be given to ophthalmologic follow-up because there is a high rate of corneal abrasions and corneal dryness associated with the inability to blink
properly or to close the eye completely.
VESTIBULAR SCHWANNOMA
Perspective
Vestibular schwannoma, formally referred to as acoustic neuroma,
is a rare but important cause of sensorineural hearing loss.
The annual incidence of vestibular schwannoma is 1 case per
100,000 population, with a mean age at the time of detection
of 46 to 58 years.39 The female-to-male ratio is 1.5 : 1. Vestibular
schwannoma is rarely bilateral, occurring in this form in appro­
ximately 5% of cases and generally associated with type 2
neurofibromatosis. Although histologically benign, vestibular
schwannoma can cause neurologic damage by direct compression
on the eighth cranial nerve and the other structures in the cerebellopontine angle.40
Principles of Disease
Vestibular schwannoma arises from the Schwann cells covering
the vestibular branch of the eighth cranial nerve as it passes
through the internal auditory canal. The tumor may compress
the cochlear (acoustic) branch of the eighth cranial nerve, causing
hearing loss, tinnitus, and dysequilibrium. Continued growth of
the tumor may result in compression of structures in the cerebellopontine angle, where the facial and trigeminal nerves may be
compressed and damaged. Larger tumors may further encroach
on the brainstem and if large enough may compress the fourth
ventricle, ultimately resulting in signs of increased intracranial
pressure (ICP).41
Clinical Features
Asymmetrical sensorineural hearing loss is the hallmark of vestibular schwannoma. Up to 15% of patients with this tumor,
however, will have normal results on audiometry. These patients
typically have symptoms such as unilateral tinnitus, imbalance,
headache, fullness in the ear, otalgia, and facial nerve weakness.
Thus, patients with asymmetrical symptoms should be further
evaluated for vestibular schwannoma even with normal findings
on audiometry.42
Vestibular schwannomas are extremely slow-growing tumors,
averaging an approximately 1-mm increase per year, although
many do not grow at all on serial examinations.43 Symptom onset
is therefore generally gradual. In one series of 126 cases, the
average time from symptom onset to discovery of a vestibular
schwannoma was approximately 4 years.44
Diagnostic Strategies
When vestibular schwannoma is suspected, the patient is evaluated by audiometry or gadolinium-enhanced MRI. This imaging
technique is extremely sensitive and has led to earlier diagnosis
and a decrease in mean size at detection of vestibular schwannoma.
CT lacks the necessary sensitivity in the posterior cranial fossa to
reliably rule out the presence of vestibular schwannoma. The
smaller the tumor at the time of diagnosis, the more options there
are for therapy and the better the potential prognosis.40
Differential Considerations
A majority of disease entities included in the differential diagnosis for vestibular schwannoma cause symmetrical sensorineural hearing loss. Asymmetrical sensorineural hearing loss
has few causes other than vestibular schwannoma. Ménière’s
disease may present a diagnostic dilemma because it can be
asymmetrical. Ménière’s disease may be differentiated from vestibular schwannoma in that the tinnitus of Ménière’s disease
usually is intermittent, whereas the tinnitus of vestibular
schwannoma typically is continuous. In addition, patients with
Ménière’s disease typically describe true vertigo, whereas patients
with a vestibular schwannoma are more likely to describe imbalance or dysequilibrium.
Vestibular schwannomas account for 80% of all cerebellopontine angle tumors. Among all other lesions, meningioma is the
most common. Meningiomas more frequently cause symptoms of
facial palsy or trigeminal nerve abnormality. Of note, however,
considerable similarity between the clinical picture of a meningioma and that of vestibular schwannoma in the cerebellopontine
angle has been described.45
Management
Vestibular schwannoma may be removed surgically or ablated
with stereotactic radiation therapy. In general, tumors larger than
3 cm are recommended for microsurgery because radiation treatments, such as with the Gamma Knife or linear accelerator, are less
effective for local control and growth arrest in larger masses.
Smaller tumors are amenable to use of stereotactic radiation
therapy, which has greater salvage rates of facial nerve function
and hearing.46,47 Stereotactic radiation therapy generally has good
long-term outcomes of local growth arrest, with nerve salvage
approaching 90% or greater. Injuries to the trigeminal, facial, and
acoustic nerves and to the cerebellum are possible complications
of both procedures. In patients who are minimally symptomatic
with small tumors, serial monitoring with MRI is a viable nonsurgical option. All patients should be evaluated by a specialist in the
evaluation and treatment of vestibular schwannoma because
smaller tumor size at detection is associated with a better longterm outcome.39,43
Disposition
Patients with suspected acoustic neuroma should be referred for
audiometry or MRI and evaluation by a specialist in either otolaryngology or neurosurgery.
DIABETIC CRANIAL
MONONEUROPATHY
Perspective
Cranial mononeuropathies occur uncommonly, usually are a
complication of diabetes, and most often affect the extraocular
muscles. The oculomotor nerve is most commonly affected, followed in order by the trochlear and abducens nerves. In one large
series in Japan, the incidence of cranial nerve palsies was 1.0%
among diabetics and 0.1% among nondiabetics.48,49 Whereas ophthalmoplegia appears to be closely related to diabetes, facial palsy
is less strongly correlated with this disease.48,50
Principles of Disease
The pathologic basis of diabetic mononeuropathy appears to be
ischemia of the affected cranial nerve caused by occlusion of an
intraneural nutrient artery serving the nerve. This occlusion leads
1414 PART III ◆ Medicine and Surgery / Section Seven • Neurology
to injury located primarily in the center of the nerve because the
core fibers are more dependent on the supply from such nutrient
arteries. The peripheral fibers are less affected because they also
are supplied by collateral vessels. In the oculomotor nerve, the
preservation of the circumferentially located parasympathetic
fibers explains the pupillary sparing that usually is found in this
syndrome. In two studies, the microvascular changes in the intraneural arteries that lead to occlusion were noted in diabetic
patients but absent in nondiabetics.51,52
Clinical Features
Patients typically describe acute onset of unilateral retro-ocular
and supraorbital pain, diplopia, and ptosis.49 The physical manifestations of a third cranial nerve palsy include the inability to
move the eye superiorly and medially, accompanied by ptosis. The
pupillary light reflex usually is present. Although it is a less
common finding, the fourth and sixth cranial nerves may be
affected. Patients with a fourth cranial nerve palsy are unable to
move the eye inferolaterally, and those with a sixth cranial nerve
palsy are unable to move the eye laterally. Because of the long
intracranial course of the sixth nerve, a patient with an isolated
sixth nerve palsy should be evaluated for an intracranial lesion or
increased ICP.53
Differential Considerations
Evaluation of cranial nerve dysfunction requires a thorough
history and physical examination and cranial imaging, usually
with MRI. Diabetic mononeuropathy should be considered a diagnosis of exclusion. Considerations in the differential diagnosis
include trauma, tumor, vertebrobasilar ischemia, aneurysm, and
hemorrhage into the brainstem.54
Management
Treatment consists of patching of the affected eye and administration of analgesics and antiplatelet therapy. The prognosis is good.
