Objectives: This study was designed to measure sympathetic skin responses (SSRs) following magnetic stimulation of the cervicothoracic spine and to evaluate its clinical usefulness.

Methods: Fifteen healthy volunteers who had no dysautonomic symptoms or signs and a patient with C6 spinal cord transection participated in this study. To evoke SSR, we stimulated the C7 spinous process (SP) and T2 SP with 90 mm circular coil (Magstim 200). We recorded the sensory nerve action potential (SNAP) from the right middle finger to ascertain whether the C7 dorsal root was depolarized by the C7 SP stimulation. The same stimulation intensity by which SNAP had been obtained was used to evoke the SSR by the C7 and T2 SP stimulation. The recording of SSR was done in both palms. SNAP was recorded by the magnetic stimulation on the C7 SP in all subjects.

Results: By the C7 SP stimulation, the latency of SSR was 1.35 sec in the right palm, 1.33 sec in the left palm and by the T2 SP stimulation, the latency was 1.24 sec, 1.23 sec in order. The right-left difference was not found by each SP stimulation, but the latency of SSR by the T2 SP stimulation was faster than that by the C7 SP stimulation (p＜0.01). The latency difference of C7 and T2 SP stimulation was 0.11 sec in the right palm, 0.10 sec in the left palm. In a case of C6 cord transection, SSR was evoked neither by the right median electric stimulation, nor by the C7 SP magnetic stimulation. However, SSR was successfully evoked by the T2 SP stimulation.

Conclusion: We believe that the latency difference of C7 and T2 spinous process stimulation reflects the central conduction time of SSR.

We studied diabetic central neuropathy(DCN) that is not well-known neurologic disorder, for confirming its existence and then presenting objective diagnostic criteria and methods. Thirty-six diabetics(NIDDM: 30, IDDM: 6), mean age 53.1 years, 21 males and 15 females, were compared with 36 controls, mean age 51.5 years, 18 males and 18 females, electrophysiologically. First, we diagnosed peripheral polyneuropathy(PN) in diabetics by means of Diabetic Neuropathy Staging(DNS) developed at the University of Michigan and classified diabetics into two groups; group I indicates diabetics with PN, group II diabetics without PN. Second, we studied central(cortico-cervical and cortico-lumbar) motor conduction time(CMCT) by means of magnetic motor-evoked potentials(MEP) and central somatosensory conduction time by means of somatosensory-evoked potentials(SEP) stimulating on median and posterior tibial nerves.

There were no significant differences(p>0.05) statistically in cortico-cervical CMCT between diabetics and controls. There were significantly more prolonged(p<0.01) in cortico-lumbar CMCT between diabetics and controls. In median nerve-evoked 3-channel SEP, N13-N20(cortico-cervical) interpeak latency was significantly more prolonged(p<0.01) in diabetics than controls. In tibial nerve-evoked 2-channel SEP, P38-N22(cortico-lumbar) interpeak latency was significantly more prolonged(p<0.01) in diabetics than controls. In 30 patients(83.3%) of 36 diabetics, the study revealed central conduction delay in view of that above 2 or more abnormalities representing central conduction delay, that is, central neuropathy. In 10 patients(33.3%, M:7, F:3) of diabetics with central neuropathy(30 patients), even though they had no PN, central conduction delay was revealed.

Conclusively, in view of representing central conduction delay in 83.3% of patients, we believe that more active evaluations are needed in diabetics representing nonspecific central neurologic symptoms, for example, psychomotor slowing or cognitive dysfunctions, and MEP and SEP are useful in diagnosing DCN.