Neuropathic pain

Neuropathic pain is a type of chronic pain caused by injury or disease of the nervous system. Nerve pain is often puzzling and frustrating for patients and physicians, as it responds poorly to commonly used painkillers. It can worsen over time and result in severe disability.

Between 1.5 percent and 7.7 percent of people are believed to be affected by neuropathic pain in the United States and in European countries, respectively. However, it is a syndrome that is often under-diagnosed and under-treated.

There are several types of neuropathic pain. These include:

• Complex Regional Pain Syndrome
• Diabetic Neuropathy
• Facial Pain
• Atypical Facial Pain
• Trigeminal Neuralgia
• Pain After Spinal Cord Injury
• Pain After Stroke
• Phantom Limb Pain
• Postherpetic Neuralgia

Neuropathic pain is commonly described as ‘burning', ‘shooting',‘stabbing” or ‘electric-shock like'. These symptoms can come and go at any time and may be worse at night. Other common symptoms associated with neuropathic pain include:

• Allodynia - pain caused by something that is generally not painful, such as contact with clothes or bedsheets.
• Paresthesias - abnormal sensations that are described as 'tingling' or 'pins and needles'.
• Dysesthesias - Unpleasant sensations and funny feelings such as ants crawling over the skin or water trickling down the skin.

These symptoms can be mild to incapacitating and may be progressive. Drugs used to treat neuropathic pain may include opioids and anti-neuropathics (anti-convulsants and anti-depressants). Other treatment modalities such as physiotherapy, relaxation and psychological management are an important part of management.

Complex Regional Pain Syndrome

Complex regional pain syndrome (CRPS) is a chronic neurological syndrome that develops when the nervous system is injured and damaged. The exact cause of CRPS is unknown, but people with CRPS experience severe burning pain and increased sensitivity to touch. This is usually confined to a specific region of the body, most commonly an arm or a leg. Early diagnosis is crucial in order to prevent progression and regain normalcy. Your doctor may suggest certain treatment to reduce your pain and to get you moving again. These may include oral medications, nerve blocks and spinal cord stimulators. In addition, multidisciplinary management by other allied health professionals are an important part of treatment.

Diabetic Neuropathy

Diabetic neuropathy is a complication of diabetes that refers to temporary or permanent nerve tissue damage. It is caused by low blood flow to nerve tissue and high blood glucose levels. Diabetic people whose blood glucose levels are not well controlled are more likely to develop this condition.

Some people with diabetic neuropathy may not have any symptoms. But others will experience some symptoms, which develop gradually over the years, such as pain in the feet, numbness in the limbs, tingling sensation in the fingers and toes, weakness, decreased or loss of sensation in a body part.

As symptoms vary depending on the nerve(s) affected, some people might experience other symptoms, such as male impotence, low blood pressure when lying down, damaged or swollen joints, inability to empty the bladder and excessive sweating.

People with diabetic neuropathy have an increased risk of injury due to loss of sensation and/or motor function. When complete loss of sensation occurs in the feet, they may not be aware when their feet get injured and consequently fail to get prompt treatment. Poor circulation coupled with slow wound healing can lead to serious infections, ulcers and even gangrene. In severe cases, toes, feet or other affected body parts may need to be amputated.

Although diabetic neuropathy often causes a loss of sensation, it sometimes causes pain, particularly in the feet and legs. This pain is often distressing to sufferers, especially at night when it can prevent sleep. Unfortunately, conventional painkillers are not very useful to treat this type of pain. Your doctor will be able to discuss other pain relief options with you.

Facial Pain

Facial pain may arise from a nerve disorder, or a local injury or infection in any of the major structures of the face. Facial pain may also originate from other parts of the body, and it sometimes occurs for no known reason.

Atypical Facial Pain

Atypical facial pain refers to pain in the face for which there is no specific cause. A sufferer often describes the pain as aching, burning, cramping, dull, nagging or throbbing on one side of the face. This pain can also extend to the upper neck or back of the scalp. Each episode usually lasts longer than a few seconds (minutes or hours), and can be intermittent or continuous with few, if any, pain-free periods. The pain can be severe enough to affect sleep. Atypical facial pain affects mainly adult men and women with equal frequency.

This condition does not respond to the usual pain medications and surgery. The most widely used medication to treat this condition is anti-depressants and anti-convulsants which have a specific effect on nerve pain. M ultidisciplinary management by other allied health professionals is also an important part of treatment.

Trigeminal Neuralgia

The trigeminal nerve is one of the largest nerves in the head. It relays touch, pressure, temperature and painful sensations from the face to the brain.

