Motor Cortex Stimulation

Abstract

In 1991 Tsubokawa first published his early results in the treatment of medically intractable central pain by epidural motor cortex stimulation. Since then a number of reviews have elaborated on the optimal indications, surgical technique, degree of pain relief achievable, and mechanism of effectiveness. Pain syndromes that have been treated by motor cortex stimulation in published series include central pain secondary to stroke, trigeminal deafferentation pain including postherpetic neuralgia and anesthesia dolorosa, peripheral deafferentation pain syndromes such as brachial plexus or sciatic nerve injury, complex regional pain syndrome, pain associated with spinal cord injury, and phantom limb and stump pain. Good to excellent pain relief has been achieved in 75 to 77% of patients after 2-year follow-up. However, when motor weakness is associated with the painful region, pain relief is achievable in only 15% of patients. Positron emission tomography studies show that cortical stimulation increases blood flow in the ipsilateral ventral lateral thalamus, cingulate gyrus, insula, and brainstem. The presence of increased blood flow in the cingulate1 gyrus suggests that motor cortex stimulation improves the suffering component of chronic pain. Observations of increased blood flow in the motor thalamus add to the hypothesis that thalamic hyperactivity secondary to deafferentation is inhibited. Motor cortex stimulation is clinically effective at thresholds below that of motor activation. Tolerance has not been seen. The best results have been achieved in patients with facial neuropathic pain. Further prospective studies are needed to more fully determine indications, optimal surgical technique, and long-term benefit from treatment.