If the neuropathy does not begin to resolve within 3 to 6 months
or if more than one nerve is affected, another cause should be
sought. Complete resolution is expected within the first year. Antioxidant preparations, including α-lipoic acid, have been used
therapeutically and have not shown harm, but such agents have
yet to be shown to have convincing clinical effect.55
CEREBRAL VENOUS
THROMBOSIS
Perspective
No exhaustive studies of the epidemiology of cerebral venous
thrombosis (CVT) have been performed. In case series, the median
patient age is 38 years; women represent 60 to 75% of those
diagnosed.56,57
Principles of Disease
Cerebral blood is drained by several major veins that lead into the
dural sinuses. The major dural sinuses are the superior sagittal
sinus, the inferior sagittal sinus, the straight sinus, the lateral
sinuses, and the sigmoid sinuses. The variability in symptoms and
signs in patients who present with CVT stems from differences in
thrombus location and acuity of thrombus formation. Symptoms
of intracranial hypertension, especially headache, are present in
most patients with sinus thrombosis, whereas those with thrombosis of the cerebral veins are thought to be more prone to hemorrhagic infarction and localizing neurologic deficits.58 As with
venous thrombosis in other locations, multiple causes and predisposing factors for CVT are recognized. Underlying causes are often
divided into infectious and noninfectious categories. Infectious
causes include local infections, such as sinusitis, otitis media, facial
cellulitis, and systemic infections. Noninfectious causes include
direct injury to the cerebral venous system from trauma, surgery,
dehydration, or any other condition that may predispose the
patient to development of a hypercoagulable state, including
the presence of a malignant neoplasm or the use of oral contraceptive agents.59
Clinical Features
The symptoms and signs associated with CVT are varied. Headache is the primary feature of CVT in 74 to 92% of affected
patients.59,60 Papilledema is noted in 28 to 45% of cases.57,60,61 Lethargy, decreased level of consciousness, or mental status changes
may be noted. Seizures occur in 35 to 50% of patients in the acute
phase.57,59,61,62 In addition to the location and acuity of thrombosis
formation, a patient’s symptom onset will vary in accordance with
the extent of collateral vessel growth in the venous territory. Early
thrombotic changes may be well compensated for by the collateral
venous drainage. Symptoms will appear only when the compensation for venous thrombosis is no longer sufficient or when hemorrhagic infarction occurs. Variability in collateralization between
patients also adds to the variability and time course of symptoms.
Two national and international observational studies documented
an average time from symptom onset to diagnosis of 7 days,
reflecting the difficulty in diagnosis of this rare disease entity.57,61,63
The reported incidence of focal neurologic signs, including seizures, on clinical examination varies widely between series,
ranging from 25 to 71%.59,60 Because of the broad spectrum of
possible clinical features, the diagnosis of CVT may be difficult
but should be a consideration in any patient with unexplained
headache, especially in combination with focal neurologic deficit,
papilledema, or seizures.
Diagnostic Strategies
Cerebral angiography no longer plays a significant role in the
diagnosis of CVT. Both MRI and CT scan with venous-phase
imaging have been evaluated as both primary and definitive
imaging modalities for the diagnosis of CVT. CT scanning is useful
in the initial workup of the patient with possible CVT, but non–
contrast-enhanced CT is neither sensitive nor specific enough to
reliably confirm or exclude the diagnosis. Findings on CT that are
consistent with CVT include hyperdensity of a thrombosed sinus
or deep vein (referred to as the cord sign or attenuated vein sign,
respectively), brain edema, and hemorrhage secondary to venous
congestion. Whereas non–contrast-enhanced CT in the diagnosis
of CVT has been evaluated only in case series, the published sensitivity and specificity typically range from 65 to 100% when it is
evaluated against MRI as the “gold standard.”64
Similar to CT scanning, MRI also can demonstrate local changes
secondary to venous congestion, such as brain edema and hemorrhage. In addition, MRI can demonstrate the possibility of CVT
by the lack of a “flow void.” On conventional MRI, a flow void
indicates the presence of moving blood within the sinus, whereas
the absence of a flow void indicates a possible thrombus. Diagnostic accuracy, however, is greatly improved through use of magnetic
resonance venography (MRV). This technique takes advantage of
the MRI signal characteristics of flowing blood to create images
of venous structures. Combination of these imaging techniques
further enhances diagnostic accuracy. For imaging of a particular
dural sinus, presence of the sinus on conventional MRI and
lack of flow on MRV are diagnostic of a sinus thrombosis. This
Chapter 105 / Brain and Cranial Nerve Disorders 1415
combined approach has diagnostic sensitivity similar to that of
conventional angiography.59,65
Several studies show similar sensitivity between MRV and CT
venography for the diagnosis of CVT when the CT study is performed on a multidetector row CT scanner. These studies, involving several hundred patients, showed sensitivity of CT venography
for CVT that approached 100% and was comparable to that of
MRV both in sensitivity and in inter-rater reliablity.66-69 The sensitivity of CT venography performed by scanners that do not use
multidetector row technology is unknown.
