Abstract

Hyperventilation may elicit nystagmus by bring out vestibular asymmetry in central as well as peripheral vestibulopathies, including compensated peripheral vestibulopathies, perilymph fistula, acoustic neuroma, lesions at craniocervical junction, and cerebellar degeneration. A recent study documented that hyperventilation-induced nystagmus (HIN) beating to the side of reduced caloric response, hearing impairment, or abnormal auditory brainstem response may be a valuable sign for bedside detection of acoustic neuroma. Disruption of the central pathways compensating for a peripheral imbalance, increased neuronal excitability, changes in intracranial pressure, and metabolic changes on cerebellar calcium channels are potential mechanisms for the generation of HIN. The Valsalva maneuver may also produce vertigo and nystagmus in patients with craniocervical junction anomalies, perilymph fistula, and canal dehiscence syndromes. Presumably, Valsalva maneuver increases intracranial or tympanic pressure and exerts force directly at the site of the fistula or dehiscence, causing deflection of the cupula of the involved semicircular canal.