gms | German Medical Science

Objective: To analyze risk factors for developing a cerebrospinal fluid (CSF) fistula after vestibular schwannoma (VS) surgery through the retrosigmoid transmeatal approach and to assess the potential role of the endoscope assisted sealing of the drilled inner auditory canal (IAC) in reducing the incidence of CSF leaks.

Methods: 238 patients were included in a historical control study. All patients were operated for VS via the retrosigmoid transmeatal approach in our Neurosurgical Department. The patients were divided into two groups. The selection criterion was the point in time of introducing the technique of endoscope assisted closure of the drilled IAC. Patients in group A (n=138) underwent a microscopic closure of the opened IAC with muscle and fibrin glue, while patients in group B (n=100) underwent an endoscope-assisted closure with bone wax, muscle and fibrin glue. Patients’ charts, operating reports, imaging studies (MRI, thin slice bone window CT scans) and follow-up records were analyzed. A horizontal line dividing the IAC perpendicular to its longitudinal axis at its midpoint graduated the pneumatization of the IAC in two categories: P1 (solid medial half of the IAC) and P2 (pneumatized medial half of the IAC).

Results: 16 CSF fistulas occurred in group A (11,6%), one in group B (1%). The difference is significant (p < 0.001). A pneumatization P2 was present in 32% of cases in group A and in 31% of cases in group B. No difference of the extent of pneumatization was noted regarding gender or side of the tumor. In group A the extent of pneumatization P2 was associated with a significantly higher risk of suffering a postoperative rhinoliquorrhea compared to P1 (p<0.001). In group B in 96 patients the IAC was opened and in 36 sealed with bone wax, muscle and fibrin glue under endoscopic visualization. Postoperative thin slice bone window CT scan demonstrated opening of air cells at the level of the IAC in 37 cases. All cases were initially treated with a lumbar CSF drainage for 7 days. In 15 patients in group A and in the single case in group B this procedure was successful. One patient in group A needed revision surgery to stop the rhinoliquorrhea (0,7%). No infection occurred.

Conclusion: The extent of pneumatization of the IAC is the determining risk factor for a postoperative CSF fistula in the retrosigmoid transmeatal approach. The endoscope-assisted sealing of the drilled IAC seems to significantly reduce the incidence of rhinoliquorrhea in VS surgery.