Several small studies have attempted to evaluate the usefulness
of the D-dimer assay as a screening tool to exclude CVT, particularly when MRI or CT venography is not available. Although the
reported sensitivity rates are fair at 83 to 100%, larger prospective
studies need to be done to further define the role of D-dimer in
the evaluation of CVT because several case reports have noted
normal D-dimer levels in the setting of documented CVT.70-74 In
general, although a normal D-dimer level does not exclude the
diagnosis of CVT, it does appear to make this diagnosis much less
likely, particularly in a patient with symptoms of less than 2 weeks
in duration.
Differential Considerations
Considerations in the differential diagnosis of CVT include the
conditions that cause patients to present with the new onset of
neurologic deficits, alteration in consciousness, or severe headache. A diagnosis of CVT should be considered in a patient with
such symptoms when the etiology is unclear, particularly when
there is the possibility of a hypercoagulable state and when the
head CT scan is normal in appearance or shows subtle signs
of CVT.
Management
CVT is a relatively rare disease, and controlled studies evaluating
its treatment are lacking. Current therapeutic consensus strongly
recommends systemic anticoagulation with low-molecular-weight
heparin (LMWH) or unfractionated heparin to prevent further
clot formation and to promote recanalization, even in patients
with intracranial hemorrhage on initial imaging.59,60,74,75 In one
placebo-controlled randomized trial comprising only 20 patients,
anticoagulation with unfractionated heparin demonstrated
benefit, even in patients with evidence of intracranial hemorrhage
on the pretreatment CT scan.76 A registry comparing outcomes of
patients treated with unfractionated heparin compared with
LMWH found more benefit in the LMWH group, although the
effect was modest.77 Two large observational trials also showed
improvement in modified Rankin scale at follow-up in the anticoagulated groups, although the trials were not randomized.57,61
Despite a paucity of randomized controlled trials, expert opinion
favors anticoagulation in all groups unless another contraindication is present.78
Catheter-based intervention with thrombolysis has been
attempted in multiple case series with use of either urokinase or
tissue plasminogen activator. Thrombolysis was shown to be relatively safe and relatively successful in very small case series.75 In
one nonrandomized study of 40 patients, 20 received systemic
heparin and 20 received catheter-based infusion of urokinase followed by systemic heparin. Despite initially worse neurologic
function in the thrombolysis group, a significant difference in
neurologic function favoring thrombolysis was observed at discharge.79 This promising therapy is typically considered only for
patients with symptoms of decreased level of consciousness, elevated ICP, or rapid deterioration on neurologic examination.
Disposition
All patients with suspected CVT should be admitted to a unit
capable of providing a high level of care with neurologic consultation. Patients should be anticoagulated if no contraindication
exists, and catheter-based thrombolysis should be considered in
patients with depressed mental status or focal findings on neurologic examination.
MULTIPLE SCLEROSIS
Perspective
Multiple sclerosis (MS) is an inflammatory disease that affects
the central nervous system (CNS). Although the exact etiology
remains uncertain, the pathologic manifestation of this inflam­
matory disease is a demyelination of discrete regions (plaques)
within the CNS with a relative sparing of axons. The clinical
picture is highly variable but is classically characterized by episodes of neurologic dysfunction that evolve in days and resolve
during weeks.
MS has an overall prevalence in the United States of 0.1%. The
peak age at onset is 25 to 30 years; women are slightly younger
than men at onset. The incidence in women exceeds that of men
by a ratio of 1.8 : 1. The worldwide prevalence is greatest in the
United Kingdom, Scandinavia, and North America. Epidemiologic
studies indicate that both genetic and environmental factors are
associated with an increased incidence of this disease. MS has a
30% concordance rate between monozygotic twins, and 20% of
patients with MS have at least one affected relative. MS is more
common in temperate climates. It is rare between 23 degrees north
and south latitudes but has a rising incidence above and below 50
degrees north and south latitudes, respectively. Although no exact
environmental factor has been identified, if a person emigrates
from an area of high prevalence to an area of low prevalence before
the age of 20 years, the risk is diminished. MS is rare in Africans
and Asians, but African Americans have a higher incidence than
their relatives who remain in Africa.80 In addition, reports of clusters or mini-epidemics support environmental factors. Thus,
an environmental cause superimposed on genetic susceptibility
appears to be a likely etiologic scenario.81,82
Principles of Disease
MS is considered to be an organ-specific autoimmune disease.
