Bedside assessment of sympathetic skin response after spinal cord injury: a brief report comparing inspiratory gasp and visual stimulus

Abstract

Study design: A case control study in five controls, and 20 tetraplegic and paraplegic patients, complete and incomplete.

Objective: The aim was to assess the feasibility of a simple test for sympathetic system preservation after spinal cord damage in a pain-free manner and which could be undertaken worldwide without specialist equipment or manpower.

Settings: Patients were attending the Southport Regional Spinal Injuries Centre, England, either as outpatients or as in-patients during rehabilitation.

Methods: The sympathetic skin response (SSR) was recorded on a single-channel ECG recorder from the right hand and right foot in turn after inspiratory gasp (IG) or visual stimulation.

Results: Unlike the visually evoked SSR, the gasp-evoked SSR was reliable, albeit of variable amplitude, and there was little difference between the hand and foot. Paraplegics had similar SSRs in the hands as the controls. There was minor insignificant habituation of response for the gasp reflex. There was occasional unexpected SSR distally in patients with complete lesions, and in patients with incomplete lesions the responses could not have been predicted from the sensory motor pattern.

Conclusions: Trained IG induces an SSR which is sufficient to elucidate sympathetic loss following spinal cord injury. It is superior to visual stimulation in this respect. Habituation is not a problem with at least 1 min between tests, and high doses of anticholinergics agents may impair the response.