title: Does optic nerve sheath diameter on MRI decrease with clinically improved pediatric hydrocephalus?
abstract: BACKGROUND
  Serial change in ventricular size is recognized as an imperfect indicator of ongoing hydrocephalus in children. Potentially, other radiographic features may be useful in determining the success of hydrocephalus interventions. In this study, optic nerve sheath diameter (ONSD), optic nerve tortuosity, and optic disk bulging were assessed as indicators of hydrocephalus control in children who underwent endoscopic third ventriculostomy (ETV) or posterior fossa tumor resection.
  
  
  METHODS
  Sixteen children underwent ETV or tumor resection for treatment of hydrocephalus. T2-weighted axial magnetic resonance images of the orbit were obtained, and the ONSD was measured posterior to the optic globe, pre- and post-intervention. Evidence of optic disk bulging and optic nerve tortuosity was also assessed. Ventricular size was estimated using the frontal and occipital horn ratio (FOR).
  
  
  RESULTS
  There was a significant reduction in the ONSD post-ETV (n = 9) and after tumor resection (n = 7). Average preoperative ONSD was 6.21 versus 5.71 mm postoperatively (p = 0.0017).There was also an 88% (p = 0.011) and 60% (p = 0.23) reduction in optic disk bulging and tortuosity, respectively. The FOR normalized in the tumor resection group but not the ETV group. After intervention, all patients showed improvement in signs and symptoms of hydrocephalus.
  
  
  CONCLUSIONS
  In our study population, ONSD decreased in response to measures to reduce hydrocephalus. Optic disk bulging also appears to resolve. Serial reduction in ONSD, and optic disk bulging may be indicators of improved hydrocephalus following pediatric neurosurgical interventions.
authors.affiliation: Department of Surgery, Division of Pediatric Neurosurgery, University of British Columbia and BC Children's Hospital, Vancouver, BC V6H 3V4, Canada. ash.singhal@cw.bc.ca
authors.forename: Ash
authors.initials: A
authors.lastname: Singhal
authors.forename: Michael M H
authors.initials: MM
authors.lastname: Yang
authors.forename: Michael A
authors.initials: MA
authors.lastname: Sargent
authors.forename: D Douglas
authors.initials: DD
authors.lastname: Cochrane
mesh_terms: D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D006849:Hydrocephalus / Q000175:diagnosis* / Q000601:surgery*; D007223:Infant; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009900:Optic Nerve / Q000473:pathology* / Q000601:surgery*; D011446:Prospective Studies; D020542:Third Ventricle / Q000473:pathology / Q000601:surgery; D016896:Treatment Outcome; D014696:Ventriculostomy / Q000379:methods