One theory proposes that genetic factors interact with an environmental trigger or infection to establish pathologically autoreactive
T cells in the CNS. After a long and variable latency period (typically 10 to 20 years), a systemic trigger, such as a viral infection
or superantigen, activates these T cells. The activated T cells, on
reexposure to the autoantigen, initiate the inflammatory response.
This sets off a complex immunologic cascade that leads to the
demyelination characteristic of MS. This demyelination process
releases CNS antigens that are hypothesized to initiate further
episodes of autoimmune-induced inflammation. The mechanisms
underlying this autoimmunity in MS are unknown.83
Clinical Features
The clinical picture in MS is one of marked heterogeneity. The
classic clinical syndrome consists of recurring episodes of neurologic symptoms that rapidly evolve during days and slowly resolve.
Variability occurs in age at onset, location of CNS lesions, frequency and severity of relapses, and degree and time course of
progression.
The clinical features of MS can be divided into areas of specific
CNS impairment: cognition; cranial nerves; motor pathways;
1416 PART III ◆ Medicine and Surgery / Section Seven • Neurology
sensory pathways; cerebellar pathways; and bowel, bladder, and
sexual dysfunction.80
Patients with MS have frequent complaints of poor memory,
distractibility, and decreased capacity for sustained mental effort.
Formal neuropsychological testing suggests that cognitive involvement is common and underreported. Specifically, neuropsychological testing has shown that 43 to 65% of patients with MS have
some degree of cognitive impairment.84,85 Of note, a correlation
has been found between the MRI-based total lesion load and
presence of cognitive impairment.86
Cranial nerve dysfunction is common in MS. The most common
associated cranial nerve abnormality is optic neuritis, a unilateral
syndrome characterized by pain in the eye and a variable degree
of visual loss affecting primarily central vision. Within 2 years of
an attack of optic neuritis, the risk of MS is approximately 20%,
and within 15 years, it is approximately 45 to 80%.87,88 Optic neuritis often is the first symptom of MS.89,90
As a result of lesions in the vestibulo-ocular connections, the
oculomotor pathways also may be affected. The deficit may be
manifested as diplopia or nystagmus. The nystagmus may be
severe enough that the patient may complain of oscillopsia (a
subjective oscillation of objects in the visual field). Cranial nerve
impairment also may include impairment of facial sensation,
which is relatively common. Unilateral facial paresis also may
occur. In addition, the occurrence of trigeminal neuralgia in a
young person may be an early sign of MS.
Motor pathways also are commonly involved. Specifically, corticospinal tract dysfunction is common in patients with MS. Paraparesis or paraplegia occurs with greater frequency than upper
extremity lesions owing to the common occurrence of lesions in
the motor tracts of the spinal cord. In patients with significant
motor weakness, spasms of the legs and trunk may occur on
attempts to stand from a seated position. This dysfunction is
manifested on physical examination as spasticity that typically is
worse in the legs than in the arms. The deep tendon reflexes are
markedly exaggerated, and sustained clonus may be demonstrated.
Although these symptoms frequently are bilateral, they generally
are asymmetrical.80
Sensory manifestations are a frequent initial feature of MS and
will be present in nearly all patients at some point during the
course of the disease. Sensory symptoms are commonly described
as numbness, tingling, “pins and needles” paresthesias, coldness,
or a sensation of swelling of the limbs or trunk.80
Impairment of the cerebellar pathway results in significant gait
imbalance, difficulty with coordinated actions, and dysarthria.
