Transcranial magnetic motor evoked potentials and magnetic resonance imaging findings in paraplegic dogs with recovery of motor function

BACKGROUND: Transcranial magnetic motor evoked potentials (TMMEP) are associated with severity of clinical signs and magnetic resonance imaging (MRI) findings in dogs with spinal cord disease. HYPOTHESIS: That in initially paraplegic dogs with thoracolumbar intervertebral disc herniation (IVDH), MRI findings before surgery and TMMEPs obtained after decompressive surgery are associated with long-term neurological status and correlate with each other. ANIMALS: Seventeen client-owned paraplegic dogs with acute thoracolumbar IVDH. METHODS: Prospective observational study. TMMEPs were obtained from pelvic limbs and MRI (3T) of the spinal cord was performed at initial clinical presentation. Follow-up studies were performed ≤ 2 days after reappearance of motor function and 3 months later. Ratios of compression length, intramedullary hyperintensities' length (T2-weighted hyperintensity length ratio [T2WLR]), and lesion extension (T2-weighted-lesion extension ratio) in relation to the length of the 2nd lumbar vertebral body were calculated. RESULTS: TMMEPs could be elicited in 10/17 (59%) dogs at 1st and in 16/17 (94%) dogs at 2nd follow-up. Comparison of TMMEPs of 1st and 2nd follow-up showed significantly increased amplitudes (median from 0.19 to 0.45 mV) and decreased latencies (from 69.38 to 40.26 ms; P = .01 and .001, respectively). At 2nd follow-up latencies were significantly associated with ambulatory status (P = .024). T2WLR obtained before surgery correlated with latencies at 2nd follow-up (P = .04). CONCLUSIONS: TMMEP reflect motor function recovery after severe spinal cord injury.