Prior CSF shunting increases the risk of endoscopic third ventriculostomy failure in the treatment of obstructive hydrocephalus in adults

Introduction: Endoscopic third ventriculostomy (ETV) is accepted as an effective treatment for obstructive hydrocephalus (OHC); however, its benefit in patients previously treated with cerebrospinal fluid (CSF) shunting remains unclear. The value of concurrent ETV and ventriculoperitoneal (VP) shunting in patients with frequent shunt failure remains unstudied. Methods: Outcomes were compared between OHC patients receiving ETV as initial CSF diversion treatment (n = 19) versus OHC patients receiving ETV for shunt failure (n = 11) by log-rank analysis and Kaplan-Meier plots of recurrence-free periods. To determine if the performance of ETV with concurrent shunt revision decreased the incidence of catastrophic treatment failure in patients experiencing frequent and emergent shunt failures (n = 8), the time to treatment failure after ETV and shunt revision was compared with the mean duration of their previous CSF shunts. Results: ETV after shunt failure was 2.5-fold more likely to fail [risk ratio (RR): 2.48, p<0.05] versus ETV as initial CSF diversion treatment for OHC. Following ETV as initial CSF diversion treatment, 17 patients (89%) experienced immediate improvement and 65% remained recurrence-free at year 2. Following ETV after shunt failure, 16 patients (71%) experienced immediate improvement, but only 25% remained recurrence-free at year 2. In patients with a history of multiple shunt revisions and complications, concurrent use of ETV and VP shunt did not significantly decrease treatment failure. However, the incidence of catastrophic shunt failure requiring acute intervention decreased (43% versus 17%). Conclusion: In our experience with ETV for OHC, prior CSF shunting in patients with obstructive hydrocephalus was associated with the decreased time to treatment failure following conversion to ETV. ETV may be less effective for the treatment of OHC in previously shunted patients. ETV combined with concurrent CSF shunting may be an important strategy to prevent catastrophic treatment failure in OHC patients with a history of multiple shunt revisions and complications.