title: Lumbar elastance and resistance to CSF outflow correlated to patency of the cranial subarachnoid space and clinical outcome of endoscopic third ventriculostomy in obstructive hydrocephalus.
abstract: OBJECTIVE
  The purpose of the present study was to elucidate the value of the lumbar and intraventricular infusion tests in the selection of patients with obstructive hydrocephalus (OH) for endoscopic third ventriculostomy (ETV), and whether the presence of a diminished cranial subarachnoid space was a source of error in the interpretation of the results.
  
  
  METHODS
  In 32 consecutive adult patients (15 M, 17 F, mean age: 46 years) with possible treatment-requiring OH, the resistance to cerebrospinal fluid (CSF) outflow (Rout) and elastance was measured with a lumbar infusion test. Eleven of the patients underwent an additional intraventricular infusion test. An ETV was subsequently performed in 20 patients, of whom 11 presented with idiopathic aqueductal stenosis and 9 with other various causes of OH.
  
  
  RESULTS
  The presence of a diminished cranial SAS correlated significantly with increased lumbar elastance, but not with lumbar Rout. However, distinctly increased Rout values (>24 mmHg/mL/min, n=4) were only measured in the presence of a diminished cranial SAS. No significant correlation was demonstrated between the clinical outcome of ETV and lumbar elastance or lumbar Rout, although seven out of the eight improving patients with aqueductal stenosis presented normal lumbar Rout values. In patients undergoing both a lumbar and an intraventricular infusion test and improving after ETV (n=6), lumbar elastance was significantly increased compared to the intraventricular elastance.
  
  
  CONCLUSIONS
  A diminished cranial SAS correlates with increased lumbar elastance and may explain the highly increased lumbar Rout values, possibly by impeding the bulk flow from the infusion. The majority of patients improving after ETV and presenting a normal sized cranial SAS presented normal lumbar Rout values. Supplementing the lumbar infusion test with an intraventricular test may help in predicting the outcome of ETV.
authors.affiliation: University Clinic of Neurosurgery, The Neuroscience Center, Rigshospitalet, Glostrup, Denmark. rbechazeddine@dadlnet.dk
authors.forename: R
authors.initials: R
authors.lastname: Bech-Azeddine
authors.forename: O A
authors.initials: OA
authors.lastname: Nielsen
authors.forename: V B
authors.initials: VB
authors.lastname: Løgager
authors.forename: M
authors.initials: M
authors.lastname: Juhler
mesh_terms: D000328:Adult; D000368:Aged; D002535:Cerebral Aqueduct / Q000473:pathology / Q000503:physiopathology; D015170:Cerebrospinal Fluid Pressure / Q000502:physiology*; D003955:Diagnostic Tests, Routine / Q000379:methods* / Q000592:standards; D004548:Elasticity; D004724:Endoscopy; D005260:Female; D006801:Humans; D006849:Hydrocephalus / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D007427:Intracranial Pressure / Q000502:physiology; D008159:Lumbar Vertebrae; D008297:Male; D008875:Middle Aged; D044583:Neuroendoscopy; D018579:Patient Selection; D011237:Predictive Value of Tests; D011300:Preoperative Care / Q000379:methods / Q000592:standards; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D012886:Skull; D013346:Subarachnoid Space / Q000033:anatomy & histology / Q000502:physiology; D020542:Third Ventricle / Q000033:anatomy & histology / Q000502:physiology / Q000601:surgery; D014696:Ventriculostomy