Hyperventilation-Induced Nystagmus Direction Reversal in Unilateral Vestibular Neuritis and Ipsilateral Facial Palsy: 2 Case Reports and Review of the Literature

Ipsilesional hyperventilation-induced nystagmus is a known clinical finding in patients with cerebellopontine angle tumors. However, it can also be present in idiopathic vestibular neuritis and Ramsay Hunt syndrome. We report two cases of unilateral vestibular neuritis and ipsilateral peripheral facial palsy who had nystagmus direction reversal after hyperventilation. A 52-year-old man presented with a new onset of right facial drop preceded by right hearing loss and dizziness. Examination revealed a right peripheral facial palsy and left beating nystagmus, which switched to right beating after hyperventilation. MRI brain showed enhancement of the right facial nerve. He was treated empirically with steroids and valacyclovir with symptom resolution. A 79-year-old man presented with a new onset of right facial weakness preceded by difficulty swallowing. Examination revealed a right peripheral facial palsy and right external auditory canal vesicles. MRI brain showed right facial nerve enhancement; and the cerebrospinal fluid, varicella zoster virus polymerase-chain-reaction was positive. He was treated with acyclovir and steroids. One month after the initial presentation, he had acute vertigo with new left beating nystagmus that reversed to right beating after hyperventilation. MRI showed persistent right facial nerve enhancement and new right vestibular nerve enhancement. He was retreated with steroids and antivirals with symptom improvement. Ipsilesional-hyperventilation-induced nystagmus is a possible clinical finding in patients with vestibular neuritis. Ramsay Hunt syndrome, anterior-inferior cerebellar artery stroke, and cerebellopontine angle tumors should be on the differential diagnosis of patients with unilateral facial palsy and ipsilateral vestibulopathy.