Motor cortex stimulation in patients with post-stroke pain: conscious somatosensory response and pain control.
We analyzed the conscious sensory responses to cortical stimulation of 31 patients with post-stroke pain who underwent motor cortex stimulation (MCS) therapy. During surgery for electrode placement, a sensory response (tingle projected to a localized peripheral area) was elicited by high-frequency stimulation (50 Hz) in 23 (84%) from the somatosensory cortex, and in 16 (52%) from the motor cortex without muscle contraction. Unpleasant painful sensation was induced or their original pain was exacerbated in 12 patients (39%) when the somatosensory cortex was stimulated and in two (6%) when the motor cortex was stimulated. Somatosensory responses were induced in eight (25%) even by low-frequency stimulation (1-2 Hz) of the motor cortex at an intensity below the threshold for muscle contraction. In contrast, among 20 nonpain patients who underwent a similar procedure for cortical mapping in epilepsy or brain tumor surgery, a sensory response was produced by high-frequency stimulation in only eight (40%; p < 0.02) from the somatosensory cortex and four (20%; p < 0.03) from the motor cortex. Pain sensation was not induced by stimulation of the somatosensory cortex (p < 0.002) or motor cortex in any of these patients. In addition, none of these patients reported a sensory response to low-frequency stimulation. In both of the two post-stroke pain patients who reported abnormal pain sensation in response to stimulation of the motor cortex, MCS failed to control their post-stroke pain. These findings imply that the sensitivity of the perceptual system even to activity of the motor cortex is heightened in post-stroke pain patients, which can sometimes hinder pain control by MCS.
Fukaya
Chikashi
C
Department of Neurological Surgery, Nihon University School of Medicine, Tokyo 173-8610, Japan. chikashi@tb3.so-net.ne.jp
Katayama
Yoichi
Y
Yamamoto
Takamitsu
T
Kobayashi
Kazutaka
K
Kasai
Masahiko
M
Oshima
Hideki
H
D003243:Consciousness; D004599:Electric Stimulation Therapy / Q000379:methods*; D004567:Electrodes, Implanted; D006801:Humans; D009044:Motor Cortex / Q000502:physiology*; D010146:Pain / Q000209:etiology; D059408:Pain Management; D010147:Pain Measurement; D017060:Patient Satisfaction; D012189:Retrospective Studies; D013003:Somatosensory Cortex / Q000502:physiology*; D020521:Stroke / Q000150:complications*