Physical examination reveals the typical features of cerebellar dysfunction, including dysmetria, dysdiadochokinesis (an impairment of rapid alternating movements), breakdown in the ability
to perform complex movements, intention tremor in the limbs
and head, truncal ataxia, and dysarthria.80
Impairment of bowel, bladder, and sexual function also is
common. The extent of sphincter and sexual dysfunction usually
parallels the motor impairment in the lower extremities. Urinary
frequency may progress to urinary incontinence as the disease
advances. An atonic bladder may develop, which empties by
simple overflow and often is associated with the loss of perception
of bladder fullness and with anal and genital hypoesthesia. Constipation becomes common in time, and almost all patients with
paraplegia require special measures to maintain effective bowel
habits. Sexual dysfunction, although frequently overlooked, is
common in MS. Approximately 50% of patients become completely sexually inactive as a result of this disease.80
Diagnostic Strategies
Although no laboratory tests are diagnostic for MS, one clinical
feature remains unique to this disease: Uhthoff ’s phenomenon,
temporary worsening of current or preexisting signs or symptoms
of MS secondary to small increases in the patient’s body temperature. Accordingly, exercise, a hot bath, exposure to a warm environment, or fever can bring about Uhthoff ’s phenomenon. This
phenomenon reflects subclinical demyelination or preexisting
injury to nerves without obvious significant clinical involvement
before heat exposure or temperature elevation.80
MS is described as a relapsing-remitting disorder with symptoms that fluctuate over time. Therefore, the clinical diagnosis
rests on occurrence of at least two clinical episodes with different
neurologic symptoms at different times.
Findings on CSF analysis are abnormal in 90% of the cases. Fifty
percent of patients will have pleocytosis, with more than five lymphocytes per high-power field in the CSF. Approximately 70% of
patients will have an elevated gamma globulin level, with immunoglobulin G (IgG) ranging from 10 to 30% of the CSF total
protein. Electrophoresis of the CSF demonstrates oligoclonal
bands of IgG in 85 to 95% of patients who carry a diagnosis of
MS; however, oligoclonal bands of IgG also are seen with neurosyphilis, fungal meningitis, and other CNS infections. Lumbar
puncture is recommended for patients with suspected MS, but
mass lesions and elevated ICP should be ruled out before lumbar
puncture is attempted.91
The initial imaging test to aid in the diagnosis of MS is
gadolinium-enhanced MRI. MRI is a sensitive test for the detection of lesions consistent with MS and also is useful to assess
disease severity.92 The lesions of MS typically appear hyperintense,
or bright white, on T2-weighted or fluid-attenuated inversion
recovery (FLAIR) MRI studies. Lesions usually are multiple and
commonly are found in the periventricular white matter.93 In
patients with an initial neurologic event consistent with CNS
demyelination and an MRI cranial study showing multiple white
matter lesions, the 5-year risk for development of MS is 60%.
Patients with similar clinical syndromes and a normal MRI
appearance have less than a 5% 5-year risk.94
Differential Considerations
Other diseases that affect the CNS white matter may be clinically
and radiographically similar to MS. Considerable care must be
taken to exclude these disease processes before a diagnosis is made.
These include CNS tumors (especially lymphomas and gliomas),
spinal cord compression, vasculitides, Behçet’s disease, neuro­
sarcoidosis, postinfectious and postvaccinal encephalomyelitis,
human immunodeficiency virus (HIV) encephalopathy, Lyme
disease, and vitamin B12 deficiency.
Management
Management of patients with MS has essentially three aspects: (1)
therapies aimed at halting the progression of the disease, (2) treatment of acute exacerbations, and (3) therapies designed to modify
complications.
