[The effects of graded spinal cord injuries on transcranial electric stimulation motor evoked potentials in the rat].
OBJECTIVE
To study the effects of graded spinal cord injury (SCI) on the motor evoked potentials (MEP) characteristics and the prognostic value of MEP for the motor function.


METHODS
Modified Allen's method was used by weight drop force of 30 gcf, 50 gcf, 80 gcf and 100 gcf on the T(8 - 9) spinal cord of 40 SD rats in order to make SCI models. MEP was recorded continuously at L(1 - 2) epidurally and bilateral gastrocnemius muscles before and after the spinal cord lesion was produced (followed up for 1 month). The inclined plane and Tarlov technique were used to assess clinical neurological function.


RESULTS
The amplitude of rat's MEP changed significantly with graded SCI, the more sever the lesion, the lower the potentials. mMEP was more sensitive than scMEP, though the abolishment of mMEP soon after SCI didn't indicate that the animals could not regain ambulation. Changes in amplitude of scMEP recorded early after SCI were collaborate significantly with inclined plane (gamma = 0.9665, P < 0.01) and Tarlov scale (gamma = 0.8893, P < 0.01) assessed 1 month later, and can be used as a chronic measure parameter of motor function prognosis. scMEP still existed 1 month after SCI in 3 of 11 rats (27.3%) without any voluntary movement in bilateral hindlimbs, suggesting that some parts of conductive function still existed in the spinal cord. So it should be called "discomplete SCI".


CONCLUSIONS
scMEP can be used as a reliable parameter for motor function prognosis, because it reflects objectively and sensitively the severity of central motor neurol fiber injury.
Yu
K
K
Department of Orthopedics, Changzheng Hospital, Second Millitary Medical University, Shanghai 200003.
Li
J
J
Jia
L
L
Bao
J
J
Yuan
W
W
Ye
T
T
Cui
Y
Y
D000818:Animals; D004558:Electric Stimulation; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005500:Follow-Up Studies; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D013997:Time Factors