This can result in cutting the facial nerve. For removal, the cerebellum is then gently elevated, the arachnoid is opened, and cerebrospinal fluid is allowed to drain. This allows exposure and visualization of the cerebellopontine angle with minimal retraction. Following placement of the self-retaining retractors, the operating microscope is positioned. Dissection along the facial and cochlear nerves is done with fine straight or curved microdissectors and sharp dissection is done with microscissors.
Dissection is alternated from different directions.
When the cochlear and facial nerves have been clearly seen, the vestibular nerves coming into the tumor are divided on both the medial and lateral aspects of the tumor. In some patients the lateral end of the tumor may not be exposed because of the limitation in bone removal. In these patients the tumor is transected near the end of the canal and the lateral extent of the tumor is removed. The facial nerve is identified in the lateral internal auditory canal at the transverse crest, and the superior and inferior vestibular and cochlear nerves are disarticulated from the lateral canal. Frequent facial nerve identification and stimulation for monitoring response is performed throughout the procedure.