Cutaneous Silent Period as A new Diagnostic Tool for Assessment of Small Fiber Neuropathy in Hypothyroid Patients

Background: Hypothyroidism is associated with various neurological complications, including sensory-motor polyneuropathy. This study aims to evaluate the cutaneous silent period (CSP) as a diagnostic tool for small fiber neuropathy in hypothyroid patients.Methods: A total of 120 participants were enrolled, comprising 60 hypothyroid patients (cases group) and 60 age- and sex-matched healthy controls (control group). Neuropathic pain was assessed using the Douleur Neuropathique 4 (DN4) questionnaire. Electrophysiological studies, including CSP evaluations, were conducted to measure nerve function.Results: The cases group exhibited a significantly higher median DN4 score (p < 0.001) compared to the control group. CSP parameters revealed significantly shorter mean CSP durations for both median and sural nerves in the cases group (median nerve: 45.2 ± 10.3 ms vs. control: 60.5 ± 12.1 ms, p < 0.001; sural nerve: 42.8 ± 9.7 ms vs. control: 58.3 ± 11.4 ms, p < 0.001). Additionally, the cases group demonstrated significantly longer mean onset and end latencies (p < 0.001). Correlational analyses indicated that the duration of hypothyroidism positively correlated with CSP onset and end latencies (r = 0.65, p < 0.01) and negatively correlated with CSP duration (r = -0.72, p < 0.01).Conclusion: The findings suggest that CSP parameters are significantly altered in hypothyroid patients, indicating the potential of CSP as a diagnostic tool for small fiber neuropathy.