[Skin sympathetic nerve activity in amyotrophic lateral sclerosis]

Skin sympathetic nerve activity (SSNA) was microneurographically analyzed in five patients with amyotrophic lateral sclerosis (ALS) (four men, one woman; age ranges between 36 and 68 years) and 16 age- and sex-matched controls. The duration of illness after the onset was ranged between 1 and 3 years. Three cases were the common form of ALS showing a moderate to severe involvement of the upper extremities and mild degree of bulbar signs. Two were the pseudopolyneuritic form with lower motor neuron sign predominant in the legs. All these patients could walk by alone and did not show any respiratory distress. SSNA was recorded directly by inserting a tungsten microelectrode into the tibial nerve at the popliteal fossa as described before. The sweat rate and skin blood flow on the area innervated by the tibial nerve were also monitored. Resting activity of the SSNA (bursts/minute) was significantly higher (p < 0.05) in patients with ALS as compared with the controls. The rate of increase in SSNA under the load of mental arithmetic, tone, electric stimulation of the median nerve and immersion of the hand into cold water were only slightly higher in ALS. The rate of increase in SSNA response by these stimuli against the basal SSNA, however, was not significant. These results indicate that skin sympathetic nerve functions are hyperactive in ALS particularly in the basal resting level, though the underlying mechanism is unclear.