Chronic motor cortex stimulation for central deafferentation pain: experience with bulbar pain secondary to Wallenberg syndrome.

Six patients with bulbar pain caused by lateral medullary infarct were treated by stimulation therapy. Dysesthesia on the opposite side of the body was subjected to stimulation therapy in these patients. Of the subjects, 4 underwent thalamic stimulation and 3 were treated by motor cortex stimulation; the effects of both thalamic and motor cortex stimulation were investigated in 1 patient. No satisfactory pain control was obtained by thalamic stimulation in any of the patients in this series. In contrast, 2 of the 3 patients treated by motor cortex stimulation reported satisfactory pain control. The pain inhibition usually occurred at intensities below the threshold for the production of muscle contraction (pulse duration, 0.1-0.5 ms; intensity, 3-8 V). This finding was consistent with our previous observations made in a series of patients with thalamic pain, indicating that motor cortex stimulation is significantly more useful than thalamic stimulation for controlling deafferentation pain secondary to central nervous system lesions. We discuss the possibility that better control of deafferentation pain may be provided by stimulation at a level more rostral to the site of deafferentation.