Ulnar nerve integrity predicts 1-year outcome in cervical spinal cord injury

Abstract

Background: Accurate predictors of neurological recovery after cervical spinal cord injury are needed. Particularly, to tailor adequate rehabilitation plans. However, objective and quantifiable predictors are sparse. Methods: Within the prospective European Multicenter Study about Spinal Cord Injury (EMSCI) registry, cervical spinal cord injury patients are monitored at fixed follow up visits (2, 4, 12, 24, and 48 weeks after injury) clinically and with ulnar nerve electroneurography. Associations of ulnar nerve compound muscle action potential amplitudes (CMAP) with American Spinal Cord Injury Association (ASIA) impairment scale (AIS) grades over time were analyzed using linear mixed modeling. Applying logistic regression, the prognostic value of within 4-week ulnar nerve CMAP for 1-year AIS was analyzed. To account for missing data, (1) last observation carried forward and (2) multiple imputation methods were applied. For model derivation, our centers' cohort (EMSCI-HD) was analyzed. For model validation the cohort of other centers (EMSCI-nonHD) was used. Results: In the EMSCI-HD cohort, the median age (interquartile range (IQR)) was 52 (34-67) years. 58% were male. The initial AIS distribution was: A = 31%, B = 17%, C = 30%, and D = 22%). In the EMSCI-nonHD cohort, the median age was 49 (32-65) years. Compared to the EMSCI-HD cohort more patients were male (79%, p = 0.0034). The AIS distribution was: A = 33%, B = 13%, C = 21%, and D = 33%). In complete-case mixed model analyses (EMSCI-HD: n = 114; EMSCI-nonHD: n = 508) higher ulnar nerve CMAP were associated with better AIS grades over the entire follow up period. In complete-case logistic regression (EMSCI-HD: n = 90; EMSCI-nonHD: n = 444) higher ulnar nerve CMAP was an independent predictor of better AIS grades. The odds ratio for within 4-week ulnar nerve CMAP to predict 1-year AIS grade D versus A-C in the EMSCI-HD cohort was 1.24 per millivolt (confidence interval 1.07-1.44). The model was validated in an independent cervical spinal cord injury (EMSCI-nonHD) cohort (odds ratio 1.09, confidence interval 1.03-1.17). Conclusions: In cervical spinal cord injury, the consideration of early ulnar nerve CMAP improves prognostic accuracy, which is of particular importance in patients with clinical grading uncertainties.

Improving Diagnostic Workup Following Traumatic Spinal Cord Injury: Advances in Biomarkers

“…Neurophysiologic techniques, such as measuring nerve conduction, motor-evoked potential (MEP), and somatosensory-evoked potentials (SEP), provide objective measures of neuronal integrity and allow the differentiation between demyelination and axonal damage [98••, 99]. Their value as independent tool for stratifying SCI patients into sub-groups and their predictive utility were already demonstrated and validated several years ago [99][100][101][102]. However, some questioned whether these electrophysiological parameters could add valuable information for improving functional outcome prediction.…”

Neuromuscular consequences of spinal cord injury: New mechanistic insights and clinical considerations

“…Hug et al 127 used the EMSCI database to determine the predictive utility of the ulnar CMAP. They showed that higher ulnar CMAP at 4 weeks was predictive of an improved AIS grade at 1 year after injury.…”

“…In general, studies using the EMSCI database show that the ulnar CMAP appears to be associated clinical severity of SCI. 40,118,127,128 It is reasonable to suppose that the "motor completeness" in SCI is, in part, dependent on LMN health. 129 The evidence that LMN lesions likely play an important prognostic role is certain to continue to expand and existing studies likely already justify the implementation of routine electrodiagnostic evaluation of the upper extremities following SCI.…”

“…Franz et al 110 showed that those with evidence of early LMN lesions were less likely to experience recovery of hand muscle strength at 12 months. Hug et al 127 used the EMSCI database to determine the predictive utility of the ulnar CMAP. They showed that higher ulnar CMAP at 4 weeks was predictive of an improved AIS grade at 1 year after injury.…”

“…Hupp et al 118 showed that an aggregate CMAP amplitude score from ulnar and tibial motor studies was not superior to early clinical motor scores, but when combined in a prediction model, explained an increased proportion of the variance in long‐term patient reported outcome, than either parameter alone, using the EMSCI database. In general, studies using the EMSCI database show that the ulnar CMAP appears to be associated clinical severity of SCI 40,118,127,128 . It is reasonable to suppose that the “motor completeness” in SCI is, in part, dependent on LMN health 129 .…”