Functional Preservation Rate of Facial Nerve after Excision of Giant Vestibular Schwannomas following Two Different Surgical Techniques

Background Excision of giant vestibular schwannomas with preservation of facial nerve function remains a surgical challenge.

Methods We present our results describing the extent of excision achieved and the rates of functional preservation of seventh nerve utilizing two different surgical techniques. A total of 115 patients were operated from 2002 to 2009 (Group A) and 100 patients were operated from 2010 to 2016 (Group B). In both groups, patients were operated in supine position. In Group A, the standard surgical technique was used for facial nerve dissection. After intratumoral decompression, the lower cranial nerves were carefully separated from the lower pole. Also, the anterior inferior cerebellar artery loop was identified and dissected from the arachnoid covering the tumor. The seventh and eighth nerve complex was identified by locating the root entry zones of the lower cranial nerves, the flocculus, and the choroid plexus at the foramen of Luschka. At the meatal end, drilling was done to identify the normal seventh and eighth nerve complex and the tumor was dissected away. In Group B, a complete extra-arachnoid dissection was done by remaining intratumoral throughout the dissection. No attempt was made to dissect or visualize the lower cranial nerves. Similarly, no attempt was made to identify the seventh and eighth nerve complex. Intratumoral dissection was performed and at no stage was the plane of dissection outside the arachnoid layers. In patients with no or minimal (<2 mm) intrameatal extension, the meatus was not drilled. With intrameatal tumor extensions, more than 2 mm, a limited metal drilling was preformed. The arachnoid layers were preserved in the meatus also.

Results In Group A, total/near-total excision was achieved in 95% of patients. Good functional preservation of seventh nerve was possible in 59% of patients. In Group B, total/near-total excision was possible in 85% of patients and good facial nerve function was preserved in 87% of patients. Fifteen percent of patients received gamma knife and two had to be reoperated.

Conclusion Complete extra-arachnoidal dissection and limited meatal drilling resulted in better functional outcome.