Therapies aimed at halting disease progress are based primarily
on the use of either interferon-β or glatiramer acetate. The interferons are a group of natural compounds with antiviral and
immunomodulatory actions used in therapy for MS. Side effects
of the agents interferon-β1a and interferon-β1b include influenzalike symptoms, depression, anxiety, and confusion. In one
study, 560 patients with MS were randomly assigned to receive
subcutaneous interferon-β1a or placebo (n = 187) three times a
week for 2 years.95 The relapse rate was significantly lower at 1 and
2 years with interferon-β1a than with placebo. The time to first
relapse was prolonged significantly and the accumulation of brain
lesions on MRI was lower in the treatment group than in the
placebo group. The investigators concluded that subcutaneous
interferon-β1a is a well-tolerated and effective treatment of
Chapter 105 / Brain and Cranial Nerve Disorders 1417
relapsing-remitting MS in terms of relapse rate, defined disability,
and all MRI outcome measures.81 Interferon-β also has been
shown to retard progression to clinically definite MS and to
decrease the total number of brain lesions seen on subsequent
MRI studies in patients who have their first demyelinating episode
with MRI abnormalities at initial presentation.96-99 This finding
highlights the importance of early evaluation and treatment.
Glatiramer acetate also has successfully been used in the treatment of MS. This agent is a mixture of synthetic polypeptides
designed to mimic myelin basic protein. The mechanism of action
by which glatiramer acetate exerts its effect is unknown, but it is
thought to modify the immune processes responsible for the
pathogenesis of MS. In one study, 251 patients with relapsingremitting MS were randomized to receive daily subcutaneous
injections of glatiramer acetate (previously called copolymer 1) or
placebo for 24 months. Patients receiving glatiramer acetate experienced significantly fewer relapses and were more likely to demonstrate neurologic improvement, whereas those receiving placebo
were more likely to worsen. This drug generally is well tolerated.100
Glatiramer acetate has also been shown to slow the progression to
clinically definite MS after a first clinical demyelinating episode.101
Current recommendations for management of relapsingremitting MS are to initiate treatment with interferon-β or glatiramer acetate. Such regimens have been demonstrated to decrease
the volume of plaques seen on MRI and to diminish relapses.83
The use of newer disease-modifying agents, such as fingolimod,
cladribine, and natalizumab, has shown promise in clinical trials,
but each has significant side effect profiles, and appropriate patient
selection is still underway.102-107 At this point, each of these agents
is considered second line for severe or refractory patients.
Acute exacerbations of MS also should be targets for therapy.
Although most such episodes will resolve without therapy, steroids
have been demonstrated to diminish the duration of acute exacerbations. More than 85% of patients with relapsing-remitting MS
show improvement with intravenous methylprednisolone. Intravenous steroids have been shown in controlled trials to speed the
recovery from the visual loss of optic neuritis compared with
placebo. In addition, when patients with acute optic neuritis are
treated with high-dose intravenous steroids, the 2-year rate of
development of MS is reduced, although this effect diminishes
over time.88,108 Of interest, oral prednisone was not found to be
helpful in the optic neuritis trials and was associated with a potential increase in the number of optic neuritis episodes.
The current standard therapy for an acute exacerbation in MS
is intravenous methylprednisolone. A typical intravenous dose is
250 to 500 mg every 12 hours for 3 to 7 days. Whether this should
be followed by an oral prednisolone taper remains controversial.
Potential adverse effects of methylprednisolone therapy include
fluid retention, gastrointestinal hemorrhage, anxiety, psychosis,
infection, and osteoporosis.
Several therapies directed toward the complications of MS may
be helpful. The associated spasticity generally is treated with
baclofen. This is a highly effective therapy aimed at reducing the
painful flexor and extensor spasms. A major side effect is drowsiness, which generally diminishes with continued use. Higher-dose
therapy can cause confusion, especially in the setting of baseline
cognitive impairment. For patients with intractable spasticity,
baclofen is available for intrathecal administration by either bolus
therapy or continuous implanted pump therapy. Additional therapeutic agents for control of spasticity include tizanidine, diazepam, and dantrolene.
