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A 34-year-old man presented with a 3-month history of progressive, unilateral lower lip and chin numbness and ipsilateral facial fullness. The hypoesthesia was limited to the distribution of the mandibular branch of the left trigeminal nerve (V3). On review of systems, the patient denied experiencing visual changes, dizziness, headaches, oral or neck pain, voice changes, weight or appetite changes, or swallowing dysfunction; however, he did report biting his lip occasionally due to the numbness. On examination, there were no palpable masses noted in the head, neck, or face. Aside from the V3 sensory deficit, the patient had no cranial nerve deficits. The patient had no significant medical history; prior surgical history was notable for tonsillectomy. Magnetic resonance imaging of the face revealed a T1 isointense, T2 hyperintense 5.9-cm lesion in the left masticator space, which appeared to be centered in the lateral pterygoid muscle with benign-appearing remodeling of the posterior maxillary wall (Figure).
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The mass lesion appears isointense on T1-weighted magnetic resonance imaging, while contrast-enhancing and hyperintense on the T2-weighted sequence, which is suggestive of a nerve sheath tumor. Chondrosarcomas also typically present as T1 isointense and T2 hyperintense lesions, but they are usually characterized by spotty calcifications on computed tomographic (CT) imaging, which was not seen in this patient. Juvenile angiofibromas usually occur in adolescent males and appear hypointense on T2. Keratocystic tumors are typically hyperintense on T1. In this case, the lesion was biopsied under CT guidance, and histology revealed a benign schwannoma.
Schwannomas are uncommon neoplasms of the nerve sheath that are rarely malignant.1 The incidence of intracranial nerve sheath tumors approximates to 1.1 per 100 000 person-years, of which an overwhelming majority (89%) are benign schwannomas.2 After vestibular schwannoma, trigeminal schwannoma is the most common and comprises 0.8% to 10% of intracranial schwannomas and 0.07% to 0.5% of intracranial tumors broadly.1,3 Trigeminal schwannomas most commonly arise near the gasserian ganglion in the middle cranial fossa but can also occur along the root and sensory branches. A rare entity, the epidemiology of extracranial trigeminal schwannomas is poorly characterized. As with other skull-base lesions, treatment typically involves surgical resection and sometimes adjuvant radiosurgery.4,5
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Corresponding Author: Alexandra T. Bourdillon, BS, Section of Otolaryngology, Department of Surgery, Yale School of Medicine, 333 Cedar St, New Haven, CT 06510 (email@example.com).
Published Online: July 2, 2020. doi:10.1001/jamaoto.2020.1100
Conflict of Interest Disclosures: None reported.
Additional Contributions: We thank the patient for granting permission to publish this information.
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