Neuropathy

There are many causes of peripheral neuropathy and in about 30% of cases; the cause is unknown and referred to as idiopathic neuropathy. Common causes include:

• Diabetes – The longer the duration of diabetes, the greater the chance of developing neuropathy. It is estimated that half of all people who have been living with diabetes for 25 years or more have diabetic neuropathy.
• Vitamin deficiencies – especially vitamin B12, but also other B vitamins such as B1, B6, B3, and vitamin E
• Alcoholism – due to nutritional deficiencies and many think as a direct effect of the alcohol
• Trauma – physical injury to a nerve; may be seen with repetitive stress and with any condition that traps, compresses, or damages a nerve (e.g., carpal tunnel syndrome).

Other causes include:

• Kidney, liver and lung disease, or other chronic illness
• Hypothyroidism and pituitary disorders
• Autoimmune disorders such as Guillain-Barré syndrome, rheumatoid arthritis, and systemic lupus erythematosus (SLE).
• Some cancers, either through production of substances that damage peripheral nerves (paraneoplastic syndrome) e.g. lymphoma, multiple myeloma or lung cancer, or through direct compression of the nerve itself.
• A wide range of infections, including: shingles (varicella zoster virus), Lyme disease, HIV/AIDS, cytomegalovirus (CMV), Epstein-Barr virus, syphilis, leprosy, diphtheria, and parasites
• Exposure to toxins, such as the heavy metals lead, arsenic, and mercury, or to other environmental toxins.
• Some medications can cause peripheral neuropathy as a side effect. These include: antiretrovirals (for treatment of HIV infections), microtubule inhibitors (a type of chemotherapy), metronidazole, thalidomide (used in treatment of multiple myeloma), phenytoin and disulfiram (for treatment of alcohol dependence).
• Other rare, inherited disorders such as Charcot-Marie-Tooth disease

The symptoms of neuropathy depend upon the nerves affected. Neuropathies often start in the longest nerve fibres, those in the feet and legs, and ascend progressively, to affect the hands and arms and other parts of the body. There may be numbness, tingling, and pain that can range from mild to extremely severe and debilitating. Symptoms may include:

• Loss of reflexes, balance, and coordination
• Muscle atrophy
• Muscle weakness, cramping, paralysis, or twitching
• Pain – burning, aching, sharp, jabbing, electric-like, shooting
• Extreme sensitivity to touch, even with very light pressure (such as from a bed sheet)
• Tingling, numbness, loss of ability to detect touch, pressure, temperature, and vibration

If autonomic nerves are affected, symptoms may include:

• Blurred vision; slow pupil reaction, which affects night vision
• Decreased or excessive sweating and heat intolerance
• Difficulty swallowing or breathing
• Dizziness and fainting when standing due to low blood pressure
• Erectile dysfunction in males; vaginal dryness in females
• Heart rate that does not change appropriately with exercise
• Incontinence and difficulty urinating and emptying the bladder
• Lack of awareness of low blood glucose
• Altered movement of food through the gastrointestinal tract, leading to constipation or diarrhoea, abdominal pressure and bloating, nausea, heartburn

Complications arise with sensory and motor nerves primarily because injuries and tissue damage are not noticed. Sores that develop may be slow to heal and can become infected. This can lead to tissue erosion, scarring, and, in some cases, the need for amputation. Decreased muscle control can lead to tripping and falling, causing additional damage.

Autonomic neuropathy can cause organ dysfunction, irregular heart rhythms, breathing difficulties, urinary infections, bowel problems, and sexual dysfunction.

The goals of testing are:

• To diagnose the presence of neuropathy and distinguish it from other conditions that may cause similar symptoms
• Identify the cause, where possible
• Identify underlying conditions that make it worse
• Detect and evaluate complications
• Evaluate the location, extent, and severity of the nerve damage and assess organ function

Laboratory Tests

Laboratory testing is used to look for underlying conditions that may cause or contribute to a neuropathy, detect complications, and evaluate organ function. Tests requested by your doctor may include:

• Glucose – to diagnose diabetes and evaluate blood glucose control in a known diabetic
• Routine biochemistry / Haematology tests to evaluate liver, kidney, and other organ function and to detect evidence of blood cell abnormalities, infection and metabolic problems
• Vitamin B12 – and possibly measurement of other vitamins to detect vitamin deficiencies
• Thyroid function tests– to detect hypothyroidism
• Specific tests for autoimmune disorders (e.g. SLE)
• Specific tests for infectious conditions, such as shingles (varicella zoster virus), Lyme disease, HIV/AIDS, cytomegalovirus (CMV), Epstein-Barr virus, and syphilis
• Heavy metals (e.g. mercury, lead) , if evidence of exposure – to detect poisoning
• Phenytoin - long-term use of which can cause peripheral neuropathy
• CSF analysis – to detect abnormalities or infections in the central nervous system
• Rarely, genetic testing to identify certain inherited disorders

Some laboratories offer a panel of antibody tests, such as a motor neuropathy antibody panel and a sensory neuropathy antibody panel, to aid in diagnosis. Elevations in certain antibodies have been associated with various neuropathies.

Non-Laboratory Tests

Testing typically begins with a neurological evaluation and clinical history and may include:

• Nerve conduction tests – to evaluate nerve transmission
• Electromyography (EMG) – to measure muscle activity

And sometimes:

• Nerve biopsy – to evaluate nerve damage
• Skin biopsy – to evaluate nerve endings

Imaging scans to evaluate internal organs, bones, and blood vessels and to detect tumours may include:

• Ultrasound
• Computed tomography (CT scan)
• Magnetic Resonance Imaging (MRI)

Examinations of affected body parts, such as the feet, are conducted to assess their condition and the degree of sensation loss.

If autonomic nerve involvement is suspected, additional testing may be performed to evaluate heart rate, blood pressure, the digestive tract, pupil response, and sweating.

The goals of neuropathy treatment are to prevent nerve damage when possible, slow its progression, maintain body function, and manage symptoms and complications. Nerves can regenerate in some cases, and symptoms may resolve or improve over time when neuropathy is due to a condition that can be treated, such as a vitamin B deficiency. Treatment will depend on and is directed against any known cause of the neuropathy.

Most cases of neuropathy are not curable and the damage done is frequently permanent. To minimise further damage, it is important to:

• Control underlying conditions, such as maintaining good glucose control in patients with diabetes and reducing the inflammation associated with autoimmune disorders
• Limit smoking and alcohol consumption
• Avoid exposure to toxins
• Avoid immobility and pressure on nerves
• Protect tissues that have decreased sensation, such as comfortable socks and shoes for the feet
• Monitor affected areas frequently, and promptly address problems such as reddened skin and sores that may worsen and become infected

Several classes of medications are used to help alleviate neuropathic pain. They range from over-the-counter analgesics (painkillers) for mild pain to anti-seizure medications such as carbamazepine, antidepressants, and opioids or opioid like drugs for more severe pain. Surgical procedures may be necessary in some cases to release trapped or compressed nerves.

Lifestyle changes, such as a balanced diet and supervised exercising and stretching, can help maintain and improve muscle control and relieve some symptoms. People should work with their doctors to determine the best treatments for their condition. A person's needs often change over time, and new and alternative treatments continue to be developed.