Motor cortex dysfunction in complex regional pain syndrome.
OBJECTIVE
Most patients with complex regional pain syndrome (CRPS) exhibit debilitating motor symptoms. The effect of continuous pain on motor system in CRPS, however, is not well known. We searched for signs of motor cortex dysfunction in chronic CRPS type 1 patients with motor impairment.


METHODS
We recorded rhythmic brain activity with magnetoencephalography (MEG) during noxious thulium-laser stimulation of both hands in eight CRPS patients and eight control subjects. We measured excitability of the motor cortex by monitoring the reactivity of the approximately 20-Hz motor cortex rhythm to laser stimuli. The reactivity was defined as a sum of the stimulus-induced suppression and the subsequent rebound of the approximately 20-Hz rhythm.


RESULTS
In CRPS, the reactivity of the approximately 20-Hz rhythm in the hemisphere contralateral to the painful hand was significantly weaker than in control subjects. The reactivity correlated with the mean level of the spontaneous pain (r=-0.64, P=0.04). Suppression of the approximately 20-Hz rhythm correlated with the grip strength in the painful hand (r=0.66, P=0.04).


CONCLUSIONS
Continuous pain in CRPS is associated with attenuated motor cortex reactivity.


CONCLUSIONS
Abnormal motor cortex reactivity may be linked with motor dysfunction of the affected hand in CRPS.
Kirveskari
Erika
E
Brain Research Unit, Low Temperature Laboratory, Aalto University, School of Science and Technology, Finland. erika@neuro.hut.fi
Vartiainen
Nuutti V
NV
Gockel
Maarit
M
Forss
Nina
N
D000328:Adult; D020918:Complex Regional Pain Syndromes / Q000175:diagnosis* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*