Motor cortex stimulation for central and peripheral deafferentation pain -Report of eight cases

The authors tested a modified motor cortex stimulation protocol for treatme nt of central and peripheral types of deafferentation pain. Four patients w ith thalamic pain and four with peripheral deafferentation pain were studie d. Preoperative pharmacological tests of pain relief were performed using p hentolamine, lidocaine, ketamine, thiopental, and placebo. In five patients we placed a 20- or 30-electrode grid in the subdural space to determine th e 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 procedur e to treat lower-extremity pain. In two patients with pain extending from t he 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 ap parent between pharmacological test results and the effectiveness of motor cortex stimulation. Patients with peripheral deafferentation pain, includin g two with phantom-limb pain and two with brachial plexus injury, attained pain relief from motor cortex stimulation, with excellent results in two ca ses. Testing performed with a subdural multiple-electrode grid was helpful in locating the best stimulation point for pain relief. Motor cortex stimul ation may be effective for treating peripheral as well as central deafferen tation pain.