Value of sympathetic skin response in multiple sclerosis

Thirty patients with definite multiple sclerosis along with fourteen healthy volunteers as control group were studied. Mean SSR latencies in the control group was 1,467 ms for upper extremities and 1,915 ms for lower extremities while 1,655 and 2,170 ms respectively in the patients with multiple sclerosis. Mean SSR amplitudes in the control group was 2.22 mV for upper extremities and 1.21 mV for lower extremities while 1.24 and 0.64 mV respectively in the patients with multiple sclerosis. All the differences between the patients and the control group was significant using T test (P = 0.001). Using Roc-curve, limits with highest sensitivity specificity products for SSR latency were calculated to be 1,700 ms for upper and 2,400 ms for lower extremities. For SSR amplitude they were 1.2 mV for upper and 0.5 mV for lower extremities. Considering absent SSR and/or at least 3 abnormal amplitudes or latencies as the criteria of abnormality, the specificity of the test was 100% and the sensitivity was 80% among our patients. Using the following criteria for abnormality, SSR study in the patients with multiple sclerosis is a test with high specificity and sensitivity: 1--Absent SSR, and/or 2--At least 3 abnormal out of the eight recordings (amplitudes and latencies of four extremities) with normal limits for SSR latency being defined as < or = 1,700 ms for upper and < or = 2,400 ms for lower extremities and for SSR amplitude as > or = 1.2 mV for upper and > or = 0.5 mV for lower extremities.