title: A nationwide survey of opsoclonus-myoclonus syndrome in Japanese children.
abstract: BACKGROUND
  Opsoclonus-myoclonus syndrome (OMS) is a rare neurological disease characterized by opsoclonus, myoclonus, ataxia, and behavioral changes. The aim of our study was to investigate the epidemiological characteristics of OMS in Japan and to clarify the association between therapy and prognosis.
  
  
  METHODS
  We retrospectively collected the data from 626 Japanese medical institutions from 2005 to 2010, and analyzed the clinical features of pediatric patients with OMS based on the data.
  
  
  RESULTS
  In this survey, there were 23 patients (10 males and 13 females). The median ages at the disease onset and the time of study were 16.5 months (range: 11-152 months) and 54 months (range: 24-160 months), respectively. The principal symptoms were opsoclonus (23 patients, 100%), myoclonus (21 patients, 91.3%), and ataxia (23 patients, 100%). The related factors were neuroblastoma (10, 43.5%), infection (9, 39.1%), and immunization (2, 8.7%). The treatments for OMS were included intravenous immunoglobulin (17, 73.9%), methylprednisolone pulse (13, 56.5%), oral prednisolone (12 patients, 52.2%), and chemotherapy and/or operation for the underlying tumors (6, 26.1%), and rituximab (2, 8.7%). Complete remissions were obtained in 35.3%, 23.1%, 33.3%, 66.7%, and 100% of these treatments, respectively. At the latest follow-up period, 8 (34.8%) and 17 patients (73.9%) showed neurological sequelae of motor and intellectual functions, respectively. Patients whose treatment was started more than 30 weeks after the disease onset suffered from the severest neurological sequelae (OMS severity 4) more frequently than those less than 30 weeks (p=0.022).
  
  
  CONCLUSIONS
  The annual incidence of OMS was estimated to be 0.27-0.40 cases per million in Japanese children. More than 70% of OMS patients had neurological sequelae, especially intellectual function. Early effective treatments within 30 weeks after the onset may be required to prevent the serious neurological outcome.
authors.affiliation: Department of Pediatrics, Yamaguchi University Graduate School of Medicine, Japan. Electronic address: shunji@yamaguchi-u.ac.jp.
authors.forename: Shunji
authors.initials: S
authors.lastname: Hasegawa
authors.affiliation: Department of Pediatrics, Yamaguchi University Graduate School of Medicine, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Matsushige
authors.affiliation: Department of Pediatrics, Yamaguchi University Graduate School of Medicine, Japan.
authors.forename: Madoka
authors.initials: M
authors.lastname: Kajimoto
authors.affiliation: Department of Pediatrics, Yamaguchi University Graduate School of Medicine, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Inoue
authors.affiliation: Department of Pediatrics, Yamaguchi University Graduate School of Medicine, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Momonaka
authors.affiliation: Department of Pediatrics, Yamaguchi University Graduate School of Medicine, Japan.
authors.forename: Momoko
authors.initials: M
authors.lastname: Oka
authors.affiliation: Department of Pediatrics, Yamaguchi University Graduate School of Medicine, Japan.
authors.forename: Shouchi
authors.initials: S
authors.lastname: Ohga
authors.affiliation: Department of Pediatrics, Yamaguchi University Graduate School of Medicine, Japan; Department of Pediatrics, Tsudumigaura Handicapped Children's Hospital, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ichiyama
mesh_terms: D000293:Adolescent; D044466:Asian People; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007564:Japan / Q000453:epidemiology; D008297:Male; D053578:Opsoclonus-Myoclonus Syndrome / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D011379:Prognosis; D012189:Retrospective Studies; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
keywords: Incidence; Japan; Opsoclonus–myoclonus syndrome (OMS); Survey