[Endoscopic third ventriculostomy: risk factors for failure and evolution of ventricular size]

Endoscopic third ventriculostomy is the treatment of choice for non communicating hydrocephalus at our institution. Several factors have been associated with failure of endoscopic third ventriculostomy. The goals of the study have been to evaluate the outcome, the influence of factors theoretically prone to failure of ventriculostomy and the evolution of ventricular size.

Fifty-six patients (mean age 48.5 yrs) treated with an endoscopic third ventriculostomy during the period 1997-2002 were analysed retrospectively. Hydrocephalus was classified as acute (68%) and chronic forms. Etiology was classified in space-occupying lesions (59%), primary aqueductal stenosis (34%) and Chiari malformation (7%). The presence of the following factors theoretically prone to failure was considered: age below one year, history of mielomeningocele, cerebrospinal fluid (CSF) infection, intracranial haemorrhage, radiotherapy, craniotomy and previous treatment of hydrocephalus with a shunt. Ventricular size was measured linearly with four ventricular index pre- and postoperatively.

The global success rate was 71.4% (mean follow-up 26 months). Endoscopic third ventriculostomy for hydrocephalus secondary to cerebral metastases obstructing CSF pathways was associated with a higher risk of failure (p=0.006). None of the risk factors considered was associated with a higher risk of failure. The evolution of the ventricular size measured with linear methods is associated with outcome. Evans ratio, third ventricle index, cella media index and ventricular score decreased in patients whose outcome is satisfactory and increased in those cases deemed clinical failures (p< 0.05).

The risk of failure increases in patients with cerebral metastases close to CSF pathways, likely due to the concurrence of mechanisms other than obstruction. Changes in ventricular size are associated with outcome.