Successful treatment of hyperventilation-induced nystagmus in vestibular schwannoma with oxcarbacepine

A 67-year-old-man suffered from attacks of rotatory vertigo and oscillopsia over a period of six months, which could be reproducibly elicited by physical activity. Symptoms ceased rapidly after the patient got to rest for a few minutes. Clinical examination revealed a mixed, clockwise torsional nystagmus with a horizontal component toward the patient's right 30 seconds after hyperventilation and ceasing about one minute after hyperventilation. MRI disclosed an enhancing mass in the right cerebellopontine angle without progression during follow up over 6 months. No specific surgical intervention was performed and the lesion was monitored clinically and radiologically. To treat paroxysmal symptoms, oxcarbacepine (2×150mg) was initiated and well-tolerated. The nystagmus could no longer be provoked by hyperventilation.

Nystagmus is very infrequently induced by hyperventilation. However, patients with demyelinating lesions of the vestibular nerve (due to compression by a tumor or a small blood vessel) or in central structures (multiple sclerosis) may show hyperventilation-induced nystagmus (HIN). In acoustic neuroma, the presumed mechanism of HIN is improved axonal conduction in the partially demyelinated vestibular nerve by hyperventilation. There is evidence that hyperventilation results in a transient increase in activity from partially demyelinated axons. Hyperventilation can cause nystagmus beating toward the side of a vestibular nerve lesion and is the only test that unmasks unilateral vestibular disease without testing the dynamic properties of the vestibulo-ocular reflex. Ipsilesional HIN in patients with hearing loss or canal paresis thus can be a sign suggesting vestibular schwannoma.

Most of the patients suffering from paroxysmal vestibular symptoms due to a neurovascular cross-compression of the eighth nerve (“vestibular paroxysmia“) benefit from treatment with antiepileptic drugs such as carbamazepine or phenytoin. In general, a positive response to antiepileptic drugs can be achieved with low dosages.

Treatment with antiepileptic drugs as symptomatic treatment can alleviate paroxysmal vestibular symptoms. To our knowledge this is the first report of a successful treatment of HIN with the anticonvulsant oxcarbacepine.