The diagnosis of vestibular disorders is complicated by overlapping symptoms among the various disorders and the lack of pathognomonic diagnostic tests. At times, determining which inner ear is causing the symptoms may even be difficult. Most patients' symptoms can be managed with the medical and physical therapy measures described elsewhere in this book. However, surgical intervention may be appropriate when the symptoms have failed to respond to aggressive nonsurgical medical management.
With the exception of acoustic tumors, vestibular disorders are a matter of lifestyle and comfort and are not life threatening. Therefore, it must be the patient living with the symptoms who makes the decision whether or not to proceed with surgery. The physician should discuss the likelihood of a successful outcome and the nature and likelihood of potential complications, and must leave the ultimate decision up to the patient. In the authors' experience, patients have a broad spectrum of responses to their symptoms of vertigo. Some patients want immediate intervention; others consider surgery only when life becomes unbearable.
Vestibular Schwannoma (Acoustic Neuroma)
Acoustic neuromas are nerve sheath tumors occurring in the internal auditory canal (IAC) or cerebellopontine angle (CPA).1 They are the third most common intracranial tumor, accounting for 8% to 10% of all intracranial tumors. Most patients with acoustic neuromas present with progressive unilateral sensorineural hearing loss. However, some patients first complain of vestibular symptoms, sudden hearing loss, or occasionally trigeminal symptoms.2
An acoustic neuroma should be suspected in any patient with an unexplained unilateral sensorineural hearing loss, particularly if the patient has discrimination scores inconsistent with pure tone audiometry, abnormal brainstem auditory responses, or hypoactive/absent caloric responses. Magnetic resonance imaging (MRI) with gadolinium contrast has become the “gold standard” for the diagnosis of these tumors. Although there are rare instances of false-positive results, usually from arachnoiditis, an enhancing mass in the cerebellopontine angle extending into the internal auditory meatus on MRI is almost always an acoustic neuroma. Meningiomas occasionally occur in the CPA or IAC. Radiologically, they frequently have a dural “tail” and are acentric to the IAC.
Once the diagnosis is established, there are three therapeutic options: watchful waiting, microsurgical removal, and stereotactic radiosurgery (SRS). Watchful waiting is indicated only in patients with small intracanalicular tumors for which the diagnosis is inconclusive, and in patients who are elderly or in poor medical condition. Several recent series have reported the results of this approach. Wiet and colleagues3 found that in 40% of 53 patients, continued growth of tumors required intervention over a mean follow-up of about 3 years. More frightening is an experience reported by Charabi and associates.4 In their series, 34% of 123 patients followed for a mean of 3.4 years required intervention for enlarging tumor and 7 died of brainstem compression secondary to the tumor. Therefore, it may be concluded that there is a significant ...