[Malignant lymphoma in a perineural spreading along trigeminal nerve, which developed as trigeminal neuralgia]

A rare cause of trigeminal neuralgia is malignant lymphoma which spread along the trigeminal nerve. We report a 79-year-old male presented with 4-month history of neuralgic pain in right cheek. He was diagnosed as classical trigeminal neuralgia. It had improved through medication of carbamazepine. Four months later, the dull pain unlike neuralgia complicated on the right cheeks, it was ineffective with the medication. Furthermore, diplopia and facial palsy as the other cranial nerve symptoms appeared. Gadolinium-enhanced magnetic resonance imaging (MRI) revealed contrast-enhanced mass lesion extend both external pterygoid muscle and brainstem through the swelling trigeminal nerve. The patient was pathological diagnosed of diffuse large B cell lymphoma by biopsy. Malignant lymphoma should be considered in the different diagnosis of cases with a minimal single cranial nerve symptom.