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.

Test-retest reliability of contact heat-evoked potentials from cervical dermatomes.

The purpose of this study was to investigate the test-retest reliability of contact heat-evoked potentials (CHEPs) in neurologically healthy subjects from cervical dermatomes (C4-C8). Seventeen individuals underwent test-retest examination of cervical CHEPs. Peak latencies and peak-to-peak amplitude of N2-P2 and ratings of perceived intensity were analyzed using test-retest reliability statistics (intraclass correlation coefficients [ICCs] and Bland-Altman confidence parameters). For comparison, a group of similar age and gender was also examined with dermatomal somatosensory-evoked potentials (dSSEPs, n = 17). The ICC values for CHEP latency and amplitude parameters were significant (P < 0.05) and corresponded to at least "fair" reliability, while peak-to-peak amplitude demonstrated "substantial" (≥0.81) reliability for all dermatomes. The coefficients of repeatability (i.e., 2SD of the difference between examinations) confirm that CHEPs and dSSEPs are reliable according to measures of latency. Superior peak-to-peak amplitude test-retest reliability was found for CHEPs. In conclusion, the test-retest reliability of dSSEP and CHEP parameters supports the fact that these outcomes can be used to objectively track changes in spinal conduction in the dorsal column and spinothalamic tract, respectively. The reliable acquisition of CHEPs may depend on the intensity of the sensation reported by the subject for a given area of skin stimulated.

Relationship between clinical assessments of function and measurements from an upper-limb robotic rehabilitation device in cervical spinal cord injury.

Upper limb robotic rehabilitation devices can collect quantitative data about the user's movements. Identifying relationships between robotic sensor data and manual clinical assessment scores would enable more precise tracking of the time course of recovery after injury and reduce the need for time-consuming manual assessments by skilled personnel. This study used measurements from robotic rehabilitation sessions to predict clinical scores in a traumatic cervical spinal cord injury (SCI) population. A retrospective analysis was conducted on data collected from subjects using the Armeo Spring (Hocoma, AG) in three rehabilitation centers. Fourteen predictive variables were explored, relating to range-of-motion, movement smoothness, and grip ability. Regression models using up to four predictors were developed to describe the following clinical scores: the GRASSP (consisting of four sub-scores), the ARAT, and the SCIM. The resulting adjusted R(2) value was highest for the GRASSP "Quantitative Prehension" component (0.78), and lowest for the GRASSP "Sensibility" component (0.54). In contrast to comparable studies in stroke survivors, movement smoothness was least beneficial for predicting clinical scores in SCI. Prediction of upper-limb clinical scores in SCI is feasible using measurements from a robotic rehabilitation device, without the need for dedicated assessment procedures.

Effect of a robotic rehabilitation device on upper limb function in a sub-acute cervical spinal cord injury population.

Robotic rehabilitation devices have been suggested as a tool to increase the amount of rehabilitation delivered after a neurological injury. Clinical robotic rehabilitation studies of the upper extremity have generally focused on stroke survivors. We present the results of a multi-center pilot study where an upper-limb robotic rehabilitation device (Armeo Spring®, Hocoma AG) was incorporated into the rehabilitation program of 12 subjects with sub-acute cervical spinal cord injury (motor level C4-C6, AIS A-D). Outcomes were measured using two tests of upper extremity function: ARAT and GRASSP. The change in scores for the arm receiving the Armeo training were not statistically significant when compared to the arm not receiving the Armeo training at discharge from therapy and over follow up assessments (8.7 +/- 2.9 compared to 7.4 +/- 2.5 for ARAT at discharge, p = 0.98, and 13.0 +/- 3.2 compared to 13.3 +/- 3.3 for GRASSP at discharge, p = 0.69). Nevertheless, subjects with some minimal (partial) hand function at baseline had a significantly larger increase in GRASSP scores than subjects with no minimal hand function preserved at baseline (19.3 +/- 2.4 compared to 6.6 +/- 4.7, p = 0.02). This suggests that the initial functional capabilities of patients can influence the benefits measured after robotic rehabilitation training and heterogeneous subject populations should be avoided in early phase studies.

Dermatomal somatosensory evoked potentials and electrical perception thresholds during recovery from cervical spinal cord injury.

BACKGROUND: Dermatomal somatosensory evoked potentials (dSSEPs) not only provide a neurophysiological readout comparable with conventional SSEPs but also provide an opportunity to track changes in sensory function corresponding to individual dermatomes (ie, a single spinal segment) above, at, and below the level of spinal cord injury (SCI). OBJECTIVES: This study aimed to determine the reliability and responsiveness of dSSEPs and electrical perception thresholds (EPTs) to monitor changes in sensory function after cervical SCI. METHODS: Initial and follow-up dSSEPs and EPTs were recorded from cervical dermatomes (C4-C8) of patients with traumatic tetraplegia (C3-C8; ASIA Impairment Scale A-D) during recovery after SCI (n = 18). RESULTS: Follow-up examination of 74 initial dSSEPs unaffected by SCI (n = 18) revealed no significant change in latency (Delta = 0.0 +/- 1.4 ms; P = .9) or EPT sensitivity (Delta = 0.1 +/- 0.8 mA; P = .3). In 41 dSSEPs initially delayed after SCI (n = 14), latencies significantly decreased on follow-up examination (Delta = -3.1 +/- 2.9 ms; P < .01) without a corresponding increase in sensitivity of the EPT (Delta = 0.2 +/- 3.4 mA; P = .7). dSSEPs that were not measurable initially were subsequently recorded in 11 dermatomes (n = 5) on follow-up examination. This conversion of abolished-to-recordable dSSEPs was often preceded by the perception of an initial EPT and associated with a concomitant recovery of EPT at follow-up. CONCLUSION: SSEPs and EPT can be reliably recorded to monitor changes in sensory function for each individual spinal segment after cervical SCI. dSSEPs may be potentially useful to monitor the safety of a therapeutic drug or cell transplant in early-phase (I/II) clinical trials as well as document the potential efficacy of interventions where the standard neurological assessment might not detect subtle therapeutic effects.