Electrophysiological Examination of the Median and Ulnar Nerve in Patients with Clinical and Subclinical Hypothyroidism: A Case-Control Study

Background: Sensorimotor polyneuropathy or mononeuropathy caused by damage of axon or myelin have been reported in patients with clinical hypothyroidism; however, there are conflicting results concerning peripheral neuropathy involvement due to subclinical hypothyroidism. Our aim in this study was to investigate the electrophysiological changes in median and ulnar nerves in patients with clinical hypothyroidism or subclinical hypothyroidism that is asymptomatic from the neurological point of view.Method: 15 patients (30 hands) with clinical hypothyroidism (group 1) and 18 patients (36 hands) with subclinical hypothyroidism (group 2), who were asymptomatic from the neurological point of view, were included in the study. 27 age- and gender-matched healthy individuals (54 hands) were taken as a control group. The median and ulnar nerves were assessed electrophysiologically in the groups.Results: Slowing of ulnar motor nerve conduction velocity (uMNCV) and ulnar nerve sensory latency (uSDL) elongation values in group 2 were found to be significant compared to the control group. When group 1 was compared with the control group, elongation in the median motor distal latency (mMDL), slowing in median motor conduction velocity (mMNCV), reduction in median nerve compound muscle action potential (mCMAP), and a significant decrease in ulnar motor conduction velocity (uMNCV) were found in group 1. When group 1 was compared with group 2, in patients with clinical hypothyroidism, elongation in mMDL and amplitude reduction in mCMAP were found, no statistically significant differences were found between the groups in terms of median sensory nerve conduction velocity (mSNCV), mMNCV, median distal sensory latency (mSDL), uMNCV, ulnar sensory nerve conduction velocity (uSNCV), ulnar compound muscle action potential (uCMAP), and uMDL values.Conclusion: Even before the emergence of neurological symptoms in patients with clinical and subclinical hypothyroidism, abnormalities can be detected in nerve conduction studies. We believe that, assessment of these patients for peripheral neuropathy by conducting routine nerve conduction studies will contribute to early diagnosis and treatment. (Archives of Neuropsychiatry 2012; 49: 304-307)