What is pain?
The International Association for the Study of Pain (IASP) defines pain as:
“An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage”1.
When reading this rather complicated definition, one should also keep the following in mind:
- Pain is a personal experience, and your individual experience of pain will be affected by physical, mental, and social factors to varying degrees.
- Your experience of pain is more than just what your sensory nerves pick up.
- Your concept of pain is something you learn and develop over the course of your life.
- While pain usually serves to protect you from harm, it can also negatively impact your life1.
The take-home message from the above is that pain is personal and that it is both a sensation and an emotional experience with several factors over the course of one’s life that influence and shape our perception of pain. It is also possible to experience pain in the absence of actual tissue damage1.
Pain receptors in the body are called nociceptors. In addition to the way one’s brain interprets the stimulation of these nociceptors, the experience of pain is also influenced by one’s memories as well as emotional, pathological (disease-related), genetic and cognitive (or intellectual) factors2.
Types of pain
It is customary to classify pain as either acute or chronic. Acute and chronic pain differ from one another to such an extent that they are considered separate entities3,4.
Acute pain
Acute pain is caused by a specific disease or injury and is self-limiting4. It serves a useful biologic purpose in that it has a protective role in the body4,5.
This is the type of pain that we experience when touching something too hot, cold, or sharp and results from stimulation of our pain receptors or nociceptors5.
Our bodies sense and process acute pain in the following manner6:
- Specific pain receptors (nociceptors), present in most body tissues, are only stimulated by damaging or potentially damaging stimuli.
- The information is converted into an electrical signal that passes from the nerves in the body (known as the peripheral nervous system) to the spinal cord.
- From the spinal cord, the signal is transmitted to the brain.
- When the signal reaches the brain, it gets processed and interpreted and one experiences the sensation of pain.
- The brain then sends a new message back down the spinal cord to the nerves that are in charge of movement, and one reacts to the pain – such as pulling your hand away from a burning hot surface.
- Some people can tolerate a painful stimulus for longer without needing to act – this is called pain tolerance. It is a complex function that may be modified by personality traits, attitudes, previous experience, economic factors, gender, and the particular circumstance under which pain is experienced. It differs widely among individuals.
Chronic pain
Chronic dysfunctional pain is pain that persists for more than three months2. It may be considered a disease state and is one of the largest medical health problems in the developed world2,4. Estimates indicate that it may affect approximately 20 % to 25 % of adults2,7.
Unlike acute pain, chronic pain serves no biologic purpose and has no recognisable endpoint4.
Imaging studies have confirmed that, with chronic dysfunctional pain, the activity of pain pathways to and from the brain are altered. Attentional state, positive emotions, and negative emotions are but a few factors unrelated to the pain stimulus itself that may alter these pain pathways. Numerous studies have shown that patients with chronic pain have alterations in brain regions involved in the cognitive and emotional modulation of pain. This may also partly explain why chronic pain is often associated with anxiety and depression7.
Examples of chronic pain syndromes include chronic headaches, fibromyalgia, irritable bowel syndrome, temporomandibular disorders, and many others7. A patient with a chronic pain syndrome may also experience fatigue, unrefreshing sleep, difficulties with concentration and mood disturbances7.
Symptoms and signs of chronic pain
In general, chronic dysfunctional pain:
- Lasts longer than three months2.
- Creates changes in the brain that are visible on a scan5,6.
- May be located in one specific area of the body or be widespread6.
- May manifest in different ways at different times (e.g., a patient may experience irritable bowel syndrome for a while, then when that clears up, may develop fibromyalgia)6.
- May be accompanied by:
- Fatigue
- Poor sleep
- Brain fog
- Anxiety and depression6.
Chronic, dysfunctional pain as described above should be differentiated from two other types of longer-lasting pain, namely neuropathic pain and inflammatory pain5,7.
Inflammatory pain is similar to acute pain in that it is also adaptive and protective. This type of pain amplifies sensory sensitivity after unavoidable tissue damage and discourages physical contact and movement of the injured body part. In doing so, it assists with the healing process. This is the type of pain that results from a surgical wound or an inflamed joint where a usually harmless stimulus (such as ordinary touching) may now elicit pain. This pain is caused by activation of the immune system by tissue injury or infection. It requires treatment in patients with ongoing inflammation, such as seen with rheumatoid arthritis5,7.
Neuropathic pain is ongoing pain that results from physical damage to a nerve or the nervous system so that the structure and function of nerves are altered. Such lesions can be seen with scans, or identified with nerve tests, nerve biopsies or certain laboratory tests. Frequent causes include strokes, inflammation or damage of the blood vessels that supply oxygen and nutrients to a nerve, diabetes, or shingles7,8. Neuropathic pain can present in several ways, including:
- Excruciating pain when anything, including clothing, touches the skin.
- Sudden intense burning sensation for no apparent reason.
- Sudden bursts of pins and needles in the feet when walking.
- Continuous, crushing pain in a “phantom limb” after an amputation.
- Band of searing pain wrapped around the body after a spinal cord injury8.
