Sympathetic skin responses evoked by different stimuli modalities in spinal cord injury patients

By using a combination of physiological and electrical peripheral nerve stimuli, the authors aimed to characterize the expected dysfunction of the circuits responsible for sympathetic skin response (SSR) in persons with spinal cord injury (SCI).

The authors examined SSR induced in the hand and foot in 50 SCI patients and 15 age-matched and gender-matched healthy volunteers. SSR was induced by deep inhalation, unexpected acoustic stimuli, brisk hand muscle contraction, and median and peroneal nerve electrical stimulation (PNS).

SSRs to any stimulus modality were absent in hand and foot in patients with complete SCI above the T4 level. They were present in the hand and absent in the foot in complete SCI patients at levels between T4 and T11 for all stimuli modalities except PNS. The elicitability of SSR was lower with peroneal nerve stimulation than the other stimuli in hand and foot. The mean latency difference between SSRs of the hand and foot was significantly longer in patients than in controls, regardless of stimulus modality. The amplitude of SSR was larger in volunteers than in patients.

SSR to various stimuli confirms the importance of supraspinal centers and the integrity of sympathetic descending pathways. Simultaneous recording of the SSR in the hands and feet provides information about the degree of sympathetic impairment possibly in the efferent pathway. To monitor spontaneous recovery or the efficacy of a drug or biological therapeutic intervention, changes in the latency delay between the hand and foot may be valuable.