Periodic alternating nystagmus of peripheral vestibular origin.
OBJECTIVE
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.


METHODS
Observation of a case series.


METHODS
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.


CONCLUSIONS
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.


METHODS
4.
Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, Korea.
Sung H
SH
Kim
Woon-Kyo
WK
Chung
Bo G
BG
Kim
Chi S
CS
Hwang
Mi J
MJ
Kim
Won-Sang
WS
Lee
D000368:Aged; D001921:Brain / Q000473:pathology / Q000503:physiopathology; D002150:Caloric Tests; D004584:Electronystagmography; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009759:Nystagmus, Pathologic / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D011379:Prognosis; D012189:Retrospective Studies; D015837:Vestibular Diseases / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D014724:Vestibular Function Tests; D014722:Vestibule, Labyrinth / Q000503:physiopathology*
Meniere's disease; Periodic alternating nystagmus; labyrinthitis; sudden hearing loss; vestibule of ear