Diagnosing and managing chronic painful diabetic neuropathy - Review

Diabetic Foot, The,  Spring, 2004  by Susan J. Benbow,  Christina Daousi,  Ian A. MacFarlane

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Introduction

A global epidemic of diabetes has emerged, largely as a result of increasingly sedentary lifestyles and a rising prevalence of obesity. Neuropathy is one of the most common and troublesome complications of diabetes, and the number of people afflicted is likely to increase steadily as the incidence of diabetes in the developed world rises. Although foot ulceration is the most commonly recognised complication of peripheral neuropathy (Boulton, 2000), neuropathic pain can also occur, causing significant morbidity and impairment in quality of life (Benbow et al, 1998). This article reviews the frequency of chronic painful neuropathy, and provides an update on its recognition and management.

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Diabetic neuropathy is not a single entity but a heterogeneous group of disorders that encompasses a wide range of abnormalities. One common classification scheme is based on anatomical distribution and includes two main types of diabetic neuropathy: diffuse neuropathies and focal neuropathies (Table 1; Thomas, 1997).

The most common diffuse neuropathy in patients with diabetes is chronic distal symmetric sensorimotor polyneuropathy affecting predominantly the feet and lower legs (Boulton, 2000). This can predispose to the development of neuropathic foot ulceration (Boulton, 2000), cause chronic neuropathic pain, or be associated with both.

Neuropathic pain is defined by the International Association for the Study of Pain (IASP) as pain 'initiated or caused by a primary lesion or dysfunction of the nervous system'--in contrast to nociceptive pain (commonly seen in medical practice) which warns the individual of actual or potential tissue damage, e.g. the pain felt when putting your hand into boiling water.

Chronic painful polyneuropathy

This is one of the clinical manifestations of chronic distal sensorimotor polyneuropathy. In some patients with diabetes, painful neuropathic symptoms can be present at the time of diagnosis or may develop insidiously over the following years, eventually becoming debilitating and often impairing the quality of life of those afflicted (Benbow et al, 1998).

The IASP defines chronic pain as pain lasting for more than 3 months. However, in clinical trials, painful symptoms lasting for 12 months or more is a better criterion for distinguishing acute from chronic pain.

Chronic painful neuropathic symptoms may last for many years. Some longitudinal studies of painful diabetic neuropathy have shown a general tendency for painful symptoms to improve (Benbow et al, 1994), whereas others have found no change. The treatment of this chronic form of painful neuropathy presents a real challenge to the physician, and the frequently encountered resistance to various forms of intervention can generate considerable frustration for both patient and doctor.

This article focuses on the chronic form of pain found most commonly in the feet and legs, although severe neuropathic pain can rarely occur in an acute form of lower leg neuropathy, or very occasionally in other sites such as the trunk or thighs.

How common is chronic painful diabetic neuropathy?

Estimates of the prevalence of painful neuropathy vary substantially, depending on the diagnostic criteria used and the populations studied.

* In a hospital clinic population, 25% of patients with diabetes had symptoms of chronic pain and 8% had typical lower limb neuropathic symptoms (Chan et al, 1990).

* One study found that 11% of insulin-treated patients had painful symptoms (Boulton et al, 1985)

* Another study reported that 20% of patients with type 2 diabetes had neuropathic pain after 10 years of diabetes (Partanen et al, 1995).

* More recently a community-based study of patients with type 1 and 2 diabetes (attending either primary or secondary care clinics or both) estimated the prevalence of chronic (duration >1 year) painful diabetic neuropathy to be 16.2% (Daousi et al, 2004). This study is the largest study to date in which well-defined criteria of painful diabetic neuropathy and validated measures of pain severity and quality were used, giving a true and representative picture of the extent of the problem in the population with diabetes in the community.

How is chronic painful diabetic neuropathy diagnosed?

Chronic painful diabetic neuropathy is diagnosed through history and examination.

History

The diagnosis of chronic painful diabetic neuropathy is based primarily on eliciting a typical history. The contribution of clinical examination and elaborate investigations to the diagnosis is probably minimal, although they are necessary to exclude other causes of the pain.

The earliest symptoms, which begin insidiously, typically involve the toes, and then advance proximally up the legs. Hand involvement can occur later, is usually less severe and far less common. There is no relationship between the severity of the neuropathy and the severity of the pain reported by patients.

The character of the pain in diabetic neuropathy can be highly diverse. Patients tend to have a range of symptoms which can also vary over time. Symptoms can develop spontaneously or be brought on by a particular stimulus.