Motor cortex rTMS restores defective intracortical inhibition in chronic neuropathic pain.
OBJECTIVE
To assess cortical excitability changes in patients with chronic neuropathic pain at baseline and after repetitive transcranial magnetic stimulation (rTMS) of the motor cortex.


METHODS
In 22 patients with unilateral hand pain of various neurologic origins and 22 age-matched healthy controls, we studied the following parameters of cortical excitability: motor threshold at rest, motor evoked potential amplitude ratio at two intensities, cortical silent period (CSP), and intracortical inhibition (ICI) and intracortical facilitation. We compared these parameters between healthy subjects and patients at baseline. We also studied excitability changes in the motor cortex corresponding to the painful hand of patients after active or sham rTMS of this cortical region at 1 or 10 Hz.


RESULTS
At baseline, CSP was shortened for the both hemispheres of patients vs healthy subjects, in correlation with pain score, while ICI was reduced only for the motor cortex corresponding to the painful hand. Regarding rTMS effects, the single significant change was ICI increase in the motor cortex corresponding to the painful hand, after active 10-Hz rTMS, in correlation with pain relief.


CONCLUSIONS
Chronic neuropathic pain was associated with motor cortex disinhibition, suggesting impaired GABAergic neurotransmission related to some aspects of pain or to underlying sensory or motor disturbances. The analgesic effects produced by motor cortex stimulation could result, at least partly, from the restoration of defective intracortical inhibitory processes.
Lefaucheur
J P
JP
Department of Physiology, Hôpital Henri Mondor, Assistance Publique-Hôpitaux de Paris, INSERM U 421, IM3-Faculté de Médecine de Créteil, Créteil, France. jean-pascal.lefaucheur@hmn.ap-hop-paris.fr
Drouot
X
X
Ménard-Lefaucheur
I
I
Keravel
Y
Y
Nguyen
J P
JP
D000328:Adult; D000368:Aged; D000698:Analgesia / Q000295:instrumentation / Q000379:methods; D002908:Chronic Disease; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D009044:Motor Cortex / Q000503:physiopathology*; D009433:Neural Inhibition / Q000502:physiology*; D009434:Neural Pathways / Q000503:physiopathology; D009437:Neuralgia / Q000503:physiopathology / Q000628:therapy*; D010523:Peripheral Nervous System Diseases / Q000503:physiopathology / Q000628:therapy*; D013003:Somatosensory Cortex / Q000503:physiopathology*; D009435:Synaptic Transmission / Q000502:physiology; D050781:Transcranial Magnetic Stimulation / Q000379:methods* / Q000592:standards; D016896:Treatment Outcome; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid