Prevalence of neuropathy in patients with impaired glucose tolerance using various electrophysiological tests

Neuropathy is often an associated feature woth long-standing type II diabetes mellitus. Neuropathy may occur even in subjects with impaired glucose tolerance.

To study the prevalence of neuropathy using different electrophysiological techniques in subjects with impaired glucose tolerance (IGT) and no other identifiable cause of neuropathy.

The study was conducted on 30 age-matched controls and 58 subjects with impaired oral glucose tolerance test (OGTT) attending diabetic awareness. Prediabetes was defined using World Health Organization (WHO) criteria. All subjects had normal glycosylated hemoglobin HbA (1c), vitamin B12 levels, and thyroid function. Neuropathy was evaluated by nerve conduction studies (NCS) performed on one upper and both lower limbs, dorsal sural nerve, medial and lateral planter nerve conductions using conventional techniques. Neuropathy was also evaluated by autononic function tests, and quantitative sensory testing (QST). The subjects were followed up for 4 years.

Out of 58 subjects, 19 (32.8%) had neuropathy. Nerve conduction studies showed evidence of neuropathy in 14 (24.13%) subjects, autonomic neuropathy was detected in 8 (13.8%), and QST was found to be abnormal in 16 (27.6%) subjects. Twenty subjects (34.5%) developed diabetes mellitus in the follow-up period.

Neuropathy was detected in 32.8% subjects with IGT. Small fiber neuropathy was most common. Of all the three parameters studied, QST was found to be most sensitive technique for the detection of neuropathy. Assessment of medial plantar and dorsal sural NCS increases the sensitivity in the detection of neuropathy.