Causes of pain
Acute pain is the result of stimulation of pain receptors (or nociceptors). It is a protective mechanism to limit physical damage as a result of disease or injury4 and will elicit immediate attention and action (such as the withdrawal reflex)5. It is self-limiting and is maintained only in the presence of the harmful stimulus4,8.
Chronic dysfunctional pain appears to be the result of amplification of painful signals inside the nervous system with a disturbed balance between excitatory and inhibitory pain pathways within the brain and spinal cord. In other words, the sensory nerves responsible for sensing pain spontaneously become overexcited and the brain starts to interpret and react to pain in an inappropriate (or overexcited) manner. It is not clear why this happens7,8. It is seen in conditions such as fibromyalgia, irritable bowel syndrome (IBS) and interstitial cystitis (a type of chronic bladder pain)8.
Chronic inflammatory pain occurs in response to tissue injury and the subsequent inflammatory response. It is usual for inflammatory pain to disappear after resolution of the initial tissue injury, but, with chronic inflammatory disorders such as rheumatoid arthritis, the pain will persist for as long as inflammation is ongoing8.
Neuropathic chronic pain is the result of damage to the nervous system. Mechanical trauma, metabolic diseases such as diabetes, infection (e.g., the chickenpox virus that causes shingles), or invasion by cancer cells are but a few of the causes of damage to nerves in the body. Spinal cord injury, stroke, or multiple sclerosis may give rise to damage to the nerves and pain pathways in the spinal cord and brain8.
Diagnosis
When you are being evaluated for pain, you can help your doctor by explaining:
- Where it hurts
- How much it hurts (e.g., only a little to extremely much)
- How unpleasant the experience is for you (e.g., bothers you only a little bit to being unpleasant to an extreme)
- How you feel about experiencing the pain (e.g., angry, depressed, or anxious).7
Apart from a physical examination, you may also require imaging scans, nerve biopsies, blood or laboratory tests, or nerve conduction tests to try and determine the cause of long-standing pain7,8.
Treatment
Management of acute pain aims to treat the underlying cause and to interrupt the pain signals arising from the stimulated pain receptors. Treatment of chronic pain is more complex and requires a multidisciplinary approach involving more than one therapeutic modality4.
To effectively treat pain and its associated conditions, it is important that both you and your doctor have a good understanding of your pain and its severity to ensure that you receive the best option for your situation9.
The World Health Organization (WHO) has issued the following guidelines to help doctors and patients manage pain more effectively:
- Generally, it is better to take oral medication and only resort to a drip or suppository when necessary.
- If your healthcare provider recommends a schedule of when to take your medicines, be sure to stick to it rather than only taking medication when you feel you need it.
- Painkillers should be matched to the intensity of your pain, and it is therefore important to have a physical examination combined with an adequate pain assessment9.
Usually for severe, acute pain, your healthcare provider would initiate treatment with potent analgesics (pain-relieving medicines) and then decrease the dosage and/or switch to less potent options as the pain subsides. In case of chronic pain, your doctor may start with a mild analgesic at a lower dosage and then increase the dosage or add other medicines as necessary9. It is important to go for follow-up consultations in order to assess your medication and whether your dosage needs to be adjusted8.
Responsible Opioid Use
Opioids, such as codeine, tramadol, and hydrocodone, are commonly prescribed for the treatment of moderate to severe pain but carry the risk of addiction9.
These medicines should therefore only be used when absolutely necessary and for as short as possible. Your healthcare provider will best be able to guide you.
Treatment options
Medical treatment options
The WHO has developed the so-called analgesic ladder. With this model, treatment of pain is approached in a stepwise fashion, where increasing “steps” represent increased pain severity with its corresponding treatment options:
- Mild pain: Non-opioid (or non-narcotic) painkillers such as non-steroidal anti-inflammatory drugs (NSAIDs) or paracetamol.
- Moderate pain: Weak opioids (such as codeine or tramadol) with or without non-opioid painkillers.
- Severe, persistent pain: Potent opioids (such as morphine or oxycodone) with or without non-opioid painkillers9.
In case of moderate or severe, persistent pain, doctors may also opt to use adjuvant pain medication. These adjuvants are typically given for conditions other than pain but have been shown to be of particular help in various painful conditions. Examples of adjuvants include antidepressants (such as amitriptyline or duloxetine), anticonvulsants (such as pregabalin), topical anaesthetics, corticosteroids, or cannabinoids9.
Non-medical treatment options
Non-medical treatment options may be recommended alongside medication in some cases8. Examples include:
- Yoga
- Acupuncture
- Psychotherapy
- Occupational therapy9.
Helpful tools
Faces Pain Scale10
This visual tool is a useful way to help young children describe the level of pain they are experiencing. It is based on the popular numerical scale where pain is rated from 0 (no pain) to 10 (extreme pain) but instead of numbers, children are shown pictures of facial expressions, ranging from relaxed to grimacing. Once the child understands that the relaxed faced indicates no pain and the grimace indicates severe pain, they simply need to point to a face on the continuum that corresponds with how they are feeling.
