Downbeat nystagmus (DBN) is commonly caused by central lesions, e.g., vestibulo-cerebellar and brainstem lesions, and there are few reports on DBN caused by peripheral lesions. We report two cases of Meniere's disease who presented with DBN and fluctuating low-tone sensorineural hearing loss. Case 1: a 55-year-old female. The patient was admitted to our hospital in September 20XX because of a vertigo attack. She exhibited rightward horizontal nystagmus in the supine position, however, the positioning test triggered DBN, which changed later to rightward horizontal nystagmus. There were no apparent neurological or neuro-otological abnormalities. Two days later, pure-tone audiometry showed low-tone sensorinueral hearing loss in the left ear. Magnetic resonance imaging (MRI) revealed no abnormal findings. Although steroid and isosorbide administrations were not effective, the symptoms resolved completely with the administration of diazepam. Case 2: A 26-year-old female. In August 20XX, the patient consulted a neighborhood clinic for hearing loss and tinnitus in the left ear. She presented with a history of repeated hearing loss and positional DBN and was referred to our hospital for further examination. Pure-tone audiometry showed low-tone hearing loss. The positional and positioning tests triggered DBN. There were no abnormal findings on neuro-otological and MRI examinations. Isosorbide administration improved the hearing loss and nystagmus. Thus, we encountered two cases of Meniere's disease presenting with DBN. The positional DBN in both cases was suspected to be caused by endolymphatic hydrops in the saccule and anterior semicircular canal.
