The authors tested a modified motor cortex stimulation protocol for treatment of central and peripheral types of
deafferentation pain. Four patients with thalamic
pain and four with peripheral
deafferentation pain were studied. Preoperative pharmacological tests of
pain relief were performed using
phentolamine,
lidocaine,
ketamine,
thiopental, and placebo. In five patients we placed a 20- or 40-electrode grid in the subdural space to determine the best stimulation point for
pain relief for a few weeks before definitive placement of a four-
electrode array. In three patients, the four-
electrode array was implanted in the interhemispheric fissure as a one-stage procedure to treat lower-extremity
pain. In two patients with
pain extending from the extremity to the trunk or hip, dual devices were implanted to drive two
electrodes. Six of eight patients experienced
pain reduction (two each with excellent, good, and fair relief) from motor cortex stimulation. No correlation was apparent between pharmacological test results and the effectiveness of motor cortex stimulation. Patients with peripheral
deafferentation pain, including two with
phantom-limb pain and two with brachial plexus injury, attained
pain relief from motor cortex stimulation, with excellent results in two cases. Testing performed with a subdural multiple-
electrode grid was helpful in locating the best stimulation point for
pain relief. Motor cortex stimulation may be effective for treating peripheral as well as central
deafferentation pain.