title: The constant flow ventricular infusion test: a simple and useful study in the diagnosis of third ventriculostomy failure.
abstract: OBJECTIVE
  The evaluation of third ventriculostomy function in hydrocephalic patients is challenging. The utility of the constant flow infusion test in predicting response to shunt insertion in normal-pressure hydrocephalus, as well as in identifying shunt malfunction, has been previously demonstrated. The object of this study was to evaluate its usefulness in determining whether a revision CSF diversion procedure was indicated in patients presenting with recurring symptoms and persisting ventriculomegaly after endoscopic third ventriculostomy (ETV).
  
  
  METHODS
  The authors conducted a prospective study of all patients who, after undergoing ETV at their institution, presented postoperatively with recurring symptoms and persisting ventriculomegaly.
  
  
  RESULTS
  Forty-six patients (mean age 40.7 years, including 11 patients younger than 18 years) underwent 56 constant flow ventricular infusion tests (VITs) at a mean of 24.7 months post-ETV. Thirty-three patients with resistance to CSF outflow (R(out)) less than 13 mm Hg/ml/min underwent follow-up (median 17 months) and experienced resolution of symptoms. In 10 episodes R(out) was greater than 13 mm Hg/ml/min; the patients in these cases underwent revisional CSF diversion. Two patients demonstrated high and frequent B (slow) waves despite a low R(out); these patients also underwent successful revisions. Patients who improved after surgery had increased B wave activity in the plateau phase of the VIT (p = 0.01). Thirty-four patients underwent MR imaging at the same time; 4 had high R(out) despite evidence of flow across the stoma. These 4 patients underwent surgery and experienced resolution of symptoms. Of 9 patients without flow, R(out) was less than 13 mm Hg/ml/min in 4; these patients were successfully treated conservatively.
  
  
  CONCLUSIONS
  The VIT is a useful and safe adjunct to clinical and MR imaging evaluation when ETV failure is suspected.
authors.affiliation: Department of Neurosurgery, Frenchay Hospital, Bristol, United Kingdom. K.Aquilina@bristol.ac.uk
authors.forename: Kristian
authors.initials: K
authors.lastname: Aquilina
authors.forename: Ian K
authors.initials: IK
authors.lastname: Pople
authors.forename: Jenny
authors.initials: J
authors.lastname: Sacree
authors.forename: Michael R
authors.initials: MR
authors.lastname: Carter
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Edwards
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002555:Cerebrospinal Fluid / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D006849:Hydrocephalus / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D007223:Infant; D008297:Male; D008875:Middle Aged; D044583:Neuroendoscopy / Q000379:methods*; D011183:Postoperative Complications / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D011446:Prospective Studies; D012086:Reoperation; D020542:Third Ventricle / Q000502:physiology* / Q000601:surgery*; D017211:Treatment Failure; D014696:Ventriculostomy / Q000009:adverse effects*; D055815:Young Adult