Assessment of posterior spinal cord function with electrical perception threshold in spinal cord injury

The objective of this study was to evaluate the relevant sensory spinal pathways involved in conveying conduction of electrical perceptual threshold (EPT). In 34 individuals with cervical spinal cord injury (SCI) and eight healthy control subjects, combined EPT and electrical pain perception (EPP), and dermatomal somatosensory evoked potentials (dSSEP) from cervical dermatomes were examined. Stimulation intensities for EPT were recorded to determine quantitative sensory perception and related neurophysiological dSSEP interpretation of posterior spinal cord conduction based on onset latency and waveform configuration. The preservation of EPP in dermatomes was examined relative to EPT to dissociate the involvement of the posterior (dorsal horn and ascending dorsal column) and anterior (decussating and ascending spinothalamic fibers) spinal cord according to different nerve fiber recruitment in the periphery. Pathological EPT values were significantly (p < 0.05) accurate at predicting pathological and abolished dSSEP recordings (>80%), and the mean EPT of pathological and abolished dSSEPs was significantly (p < 0.05) increased compared to non-affected and control dSSEPs. dSSEPs demonstrated normal early onset latency at perceptually low stimulation intensities (<2.5 mA), and selectively absent EPP was dissociated from preserved EPT and/or dSSEP in 22.2% of dermatomes with incomplete sensory deficit. The relationship between EPT and dSSEP interpretation, dSSEP early onset latency and perceptual stimulation intensity, and the dissociation of EPT from EPP suggests that EPT is conducted within the posterior spinal cord. The combination of EPT and EPP with dSSEPs provides reliable quantitative sensory information to assess the segmental integrity of the posterior and anterior spinal cord, and may improve the sensitivity to monitor changes in sensory function after SCI.