A Comparative study of Visual Evoked Potentials in Hypothyroid and Hyperthyroid Individuals

Vengadesh Prabhu, V (2017) A Comparative study of Visual Evoked Potentials in Hypothyroid and Hyperthyroid Individuals. Masters thesis, Stanley Medical College, Chennai.

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Abstract

The normal growth and development of an individual is profoundly influenced by the hormones produced by the Thyroid gland. Thyroid hormones play a very important role in the development and differentiation of the neuromuscular system and brain in foetal and neonatal life Thyroid hormones affect the central and peripheral nervous system through its role in gene expression, myelin production and its effects on the neurotransmitter system and axonal transportation. Hypothyroidism affects both central and peripheral nervous system. The peripheral nerve involvement may be due to the defect in axons, nerve cell body or myelin sheath. The central effects of Hyperthyroidism on are most pronounced, during the development of the central nervous system Thyroid hormones affect myelination. Therefore increased levels of thyroid hormones lead to oxidative damage of the myelin sheath and /or the oligodendroglial cells. The Visual Evoked Response (VER) is the visual response to the specific alterations in the electroencephalogram caused by the sensory stimuli. Visual evoked potentials provide a reliable and objective measure of function of the anterior visual pathway which refers to the structures in the anterior part of visual pathway up to the lateral geniculate nucleus. Since VEP is a relatively easy and safe technique, it can be used for early assessment of defects caused in the anterior visual pathway by alteration in the functions of thyroid gland AIM OF THE STUDY: To assess and compare the neurological dysfunction of anterior visual pathway in Hypothyroidism and Hyperthyroidism using Visual Evoked Potential (VEP). OBJECTIVES: 1. To record VEP and compare the latencies and amplitude of visual evoked potential in hypothyroid and hyperthyroid patients with that of normal subjects. 2. To correlate the duration of thyroid disease with the P100 latencies and P100-N75 amplitude of visual evoked potential in hypothyroid and hyperthyroid patients. 3. To correlate the thyroid function tests with the P100 latencies and P100-N75 amplitude of visual evoked potential in hypothyroid and hyperthyroid patients. INCLUSION CRITERIA: 1. Hypothyroidism patients of age between 18-45 years. 2. Hyperthyroidism patients of age between 18-45 years. EXCLUSION CRITERIA: 1. Hypothyroid and hyperthyroid patients of age less than 18 years or greater than 45 years. 2. Individuals with known Diabetes, Systemic hypertension ischemic heart disease, renal failure, liver failure. 4. Individuals with epilepsy, brain tumour and other space occupying brain lesions. 5. Individuals on treatment for Tuberculosis. 6. Individuals with neurological disease like multiple sclerosis. 7. Individuals with Corneal opacity, squint, color blindness, on miotic or mydriatic drugs. SUBJECT GROUP: 30 willing hypothyroid patients & 30 hyperthyroid patients were recruited from Medicine - Endocrinology OPD of Stanley Medical College. CONTROL GROUP: 30 age and gender matched individuals with normal thyroid profile attending the Master Health Checkup Program in Stanley Medical College were selected for the study. RESULT: Hypothyroid patients showed a statistically significant increase in P100 latency and decrease in amplitude of the N75-P100 wave. In hyperthyroid subjects there were no statistically significant change5 in latencies of N75, P100 and N145 waves and N75-P100 amplitude. When the levels thyroid hormones were analysed, there was no statistically significant change with P100 latency and N75-P100 amplitude except for a statistically significant positive correlation of TSH level with P100 latency in one eye and a statistically significant negative correlation of FT4 level with P100 latency in one of the eyes. CONCLUSION: Thus, we can infer that thyroid disorders cause neuropathy. VEP can be used as a tool for early identification of subclinical neuropathy in individuals with thyroid disorders. Large scale studies of VEP in thyroid dysfunction can be undertaken to further enlighten our knowledge about neuropathy in thyroid disorders so that VEP can be used as a diagnostic tool during routine workup of thyroid patients.

Item Type: Thesis (Masters)
Additional Information: Reg.No.201415052
Uncontrolled Keywords: Hypothyroidism, Hyperthyroidism, Visual evoked potential, Thyroid function test, P100 latency, P100-N75 amplitude.
Subjects: MEDICAL > Physiology
Depositing User: Subramani R
Date Deposited: 18 Jul 2020 17:56
Last Modified: 19 Jul 2020 07:31
URI: http://repository-tnmgrmu.ac.in/id/eprint/12553

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