Temporomandibular joint cyst presenting as trigeminal neuropathy and middle fossa mass: case report

We describe the case of a temporomandibular joint cyst eroding into the middle fossa, initially causing compression of the trigeminal nerve and trigeminal neuropathy, and ultimately causing destruction of the second division of the nerve with facial numbness.

A 50-year-old woman with rheumatoid arthritis on prednisone developed right-sided, initially lancinating facial pain that ultimately became dull in nature in the maxillary division of the trigeminal nerve. This change in pain was associated with the development of numbness in the same distribution. The facial pain gradually resolved, but the facial numbness persisted. Imaging revealed a heterogeneously enhancing mass in the middle fossa lateral to Meckel's cave.

During surgery, the dura was elevated, and a smooth, firm lesion with several thinly encapsulated, cystic areas containing viscous, white fluid was identified. The mass had eroded through the floor of the middle cranial fossa. The thick, fibrous capsule was freed from the bone edges and was sectioned sharply extracranially. Pathological evaluation was consistent with a cyst originating from the temporomandibular joint.

Extracranial mass lesions involving the middle fossa structures are uncommon and typically arise from the parotid gland. This case represents the first example of a middle fossa mass originating from an abnormal temporomandibular joint and a unique cause of trigeminal neuropathy. After excision, there has been no recurrence after 2 years of follow-up.