Long-lasting involuntary motor activity after spinal cord injury.
METHODS
The study design used is prospective cohort study.


OBJECTIVE
This study was designed to neurophysiologically characterize spinal motor activity during recovery from spinal cord injury (SCI).


METHODS
University of Louisville, Louisville, Kentucky, USA.


METHODS
Twenty-five consecutive acute SCI admissions were recruited for this study. The American Spinal Injury Association Impairment Scale (AIS) was used to categorize injury level and severity at onset. Surface EMG recording was carried out initially between the day of admission and 17 days post-onset (6.0 ± 4.3, mean ± s.d. days). Follow-up recordings were performed for up to 9 months after injury. Initial AIS distribution was 7 AIS-A; 3 AIS-B; 2 AIS-C; 13 AIS-D.


RESULTS
Twelve subjects (48%) showed long-duration involuntary motor-unit activation during relaxation. This activity was seen on initial examination in nine and on follow-up by 3 months post-injury in three others. It was seen in muscles innervated from the injury zone in 11 and caudal to the lesion in 9 subjects. This activity was independent of the presence or absence of tendon reflexes and the ability to volitionally suppress plantar stimulation elicited reflex withdrawal.


CONCLUSIONS
The form of involuntary activity described here is the likely result of the altered balance of excitation and inhibition reaching spinal motor neurons because of the loss of inhibitory interneurons or their reduced activation by damaged supraspinal drive and the synaptic reorganization that follows SCI. As such, this activity may be useful for monitoring the effects of neuroprotective and restorative intervention strategies in persons with SCI.
McKay
W B
WB
Norton Neuroscience Institute, Louisville, KY 40202, USA. william.mckay@nortonhealthcare.org
Ovechkin
A V
AV
Vitaz
T W
TW
Terson de Paleville
D G L
DG
Harkema
S J
SJ
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D020820:Dyskinesias / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009128:Muscle Spasticity / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology*; D013116:Spinal Cord / Q000473:pathology / Q000503:physiopathology*; D013119:Spinal Cord Injuries / Q000150:complications / Q000503:physiopathology*; D013995:Time; D055815:Young Adult