Perineural invasion of sinonasal lymphoma: a rare cause of trigeminal neuropathy.

Trigeminal neuropathy is characterized by sensory disturbance of the division of trigeminal nerve, and sometimes is associated with pain. Trigeminal neuropathy secondary to perineural invasion of sinonasal lymphoma is extremely rare. Likewise, sinonasal lymphoma is infrequently demonstrated initially with cranial neuropathy. The present case served to broaden the differential diagnosis of secondary trigeminal neuropathy and to alert clinicians to cautiously assess perineural spread of occult neoplasm in sinonasal tract and larynx or pharynx for cases with evolving trigeminal neuropathy or even other cranial nerve neuropathy in which no definite cause is identified.