A Cranio-Orbital-Zygomatic Approach to Dumbbell-Shaped Trigeminal Neurinomas Using the Petrous Window

Abstract

We applied a cranio-orbital-zygomatic approach that extends the temporal craniotomy more posteriorly and minimizes the frontal orbitotomy of an ordinary orbitozygomatic approach in order to provide wide access to the already eroded petrous apices along the long axis of trigeminal neurinomas. We treated seven dumbbell-shaped trigeminal neurinomas between 1991 and 1998 (mean follow-up, 38 months; range, 9 to 109 months). The configuration of the tumor mass was assessed on magnetic resonance imaging by measuring its long diameter in the middle and posterior fossae and the width of petrous erosion. Tumors were then classified into five types based on their distribution over the petrous ridge. Total removal was achieved in six patients, who showed no evidence of tumor recurrence during the follow-up period. The only major complication was one case of anesthesia dolorosa. The one patient with a subtotal removal developed a recurrence 12 months after surgery, in the posterior fossa. The cranioorbital-zygomatic approach could be an effective method for removing dumbbell-shaped trigeminal neurinomas, particularly in cases of wide petrous erosion from the tumor. If, however, the tumor has a larger posterior fossa component, this approach may not provide adequate exposure to achieve a total resection.