Somatosensory and motor evoked potentials at different stages of recovery from severe traumatic brain injury

Abstract

Objective: To detect changes of somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) at different stages of recovery from severe brain injury and to determine whether they can be used to predict late functional outcome. Design: Correlational study on a prospective cohort. Setting: Brain injury rehabilitation center. Patients: Twenty-seven consecutively sampled patients with severe traumatic brain injury referred to the inpatient intensive rehabilitation unit of primary care in a university-based system. Main Outcome Measures: (1) Glasgow Outcome Scale, Disability Rating Scale, and Functional Independence Measure; (2) SEPs and MEPs from upper limbs (ULs) and lower limbs (LLs). Outcome was assessed at 6 and 12 months after trauma. Correlations were computed with the nonparametric test of Spearman-Rank. Results: Both SEPs and MEPs showed dynamic changes ( p < .02 for N20, p < .05 for N30, P40, and N45), with a trend toward a progressive normalization. N30 was more frequently abnormal than N20. SEPs from LLs were more frequently and more persistently abnormal than those from ULs. Clinical and functional outcome was strongly correlated with the degree of abnormality of SEPs from LLs ( p < .002), whereas only mild relationships were found with SEPs from ULs. Both SEPs and MEPs showed a high negative predictive value (83% for N30 and 83% for P40), but only SEPs from LLs also had a high positive predictive value (72% for P40). Sensitivity was 88% both for N30 and P40. Specificity was 50% for N30 and 70% for P40). Conclusion: SEPs from LLs can be very useful in monitoring the postacute phase of traumatic brain injury and in identifying patients who require further intensive rehabilitation. MEPs may be of questionable value.