Brain stimulation.

Electrical stimulation in the PAG has been shown to elicit profound analgesia in experimental animals that is at least in part due to the release of endogenous opioid substances. Electrical stimulation in the thalamic nuclei VPL and VPM inhibits the activation of spinal dorsal horn neurons by noxious stimuli. Acute electrical stimulation in these two targets relieves chronic pain in about 80% of patients. Chronic electrical stimulation by permanently implanted electrodes relieves pain in about 70% of patients with pain of peripheral or nociceptive origin but in only about 50% of patients with central pain resulting from deafferentation. Stimulating electrodes are implanted stereotactically by a burr hole under local anesthesia. Transient complications occur in 15% to 25% of patients and include infections, malfunctions of the stimulating hardware, pain at the implant sites, and mild temporary neurologic deficits. Permanent complications, including hemiparesis, intracranial hemorrhage, and death, occur in 1% to 2% of patients. Brain stimulation is recommended for the treatment of chronic pain in patients in whom other forms of treatment have failed. The technique is reasonably safe and provides pain relief for a group of patients who have exhausted all other therapeutic modalities. Unfortunately, not all patients receive effective pain relief with brain stimulation. Other stimulation targets such as the K-F nucleus in the parabrachial region of the brain stem are currently being explored in an attempt to provide pain relief to a greater proportion of patients. In addition, improvements in stimulation hardware have made the technique easier and more effective.