[Isolated trigeminal neuropathy involved with motor dysfunction due to small infarction in the pontine tegmentum].

We present a case of isolated trigeminal neuropathy involved with motor dysfunction due to a small infarction in the pontine tegmentum. A 70-year-old man presented with sudden numbness around the left mouth accompanied by maxillary pain. Neurological examinations revealed jaw deviation to the left when opening the mouth, but no other abnormal findings including those of the cranial nerves were detected. X-rays indicated hypomobility of the left temporomandibular joint, and diffusion-weighted magnetic resonance imaging (MRI) revealed a small infarction in the left pontine tegmentum. Unilateral limitation of the temporomandibular joint movement, numbness, and pain in the territory of the left trigeminal nerve resolved within 2 months. This case suggests that a small infarction in the pontine tegmentum can simultaneously cause trigeminal neuralgia and masticatory muscle weakness with no other symptoms and signs. MRI, especially diffusion-weighted imaging, should be considered for patients with isolated trigeminal neuropathy.