Otoneurologic Manifestations of Otologic and Systemic Disease

Complications of Middle Ear Pathology

Intracranial complications occur in 0.25 to 0.5 percent of all cases of otitis media. The mortality rate of intracranial complications has decreased dramatically over the last century, from approximately 90 percent in the preantibiotic era to 10 percent now. However, significant morbidity still exists despite this improvement in survival. Diagnosis of an intracranial complication of otitis media relies heavily on an accurate history and a high index of suspicion. Important elements include determining whether the patient has acute or chronic otitis media, a prior history of otologic disease or surgery, a history of head trauma or temporal bone fracture, previous antibiotic treatment, and symptoms suggesting intracranial involvement such as headache, lethargy, visual changes, fever, and nausea or vomiting.

The differential diagnosis for a patient with otitis media and symptoms and signs of intracranial involvement is long, and potential complications are numerous, including extradural abscesses or granulation tissue, dural venous sinus thrombosis, petrous apicitis (Gradenigo syndrome; Fig. 23-1 ), intraparenchymal brain abscesses, subdural abscesses, otitic hydrocephalus, and meningitis (most commonly purulent).

The microbiology of the intracranial complications of otitis media varies with the duration of otitis as well as the type of complication. Complications of acute otitis media usually are secondary to Streptococcus pneumoniae or Haemophilus influenzae . Chronic otitis media frequently leads to complications with gram-negative bacteria, such as Pseudomonas aeruginosa , or anaerobes. The most common organisms implicated in otitic meningitis include S. pneumoniae , H. influenzae , Proteus species, P. aeruginosa , and Staphylococcus aureus. Brain abscesses are typically polymicrobial.

If an intracranial complication is suspected on the basis of the history or physical findings, further evaluation should include computerized tomography (CT) of the temporal bones to evaluate for bony erosion, congenital malformation, or fracture; contrast-enhanced magnetic resonance imaging (MRI) or CT of the head to evaluate for enhancement of the meninges, dural sinus thrombosis ( Fig. 23-2 ), or brain abscess; and a lumbar puncture if no mass effect is visualized on imaging. The cerebrospinal fluid (CSF) will typically show increased protein and decreased glucose concentrations along with organisms on Gram stain in bacterial meningitis; those patients given antibiotics in the days or weeks preceding the spinal tap may have more normal-appearing CSF chemistries and a negative Gram stain, but should be treated with antibiotics until cultures are negative, given the possibility of a partially treated bacterial meningitis. In otitic hydrocephalus, the opening pressure will be increased, but the other studies will be normal.

Treatment of the intracranial complications of otitis media includes medical stabilization and usually requires inpatient admission. Broad-spectrum intravenous antibiotics should be initiated empirically. Surgical consultation with an otolaryngologist or neurosurgeon should be obtained to assess for drainage of the primary source and address intracranial complications that warrant such procedures (such as intracranial abscess). Complications due to acute otitis media may be treated with a second- or third-generation cephalosporin to target the usual three pathogens: H. influenzae , Moraxella catarrhalis , and S. pneumoniae. Gram-negative and anaerobic coverage should be added for complications of chronic otitis media. Corticosteroids such as dexamethasone should be administered concurrently with intravenous antibiotics for otogenic meningitis in order to reduce the chance of sensorineural hearing loss and, in meningitis caused by S. pneumoniae , to reduce mortality.

Labyrinthine Disorders

Meniere disease and benign paroxysmal positional vertigo are two of the most common labyrinthine disorders that cause vertigo and dysequilibrium. The pathologic correlate of Meniere disease is endolymphatic hydrops, which is usually idiopathic but may occur following inner ear trauma or infection. Patients with Meniere disease typically experience episodes of unilateral tinnitus, unilateral hearing loss, unilateral ear fullness, and vertigo lasting for minutes to hours. They do not typically experience neurologic symptoms that cannot be attributable directly to the inner ear. However, some patients experience visual changes, especially blurred vision, during attacks of Meniere disease, and headaches may occur. Other patients become anxious during attacks and may experience numbness and paresthesias. The first attack of Meniere disease often prompts an evaluation in an emergency department, leading to brain imaging to exclude cerebellar hemorrhage or infarction. First-line treatment of Meniere disease consists of sodium restriction and a diuretic, typically a combination of hydrochlorothiazide and triamterene. Nonablative procedures, such as intratympanic steroid infusion, and ablative procedures, such as intratympanic gentamicin or labyrinthectomy, are options for patients who do not respond to conservative management.

