title: A late complication of CSF shunting: acquired Chiari I malformation.
abstract: OBJECTIVE
  Acquired Chiari I malformation developing after cerebrospinal fluid (CSF) shunting is an intriguing late complication of CSF shunt surgery and not only raises questions as to its pathogenesis but also poses many queries about the possible adverse effects on the subsequent child development as well as on the indications and possibilities of surgical correction.
  
  
  METHODS
  We report a series of 17 patients with the neuroradiological evidence of an "acquired" Chiari type I malformation. These patients, 3 to 24 years (mean 11.3 years), had been treated previously with an extrathecal CSF shunt. The follow-up varied from 2 to 12 years (mean, 6).
  
  
  RESULTS
  Neuroradiological investigation demonstrated a small posterior cranial fossa, small ventricles, markedly reduced periencephalic subarachnoid spaces, and thickening of the skull vault and base. The degree of tonsillar herniation did not correlate with clinical manifestations. All patients with severe clinical manifestations or with progressive worsening of neuroradiological findings were considered for surgical treatment. Decompressive supratentorial craniotomy seemed to fit with the purpose of enlarging the intracranial volume without the risk of aggravating the hindbrain herniation. An immediate relief of clinical manifestations was observed in all patients. Not surgically treated patients did not show any clinical or radiological modification during all the follow-up.
  
  
  CONCLUSIONS
  This study contributes to the understanding of the underlying pathogenetic mechanisms of acquired Chiari type 1 malformation in cases of long-lasting supratentorial CSF shunting and provides a base for planning the best management, whether conservative or surgical.
authors.affiliation: Department of Pediatric Neurosurgery, Catholic University Medical School, Largo A. Gemelli 1, 00168, Rome, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Caldarelli
authors.forename: Federica
authors.initials: F
authors.lastname: Novegno
authors.forename: Concezio
authors.initials: C
authors.lastname: Di Rocco
mesh_terms: D000293:Adolescent; D001139:Arnold-Chiari Malformation / Q000209:etiology* / Q000473:pathology / Q000601:surgery; D001921:Brain / Q000473:pathology / Q000503:physiopathology; D002557:Cerebrospinal Fluid Shunts / Q000009:adverse effects*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006849:Hydrocephalus / Q000473:pathology / Q000601:surgery; D019586:Intracranial Hypertension; D008279:Magnetic Resonance Imaging; D008297:Male; D012886:Skull / Q000473:pathology / Q000601:surgery; D055815:Young Adult