Severity of autonomic dysfunction in patients with complete spinal cord injury

There is limited information on the relationship between the level and completeness of the spinal cord injury (SCI) lesion and the degree of autonomic dysfunction. We aimed to study the impairment of sympathetic function in chronic SCI patients presenting with a motor and sensory complete lesion above T6.

26 consecutive traumatic SCI patients were enrolled (14 tetraplegics and 12 paraplegics). They took a battery of tests that included pressor stimuli above (mental arithmetic, hand cold pressor test, sympathetic skin responses (SSR)) and below the lesion (foot cold pressor test, abdominal electrical stimulation), and Valsalva maneuver.

All patients showed abolished plantar SSR, while a significant rise in systolic blood pressure in at least one of the pressor tests below the lesion was seen in all but one paraplegic patient. Palmar SSR and blood pressure overshoot at the end of the Valsalva maneuver were abolished in all tetraplegics, whereas at least one of those responses was seen in each paraplegic. Hand cold pressor test and mental arithmetic induced cardiovascular changes in most patients.

A complete loss of supraspinal control was observed in all, with a reflex isolated spinal cord in all but one patient. We confirm that in most SCI subjects there is concordance between the impairment of sympathetic function and somatic impairment. To assess autonomic dysfunction, a battery of tests should include SSR, abdominal electrical stimulation and Valsalva maneuver, as they combine pressor stimuli above and below the lesion and assess both cholinergic and sudomotor pathways.