[Reflex reaction in the abductor pollicis brevis muscle after mechanical and electrical stimulation in patients with central hemiparesis and Parkinsonism. Electromyographic study].

The reflex responses in the abductor pollicis brevis muscle were examined in 22 patients with mild central hemiparesis and in nine patients with Parkinson's disease. In the group of patients with central hemiparesis there were 15 subjects with a spastic and seven subjects with a flaccid type of affection. The reflex responses in the abductor pollicis brevis muscle were evoked during isometric contraction. The recorded muscular potentials were unidirectionally rectified and averaged. The reflex responses were then identified as excitatory and inhibitory modulations of basal activity of the muscle after the evoking stimulus. The reflexes were evoked by percussion with a hammer on the lateral area of the base of the distal digit of the thumb, by electrical stimulation of the median nerve on the wrist and by electric stimulation of the cushion of the thumb and the superficial radial nerve on both sides. On the side of the spastic or flaccid central hemiparesis the long-latency parts of the reflex responses after percussion on the distal digit of the thumb and after electrical stimulation of the median nerve were either not elicitable or had a lower amplitude than on the non-paretic extremity. In three subjects on the affected side also the of long-latency part of the reflex response was prolonged after percussion of the distal digit of the thumb. The short-latency parts of the reflex response on the side of the spastic hemiparesis were more expressed, contrary to the finding on the side with the flaccid hemiparesis where suppressed.(ABSTRACT TRUNCATED AT 250 WORDS)