Motor cortex stimulation in patients with deafferentation pain: activation of the posterior insula and thalamus.
OBJECTIVE
The mechanisms underlying deafferentation pain are not well understood. Motor cortex stimulation (MCS) is useful in the treatment of this kind of chronic pain, but the detailed mechanisms underlying its effects are unknown.


METHODS
Six patients with intractable deafferentation pain in the left hand were included in this study. All were righthanded and had a subdural electrode placed over the right precentral gyrus. The pain was associated with brainstem injury in one patient, cervical spine injury in one patient, thalamic hemorrhage in one patient, and brachial plexus avulsion in three patients. Treatment with MCS reduced pain; visual analog scale (VAS) values for pain were 82 +/- 20 before MCS and 39 +/- 20 after MCS (mean +/- standard error). Regional cerebral blood flow (rCBF) was measured by positron emission tomography with H2(15)O before and after MCS. The obtained images were analyzed with statistical parametric mapping software (SPM99).


RESULTS
Significant rCBF increases were identified after MCS in the left posterior thalamus and left insula. In the early post-MCS phase, the left posterior insula and right orbitofrontal cortex showed significant rCBF increases, and the right precentral gyrus showed an rCBF decrease. In the late post-MCS phase, a significant rCBF increase was detected in the left caudal part of the anterior cingulate cortex (ACC).


CONCLUSIONS
These results suggest that MCS modulates the pathways from the posterior insula and orbitofrontal cortex to the posterior thalamus to upregulate the pain threshold and pathways from the posterior insula to the caudal ACC to control emotional perception. This modulation results in decreased VAS scores for deafferentation pain.
Kishima
Haruhiko
H
Department of Neurosurgery, Osaka University Medical School, Suita, Osaka, Japan.
Saitoh
Youichi
Y
Osaki
Yasuhiro
Y
Nishimura
Hiroshi
H
Kato
Amami
A
Hatazawa
Jun
J
Yoshimine
Toshiki
T
D000368:Aged; D001930:Brain Injuries / Q000150:complications / Q000503:physiopathology; D001933:Brain Stem / Q000098:blood supply / Q000293:injuries / Q000503:physiopathology; D002421:Caudate Nucleus / Q000098:blood supply / Q000503:physiopathology; D002540:Cerebral Cortex / Q000033:anatomy & histology* / Q000098:blood supply / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D046690:Deep Brain Stimulation / Q000295:instrumentation*; D005260:Female; D006179:Gyrus Cinguli / Q000098:blood supply / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000098:blood supply / Q000503:physiopathology*; D010146:Pain / Q000175:diagnosis / Q000209:etiology; D059408:Pain Management; D010147:Pain Measurement; D049268:Positron-Emission Tomography; D012720:Severity of Illness Index; D013124:Spinal Injuries / Q000150:complications / Q000503:physiopathology; D013788:Thalamus / Q000098:blood supply / Q000503:physiopathology*