Electrophysiological Evaluation of Diabetic Polyneuropathy in Individuals Aged 40 Years and Above

Abstract

 Introduction: Diabetic polyneuropathy (DPN) is one of the important neurological complications of diabetes mellitus and may remain clinically asymptomatic despite demonstrable peripheral nerve dysfunction. Nerve conduction studies provide an objective method for evaluating peripheral nerve involvement and may help identify electrophysiological abnormalities before the development of overt clinical manifestations. Objectives: To evaluate nerve conduction study parameters in diabetic individuals aged 40 years and above, determine the prevalence and electrophysiological pattern of diabetic polyneuropathy, and assess the relationship of nerve conduction abnormalities with clinical symptoms, age, duration of diabetes, and fasting blood sugar. Methodology: This cross-sectional analytical study was conducted in the Outpatient Departments of Neurology, General Medicine and Endocrinology and the Department of Physiology, Medical College and Hospital, Kolkata, over 18 months from April 2017 to November 2018. A total of 31 confirmed diabetic individuals aged 40 years and above were evaluated. Clinical assessment was performed using the Toronto Clinical Scoring System, along with assessment of sensory, motor and autonomic symptoms. Nerve conduction studies were performed bilaterally on the median, peroneal and sural nerves, assessing latency, amplitude and conduction velocity. Data were analyzed using Microsoft Excel Statistical Package, with p<0.05 considered statistically significant. Results: The study population comprised 26 males and 5 females, with a mean age of 55.39±9.74 years. DPN was detected in 16 of 31 participants, giving an overall prevalence of 51.61%. Notably, 23 participants (74.19%) were asymptomatic, yet nerve conduction studies detected electrophysiological abnormalities consistent with DPN in 8 of these 23 asymptomatic individuals (34.78%). All 8 symptomatic participants demonstrated DPN. The predominant electrophysiological pattern was mixed sensory-motor axonal polyneuropathy (75%), followed by predominantly motor involvement (18.75%) and pure sensory involvement (6.25%). Significant abnormalities were observed in motor nerve amplitude and conduction velocity, while bilateral sural sensory nerve parameters showed significant differences between DPN and non-DPN groups. Mean fasting blood sugar was significantly higher in the DPN group (184.0±96.69 vs. 133.6±17.07 mg/dL; p = 0.028). Duration of diabetes and fasting blood sugar showed negative correlations with sural nerve amplitude, although these were not statistically significant. Conclusion: Diabetic polyneuropathy was common among diabetic individuals aged 40 years and above, with a substantial proportion of electrophysiological abnormalities occurring in clinically asymptomatic subjects. The predominant pattern was mixed sensory-motor axonal polyneuropathy, with prominent abnormalities in sural sensory nerve conduction parameters. Nerve conduction studies may therefore be valuable for objective detection of diabetic polyneuropathy, particularly in asymptomatic or minimally symptomatic patients. Larger studies are required to further substantiate these findings.