title: Endoscopic third ventriculostomy for the management of Chiari I and related hydrocephalus: outcome and pathogenetic implications.
abstract: BACKGROUND
  Hydrocephalus affects 7% to 10% of patients with Chiari I malformation (CIM). It can be successfully treated by endoscopic third ventriculostomy (ETV), possibly improving related CIM and syringomyelia.
  
  
  OBJECTIVE
  To confirm the effectiveness of ETV in the management of Chiari-related hydrocephalus and symptoms and to estimate the posterior cranial fossa volume (PCFV) to find the possible reasons for the success or failure of ETV.
  
  
  METHODS
  Fifteen patients (11 children and 4 adults) underwent ETV for hydrocephalus associated with CIM (syringomyelia was present in 6 patients). Preoperative PCFV, posterior fossa brain volume (PFBV), and PFBV/PCFV ratio were calculated in the last 12 patients in the series by a magnetic resonance imaging-based computerized method.
  
  
  RESULTS
  All patients had symptomatic hydrocephalus (mean third ventricle diameter, 14.1 mm). Mean tonsillar ectopia was 12.7 mm. Postoperatively, hydrocephalus symptoms improved in all cases (mean third ventricle diameter, 8.3 mm); signs and symptoms of CIM and syringomyelia resolved or improved in all patients, although the malformation remained radiologically stable in half of the patients (postoperative mean tonsillar ectopia, 8.8 mm). There were no remarkable differences between cases and controls with regard to PCFV and PFBV. The PFBV/PCFV ratio was comparable in pediatric cases and controls but not among adult patients, suggesting a PCF overcrowding in the controls.
  
  
  CONCLUSIONS
  ETV is an effective treatment for hydrocephalus associated with CIM. It is successful in improving CIM and syringomyelia in patients with no overcrowding (mainly in children) or with reversible overcrowding of the PCF (mainly in adults).
authors.affiliation: Institute of Neurosurgery, A. Gemelli Hospital, Rome, Italy. lmassimi@email.it
authors.forename: Luca
authors.initials: L
authors.lastname: Massimi
authors.forename: Emanuele
authors.initials: E
authors.lastname: Pravatà
authors.forename: Gianpiero
authors.initials: G
authors.lastname: Tamburrini
authors.forename: Simona
authors.initials: S
authors.lastname: Gaudino
authors.forename: Benedetta
authors.initials: B
authors.lastname: Pettorini
authors.forename: Federica
authors.initials: F
authors.lastname: Novegno
authors.forename: Cesare
authors.initials: C
authors.lastname: Colosimo
authors.forename: Concezio
authors.initials: C
authors.lastname: Di Rocco
mesh_terms: D000293:Adolescent; D000328:Adult; D001139:Arnold-Chiari Malformation / Q000150:complications / Q000473:pathology / Q000601:surgery*; D002648:Child; D002675:Child, Preschool; D019468:Disease Management; D005260:Female; D006801:Humans; D006849:Hydrocephalus / Q000209:etiology / Q000473:pathology / Q000601:surgery*; D007223:Infant; D008297:Male; D008875:Middle Aged; D044583:Neuroendoscopy / Q000379:methods*; D020542:Third Ventricle / Q000473:pathology / Q000601:surgery*; D016896:Treatment Outcome; D014696:Ventriculostomy / Q000379:methods*; D055815:Young Adult