Abstract
Summary: A quantitative electromyographic study of rigidity in 20 Parkinsonian patients demonstrated that the stretch reflex in biceps was more affected than that of triceps, and of hamstrings more than quadriceps.Increasing disability from Parkinsonian rìgìdity was found to be associated with a lowered sensitivity of the stretch reflex to the dynamic phase of stretch and an increase in the static response to maintained stretch. Treatment with L‐dopa for six months reversed this pattern in extensor muscles much more readily than in flexor muscles. Since animal experiments have shown that L‐dopa diminishes the fusimotor activity of dynamic flexor muscles by its action on the spinal cord, and that the spinal action of L‐dopa can be blocked by phenoxy‐benzamine, the latter agent has been used in Parkinsonian patients who were under treatment with L‐dopa.Phenoxybenzamine was given to five Parkinsonian patients intravenously and one patient orally. In all patients the dynamic sensitivity of the stretch reflex in flexor muscles improved and rigidity was diminished. Three patients treated with oral phenoxybenzamine showed subjective and objective clinical improvement. This study suggests that the effect of L‐dopa on the spinal cord limits its effectiveness in the treatment of Parkinson's Disease and that this undesirable action may be eliminated by the concomitant use of phenoxybenzamine.
Published Version
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