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).


OBJECTIVE
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.


CONCLUSIONS
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.
Kramer
John K
JK
International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada. jkramer@icord.org
Taylor
Philippa
P
Steeves
John D
JD
Curt
Armin
A
D000293:Adolescent; D000328:Adult; D002574:Cervical Vertebrae; D015331:Cohort Studies; D020405:Dermis / Q000502:physiology*; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011782:Quadriplegia / Q000503:physiopathology; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012684:Sensory Thresholds; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult