Prevalence and causes

Peripheral neuropathy is a common complication of diabetes mellitus. On average the onset of symptoms occurs 10 to 20 years after diabetes has been diagnosed. Common symptoms of diabetic peripheral neuropathy (DPN) include numbness and/or insensitivity; prickling and/or tingling sensation; burning sensation; aching pain and/or tightness; sharp, shooting, lancinating pain; and allodynia and/or hyperalgesia (Bastyr 2005). Abnormal sensations and pain are features of approximately 10% of all cases of diabetic neuropathy and can cause marked diminution in quality of life for these patients. It is a chronic progressive disease accounting for considerable morbidity. Diabetic neuropathy was observed in 56% of patients with type 1 diabetes (Iwanicka 2000). It is the most common peripheral neuropathy in developed countries (Yasuda 2003). In the United States, diabetic symmetrical distal neuropathy or diabetic polyneuropathy is the most common form of neuropathy (Poncelet 2003).
The mechanisms of this disease include persistent hyperglycaemia, microvascular disease, modification of proteins critical to neural function by glycation and glycosylation, altered metabolism of fatty acids, increased activity in the polyol pathway and decreased neurotrophic factors.

Pathology

The pathogenesis of diabetic neuropathy has not been fully elucidated but is multifactorial. Some people with diabetes experience painful diabetic neuropathy (PDN), while others experience an asymptomatic, progressive loss of peripheral nerve function (Page 1997). Painful diabetic neuropathy is a major cause of morbidity in diabetes mellitus (Emanuele 1997). Painful diabetic neuropathy tends to develop in stages. Early on, intermittent pain and tingling is noted in the extremities, particularly the feet. In later stages, the pain is more intense and constant. In the second type of neuropathy, a painless neuropathy develops. This greatly increases the risk of severe tissue injury because pain no longer alerts the person to injury. Loss of sensation predisposes the patient to the development of diabetic foot ulcers and infection. Resulting infections may lead to serious sequelae of cellulitis, osteomyelitis, or gangrene, with amputation as the only possible cure in some instances (Hemstreet 2001).

Treatment

Glucose control has been proven to prevent or slow the progression of diabetic neuropathy. The goals of treating diabetic neuropathy are to prevent progression and reduce the symptoms of the disease. Treatment options include oral medication and insulin. Supportive therapies, including pain management and podiatric care, can improve quality of life and prevent chronic ulcerations (Poncelet 2003). Until now, there has not been an effective therapy for this disease.

Acupuncture for diabetic peripheral neuropathy

Acupuncture has been used for a long time in China to treat symptoms of diabetic neuropathy. Acupuncture therapy includes body acupuncture, scalp acupuncture, acupoint injection, electroacupuncture, laser acupuncture, moxibustion (an external method of preventing and treating diseases by ignition of moxa to stimulate the acupuncture points. It has the function of warming channels, to expel cold, and to induce the smooth flow of Qi and blood) or a combination of the above approaches. This ancient therapy hinges on the belief that a person's state of health depends on the balance and level of energy in the body.

It is known that acupuncture relieves pain by controlling the activities of the autonomic nervous system. It has been shown that opioid‐signaling events are involved in both neuropathic pain and the analgesic effects of acupuncture (Ko 2002), and the analgesic effect of acupuncture has a physiological basis. Using neurophysiological, neuropharmacological, neurobiochemical and neuromorphological methods, the neurohumoral mechanism of the analgesic effect of acupuncture was studied from the peripheral neural pathway of acupuncture sensation De‐Qi (needling sensation in Chinese Traditional Medicine (CTM)) to the central neuromodulatory effect (Cao 2002). This study indicated that needling of the acupuncture point could elicit De‐Qi sensation. De‐Qi refers to induction of the channel Qi after the needle is inserted. During the needling sensation, the patients have soreness, numbness, and a feeling of distension or heaviness around the point. This means acupuncture could activate nerve fibres ascending in the anterolateral spinothalamic tract which conduct pain and temperature sensation and activate the anti‐nociceptive system causing release of opioid peptides which stimulate descending inhibitory pathways resulting in analgesia (Cao 2002).

Although acupuncture was traditionally not recommended in patients with diabetes due to fear of infection and subsequent gangrene, modern advances in needle manufacture and sterilization have allowed practitioners to perform acupuncture safely on patients with diabetes.

Present status

Drug treatment for the symptoms of diabetic peripheral neuropathy is often inadequate. Uncontrolled studies of TENS and of acupuncture have been reported to decrease pain in >75% of patients with diabetic neuropathy (Julka 1998). Limited evidence from previous studies of acupuncture for pain relief suggests that 50 to 80% of patients appear to benefit from treatment and that some pain relief may be maintained after treatment ends. One recent study indicated that acupuncture has the action of improving the metabolism of blood sugar and blood‐lipid, lowering blood viscosity, and restoring the functions of peripheral nerve cells, thus giving definite therapeutic effects for diabetic peripheral neuropathy (Jiang 2006). Very few adverse effects are associated with acupuncture.

Our preliminary searches identified about 90 trials on treatment of diabetic peripheral neuropathy with acupuncture in the Chinese Biomedical Database (December 2001). The role and efficacy of acupuncture for treatment of the symptoms of diabetic peripheral neuropathy are still unclear. A systematic review of controlled trials comparing acupuncture to placebo, no treatment or other treatments is needed.