How reliable are sympathetic skin responses in subjects with spinal cord injury?
OBJECTIVE
To determine the test-retest reliability of sympathetic skin responses (SSR) in individuals with spinal cord injury (SCI).


METHODS
Fourteen men and four women with traumatic SCI (age: 44 ± 18 years; C2-T11; AIS A-D; 1-383 months post-injury) participated in two electrophysiological testing sessions separated by an average of 1 day. During each session, sudomotor function was tested supine by recordings of SSRs in both hands and feet. Two stimulation approaches were chosen: median nerve stimulation and a deep breath maneuver. SSR recordings were analyzed as SSR scores representing the presence or absence of responses. In addition, SSR amplitude and latencies were calculated. Test-retest reliability for the SSR score was calculated by the intraclass correlation coefficient (ICC) and its confidence interval. Coefficient of variation (CV) was calculated for SSR amplitudes and latencies.


RESULTS
SSR score to median nerve stimulation demonstrated 'almost perfect' reliability with ICCs of 0.97 and 0.96, for both hands and feet, respectively. The SSR score to deep breath maneuver was slightly lower, such as 0.89 and 0.74 for hands and feet. The CV of SSR amplitudes to median nerve stimulation was 48 and 18% for hands and feet, respectively, and 7 and 12% for the latency.


CONCLUSIONS
The qualitative interpretation of SSR by its presence or absence is a reliable way to assess sudomotor function in individuals with SCI. Although methodical procedures try to standardize SSR testings, quantitative SSR outcomes (amplitude, latency) are still highly variable.
International Collaboration on Repair Discoveries (ICORD), Blusson Spinal Cord Centre (BSCC), University of British Columbia, 818 West 10th Avenue, Vancouver, BC, V5Z 1M9, Canada.
Michèle
M
Hubli
Andrei V
AV
Krassioukov
D000293:Adolescent; D000328:Adult; D000368:Aged; D001342:Autonomic Nervous System Diseases / Q000175:diagnosis* / Q000209:etiology; D004558:Electric Stimulation; D004594:Electrophysiology / Q000379:methods; D005260:Female; D005712:Galvanic Skin Response / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012867:Skin / Q000294:innervation; D013119:Spinal Cord Injuries / Q000150:complications*; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D055815:Young Adult