Diabetes Nerve Damage | Types of Neuropathy and Symptoms

Diabetic neuropathy is the nerve damage that arises as a consequence of long standing, poorly controlled diabetes mellitus (sugar diabetes). The signs and symptoms of diabetic neuropathy may vary depending on the nerves that are affected and the pattern of neurological involvement. Other causes of these types of neuropathy should also be excluded before it is attributed solely to diabetes.

Types of Diabetic Neuropathy

Distal Symmetrical (Sensorimotor) Polyneuropathy

This is the most common type of diabetic neuropathy and is seen in both type 1 and 2 diabetes. It affects the distal parts of the limbs – forearm, hand and fingers of the upper limb or lower leg, foot, toes of the lower limb.

Although the sensorimotor nerves are affected, it is the sensory component that is more severely impaired. This means that the sensory fibers involving pain, touch, temperature and vibration are affected and these sensations are disrupted. This type of diabetic neuropathy does not set in immediately but gradually progresses over months and years.

In the early stages, a patient is asymptomatic but a thorough neurological examination can reveal some level of impairment. As the condition progresses the patient develops tingling and numbness of the distal extremities distributed in the “glove-stocking” pattern. Patients may also complain of pain which gradually increases in severity.

Severe sensory loss is only seen in the late stages. There is also wasting of the small muscles of the hands and feet and this may even cause difficulty in walking. There may also be joint involvement (Charcot joints / neuropathic joints).

Autonomic Neuropathy

Autonomic neuropathy can affect the autonomic nerve supply of any organ in body. It is more frequently seen in type 1 diabetes and commonly occurs in patients with distal symmetric polyneuropathy (above). Autonomic neuropathy symptoms can range from very mild to very severe. The prognosis for autonomic diabetic neuropathy is poor and severe forms can even cause sudden death.

Majority of patients with clinically significant symptoms have autonomic neuropathy that predominantly affects the cardiovascular, gastrointestinal or genitourinary systems. The symptoms depends on the organ involved.

1. Cardiac

Cardiovascular autonomic neuropathy can lead to increased heart rate at rest, defective heart rate responses to exertion, and painless myocardial ischemia. Such patients are at high risk for myocardial infarction (heart attack) and sudden cardiac death.

2. Vascular

Impairment of sympathetic vasoconstrictor responses and defective cardiac reflexes leads to postural hypotension. This may be serious enough to warrant the use of medication.

3. Gastrointestinal

The most common manifestation of gastrointestinal neuropathy is constipation. Another common complaint seen is diarrhea. Diabetic diarrhea can also be caused by increased motility of gut, intestinal irritation caused by bile, decreased motility with bacterial overgrowth, or pancreatic dysfunction. Patients can suffer from disabling gastroparesis which is manifested by nausea, vomiting, abdominal bloating and loss of appetite.

4. Genitourinary

Autonomic neuropathy of the genitourinary system leads to dribbling, incomplete emptying of the bladder and urinary incontinence. Male diabetic patients are also susceptible to erectile dysfunction.

5. Sudomotor Dysfunction

Sudomotor dysfunction is characterized by abnormal sweat production which can affect the moisture of the skin and thermoregulation (temperature control). It can lead to xerosis (dry skin), skin cracking, heat intolerance, heat stroke and a risk of skin infections. Other sudomotor dysfunctions may include reduced sweating in the lower limbs with excessive sweating in the upper body or increased sweating in relation to eating (gustatory sweating).

Focal Diabetic Neuropathies (Mononeuropathy)

Focal diabetic neuropathies usually have an abrupt onset and are frequently associated with pain. It may affect the peripheral and cranial nerves. These types of neuropathies are usually self-limiting and patients may recover spontaneously within 6 to 8 weeks. Commonly affected nerves include the median, radial, oculomotor and lateral popliteal nerves.

Diabetic patients are also found to have entrapment neuropathies which are chronic and slow progressing. Common entrapment neuropathies can involve the median (carpal tunnel syndrome), ulnar, radial, lateral popliteal, peroneal, and plantar nerves.

Proximal Motor Neuropathy (Diabetic Amyotrophy)

Proximal motor neuropathy usually affects type 2 patients and is more frequently seen in elderly men. The disease classically results in pain and weakness in thighs, hips, and buttocks.

Article reviewed by Dr. Greg. Last updated on December 2, 2010