Pain is an unpleasant sensation that can range from mild, localized discomfort to agony. Pain has both physical and emotional components. The physical part of pain results from nerve stimulation. Pain may be contained to a discrete area, as in an injury, or it can be more diffuse, as in disorders like fibromyalgia. Pain is mediated by specific nerve fibers that carry the pain impulses to the brain where their conscious appreciation may be modified by many factors.
According to the pattern of pain there are three classes of pain
- Nociceptive pain,
- Inflammatory pain which is associated with tissue damage and the infiltration of immune cells, and
- Pathological pain is a disease state caused by damage to the nervous system or by its abnormal function (e.g. fibromyalgia, peripheral neuropathy, tension-type headache, etc.)
According to the severity three main categories of pain
- Acute pain – lasts for a short time and occurs following surgery or trauma or other condition. It acts as a warning to the body to seek help. Although it usually improves as the body heals, in some cases, it may not.
- Chronic pain – lasts beyond the time expected for healing following surgery, trauma or other condition. It can also exist without a clear reason at all. Although chronic pain can be a symptom of another disease, it can also be a disease in its own right, characterized by changes within the central nervous system.
Acute pain can last a moment; rarely does it become chronic pain. Chronic pain persists for long periods.
According to the treatment pattern, pain is following
- Chronic Pain –
- Nerve Pain –
- Psychogenic Pain –
- Musculoskeletal Pain –
- Chronic Muscle Pain –
- Abdominal Pain –
- Joint Pain –
- Central Pain Syndrome –
- Complex Regional Pain Syndrome –
- Diabetes-Related Nerve Pain (Neuropathy) –
- Shingles Pain (Postherpetic Neuralgia) –
- Trigeminal Neuralgia –
- Phantom pain – Phantom pain is pain felt in a part of the body that has been amputated, or from which the brain no longer receives signals. It is a type of neuropathic pain. The prevalence of phantom pain in upper limb amputees is nearly 82%, and in lower limb amputees is 54%. One study found that eight days after amputation, 72% of patients had phantom limb pain, and six months later, 67% reported it. Some amputees experience continuous pain that varies in intensity or quality; others experience several bouts of pain per day, or it may reoccur less often.
- Nociceptive – Nociceptive pain is caused by stimulation of sensory nerve fibers that respond to stimuli approaching or exceeding harmful intensity (nociceptors), and maybe classified according to the mode of noxious stimulation. The most common categories are “thermal” (e.g. heat or cold), “mechanical” (e.g. crushing, tearing, shearing, etc.), and “chemical” (e.g. iodine in a cut or chemicals released during inflammation). Some nociceptors respond to more than one of these modalities and are consequently designated polymodal.
- Breakthrough – Breakthrough pain is transitory acute pain that comes on suddenly and is not alleviated by the patient’s regular pain management. It is common in cancer patients who often have background pain that is generally well-controlled by medications, but who also sometimes experience bouts of severe pain that from time to time “breaks through” the medication. The characteristics of breakthrough cancer pain vary from person to person and according to the cause.
- Neuropathic -Neuropathic pain is caused by damage or disease affecting any part of the nervous system involved in bodily feelings (the somatosensory system). Peripheral neuropathic pain is often described as “burning”, “tingling”, “electrical”, “stabbing”, or “pins and needles”.Bumping the “funny bone” elicits acute peripheral neuropathic pain.
- Allodynia – Allodynia is pain experienced in response to a normally painless stimulus. It has no biological function and is classified by stimuli into dynamic mechanical, punctate and static. In osteoarthritis, NGF has been identified as being involved in allodynia. The extent and intensity of sensation can be assessed through locating trigger points and the region of sensation, as well as utilizing phantom maps.
The suggested ICD-11 chronic pain classification suggests 7 categories for chronic pain
- Chronic primary pain: defined by 3 months of persistent pain in one or more anatomical regions that is unexplainable by another pain condition.
- Chronic cancer pain: defined as cancer or treatment-related visceral, musculoskeletal, or bony pain.
- Chronic posttraumatic pain: pain lasting 3 months post-trauma or surgery, excluding infectious or preexisting conditions.
- Chronic neuropathic pain: pain caused by damage to the somatosensory nervous system damage.
- Chronic headache and orofacial pain: pain that originates in the head or face, and occurs for 50% or more days over a 3 months period.
- Chronic visceral pain: pain originating in an internal organ.
- Chronic musculoskeletal pain: pain originating in the bones, muscles, joints, or connective tissue.
|Common types of pain and typical drug management|
|Pain type||typical initial drug treatment||comments|
|headache||paracetamol /acetaminophen, NSAIDs||doctor consultation is appropriate if headaches are severe, persistent, accompanied by fever, vomiting, or speech or balance problems; self-medication should be limited to two weeks|
|migraine||paracetamol, NSAIDs||triptans are used when the others do not work, or when migraines are frequent or severe|
|menstrual cramps||NSAIDs||some NSAIDs are marketed for cramps, but any NSAID would work|
|minor trauma, such as a bruise, abrasions, sprain||paracetamol, NSAIDs||opioids not recommended|
|severe trauma, such as a wound, burn, bone fracture, or severe sprain||opioids||more than two weeks of pain requiring opioid treatment is unusual|
|strain or pulled muscle||NSAIDs, muscle relaxants||if inflammation is involved, NSAIDs may work better; short-term use only|
|minor pain after surgery||paracetamol, NSAIDs||opioids rarely needed|
|severe pain after surgery||opioids||combinations of opioids may be prescribed if pain is severe|
|muscle ache||paracetamol, NSAIDs||if inflammation involved, NSAIDs may work better.|
|toothache or pain from dental procedures||paracetamol, NSAIDs||this should be short term use; opioids may be necessary for severe pain|
|kidney stone pain||paracetamol, NSAIDs, opioids||opioids usually needed if pain is severe.|
|pain due to heartburn or gastroesophageal reflux disease||antacid, H2 antagonist, proton-pump inhibitor||heartburn lasting more than a week requires medical attention; aspirin and NSAIDs should be avoided|
|chronic back pain||paracetamol, NSAIDs||opioids may be necessary if other drugs do not control pain and pain is persistent|
|osteoarthritis pain||paracetamol, NSAIDs||medical attention is recommended if pain persists.|
|fibromyalgia||antidepressant, anticonvulsant||evidence suggests that opioids are not effective in treating fibromyalgia|
Causes of Pain
Common causes of musculoskeletal pain include:
- Chronic exertional compartment syndrome
- Chronic fatigue syndrome
- Hypothyroidism (underactive thyroid)
- Influenza (flu) and other viral illness (influenza-like illness)
- Lyme disease
- Medications, especially the cholesterol medications known as statins
- Muscle cramp
- Myofascial pain syndrome
- Polymyalgia rheumatica
- Polymyositis (inflammatory disease that causes muscle weakness)
- Repetitive strain injuries
- Rheumatoid arthritis (inflammatory joint disease)
- Rocky Mountain spotted fever
- Sprains and strains
- Years of poor posture
- Improper lifting and carrying of heavy objects
- Being overweight, which puts excess strain on the back and knees
- A congenital condition such as curvature of the spine
- Traumatic injury
- Wearing high heels
- Sleeping on a poor mattress
- No obvious physical cause
- Ordinary aging of the spine (degenerative changes)
Treatment of Pain
Medications for chronic pain
Several types of medications are available that can help treat chronic pain. Here are a few examples:
- over-the-counter pain relievers, including acetaminophen (Tylenol) or nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin (Bufferin) or ibuprofen (Advil).
- opioid pain relievers, including morphine (MS Contin), codeine, and hydrocodone(Tussigon)
- adjuvant analgesics, such as antidepressants and anticonvulsants
- Medication – Acute pain is usually managed with medications such as analgesics and anesthetics. Caffeine when added to pain medications such as ibuprofen, may provide some additional benefit. Ketamine can be used i nstead of opiods for short term pain. Management of chronic pain, however, is more difficult, and may require the coordinated efforts of a pain management team, which typically includes medical practitioners, clinical pharmacists, clinical psychologists, physiotherapists, occupational therapists, physician assistants, and nurse practitioners.
- Sugar (sucrose) – when taken by mouth reduces pain in newborn babies undergoing some medical procedures (a lancing of the heel, venipuncture, and intramuscular injections). Sugar does not remove pain from circumcision, and it is unknown if sugar reduces pain for other procedures. Sugar did not affect pain-related electrical activity in the brains of newborns one second after the heel lance procedure. Sweet liquid by mouth moderately reduces the rate and duration of crying caused by immunization injection in children between one and twelve months of age.
- Psychological – Individuals with more social support experience less cancer pain, take less pain medication, report less labor pain and are less likely to use epidural anesthesia during childbirth, or suffer from chest pain after coronary artery bypass surgery.
- Cognitive behavioral therapy (CBT) – has been shown effective for improving quality of life in those with chronic pain but the reduction in suffering is modest, and the CBT method was not shown to have any effect on outcome.Acceptance and Commitment Therapy(ACT) may also effective in the treatment of chronic pain.
Medical procedures for pain
Certain medical procedures can also provide relief from chronic pain. An example of a few are:
- electrical stimulation, which reduces pain by sending mild electric shocks into your muscles
- nerve block, which is an injection that prevents nerves from sending pain signals to your brain
- acupuncture, which involves lightly pricking your skin with needles to alleviate pain
- surgery, which corrects injuries that may have healed improperly and that may be contributing to the pain
Additionally, various lifestyle remedies are available to help ease chronic pain. Examples include:
- Cognative behaviour therapy
- Art and music therapy