[A case of unilateral masticatory spasm without hemifacial atrophy].

Masticatory spasm is a rare clinical feature and mostly associated with disorders of general movement. Usually it occurs bilaterally. Unilateral masticatory spasm is mostly associated with facial hemiatrophy. So, unilateral masticatory spasm without facial hemiatrophy is extremely rare. As far as we have investigated, only one case has been reported in the literature. We will report one more case herein, with some discussion on its pathogenesis. Case report A 44-year-old man presented with a 8 month history of slowly progressive recurrent spasm of the left masseter muscle. The spasm was exaggerated by tension and lasted for up to 10 seconds. Several drugs could not reduce the frequency of spasm, but only clonazepam could decrease it slightly. On admission, the spasm lasted usually for 1 or 2 seconds. Except for masticatory spasm, neurological examination comprising trigeminal nerve function, was normal and facial atrophy was not observed. On the contrary, hypertrophy of the left masseter muscle was noted. Needle electromyography (EMG) study revealed synchronized spasm discharges of the ipsilateral masseter, lateral and medial pterygoid muscles. All of other investigations, including CSF analysis, electroencephalography, somatosensory evoked potential, visual evoked potential, CT scan and vertebral angiography, showed normal findings. After all, we could not find any apparent organic lesions which cause masticatory spasm, so surgical treatments were not carried out. He was discharged and now, continues to take clonazepam daily.(ABSTRACT TRUNCATED AT 250 WORDS)