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In both Minamata disease (MD) and HTLV-I associated myelopathy (HAM), sensory disturbance is one of the most characteristic clinical symptoms. We have examined median nerve SSEPs (MN-SEP) and posterior tibial nerve SEPs (PTN-SEP) of both patient groups, and reported their specific abnormalities. MN-SEP of MD patients never showed any conduction delay nor conduction block at the cervical cord. However, they demonstrated the initial positive cortical response with low amplitude instead of the initial negative response (N20) seen in healthy subjects. In PTN-SEP, MD patients showed the initial positive cortical response with significantly shorter latency and lower amplitude than healthy subjects. These findings have never been seen in any other diseases. On the other hand, the conduction delay and conduction block on peripheral nerve, spinal cord and/or intracranial sensory tracts have been demonstrated in many cases with HAM. The patient was a 60-year-old man. About 40 years ago, he suffered with typical clinical symptoms of MD such as cerebellar ataxia, intention tremor and sensory disturbance of upper and lower extremities, and then his condition was complicated with progressive spastic paraplegia and urinary bladder dysfunction since 30 years ago. Both MN-SEP and PTN-SEP were studied so that we could make the electrophysiological differential diagnosis of MD and HAM. His MN-SEP indicated both the conduction delay at his cervical cord and intracranial sensory tract and the initial positive potential from cephalic recording. Furthermore, his PTN-SEP demonstrated severe conduction block at the spinal cord and neither cervical response (N28) nor cortical response (P37) was evoked. In conclusion, the clinical electrophysiologic studies supported our notion that the case might be affected with both MD and HAM.

The patients belonged to three different families and were products of consanguineous marriage. The neurological symptoms and signs in these patients began in infancy or childhood and included gait disturbance, horizontal nystagmus, distention tremor of the hands, muscular wasting and sensory impairment of the hands and legs. CT-scan and/or MRI showed atrophy of the cerebellum. Serum biochemical analyses revealed hypoalbuminemia with hyperlipidemia. There were no abnormalities in the heart, liver, kidney, gastrointestinal tract, or endocrine systems. The autopsy revealed degenerative changes in the spinal cord including posterior column and lateral pyramidal tract, as well as in the peripheral nerves and cerebellar cortex. Although we have speculated that the disease presented here would be a clinical variants of Friedreich's disease, it would make a new clinical entity because there was no report about the association to hypoalbuminemia and hyperlipidemia with spinocerebellar degeneration.

By using a transparent digitizer and a personal computer, we tried a quantitative analysis of ataxia in the upper limbs. A total of 25 upper extremities of 13 patients with spino-cerebellar degeneration (SCD) and 140 upper extremities of 70 normal volunteers were tested by two types of tasks. One was the free speed trace of a circle presented on the display (free circle), and the other was the pursuit of a target moving on a circle at a fixed speed (pursuit circle). The digitizer was put on a color display stabilized horizontally. For 1024 points with a 25 msec sampling time, the trajectory of the stylus pen was transmitted to the computer in real time. Circle diameters of 3 cm and 6 cm were selected. The target rounded the circle at a speed of 6 or 3 times per 1024 points. The mean velocity (MV), mean acceleration (MA), and MA/MV ratio were calculated for the extent of one circle period. And the coefficient of variation (CV) of the shifted distance in each sampling time and the power spectrum by Fast Fourier Transform (FFT) to the acceleration wave were calculated for the total input data. In the free circles, the MV and logarithm of MA varied widely and showed positive correlations. In contrast, those of the pursuit circles converged narrowly near the values of the target. On the other hand, in the SCD group, many patients could not draw the small free circle.(ABSTRACT TRUNCATED AT 250 WORDS)