[Effect of diazepam on somatosensory evoked potentials]

Somatosensory evoked potentials (SEP) were recorded in 15 patients with extrapyramidal disturbances after intravenous administration of 10 mg of diazepam (Relanium, Polfa). Cortical SEP were recorded before and after operations and thalamic SEP were recorded during stereotaxic interventions on thalamic nuclei VL and Vim. The results demonstrated that diazepam had a significant positive influence on the recording of SEP, eliminating muscular artifacts caused by increased muscular tonus and extrapyramidal tremor. Diazepam had no evident effect on the SEP and caused no changes of the short-latency specific cortical SEP. This effect was, however, evident on the later components of the SEP and it seemed to affect mainly the N63 wave whose amplitude was always reduced or absent. In the postoperative investigations the cortical SEP in the hemisphere operated on (contralateral to the site of stimulation) were reduced in the phase of short-latency components. In the ipsilateral hemisphere the cortical SEP remained similar to the normal ones, and after diazepam their amplitude was markedly reduced. Intraoperatively recorded thalamic SEP showed after diazepam a considerable decrease of the amplitude of all components, sometimes the curve was completely flat, including the specific phase of the potential. On the other hand, diazepam failed to extinguish cortical SEP which showed even a greater amplitude of short-latency and long-latency components than in the records obtained without this drug, with the exception of disappearing N63 component.