A giant trigeminal schwannoma of the infratemporal fossa removed by transmandibular approach and coronoidectomy

Abstract

The whole spectrum of infratemporal fossa (IF) tumors comprises both intra- and extracranial tumors. Schwannomas are benign nerve tumors arising from the Schwann cells. Approximately 25%-45% of schwannomas occur in the head and neck region. The lesions commonly arise from the roots of cranial and cervical nerves in the parapharyngeal space, with the majority originating from the vagus nerve. Trigeminal schwannomas account for about 0.2% of all intracranial tumors, and 0.8% and 8% of intracranial schwannomas. Trigeminal schwannomas are commonly located in the intracranium. Exclusive extracranial trigeminal schwannoma are exceptional lesions that may also involve the maxillary sinus, the orbit, and the parapharyngeal space. Schwannomas of the head and neck can originate from any section of the fifth cranial nerve, from the root to the distal extracranial branches, but the majority develops at the Gasserian ganglion, usually growing in the middle cranium. Schwannomas arising primarily within the IF, without intracranial extension, are extremely rare. Many approaches were described for extracranial trigeminal schwannomas originating from the skull base, such as transmaxillary approach, or Le Fort I type I osteotomy, or facial translocation approach, or infratemporal approach, or transmandibular transcervical approaches. We present a case of voluminous extracranial schwannoma, arising from the extradural divisions of the trigeminal nerve, extending in the IF and parapharyngeal space, treated via a transmandibular approach. The literature regarding extracranial schwannomas of the IF and parapharyngeal space, and their approaches are reviewed.