[Regional modulation of primary motor cortex after peripheral nerve injury: a functional magnetic resonance imaging study].
OBJECTIVE
To map dynamic changes of primary motor cortex after total brachial plexus traction injury by using functional magnetic resonance imaging, and to explore underlying probable mechanisms.


METHODS
Five patients with total traumatic root avulsions of the brachial plexus underwent varied kinds of nerve transfer to restore partially shoulder or elbow function. Four of them (cases 1, 3, 4, 5) accepted the first fMRI examination prior to surgery treatment, and four of them (cases 2, 3, 4, 5) accepted second or third or fourth fMRI follow-up re-examinations after surgery treatment. Maps of neuronal activation within the motor cortex were generated for both hands in each patient by using BOLD-fMRI and the cluster size and position were recorded. The motor tasks consisted of simple hand grasping of both hands respectively. Patients with paralytic hand were asked to complete task under "virtual" condition. The cluster size and intensity as well as location of motor activation within the primary motor cortex of the affected hand generated were compared with those of unaffected hand generated as reference in single subject, and the resultant maps of follow-up re-examinations were also compared with those of the prior examinations.


RESULTS
All patients' unaffected hand movement generated strong signal change within the contralateral primary motor cortex. In contrast, the clusters generated by affected hand showed very small and lower intensity than usual (2 cases) or could not be induced (2 case) in the first examination that prior to surgery treatment and seemed larger gradually in the following re-examination with time increasing.


CONCLUSIONS
Peripheral nerve injury can produced significant changes in the motor cortex of human brain. fMRI is a valuable tool to evaluate neural plasticity in motor cortex after peripheral nerve injury.
Gao
Ge-jun
GJ
Department of Radiology, Huashan Hospital, Shanghai 200040, China.
Feng
Xiao-yuan
XY
Xu
Wen-dong
WD
Gu
Yu-dong
YD
Tang
Wei-jun
WJ
Li
Ke
K
Li
Yuan
Y
Geng
Dao-ying
DY
D000293:Adolescent; D000328:Adult; D001917:Brachial Plexus / Q000293:injuries* / Q000473:pathology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000503:physiopathology*; D016067:Nerve Transfer; D009473:Neuronal Plasticity