Normal Values of Sympathetic Skin Responses in Children and Their Clinical Significance.

Introduction/aims: The sympathetic skin response (SSR) is a well-established measure of sudomotor function in adults, but pediatric reference values remain undefined. We established age-stratified normative values for SSR latency and amplitude in healthy children and investigated how these values change during development.

Methods: The study enrolled 185 pediatric participants: 176 in the healthy group (no anticholinergic medications, neurological/autoimmune/oncological disorders) and 9 in the clinical group with suspected sympathetic dysfunction.

Results: SSR waveforms were not elicitable in 4 children under 4 years of age, but were recordable in all children over 4 years old. SSR latency for the hand was significantly shorter than that for the foot across all age groups; although the latencies for the hand and foot correlated positively with age, the correlations were weak to moderate (p < 0.05). Participants were categorized into four age groups (≤ 4, 5-9, 10-13, and ≥ 14 years) based on the latency-age trend inflection points established from the plotted trajectory. SSR amplitude for the hand (6.8 mV (interquartile range [IQR] 3.38, 12.5)) was significantly higher than that for the foot (3.5 mV (IQR 1.77, 6.50)), but neither correlated with age and the variation was large. The manifestation of suspected sympathetic nerve dysfunction in the patients was primarily a decrease in amplitude, absent response, or increased latency.

Discussion: This study provides a reliable method for clinicians and researchers to assess sympathetic nerve function in children by combining SSR amplitude and latency.