Mechanisms of failure after endoscopic third ventriculostomy in young infants.

Objective: The cause of failed endoscopic third vetriculostomy (ETV) surgery in the treatment of hydrocephalus may be a poor absorption of cerebrospinal fluid (CSF) or a new or continuing obstruction of CSF pathways. Particularly in infants, ETV failures often are ascribed to a still poorly developed CSF absorptive capacity.

Methods: The authors report on a series of 11 infants younger than 1 year of age undergoing at least one repeated endoscopic surgery after a failed initial ETV for aqueductal stenosis. The following three patterns of endoscopic findings were observed: 1) reclosure of the ventriculostoma; 2) narrowing of the ventriculostoma; and 3) patent ventriculostoma with new arachnoid membranes in the basal cisterns below the floor of the third ventricle, not present at the time of the first ETV. In all patients, a new obstruction of CSF pathways was seen during repeated ETV or shunt surgery.

Conclusions: The authors' data strongly suggest that CSF pathway reclosure is the factor most responsible for ETV failure in obstructive hydrocephalus. According to both their experiences and to studies published in the literature, the formation of new arachnoid membranes or scars plays a far greater role in ETV failure than does poor CSF absorption, at least in aqueductal stenosis. It is hypothesized that infants have a higher tendency to form new arachnoid membranes than do older patients and that this factor may explain (at least in part) the higher ETV failure rate in patients younger than 1 year old.