Introduction

Diabetic polyneuropathy is one of the most common complications of the diabetes and the most common form of neuropathy in the developed World. It encompasses several neuropathic syndromes the most common of which is distal symmetrical neuropathy, the main initiating factor for foot ulceration. The epidemiology of diabetic neuropathy has been reviewed in reasonable detail (1). Several clinic- (2,3) and population-based studies (4,5) show surprisingly similar prevalence rates for distal symmetrical neuropathy, affecting about 30% of all diabetic people. The EURODIAB Prospective Complications Study, which involved the examination of 3250 type I patients, from 16 European countries, found a prevalence rate of 28% for distal symmetrical neuropathy (2). After

From: Contemporary Diabetes: Diabetic Neuropathy: Clinical Management, Second Edition Edited by: A. Veves and R. Malik © Humana Press Inc., Totowa, NJ

Table 1

Differential Diagnosis of Distal Symmetrical Neuropathy

Metabolic Diabetes Amyloidosis Uremia Myxedema Porphyria

Vitamin deficiency (thiamin, B12, B6, pyridoxine) Drugs and chemicals Alcohol

Cytotoxic drugs e.g., Vincristine Chlorambucil Nitrofurantoin Isoniazid Neoplastic disorders

Bronchial or gastric carcinoma Lymphoma Infective or inflammatory Leprosy

Guillain-Barre syndrome Lyme borreliosis

Chronic inflammatory demyelinating polyneuropathy Polyarteritis nodosa Genetic Charcot-Marie-Tooth disease Hereditary sensory neuropathies excluding those with neuropathy at baseline, the study showed that over a 7-year period, about one quarter of type 1 diabetic patients developed distal symmetrical neuropathy; age, duration of diabetes and poor glycamic control being major determinants (6). The development of neuropathy was also associated with potentially modifiable cardiovascular risk factors such as hyperlipidaemia, hypertension, body mass index, and cigarette smoking (6). Furthermore, cardiovascular disease at baseline carried a twofold risk of neuropathy, independent of cardiovascular risk factors (6). Based on recent epidemio-logical studies, correlates of diabetic neuropathy include increasing age, increasing duration of diabetes, poor glycemic control, retinopathy, albuminuria, and vascular risk factors (1,2,4,6). The differing clinical presentation of the several neuropathic syndromes in diabetes suggests varied etiological factors.

The clinical consequences of diabetic neuropathy are also varied. Some may have minor complaints, such as tingling in one or two toes; others may be affected with the devastating complications such as "the numb diabetic foot," or severe painful neuropathy that does not respond to drug therapy (7). Moreover, diabetic neuropathy is a major contributor to male erectile dysfunction and other autonomic symptoms that are thankfully rare.

Diabetic peripheral neuropathy presents in a similar way to neuropathies of other causes, and thus, the physician needs to carefully exclude other common causes before attributing the neuropathy to diabetes (Table 1). Absence of other complications of diabetes, rapid

Table 2

Classification of Diabetic Neuropathy Based on Natural History

1. Progressive neuropathies. These are associated with increasing duration of diabetes and with other microvascular complications. Sensory disturbance predominates and autonomic involvement is common. The onset is gradual and there is no recovery.

2. Reversible neuropathies. These have an acute onset, often occurring at the presentation of diabetes itself, and are not related to the duration of diabetes or other microvascular complications. There is spontaneous recovery of these acute neuropathies.

3. Pressure palsies. Although, these are not specific to diabetes only, they tend to occur more frequently in patients with diabetes than the general population. There is no association with duration of diabetes or other microvascular complications of diabetes.

Table 3

The Varied Presentations of the Neuropathic Syndromes Associated With Diabetes

1. Chronic insidious sensory neuropathy

2. Acute painful neuropathy

3. Proximal motor neuropathy

4. Diffuse symmetrical motor neuropathy

5. The neuropathic foot

6. Pressure neuropathy

7. Focal vascular neuropathy

8. Neuropathy present at diagnosis

9. Treatment induced neuropathy 10. Hypoglycemic neuropathy

Adapted from ref. 9.

weight loss, excessive alcohol intake, and other atypical features in either the history or clinical examination should alert the physician to search for other causes of neuropathy (8).

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