title: No significant difference between chiari malformation type 1.5 and type I.
abstract: OBJECTIVE
  Chiari malformation Type 1.5 (CM 1.5) was defined as the association of Chiari malformation Type I (CM I) and brainstem herniation. The objective was to demonstrate the difference of clinical features and surgical outcomes between CM 1.5 and CM I.
  
  
  METHODS
  All CM 1.5 and CM I adult patients who underwent posterior fossa decompression with duraplasty at our institution between 2006 and 2010 were retrospectively reviewed. Clinical characteristics, imaging features, and long-term outcomes were compared between CM 1.5 and CM I patients.
  
  
  RESULTS
  A total of 142 adult patients were enrolled, including 27 CM 1.5 and 115 CM I patients. The average follow-up period was 102 months. Age at diagnosis was significantly younger in CM 1.5 group than CM I group (p=0.039). And the degree of tonsillar herniation was significantly more severe in CM 1.5 group than CM I group (p<0.001). There was no significant difference in other clinical and imaging characteristics. Moreover, improvement of symptoms was observed in 21 CM 1.5 patients (77.8%) and 94 CM I patients (81.7%), and no significant difference was detected (p=0.637). There was no significant difference in the resolution of syringomyelia between CM 1.5 (72.7%) and CM I (76.5%) patients, either (p=0. 710).
  
  
  CONCLUSIONS
  Although CM 1.5 patients presented with brainstem herniation and more severe tonsillar herniation, other clinical and imaging features and surgical outcomes were similar with CM I patients. We think CM 1.5 is just a subtype of CM I, rather than a unique type of Chiari malformations.
authors.affiliation: Department of Neurosurgery, People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, Xinjiang Uygur Autonomous Region, China. Electronic address: liuwei1447@163.com.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: Department of Neurosurgery, People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, Xinjiang Uygur Autonomous Region, China. Electronic address: hongxing1028@163.com.
authors.forename: Hongxing
authors.initials: H
authors.lastname: Wu
authors.affiliation: Department of Neurosurgery, People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, Xinjiang Uygur Autonomous Region, China. Electronic address: xyz000007@sina.com.
authors.forename: Yalikun
authors.initials: Y
authors.lastname: Aikebaier
authors.affiliation: Department of Neurosurgery, People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, Xinjiang Uygur Autonomous Region, China. Electronic address: Wulalabieke@126.com.
authors.forename: Maoliti
authors.initials: M
authors.lastname: Wulabieke
authors.affiliation: Department of Neurosurgery, People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, Xinjiang Uygur Autonomous Region, China. Electronic address: Parhat469@sohu.com.
authors.forename: Rexiti
authors.initials: R
authors.lastname: Paerhati
authors.affiliation: Department of Neurosurgery, People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, Xinjiang Uygur Autonomous Region, China. Electronic address: yxp3862@163.com.
authors.forename: Xiaopeng
authors.initials: X
authors.lastname: Yang
mesh_terms: D000328:Adult; D000368:Aged; D001139:Arnold-Chiari Malformation / Q000175:diagnosis* / Q000601:surgery*; D003388:Cranial Fossa, Posterior / Q000601:surgery*; D019299:Decompression, Surgical / Q000379:methods; D004388:Dura Mater / Q000601:surgery; D004677:Encephalocele / Q000601:surgery; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013595:Syringomyelia / Q000601:surgery*; D016896:Treatment Outcome
keywords: Brainstem herniation; Chiari malformation; Posterior cranial fossa; Syringomeylia; Tonsillar ectopia