Benign paroxysmal positional vertigo is caused by free-floating otolithic debris in the posterior semicircular canal. As with Meniere disease, benign paroxysmal positional vertigo may follow inner ear trauma or infections but usually is idiopathic. Patients typically have positionally induced vertigo when rolling over in bed or looking up. The vertigo typically lasts for less than 1 minute but more generalized symptoms of dizziness and dysequilibrium may persist for several hours. Neurologic symptoms other than vertigo and transitory visual difficulties are generally absent, although patients may have difficulty in walking due to their vertigo. On physical examination, the findings on Dix–Hallpike maneuvers, illustrated in Fig. 23-3 , are diagnostic. Treatment consists of a particle repositioning maneuver ( Fig. 23-4 ), which is highly successful and can be taught to the patient for use in future attacks. Despite the “benign” nature of benign paroxysmal positional vertigo, the initial episode often leads to emergency medical care. Since several nonbenign conditions, such as posterior fossa tumors, may present with positional dizziness, a thorough neurologic evaluation of all patients with positional vertigo is warranted.

Eighth Nerve Lesions

Eighth nerve lesions leading to neurologic manifestations include auditory neuropathy and vestibular neuronitis. Auditory neuropathy is a disorder of dysfunction or dyssynchrony of the inner hair cells or cochlear nerve, leading to hearing loss and impaired speech discrimination with intact outer hair cell function. Risk factors for auditory neuropathy include prematurity, hyperbilirubinemia, and exposure to ototoxic medications, although genetic factors have also been implicated. This type of hearing loss can be associated with other neurologic diseases and may be seen in up to 11 percent of children with sensorineural hearing loss.

Vestibular neuronitis is an idiopathic inflammation of the vestibular portion of the eighth cranial nerve leading to acute symptoms of vertigo, nystagmus, nausea, and vomiting. Acute symptoms persist for several days and are often preceded by viral illness. In some patients, mild symptoms can last for weeks or months. Unilateral reduction in vestibular response is seen on caloric testing or vestibular evoked myogenic potentials. Possible etiologies include viral infection, immunologic causes, or vascular occlusion. The superior or inferior vestibular nerve, or both, may be involved.

Cerebellopontine Angle Disorders

Cerebellopontine angle masses may cause hearing loss, tinnitus, and vertigo. The most common type of mass found in this location is a vestibular schwannoma, commonly referred to as an acoustic neuroma. Symptoms are typically of insidious onset, but sudden hearing loss or vertigo may occur. Additionally, facial numbness may be seen with large tumors due to compression of the trigeminal nerve. Facial nerve dysfunction from vestibular schwannoma is uncommon. Without treatment, lower cranial nerve involvement and brainstem compression may eventually occur ( Fig. 23-5 ). MRI of the internal auditory canal is the typical modality used to identify these lesions. Acoustic neuromas are treated with surgical excision or stereotactic radiation; small tumors may be observed for evidence of growth. Other masses occurring in the cerebellopontine angle include meningiomas, epidermoid tumors, and metastases, which may cause similar symptoms, although the time scale of symptomatology is typically more rapid with metastatic lesions in this area.

Superior Semicircular Canal Dehiscence Syndrome

Superior semicircular canal dehiscence syndrome was first recognized in 1998 as a cause of vertigo. The disorder is caused by a defect in the bone over the superior semicircular canal, which renders the canal sound sensitive. Symptoms of superior semicircular canal dehiscence syndrome include vertigo induced by sound or pressure (such as during a Valsalva maneuver), hearing loss, and autophony. Systemic neurologic symptoms are absent. Noncontrast CT scan of the temporal bone demonstrates the absence of bone over the superior semicircular canal. Treatment consists of surgically plugging the superior canal in patients with bothersome vestibular symptoms ( Fig. 23-6 ).

