Hypothyroidism Effect on Motor and Sensory Nerve Functions: A Crosssectional Nerve Conduction Study on Tibial and Sural Nerves

Background: Altered levels of thyroid hormones can impact various body systems, including the nervous system. Hypothyroidism may disrupt nerve conduction due to pathophysiological changes associated with hormone deficiency. To study nerve conduction abnormalities and to correlate electrodiagnostic findings with clinical features in patients with primary hypothyroidism. Materials & Methods: History regarding the duration of the disease, clinical and neurological complaints, use of medicines and level of control of hypothyroidism was recorded in history record sheet. After history taking, general clinical examination was done. Then neurological examination was conducted with special attention. Neuro-MEP-Micro (version 2009) Machine and it’s all accessories (Manufactured by Neurosoft Medical Diagnostics Limited, Ivanova, Russia). Electrophysiological parameters like nerve conduction study parameters (latency, amplitude, conduction velocity) of bilateral tibial, and sural motor nerves and tibial, and sural sensory nerves were recorded. Biochemical parameters like T3, T4, TSH values were recorded from patients’ test reports and from Endocrinology OPD prescriptions. Results: Study results show mean (±SD) of serum T3 was significantly less in cases (5.27±4.83) than that of the control (15.93±26.63) whereas mean (±SD) of TSH was significantly increased in cases (20.09±28.16) than that of the control (2.62±0.93). Similarly, there was significant increase in mean (±SD) of serum FT4 levels in cases (1.66±1.740) as compared to control subjects (1.22±0.37). In lower limbs the mean (±SD) of distal motor latency (DML) of both tibial motor nerves were significantly increased in cases (Right: 6.71±0.77, Left: 6.19±1.16) than that of the control (Right: 4.24±0.69, Left: 4.16±0.74). No significant differences were found in mean (±SD) of compound muscle action potential (CMAP) of both tibial motor nerves than that of the control. Table 6 shows DSL of right sural nerve decreases but DSL of left sural nerve increases with increase in duration of disease. SNAP of right sural shows positive correlation with duration of disease but the findings are not significant (r=0.072, p= 0.479). SNAP of left sural nerve decreases with increase in duration of disease but it is not significant (r= -0.131, p= 0.193). Positive correlation is there in between SNCV of sural nerve with duration of disease in both sides but these relations are not strong and significant (r= 0.016, p=0.875 and r=0.193, p=0.054). Conclusion: In our study we found that there were significant differences of both sensory and motor NCS parameters between cases and control. We found that CMAP, SNAP and MNCV, SNCV were significantly decreased and distal motor and sensory latencies were significantly increased in cases than controls which indicate mixed type of polyneuropathy, both axonal and demyelinating in hypothyroid patients. Therefore, we can conclude that peripheral neuropathy in hypothyroidism due to axonal loss and/or demyelination can be evaluated effectively by nerve conduction studies. So, the hypothyroid patients should be routinely screened by nerve conduction study.