LONG-LATENCY RESPONSES IN PURE SENSORY STROKE DUE TO THALAMIC INFARCTION

Objectives - Our study was designed to clarify the role of the thalamu s in the generation of the electrically elicited long-latency reflexes (LLR) in voluntarily activated hand muscles. Materials and methods - EMG responses of the thenar muscles were evoked by electrical stimulat ion of the median nerve at the wrist at motor threshold intensity in 1 0 patients with acute pure sensory stroke due to thalamic infarction. Concomitant recording of somatosensory evoked potentials (SEPs) was pe rformed. The subjects were asked to steadily abduct the thumb at 20-30 % of maximal force against a force transducer. Rectified and averaged EMG activities were recorded. Results - The LLR II was missing complet ely or significantly attenuated in the majority of the patients (9 of 10), of whom 3 also had delayed latency. Abnormal SEPs were documented in 7 patients (7 of 10). In the follow-up, 5 patients had partial rev ersal of LLR II. LLR II was still pathological in 1 fully recovered pa tient. Conclusion - Our results further confirm the transcortical gene ration of LLR II and imply that a thalamic relay is present in the aff erent limb of the LLR.