The tremor and ataxia associated with MS occasionally are
treated with propranolol, diazepam, or clonazepam. The results of
these therapies, however, generally are unsatisfactory. Pain often is
associated with MS and affects the shoulders, pelvic girdle, and
face. The facial pain may be indistinguishable from that of trigeminal neuralgia. Treatment options include carbamazepine,
baclofen, and tricyclic antidepressants. Fatigue, which is common,
may be ameliorated with amantadine. This agent produces partial
relief for a minority of patients. In controlled studies, the effect is
only slightly better than placebo.83
Disposition
Patients with a history of MS who seek treatment for significant
symptoms must first be evaluated to rule out other, non–
MS-related pathologic processes. Also, other systemic illnesses,
especially infections, which can worsen the symptoms of MS,
should be excluded. If the problem is thought to be an exacerbation of MS, most patients will require hospital admission for intravenous steroid therapy. An alternative to hospitalization may be
to initiate intravenous steroids in the ED and to arrange for
a next-day follow-up visit with the primary care physician or
neurologist if outpatient intravenous steroid administration is
an option.
Patients with the new onset of symptoms suggestive of MS
should be admitted or referred to a neurologist because early
treatment has been shown to significantly decrease progression of
the disease.
KEY CONCEPTS
Trigeminal Neuralgia
■ Patients with unilateral, intermittent, lancinating facial pain
without abnormalities on physical examination are likely to
have trigeminal neuralgia.
■ Carbamazepine is the first-line agent for medical treatment.
■ Patients who do not tolerate or whose pain is refractory to
medical management may be candidates for microvascular
decompression or ablation.
Facial Nerve Paralysis
■ Patients with Bell’s palsy should be treated early in the course
with corticosteroids, and antiviral medication is warranted in
patients with severe loss of function.
■ Slowly progressive or recurrent facial paralysis is suggestive of
a neoplasm. Recurrent unilateral paralysis may occur with
Bell’s palsy but frequently (30%) is seen in patients with
tumor.
■ Simultaneous bilateral facial paralysis is suggestive of Lyme
disease, especially in endemic regions.
■ Patients who have facial muscle paresis with intact forehead
movement should be considered to have a central (upper
motor neuron) lesion until the diagnostic investigation proves
otherwise.
Vestibular Schwannoma
■ The onset of unilateral auditory symptoms, especially
sensorineural hearing loss, requires evaluation and referral to
an ear, nose, and throat specialist.
■ Neurologic symptoms of lower cranial nerve dysfunction,
ataxia, or raised ICP may be caused by a benign tumor of the
cerebellopontine angle.
Diabetic Cranial Mononeuropathy
■ Diabetic neuropathy is a diagnosis of exclusion because no
definitive diagnostic testing is available.
■ Both ischemic and hemorrhagic brainstem lesions must be
ruled out in the case of an acute ophthalmoplegia.
■ Extraocular mononeuropathy is sufficiently common in
patients with diabetes mellitus that its occurrence in isolation
warrants evaluation of the patient for previously undiagnosed
diabetes.
Cerebral Venous Thrombosis
■ The differential diagnosis for CVT includes other conditions
that present with new-onset neurologic deficits, alteration in
1418 PART III ◆ Medicine and Surgery / Section Seven • Neurology
consciousness, or severe headache. CVT is more likely to be
present in such patients when the etiology is unclear, the
patient is thought to have a hypercoagulable state, and the
head CT is normal in appearance or shows subtle signs of CVT.
■ Non–contrast-enhanced CT scanning is not adequate to rule
out CVT. MRI with MRV is recommended, although
multidetector row CT venography is an acceptable
alternative.
■ Treatment of most patients with CVT includes systemic
anticoagulation, even in the setting of hemorrhagic cerebral
infarcts, unless another contraindication exists.
Multiple Sclerosis
■ Any patient with a long-term illness, such as MS, must be
evaluated to rule out pathologic processes not related to that
illness before an exacerbation of the illness can be assumed
to be the cause of any problems experienced by the patient.
■ Therapy for patients with MS will require consultation with
the patient’s primary care provider or neurologist to provide
consistent disease management.
■ Intravenous methylprednisolone effectively promotes earlier
resolution of recurrences.
■ Intravenous methylprednisolone has been shown to speed
the recovery from vision loss from optic neuritis.
The references for this chapter can be found online by
accessing the accompanying Expert Consult website.
Chapter 105 / Brain and Cranial Nerve Disorders 1418.e1
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