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Periodic Alternating Nystagmus Caused by a Medullary Lesion in Acute Disseminated Encephalomyelitis

Tsutsumi, Takeshi*; Ikeda, Takuo; Kikuchi, Shigeru*

doi: 10.1097/MAO.0000000000000344
Vestibular Disorders

Objective To document a patient with periodic alternating nystagmus (PAN) caused by acute disseminated encephalomyelitis (ADEM) and suggest a mechanism to explain her PAN.

Patient A 34-year-old woman with PAN caused by ADEM.

Intervention Diagnostic.

Results The patient complained of severe disequilibrium from the disease onset. Four years after onset, when she visited us, the patient exhibited prominent PAN consisting of alternating rightward and leftward components, which cycled about every 90 seconds and were accompanied by a 5-second translating phase with downbeating nystagmus. Eye movement analysis that separated the horizontal and vertical components revealed the presence of downbeating movements throughout all phases of the PAN. ENG recordings revealed slightly saccadic pursuit, slightly impaired optokinetic eye movement and an absence of visual suppression of the caloric response. MRI recorded at the onset of the disease revealed lesions in the medulla, the spinal cord at the C2 level, and the frontal horn of the left lateral ventricle, but not the cerebellum.

Conclusion We attribute this patient’s PAN to impairment of the nucleus prepositus hypoglossi in the medulla, which plays a role in the velocity storage system. In addition, cerebellar dysfunction is indicated by the occurrence of PAN while fixating.

*Department of Otolaryngology, Saitama Medical University, Saitama Medical Center, Kawagoe-shi, Saitama; and †Tsuzumigaura Handicapped Children’s Hosipital, Yamaguchi, Japan

Address correspondence and reprint requests to Takeshi Tsutsumi, M.D., Department of Otolaryngology, Saitama Medical University, Saitama Medical Center, Kamoda 1981, Kawagoe-shi, Saitama 350-8550, Japan; E-mail:

The authors disclose no conflicts of interest.

Copyright © 2014 by Otology & Neurotology, Inc. Image copyright © 2010 Wolters Kluwer Health/Anatomical Chart Company