Neurophysiological Changes in Neurologically Asymptomatic Hypothyroid Patients: A Prospective Cohort Study

Abstract

This is a prospective cohort study on neurologically asymptomatic patients with primary hypothyroidism. It was conducted to evaluate the frequency and pattern of neurophysiological changes in this group of patients. Twenty-three subjects were included over a period of 2(1/2) years. Neurophysiological evaluation included nerve conduction studies (NCS) of median, ulnar, and peroneal motor nerves as well as median palmar and ulnar and sural sensory responses. Electromyography of deltoid, first dorsal interosseous, vastus lateralis, and tibialis anterior muscles was performed with concentric needle electrodes in which duration, amplitude, and stability of motor unit action potentials, recruitment, and interference pattern were evaluated. NCS showed that 52% of the patients had some abnormality, predominantly of the motor demyelinating pattern, as evidenced by prolonged F-wave and distal latencies with normal amplitudes in most affected nerves. Thirty percent of patients had median mononeuropathy consistent with carpal tunnel syndrome. Nondisfigurative myopathic changes in the form of myopathic motor unit action potentials without spontaneous activity were seen in 74% of the patients, most commonly in deltoid (70%). Frequencies of involvement of other muscles were 39% in the vastus lateralis muscle, 26% in tibialis anterior muscle, and 9% in the first dorsal interosseous muscle. We conclude that electromyographic/NCS changes commonly exist in treated, neurologically asymptomatic patients with hypothyroidism and are most frequently myopathic. Median neuropathy is the most common nerve abnormality. Other nerves are involved, with a higher tendency for motor nerve demyelination. We speculate that some neuromuscular changes secondary to hypothyroidism persist after treatment and that motor nerve abnormalities are less likely to be symptomatic than sensory nerve changes in these patients.

Effect of Nerve Conduction Studies in Hypothyroidism - An Observational Study

“…These findings are consistent with that reported by Kececi et al 2006 [14] and El-Salem K et al 2006 [15]. However, the sample size for Kececi et al is more than our study.…”

Pathological Features of Polyneuropathy in Three Dogs

“…Altered Schwann cell metabolism may cause mucinous deposition, which results in nerve entrapment and demyelination [9,15,29]. Severe metabolic defects in neurons may also disturb axonal transport and lead to axonal atrophy [9,15,29]. Vascular nerve damage secondary to hypothyroid-induced alternations in the blood-nerve barrier may also cause demyelination [9,15,29].…”

“…Altered Schwann cell metabolism may cause mucinous deposition, which results in nerve entrapment and demyelination [9,15,29]. Severe metabolic defects in neurons may also disturb axonal transport and lead to axonal atrophy [9,15,29].…”

Cross-sectional area of the median nerve is increased in primary autoimmune hypothyroidism and decreases upon treatment with thyroxine

“…Several studies that have examined nerve conduction parameters in hypothyroid patients reported that deficiency of thyroid hormones causes motor neuropathy by affecting different peripheral nerves, but, more commonly, the median nerve (4,5,6). A number of retrospective studies reported the prevalence of neuropathy to be between 10 and 70% in patients with hypothyroidism (1,7,8,9). The most common form of peripheral entrapment neuropathy is carpal tunnel syndrome (CTS) (10).…”