[Disturbance of jaw-opening due to extension of syringobulbia to the pons--a case report].

We report a patient with syringobulbia extending to the pons, who could not open his mouth widely. He had been involved in the traffic accident at 16 years of age. Since them he had suffered numbness in the left neck and arm. At age 30, he became unable to open the mouth widely with pain in the left jaw joint. He also noted dysphagia and tinnitus. Neurologically, there were vocal cord paresis, dysesthesia of the face, ageusia and cerebellar ataxia all on the left side. Brain MRI revealed syringobulbia which extended to the pons. Spinal MRI revealed syringomyelia through the entire spinal cord. The syrinx of the spinal cord seemed to connect with the brainstem lesion. EMG of the masticatory muscles revealed paradoxical activity in the left masticatory muscles. We concluded that disturbance of jaw-opening in this case was caused by syringobulbia, the lesion of which could involve masticatory central pattern generator in the brainstem.