[A case of chronic toluene intoxication presenting stimulus-sensitive segmental spinal myoclonus]

We reported a 48-year-old male who showed stimulus-sensitive spinal myoclonus due to chronic toluene intoxication. He has been exposed to thinner for more than 30 years as a painter, and occasionally experienced an episode of headache, nausea and dizziness because of acute thinner intoxication. He noted tremor of his hands 10 years ago. He also noticed memory disturbance since the end of 1997. Neurological examination revealed postural tremor of his fingers on the bilateral sides and the left arm. In addition, rhythmic myoclonic jerks were induced in the right upper limb muscles by a tendon tap given on the right brachioradialis muscles. Surface EMG revealed repetitive grouping discharges in those two muscles approximately 100 msec after the tendon tap which continued for about 30-50 msec. A long loop reflex (C-reflex) and giant SEPs were not observed in his right upper limb, and EEG showed no spike. Urinary excretion of N-benzoylglycine, which was a metabolite of toluene was increased (1.17 g/l). Therefore, he was diagnosed as a case of chronic toluene intoxication. His myoclonic jerks were considered to be stimulus-sensitive spinal myoclonus, because they were induced segmentally and because cortical hyperexcitability was not seen. This is the first report to describe the occurrence of stimulus-sensitive spinal myoclonus in the case of chronic toluene intoxication.