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What is chronic pain?
Pain can be described as either acute or chronic. Acute pain is generally the result of an injury, illness or surgery and usually eases after its initial onset. By three months, the body has had enough time to heal from most causes of acute pain. Any pain that lingers past this three-month healing time is described as chronic. It occurs as a result of the pain pathway becoming hypersensitive.
Chronic pain has a variety of underlying causes, and there is a wide range of signs and symptoms that may accompany it. It is estimated that up to one in five people may experience chronic pain. Its incidence increases with age, with up to one in three people over the age of 65 years experiencing some form of chronic pain. 
Chronic pain is complex and different to acute pain. With acute pain, injury or illness activate pain receptors, known as nociceptors, which signal to the brain to feel the unpleasant sensation of pain. It is a protective mechanism to warn the body of potential injury or damage.
In contrast, chronic pain is thought to be due to an increased sensitivity in the pain pathways leading to and from the brain. This can result in a simple touch or the slightest bump being interpreted as severe pain. This is caused by changes in levels of chemicals in the brain, such as serotonin, noradrenaline and dopamine. Even if there is an underlying painful condition, such as arthritis, the level of pain is usually out of proportion to the damage. It no longer serves the purpose of warning the body to protect itself from potential injury.
Distinguishing between acute and chronic pain is important as the approaches to treatment for each differ.
Types of chronic pain
There are numerous ways of categorising chronic pain. However, the common types are:
Nociceptive pain is thought to be due to ongoing, inadvertent stimulation of pain receptors, due to actual painful stimuli. These pain receptors can be found within the skin, muscles, lining of bones and joints, and internal organs. Causes include arthritis, fractures, and back injuries.
Neuropathic pain, also known as nerve pain, is caused by damage to or dysfunction within the nervous system, which do not include the pain receptors. It can affect any part of the nervous system, from the nerves in the fingers and toes, through to the spinal cord and even the brain. It can be felt as burning, tingling or shooting pains. In some cases, pain can be felt even when there is no painful stimulus. Causes include carpal tunnel syndrome, diabetes, and stroke.
There are also certain specific neuropathic syndromes:
Painful neuropathies are caused by damage to nerves, which leads to the further activation of nerves as being interpreted as painful sensations. There are numerous causes for painful neuropathies; however, the most common cause is diabetes neuropathy. This affects as many as one in two people with diabetes, usually after several years with the condition. It can affect any nerve in the body.
Complex regional pain syndrome
Complex regional pain syndrome (CRPS), also known as reflex sympathetic dystrophy (RSD) or causalgia, is marked by severe, debilitating pain in an area of the body, often following an injury. The pain can be so intense that even the slightest touch can be excruciating. It can also be associated with changes in blood flow, sweating, skin changes, muscle wasting and bone loss in the affected region.
Post shingles neuralgia
Post shingles neuralgia, also known as postherpatic neuralgia, is a complication of shingles, in which after the shingles resolves, a burning, aching or sharp pain remains.
Phantom limb pain
Phantom limb pain is the bizarre feeling of pain in an amputated area of the body. This is different from phantom limb sensation, which is the feeling that the amputated part is still there.
Cancer pain is different from other types of pain, as it can actually arise from many different causes. Cancers can cause both nociceptive and neuropathic pain. Cancers invading surrounding tissues can stimulate pain receptors (nociceptive pain) and if it affects nerves, either directly or related to cancer treatments, it can cause neuropathic pain. Unlike other causes of chronic pain, cancer pain can be progressive, which then requires continued changes to treatments to help manage the pain.
The leading physical factors that may increase the likelihood of developing chronic pain may include:
Methods for diagnosis
Because pain is a personal and subjective experience, diagnosis of chronic pain can prove challenging. Furthermore, chronic pain may be localised to a particular region of the body, or be generalised.
The underlying cause of the pain is often not found. This does not mean that you do not have a physical reason for the pain. It is because modern tests are not yet capable of detecting these changes. Extensive investigations are usually not needed; however, they may be performed in particular situations, especially if there is a high suspicion of a serious underlying condition.
When a person with chronic pain visits their doctor, the initial assessment focuses on obtaining a detailed medical history. The medical history will involve questions relating to the pain location, its triggers, what modifies it and whether there are any other existing medical conditions.
Your doctor may use a pain diagram to compile a pain history. Using this diagram, you can indicate the location of your pain and describe its intensity and frequency, what triggers it and what makes it better. This can help your doctor form a better understanding of what may be causing the chronic pain.
Your doctor may also carry out a physical examination to assess your gait, range of motion, reflexes, balance, joint stiffness, nerves and tender points.
X-rays may be used during diagnosis if a patient appears to be suffering from traumatic pain, spinal pain, or has evidence of joint dysfunction. X-rays can help identify fractures, osteoarthritis, bone lesions and arthritic changes.