Central Vestibular Disorders

The most common central vestibular disorders include vestibular migraine, vascular disease affecting the brainstem and cerebellar vestibular pathways, cerebellar degeneration, and Chiari malformation. Vestibular migraine, which can be considered a migraine variant, affects women more often than men, particularly women in their childbearing years. As with migraine headache, it is a diagnosis of exclusion, since there are no pathognomonic tests for this condition. Diagnostic criteria consist of a combination of the International Headache Society criteria for migraine headache and criteria developed specifically for vestibular migraine. Establishing a diagnosis of vestibular migraine requires a temporal association between dizziness and either migraine headache or typical migrainous symptoms and the absence of another diagnosis that can account for the dizziness. The pathophysiology is uncertain but is likely to be related to serotonin effects on central vestibular structures. Treatment is similar to the treatment for migraine headache and includes both decreasing triggers for migraine and use of pharmacotherapy. For patients with frequent (greater than one per week) episodes of vestibular migraine, prophylactic medications are indicated to reduce the frequency and severity of attacks and include antidepressants, β-blockers, anticonvulsants, and calcium-channel blockers. Some patients may benefit from triptans for acute attacks.

Central vestibular structures in the brainstem and cerebellum are supplied by the posterior inferior cerebellar artery and the anterior inferior cerebellar artery. Infarction of the lateral medulla in the territory of the posterior inferior cerebellar artery leads to a Wallenberg syndrome, wherein one of two vestibular nuclear complexes is damaged, leading to central vestibular imbalance. Accompanying symptoms are caused by involvement of the ascending spinothalamic tract and descending sympathetic tracts. Patients with Wallenberg syndrome may experience lateropulsion (i.e., a sense of being pushed or pulled to one side). Infarction in the territory of the anterior inferior cerebellar artery leads to a similar syndrome but may also include the presence of unilateral hearing loss resulting from cochlear ischemia because the internal auditory artery arises from the anterior inferior cerebellar artery.

Another condition to be considered in patients with acute vertigo and accompanying neurologic disturbances referable to the brainstem and cerebellum is that of cerebellar hemorrhage or infarction with concomitant brainstem compression. This condition represents a neurosurgical emergency. Brain imaging provides definitive diagnostic information.

Vertebrobasilar insufficiency may present with various neurologic symptoms including vertigo and changes in hearing as well as symptoms referable to posterior fossa structures, such as changes in vision, sensation, strength, or level of consciousness. Symptoms typically last for minutes. Isolated vertigo is rarely a result of vertebrobasilar insufficiency. Diagnostic imaging such as MR or CT angiography is helpful in establishing a diagnosis of vertebrobasilar insufficiency in the context of appropriate symptoms. Treatment with antiplatelet agents and management of risk factors for cardiovascular disease are warranted for most cases; endovascular treatment with angioplasty, stenting, or both, is rarely employed.

Cerebellar degeneration can be associated with dizziness and dysequilibrium. Some types of cerebellar degeneration (particularly spinocerebellar ataxia type 6) can also be associated with episodic features including episodic vertigo and dysequilibrium. In association with such symptoms, patients with cerebellar degeneration often demonstrate limb ataxia and sometimes long-tract signs. Chiari malformations sometimes present with “dizziness” and dysequilibrium. Physical examination may disclose down-beating nystagmus (i.e., vertical nystagmus with a downward fast component), which may reflect a central vestibular imbalance. Additionally, patients with a Chiari malformation often have nonvestibular symptoms such as dysphagia and long-tract signs. A diagnosis of a Chiari malformation can be confirmed by sagittal MRI ( Fig. 23-7 ). Treatment is surgical and involves suboccipital craniotomy.