Trigeminal neuralgia, also known as tic douloureux, is a non-fatal disorder of the trigeminal nerve. This disorder is more common in women than men and in people older than 50 years, although it can occur at any age. It is generally characterized by episodes of sudden, intense, stabbing or electric shock-like pain on one side of the face. This pain attack is spasmodic, lasts a few seconds and can occur several times consecutively and can repeat many times over the course of the day. The pain often starts when specific trigger points on the face are touched. For eg, simple acts of brushing teeth, chewing, applying make-up, shaving and talking can trigger an attack and cause severe pain. These triggers vary from person to person.In between attacks, the patient is completely pain-free and sleep is not affected.

People with trigeminal neuralgia are usually treated with anti-neuropathic medications, such as gabapentin or carbamazepine. Other medications, such as anti-depressants, may be given to for their neuropathic pain-relieving effects. If medications are ineffective in relieving pain or produce undesirable side effects, surgery may be required.

Pain After Spinal Cord Injury

A spinal cord injury usually begins with a sudden, traumatic blow to the spine that fractures or dislocates vertebrae. This may result in complete or partial paralysis. Depending on the level of the injury, the person may be paralysed from the waist downwards (paraplegic) or from the neck downwards (quadriplegic). Usually the person loses sensation (feeling) in the affected parts of the body as well.

Sometimes, paraplegics or quadriplegics also have what is called neuropathic (or neurogenic) pain resulting from damage to nerves in the spinal cord. This pain is usually described as an intense burning or stinging sensation in the affected part of the body. This pain is often very puzzling to the person affected, as it occurs in a part of the body with no feeling. The person may also experience sharp shooting or stabbing pains which occur intermittently, often spontaneously (without any reason or trigger).

Treatments for neuropathic pain from spinal cord injury include medications for nerve pain (antineuropathic medications) which include antidepressants and anticonvulsants, acupuncture, spinal or brain electrical stimulation, and surgery . As this kind of pain is usually very difficult to eliminate completely, physical therapy, psychological therapy including relaxation and other pain management skills are also an essential part of the holistic treatment of this kind of pain.

Pain After Stroke

Stroke occurs when blood flow to part of the brain is disrupted. Depending on the affected area in the brain, a stroke survivor may develop weakness, numbness, slurred speech, confusion, or paralysis.

Post-stroke pain is sometimes referred to as thalamic pain, neurogenic pain or central post-stroke pain. The exact cause of this type of neuropathic pain is unknown, but it results from injury to the brain following a stroke. The pain may start immediately after the stroke, or it may occur several months later. Post-stroke pain is felt on the face, arm, leg or trunk of the affected side of the body, and is often described as burning, throbbing, shooting or stabbing.

Conventional pain medications do not relieve post-stroke pain. Your doctor may prescribe you with anti-depressants or anti-convulsants that have been shown to be effective in treating post-stroke pain. These medications must be taken regularly for them to be effective. Multidisciplinary management by other allied-health professionals is also an important part of treatment.

Phantom Limb Pain

Amputation involves the removal of single or multiple body parts. It is common for people who underwent amputation to experience pain or discomfort in where their missing body parts or limbs used to exist. In most cases, it is those who had an arm or a leg removed that experience phantom limb pain.

This type of pain is unpredictable – it can occur at any time, and the level and duration of pain vary from episode to episode. The exact cause of phantom limb pain is not known.

Treatment includes:

• Medications (eg, anti-depressants, anti-neuropathics, opioids)
• Non-surgical procedures (eg, transcutaneous electrical nerve stimulation, electroconvulsive therapy)
• Surgical procedures (eg, spinal cord stimulation)
• Hypnosis
• Postherpetic Neuralgia

Shingles (herpes zoster) is a painful rash caused by the same virus that causes chickenpox (varicella zoster virus). It occurs more commonly in the elderly and people with compromised immune system, and it usually takes several weeks to resolve.

About half of those aged over 50 years who had shingles would experience continuing pain even after the rash has settled. This painful condition is known as postherpetic neuralgia, and it can last from a few weeks to months or years.

As postherpetic neuralgia can be an extremely painful and debilitating condition, sufferers are sometimes unable to carry out their usual daily tasks. This can result in weight loss, depression and the loss of independence.

The pain arising from postherpetic neuralgia may not respond well to simple pain medication. Instead your doctor might treat you with other pain medications, such as anti-neuropathics, anti-depressants or local anaesthetics.