In 1991 Tsubokawa and colleagues first published their landmark results from a series in which epidural motor cortex stimulation (MCS) was used in the treatment of eight patients with central and
neuropathic pain. In ensuing studies authors have elaborated on the indications, technique, hypotheical mechanisms, and beneficial results of this treatment. Epidural MCS is effective for
trigeminal neuropathy, lateral medullary and thalamic
infarction,
anesthesia dolorosa,
postherpetic neuralgia,
spinal cord injury, and limb stump
pain. Postoperative outcomes are better when patients present with only mild or absent motor weakness in the region of
pain and when there is
pain in the trigeminal region. It is hypothesized that MCS is effective because it increases regional cerebral blood flow in the ipsilateral ventrolateral thalamus in which corticothalamic connections from the motor and premotor areas predominate. The extent of
pain alleviation also correlates with the increase of blood flow in the cingulate gyrus. This suggests that stimulation reduces the suffering experienced by a patient with
chronic pain. Procedure-related morbidity has included epidural
hematoma, subdural effusion, gradual diminution of benefit, and painful stimulation. Although of concern, treatment-induced chronic
seizure disorders have not occurred as a complication or in animal models of chronic cortical stimulation. Stimulation-induced
pain relief occurs within minutes. There are no associated
paresthesias or muscle contractions that confirm function.
Pain relief may last for hours after electrical stimulation is discontinued. Motor cortex stimulation is an established
therapy for the treatment of complex central and
neuropathic pain syndromes that have proved refractory to medical treatment.