Acoustic neuroma presenting as exercise-induced vertigo.

We present two subjects with previously undiagnosed acoustic neuromas who complained of vertigo whenever they ran. One had normal hearing while the other already had a unilateral sensorineural deafness. Hyperventilation for 30 seconds provoked an ipsilateral beating nystagmus and reproduced the vertiginous sensation in both subjects. Hyperventilation is a simple bedside test that should be performed when assessing a subject with vertigo or when there is a clinical suspicion of an acoustic neuroma.