Electromyographic evaluation of blink reflex as a tool for early diagnosis of neurological dysfunction in patients of hypothyroidism.

Abstract

BackgroundNeurological dysfunction is an important consequence of hypothyroidism. Some of the neurologic manifestations of hypothyroidism include somnolence, lethargy, impaired memory and concentration, depression and entrapment neuropathy. Rarer but reversible neurological manifestations include cerebellar ataxia, psychosis, dementia and myxedema coma.PurposeThe aim of the present study was to evaluate the usefulness of the blink reflex as a method for obtaining an early diagnosis of central nervous system dysfunction in hypothyroid patients who do not have signs or symptoms of nervous system dysfunction.MethodsForty-eight patients with mean age 40 (± 11), with newly diagnosed primary hypothyroidism and 20 healthy control subjects were included in the study. The patients were divided into subclinical and overt hypothyroidism. Patients with normal T3/T4 with elevated TSH were considered subclinical hypothyroids. For blink reflex testing, subjects lay supine on a bed in a warm room with eyes gently closed. Recordings were performed with an EMG machine (Nihon Kohdeni’Neuropack), with a filter setting of 20 Hz to 10 kHz, using an analysis time of 50 ms. Recordings were performed with surface recording electrodes (Dantec 13K60, Copenhagen, Denmark).ResultsSecond ipsilateral response (R2I) and second contralateral response (R2C) latencies in hypothyroidism were prolonged relative to controls, and the differences were statistically significant (P<0.001 and P<0.001, respectively). Latency of Rl, R2I, and R2C did not correlate linearly free T3, free T4, or TSH values in the hypothyroid group.ConclusionThe finding of abnormal blink reflex responses in hypothyroid individuals raises the notion that they may be useful in detecting early changes and in the follow-up of the patients with the disorder.

Association of Thyroid Hypofunction with Clinical Outcomes after Microvascular Decompression for Hemifacial Spasm

“…Multiple cranial neuropathy is an uncommon clinical finding in hypothyroidism, which is an important differential diagnosis in the workup of new neurological deficits [11]. Another study reported that electrophysiological evaluation, such as blink reflex responses in hypothyroid patients, may be useful in screening for neurological dysfunction in patients [12]. Although there is still insufficient evidence of a definitive relationship between neurological disorders and thyroid diseases, many studies have found an association between them.…”

“…We suggest that thyroid hypofunction may worsen physical and emotional problems in HFS patients. The reason why thyroid hypofunction worsens surgical outcomes in HFS, which is considered a hyperfunctional condition of the nervous system, may be because insufficient thyroid hormones affect the central and peripheral nervous systems through their role in gene expression, myelin production, neurotransmitter system, or axonal transportation and are associated with emotional function [12, 20, 26].…”

Correlation of Median Motor Nerve Parameters with TSH Values in Newly Diagnosed Hypothyroid Patients in a Tertiary Care Centre Alappuzha

“…Myelination is the most important factor determining conduction velocity 12 . Metabolic alteration caused by hormonal imbalance affects Schwann cells, inducing a segmental demyelination 14 . Demyelination can also occur as a result of oxidative damage to myelin sheath 15 .…”