Trigeminal neurinomas with extracranial extension: analysis of 28 surgically treated cases

Abstract

Object The object of this paper was to review the authors' experience with 28 cases of trigeminal neurinomas having an extracranial extension. Methods The authors analyzed 28 cases of trigeminal neurinoma in which there was an extracranial extension of the tumor. All patients were treated in their department between the years 1989 and 2009. Results There was tumor extension along the ophthalmic division of the nerve in 4 cases, along the maxillary division in 5, and along the mandibular division in 13. In 6 tumors there was diffuse extracranial extension and the exact extracranial division of nerve involvement could not be ascertained. In 10 cases, the tumor had a multicompartmental location—in the posterior fossa, the middle fossa, and the extracranial compartment. Tingling paraesthesiae, numbness, and diffuse pain in the distribution of the trigeminal nerve were common symptoms and were present in 90% of patients. The extracranial component had a well-defined perineural/meningeal membrane cover that was continuous with the middle fossa dura mater and isolated the tumor tissue from the adjoining critical structures. In 7 out of 10 cases, even the posterior fossa component of the tumor was entirely “interdural” (within the confines of the dura). The maximum dimension of the tumor was > 4 cm in 22 cases. A limited “transcranial” approach with (12 cases) or without (16 cases) zygomatic osteotomy was found suitable for resection of these tumors. In 4 cases a lateral orbitotomy was performed. Total tumor resection was performed in 20 cases and partial resection in 8. The duration of follow-up ranged from 6 months to 19 years. Two patients required additional surgery for symptomatic recurrence. Conclusions Extracranial extensions of trigeminal neurinomas have a well-defined meningeal covering. In most cases resection was performed via a minimally invasive cranial avenue (a “reverse skull base approach”). Radical resection was associated with an excellent long-term outcome.