Periodic alternating nystagmus of peripheral vestibular origin.

OBJECTIVES/HYPOTHESIS: Periodic alternating nystagmus (PAN) is most commonly found either in its congenital form or after cerebellar/pontomedullary lesions. However, we identified PAN in 10 patients with peripheral vestibular disorders and will try to describe their characteristics to aid in the differential diagnosis between peripheral and central etiologies. STUDY DESIGN: Observation of a case series. METHOD: Peripheral vestibular lesions were confirmed by neurological examinations, vestibular function tests, and brain magnetic resonance imaging (MRIs). Eye movements of the patients were recorded using electronystagmography or video nystagmography for a minimum of 10 minutes to confirm the nystagmus change in direction. RESULTS: The final diagnoses of the patients included Meniere's disease (n = 3), acute labyrinthitis (n = 4), sudden sensorineural hearing loss with vertigo (n = 2), and vestibular schwannoma (n = 1). Direction-changing spontaneous horizontal nystagmus with quiescent intervals was observed in all patients under dark conditions. The nystagmus was suppressed by visual fixation; and the results of oculomotor tests were normal for saccadic and smooth pursuit eye movements and optokinetic nystagmus. All patients showed mild to complete canal paresis on a bithermal caloric test. PAN progressed into unidirectional nystagmus of the contra-lesion side in all patients within 48 hours. CONCLUSION: PAN can be observed in patients with peripheral vestibular disorders, but detecting PAN in this subpopulation is difficult because of its transitory nature. The absence of central symptoms and signs, the visual suppression of PAN, normal oculomotor tests, and transient persistence are important diagnostic clues for differentiating peripheral from central PAN. LEVEL OF EVIDENCE: 4.

A cupulolith repositioning maneuver in the treatment of horizontal canal cupulolithiasis.

OBJECTIVE: We evaluated outcomes and their significance of a new treatment method for horizontal canal cupulolithiasis that could be applied regardless of the side of the cupula where otoliths are attached. METHODS: Consecutive 78 patients who showed persistent apogeotropic horizontal canal positional vertigo (horizontal canal cupulolithiasis) were enrolled, and they were treated with the new cupulolith repositioning maneuver. RESULTS: Horizontal semicircular canal cupulolithiasis was alleviated in 97.4% of patients, after an average of 2.1 repetitions of the maneuver. Otoliths were suspected to be attached to the canal side of the cupula in 30 cases and the utricular side in 44 cases. CONCLUSION: The cupulolith repositioning maneuver is an effective method for treating horizontal canal cupulolithiasis. It may also provide an insight into the side of the cupula where otoliths are attached.