Patients and methods: Between January 2007 and September 2007, a total of 54 patients with Hashimoto`s thyroiditis including 35 euthyroid (3 males, 32 females; mean age: 45.2±10.2 years; range, 35 to 60 years) and 19 with subclinical hypothyroidism (2 males, 17 females; mean age: 43.2±12.6 years; range, 40 to 65 years) were included in the study. The control group consisted of 35 healthy individuals (5 males, 30 females; mean age: 39.1±9.3 years; range, 29 to 52 years). Nerve conduction studies (NCSs), SSRs of the hand and foot obtained by stimulation of the contralateral median nerve, and EMG reaction times of the extensor indicis proprius muscle were performed in all subjects.

Results: There was no significant difference in peripheral NCSs and SSRs between patients and the control group. However, reaction times were longer in the AIT patients compared to the healthy individuals suggesting alterations in cognitive function related to the primary disease process in AIT.

Conclusion: Electrodiagnosis of autonomic nervous system involvement and cognitive impairment can be challenging in AIT. However, EMG reaction times and SSRs are practical and useful tools that are often overlooked. On the other hand, SSRs may be combined with more quantitative tests, such as sudomotor axon reflex testing, to allow us to better determine the extent of involvement of the autonomic nervous system in AIT. Keywords : Autonomic nervous system, chronic autoimmune thyroiditis, electromyographic reaction times, peripheral neuropathy, sympathetic skin responses