Effects of Glycemic Control and Clinical Parameters on Tibial Nerve Conduction Latency in Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy is one of the most common chronic complications of diabetes mellitus and is associated with sensory loss, pain, and sensorimotor impairment, particularly in the distal extremities. Persistent hyperglycemia may contribute to structural and functional damage in peripheral nerves through metabolic and microvascular mechanisms. Electrophysiological abnormalities such as prolonged latency and reduced conduction velocity are commonly observed in affected individuals. Tibial nerve conduction latency may provide clinically relevant information for the evaluation of diabetic peripheral neuropathy.

The aim of this observational, cross-sectional, analytical study is to investigate the effects of glycemic control parameters and clinical variables on tibial nerve conduction latency in individuals with diabetic peripheral neuropathy.

The study will be conducted at Uzm. Dr. Gaye Yildirim Neurology and Clinical Neurophysiology Clinic. Participants will include individuals aged 45 to 76 years with diabetic peripheral neuropathy diagnosed on the basis of laboratory findings, clinical findings, and nerve conduction test results. Individuals with autoimmune disease, cerebrovascular disease, chronic infectious disease, cancer, history of chemotherapy or radiotherapy, radicular neuropathy, chronic kidney failure, liver failure, alcoholism or substance dependence, mental or physical disability, or inability to speak Turkish will be excluded.

Data will be collected through face-to-face assessment, clinical evaluation, and review of routine clinical records. Demographic and clinical variables will include age, height, weight, education level, diabetes type, and diabetes duration. Glycemic control parameters will include fasting blood glucose and HbA1c values obtained from routine laboratory tests; no additional laboratory testing will be requested specifically for the study.

Neuropathy assessment will include the Michigan Neuropathy Screening Instrument (MNSI), consisting of both the questionnaire and physical examination components. The questionnaire will be completed by participants, and the examination component will be performed by the researcher. Clinical assessment will include vibration sensation, ankle reflexes, and the presence of foot ulceration or deformity.

Nerve conduction studies will be performed in the clinical neurophysiology laboratory using standard electromyography procedures. Motor and sensory conduction parameters of upper and lower extremity nerves will be evaluated, and tibial nerve conduction latency will be recorded as the main electrophysiological outcome. Peripheral neuropathy will be defined on the basis of abnormalities in at least two different nerves, including changes in conduction velocity, reduced amplitude, and/or prolonged F-wave latency.

The primary analysis will examine the relationship between tibial nerve conduction latency and fasting blood glucose, HbA1c, MNSI questionnaire score, MNSI examination score, and diabetes duration using multiple linear regression analysis. Descriptive statistics will be presented as mean, standard deviation, number, and percentage, and statistical significance will be set at p\<0.05.

The planned sample size is at least 50 participants, based on an a priori power analysis for multiple linear regression. The study is expected to contribute to the early identification, risk evaluation, and clinical follow-up of diabetic peripheral neuropathy.