Hearing preservation in medial vestibular schwannomas.

OBJECT

Vestibular schwannomas (VSs) with no or little extension into the internal auditory canal have been addressed as a clinical subentity carrying a poor prognosis regarding hearing preservation, which is attributed to the initially asymptomatic intracisternal growth pattern. The goal in this study was to assess hearing preservation in patients who underwent surgery for medial VSs.

METHODS

A consecutive series of 31 cases in 30 patients with medial VSs (mean size 31 mm) who underwent surgery between 1997 and 2005 via a suboccipitolateral route was evaluated with respect to pre- and postoperative cochlear nerve function, extent of tumor removal, and radiological findings. Intraoperative monitoring of brainstem auditory evoked potentials was performed in all patients with hearing. Patients were reevaluated at a mean of 30 months following surgery.

RESULTS

Preoperative hearing function revealed American Academy of Otolaryngology-Head and Neck Surgery Foundation Classes A and B in 7 patients each, Class C in 4, and D in 9. Four patients presented with deafness. Hearing preservation was achieved in 10 patients (Classes A-C in 2 patients each, and Class D in 4 patients). Tumor removal was complete in all patients with hearing preservation, except for 2 patients with neurofibromatosis. In 4 patients a planned subtotal excision was performed due to the individual's age or underlying disease. In 1 patient a recurrent tumor was completely removed 3 years after the initial procedure.

CONCLUSIONS

The cochlear nerve in medial VSs requires special attention due to the atypical intracisternal growth pattern. Even in large tumors, hearing could be preserved in 37% of cases, since the cochlear nerve in medial schwannomas may not exhibit the adherence to the tumor capsule seen in tumors with comparable size involving the internal auditory canal.