Control of dyskinesias due to sensory deafferentation by means of thalamic stimulation.

Intermittent stimulation of the parvocellular portion of the nucleus ventralis posterolateralis (V.P.L.) by means of chronically implanted electrodes and stimulus generator was performed in 124 patients for the control of chronic intractable pain. Among these, 11 showed spontaneous abnormal movements within the painful area: 6 post amputation "jumping stumps"; 4 pseudothalamic syndromes and 1 Von Benedikt's syndrome following a cerebrovascular accident. Electrical stimulation of the V.P.L. was able to control both pain and abnormal movements in all cases. The technique was applied with an equally good result in a case of choreoathetotic syndrome without pain but with severe sensory disturbances following a demyelinating process. Attempts made to control action tremor, parkinsonism and other dyskinesias not associated with sensory deafferentation in 12 cases failed. The same mechanism seems to be responsible for pain and dyskinesia in cases of sensory deafferentation, and thalamic stimulation might work as a substitute for sensory information delivered to the nucleus ventralis posterolateralis.