Chronic motor cortex stimulation for phantom limb pain: a functional magnetic resonance imaging study: technical case report

Chronic motor cortex stimulation has provided satisfactory control of pain in patients with central or neuropathic trigeminal pain. We used this technique in a patient who experienced phantom limb pain. Functional magnetic resonance imaging (fMRI) was used to guide electrode placement and to assist in understanding the control mechanisms involved in phantom limb pain. A 45-year-old man whose right arm had been amputated 2 years previously experienced phantom limb pain and phantom limb phenomena, described as the apparent possibility of moving the amputated hand voluntarily. He was treated with chronic motor cortex stimulation. Data from fMRI were used pre- and postoperatively to detect shoulder and stump cortical activated areas and the "virtual" amputated hand cortical area. These sites of preoperative fMRI activation were integrated in an infrared-based frameless stereotactic device for surgical planning. Phantom limb virtual finger movement caused contralateral primary motor cortex activation. Satisfactory pain control was obtained; a 70% reduction in the phantom limb pain was achieved on a visual analog scale. Postoperatively and under chronic stimulation, inhibiting effects on the primary sensorimotor cortex as well as on the contralateral primary motor and sensitive cortices were detected by fMRI studies. Chronic motor cortex stimulation can be used to relieve phantom limb pain and phantom limb phenomena. Integrated by an infrared-based frameless stereotactic device, fMRI data are useful in assisting the neurosurgeon in electrode placement for this indication. Pain control mechanisms and cortical reorganization phenomena can be studied by the use of fMRI.