Magnetic resonance imaging of the spine
Magnetic resonance imaging (MRI) scans may be carried out if there is suspicion of spinal injury or damage. MRI scans of the spine can help to identify disc prolapse, spinal stenosis or other conditions, which may benefit from surgical treatment.
Electromyography and nerve conduction studies
Types of treatment
The treatment of chronic pain is focused on helping people to manage their pain, so they can continue everyday activities. Often, it is difficult to completely stop the pain.
Other principles of treatment include:
- Self care is important to enable a person to manage the day-to-day symptoms of chronic pain;
- The involvement of a group of different health professionals, including pain specialists and physiotherapists, to help manage the condition;
- Lifestyle changes aimed at avoiding common triggers;
- Limiting the use of strong medications, where possible;
- Using treatments with the least side effects, and;
- Treating associated emotional symptoms, such as depression.
Physical activity and exercise are important, where possible, as these can often help in the management of pain levels, improve self-esteem and help prevent conditions such as weight gain and muscle wasting, which are often the long-term effects of living with chronic pain. A physiotherapist may help a person with posture correction, stretching exercises and a range of motion exercises. People may initially need several sessions with a physiotherapist to establish a proper technique before being able to independently continue a home-based program on a long-term basis.
People with chronic pain who experience difficulty with social or work duties may find benefit in a review by an occupational therapist, to be given guidance about work modification and receive pain-management training.
People who know what triggers their pain are advised to avoid the triggers, such as repetitive movements or heavy lifting.
Each person responds differently to medication, so your doctor may try different medications and dosages to find the combination that provides the most relief. Broadly, there are two main groups of medications - non-opioids and opioids.
These comprise the following:
- Paracetamol - regular use can be beneficial for mild chronic pain;
- Non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen - can be useful in the short-term when chronic pain flares up. However, long-term use is generally not encouraged, due to potential side effects;
- Antidepressants, such as amitriptyline - when used in low doses, certain antidepressants can help reduce neuropathic pain. They can also be used in the treatment of chronic pain, if there are associated depressive symptoms, and;
- Medications used for epilepsy, such as pregabalin and gabapentin - certain antiepileptic medications have been shown to be effective in treating chronic pain in some individuals.
Any drug may be associated with a range of side effects of varying severity, so it is important to follow the recommended dosage and instructions of your healthcare provider.
Opioid medications, such as morphine and oxycodone, are strong pain-relief medications that help treat acute pain. However, they are less effective in treating chronic pain that is not caused by cancers. They are commonly associated with side effects, especially when used in the long-term, and higher doses are linked to overdose and potential death.
A trial of opioids may be used if other treatments have proven unsuccessful. However, these must be used cautiously and as strictly prescribed by your doctor, to avoid potential complications. If the opioids are not helping, then they should be ceased by your doctor. It is also a good idea to agree on the duration and dosing of the opioids, before starting the trial phase, so there is no temptation to keep increasing the medications and run the risk of developing complications.
Surgery is rarely used for management of chronic pain; however, in particular situations, it may be beneficial. Surgery may be used to treat nerve pain caused by carpal tunnel syndrome, disc prolapse of the spine and spinal stenosis. This type of surgery is known as decompression surgery. The operation relieves the pressure put on an irritated nerve by tissues surrounding it.
Occasionally, surgery can also be used to administer chemicals or implant devices that can help control the pain. Devices can be implanted to deliver pain medications or electrical impulses to nerve endings to interrupt pain signals. Chemicals can be used to deliberately destroy nerves that may be chronically irritated and contributing to long-term pain.
Not all individuals are suitable for surgical treatment. Often, the success of decompressive surgery is specific to how early it is performed before permanent nerve injury occurs. Also, a patient often needs to be very motivated to follow through with intense physical therapy after the surgery to achieve adequate recovery.
There have been numerous studies looking at acupuncture and transcutaneous electrical nerve stimulation (TENS), a procedure that uses electrical stimulation of the skin, in the management of chronic pain. Overall the studies have not conclusively proven either therapy to be significantly effective.
If chronic pain is poorly managed, it can be associated with considerable disability and may seriously affect a person's quality of life. Poorly-managed chronic pain can lead to disability that may impair employment, relationships and everyday activities. In addition, poorly-controlled chronic pain can also affect a person's emotional wellbeing, which may result in psychological distress.
As a means of coping with their condition, some people with chronic pain may abuse or misuse medication, especially opioids. Regular consultations with your doctor can help identify these complications early and minimise their impact on your health.
Pain that is persistent, severe and continuous can severely affect a person's quality of life. Although chronic pain may be a lifelong affliction for some people, there is still much that can be done to reduce its severity and improve health outcomes. Prognosis depends on the cause.
Chronic pain cannot always be prevented, but there are some measures that may reduce the risk of developing it, which include: