Dr. S.M.Sadikot.
Hon. Endocrinologist,
Jaslok Hospital and Research Centre,
Mumbai 400026

The relationship between diabetes and the peripheral nerves has been known for quite a long time. Rollo is credited as being the first to record this association almost two hundred years ago. In fact, most of the observers in the 19th Century felt that diabetes was caused by the involvement of the nervous system through some unknown mechanism. It was only in 1864 that Michael de Calvi first suggested that diabetes may be the cause of, rather than be caused by, neuropathy. He also recorded the occurrence of pain in the distribution of the sciatic nerve and loss of peripheral sensations. Later, Bouchard noted the loss of tendon reflexes, and Pavy and Althus provided a further account of the nerve involvement. As late as 1945, Rundles first definitively ascribed diabetes to be the cause of peripheral nerve involvement and gave the first comprehensive description.

Estimates of the prevalence of diabetic neuropathy vary widely with studies showing a range from 0% to as much as 93%. This is due to the fact that the criteria used for the estimation of prevalence are not standardised and also to the differences in the duration of diabetes before one tests for the presence of neuropathy. Pirart's classic 25 year prospective study of 4400 unselected patients would give the best idea about the prevalence. He defined neuropathy as the loss of the ankle reflex and/or patellar reflex plus diminished vibration sense irrespective of other clinical signs and symptoms of nerve involvement. Neuropathy was detected at the time of diagnosis of diabetes in 12% of the patients, mostly in those with mild Type 2 diabetes. These were patients in whom it is the most difficult to rule out pre-existing hyperglycemia. In the series reported by Pirart, prevalence increased linearly with the duration of diabetes, reaching about 50% of the patients after 25 years of diabetes. He also reported that patients with retinopathy and/or nephropathy were more likely to have evidence of neuropathy.

Our own study CINDI carried out by DiabetesIndia showed a prevalence of around 15% in patients who were evaluated within three months of initial diagnosis.

In Type I patients in whom the onset is usually easy to pinpoint, Eng has reported that it is quite rare for neuropathy to be detected within the first five years of diabetes.

Although various classifications of diabetic neuropathy have been published, none of them have gained wide acceptance. From a review of the different classifications, I have compiled a clinical classification, which is arbitrary but would help in understanding the various clinical manifestations of diabetic peripheral neuropathy. It should be clear that the different categories are not absolutely independent and patients may show the signs and symptoms of more than one of the classified categories.