Behavior of Residual Tumor in Vestibular Schwannoma Surgery—Does Functional Preservation Justify Leaving Behind Tumor Remnants?

Introduction: During 1994 to 2003, 615 vestibular schwannomas were operated according to the “Würzburg concept.” This concept consists of an interdisciplinary approach using the joint expertise of the ENT surgeon and neurosurgeon during the same operation. In 89 cases (14%) some residual tumor had to be left behind.

Material and Methods: All tumors were removed under multimodal cranial nerve monitoring (AEPs, trigeminal, and facial EMG). Caudal cranial nerve monitoring was used if the tumor extension reached nerve IX, X, XI, or XII. The patients were followed up clinically and the tumor remnants were monitored by MRI. Clinical records and operation reports were reviewed for the reasons of subtotal removal and to determine the radiological behavior of residual tumor and its clinical consequences.

Results: The main reasons for subtotal removal were: strong adherence to the cranial nerves (especially acoustic and facial); interfascicular growth pattern; drop of EMG or acoustic evoked potentials working directly at the cranial nerves or close to them; strong adherence to the brainstem; or excessive scarring due to previous operations/treatments. Most of the tumor remnants consisted of residual capsula or a thin tumor layer. Gross total resection was the absolute exception; 53 (59.6%) showed no progression; 4 (4.5%) had progressive tumor without clinical and operative consequence; 8 (9%) had to be operated again; and 24 (26.9%) were lost to follow-up.

Conclusions: The low percentage of tumor progression with an even lower necessity to operate again seems to justify leaving some tumor behind. In some cases the tumor and the fragile vascular and electrophysiological condition of the cranial nerves force the surgeon to terminate the procedure in order to preserve neural function. The above data support the concept “function before radicality.”