Severe degeneration of peripheral motor axons after spinal cord injury: a European multicenter study in 345 patients.
OBJECTIVE
There are indications that perilesional and remote peripheral motor axons may degenerate after spinal cord injury (SCI). The authors investigated the magnitude and dependence on severity of SCI of this degeneration as well as whether motor axons so affected can recover.


METHODS
The function of the peripheral motor axons was investigated by recording compound muscle action potentials (CMAPs) in 345 patients with cervical SCI. CMAP amplitude changes in the abductor digiti minimi (ADM) and abductor hallucis (AH) muscles were investigated in 3 groups with SCIs of differing severity: patients with permanent complete SCI (ASIA Impairment Scale [AIS] A-remain), patients with initially complete SCI converting to incomplete lesion (AIS A-convert), and patients with incomplete injury (Incomplete).


RESULTS
Significant decreases in ADM and AH CMAP amplitudes were found in groups A-remain and A-convert. In group A-remain and group A-convert, the authors found a partial, although significant, recovery of ADM CMAP amplitude occurring between 5 and 12 months postinjury. In group A-remain, they found significant recovery of the AH CMAP amplitude.


CONCLUSIONS
Following SCI, peripheral motor axons below the level of the lesion exhibit severe degeneration. There is partial, although significant, recovery of CMAP during the second half year following SCI. The observed motor axon dysfunction is likely a result of transsynaptic degeneration. The peripheral motor axon dysfunction observed after SCI is of sufficient magnitude that it may affect muscle power and thus contribute to impairment of recovery of functional activities in patients with SCI.
Van De Meent
Hendrik
H
Department of Rehabilitation Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. h.vandemeent@reval.umcn.nl
Hosman
Allard Jf
AJ
Hendriks
Jan
J
Zwarts
Machiel
M
Schubert
Martin
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001369:Axons / Q000473:pathology*; D005060:Europe; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000473:pathology*; D010523:Peripheral Nervous System Diseases / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D011446:Prospective Studies; D020127:Recovery of Function / Q000502:physiology; D013119:Spinal Cord Injuries / Q000150:complications / Q000473:pathology* / Q000503:physiopathology; D014855:Wallerian Degeneration / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D055815:Young Adult