title: Periodic alternating nystagmus caused by a medullary lesion in acute disseminated encephalomyelitis.
abstract: OBJECTIVE
  To document a patient with periodic alternating nystagmus (PAN) caused by acute disseminated encephalomyelitis (ADEM) and suggest a mechanism to explain her PAN.
  
  
  METHODS
  A 34-year-old woman with PAN caused by ADEM.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: *Department of Otolaryngology, Saitama Medical University, Saitama Medical Center, Kawagoe-shi, Saitama; and †Tsuzumigaura Handicapped Children's Hosipital, Yamaguchi, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tsutsumi
authors.forename: Takuo
authors.initials: T
authors.lastname: Ikeda
authors.forename: Shigeru
authors.initials: S
authors.lastname: Kikuchi
mesh_terms: D000328:Adult; D004584:Electronystagmography; D004673:Encephalomyelitis, Acute Disseminated / Q000150:complications* / Q000473:pathology / Q000503:physiopathology; D053483:Eye Movement Measurements; D005260:Female; D006801:Humans; D020547:Lateral Ventricles / Q000473:pathology; D008526:Medulla Oblongata / Q000473:pathology*; D009759:Nystagmus, Pathologic / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D013116:Spinal Cord / Q000473:pathology