ASSESSMENT OF THE STRENGTH OF CORRELATION OF PHYSICAL VARIABLES WITH MOTOR NERVE CONDUCTION TEST VALUES IN COMMONLY TESTED UPPER LIMB NERVES OF HEALTHY INDIVIDUALS AND VALIDATION OF THE PREDICTIVE MODEL

Background: Nerve conduction studies involve electrically stimulating a nerve to initiate the impulse which travels along the nerve fibre and results in an evoked potential which is recorded, analysed and interpreted. Nerve conduction studies (NCS) are a key diagnostic tool for various neurological conditions. Research findings indicate that several anthropological and physiological factors play a significant role in influencing the parameters of nerve conduction studies, ultimately influencing diagnostic precision and sensitivity. Objective: The study aims to determine if age, gender, height, weight, body temperature, wrist ratio, finger circumference and length of upper limb can be used to predict the distal latency, CMAP (Compound Motor unit Action Potential) amplitude, MNCV (Motor Nerve Conduction Velocity) values of commonly tested upper limb nerves. Method: After obtaining ethical approval, participants were screened for inclusion and exclusion criteria. A total of 101 (49 females, 52 males) participants from 20 to 60 years of age were included in the study after screening. Independent variables (IV) included – Age, height, weight, body temperature, limb length, wrist ratio, gender, finger circumference and side of the limb. Dependent variables (DV) included – DL (distal latency), CMAP amplitude, and MNCV. The study design was cross-sectional and after the measurements of IVs and DVs, the data was analysed for normality distribution. The variables that were not normally distributed, were transformed using Tukey’s ladder of powers. Correlation analysis (for continuous variable) and univariate regression analysis (for dichotomous variable) was performed for each DV with all the IVs. A multiple regression stepwise analysis was run on the significantly correlated IVs with DV. A subset of the IVs that produced the maximum R-squared 5-fold value was then selected for model preparation. Results: Temperature emerged as the significant predictor for distal motor latencies of all the tested nerves. Length of upper limb is a significant predictor for median and ulnar DLs and height is found to be significant predictor of radial DL. Gender is a significant predictor for ulnar DL. Age has been identified as a significant predictor for CMAP amplitudes across all the tested nerves. The wrist ratio is a significant predictor of median CMAP amplitude. Age and temperature have been identified as the most significant variables influencing the values of median and ulnar MNCV. None of the independent parameters examined in the current study were able to accurately predict the value of radial NCV. Conclusion: The current study emphasizes the critical role of physiological factors such as temperature, age, sex, and anatomical measurements on nerve conduction parameters. These findings highlight the necessity of adjusting nerve conduction studies for these variables to improve diagnostic accuracy. Keywords: Nerve conduction, Age, gender, height, weight, wrist ratio, limb length, temperature, finger circumference, distal latency, CMAP amplitude