Pain can have numerous causes as already highlighted in "What are the symptoms of pain".
Acute pain can usually be linked directly to the noxious influence or injury that caused the pain, like the pain you feel after burning your skin or following a surgical intervention.
For chronic pain the connection is far more difficult to establish as the original cause of pain might not exist any longer and the nerves may have become oversensitive and react already to the slightest stimulus, which would not cause any pain in otherwise healthy subjects.
Sometimes intensive, multi-disciplinary examination may be needed to reveal the underlying cause.
Frequent causes of pain:
-
Cancer
-
‘Musculoskeletal’ pain
- Osteoarthritis
- Rheumatoid arthritis
- Low back pain
- Failed back surgery
- Fractures & osteoporosis
-
Nerve pains due to
- Diabetic neuropathy
- Peripheral blood vessel disorders and stroke
- Herpetic infection
- Trauma
To learn more about pain according to the underlying mechanism or its location in the body…
Pain can be divided into different types according to the mechanism involved (nociceptive and neuropathic pain), and further by the part of the body affected by it. Doctors may classify the pain as it may help them in choosing an appropriate medicine or better managing your pain.
Nociceptive pain
Neuropathic pain
Mixed pain
Nociceptive pain
In this type of pain, so-called ‘nociceptors’ play a central role. Nociceptors are the receptors of sensory neurons that located in the skin or mucosa or internal organs. Pain arises when these receptors are activated by a possibly damaging stimulus. Different types of nociceptors perceive different types of stimuli:
- Thermal nociceptors are activated by noxious heat or cold.
- Mechanical nociceptors notice excess pressure or deformation.
- Chemical nociceptors are sensitive to chemical substances.
The perception of pain occurs when nociceptors are stimulated and transmit signals through sensory neurons in the spinal cord. The signals are then sent to the hypothalamus, the part of the brain in which pain perception occurs. From the thalamus, the signal travels to the brain, at which point the individual becomes completely aware of the pain.
Nociceptive pain can be further divided according to the part of the body into:
Somatic pain:
- originates from bones, muscles, tendons or blood vessels and is often known as musculo-skeletal pain
- usually sharp, well-localized
- can be reproduced by touching or moving the involved area
- usually of longer duration
e.g. inflammation on sprains or broken bone, ischaemic muscle cramps (because of oxygen starvation) or muscle pain on stretching.
Cutaneous pain:
- is due to injury of the skin or the superficial tissues
- usually well-described, localised pain of short duration
e.g. paper cut, minor burns.
Visceral pain:
- originates from the internal organs of the body’s cavities such as thorax (heart and lungs), abdomen (liver, kidneys, spleen and bowels) and pelvis (ovaries, bladder and womb)
- more aching, vague and often difficult to localise
- of longer duration
- sometimes colicky or cramping
e.g. gastro-intestinal spasms.
Neuropathic pain
This pain type follows damage to the central or peripheral nervous system. There are no specific receptors involved and pain is generated by nerve cell dysfunction. In the case of nerve pain, the pain is generated within the nervous system itself. In the case of so-called ‘sympathetic’ pain, the pain is due to overactivity of peripheral and/or nervous system mechanisms.
Neuropathic pain can be due to:
Peripheral neuropathy
- means that the peripheral nerves are not working properly
- is usually the result of an injury to or a disease process, such as diabetes associated with loss of function in the nerve
- often starts in the hand and feet and often affects the body symmetrically
Entrapment of a nerve
- a pinched or trapped nerve due to compression in the spine or elsewhere in the body, such as elbow, shoulder, wrist or foot
Phantom limb pain
- sensation of pain from a limb that has been lost or from which no longer physical signals are being received
- reported after amputation or in quadriplegics
Chronic central neuropathic pain
- can follow traumatic spinal cord injury or diseases of the brain itself, like stroke.
Other causes
Other causes with ensuing damage of the nervous tissue include post-herpes infection.
Mixed pain
In this type of pain both nociceptive and neuropathic pain mechanisms are involved. For instance in cancer pain, the pain can be due to the tumour causing inflammation of tissue around the tumour (nociceptive) and causing entrapment of a nerve (neuropathic). Also chronic low back pain is often a combination of nociceptive and neuropathic pain: The back itself may hurt with a constant aching (nociceptive pain) and there may be additionally sudden burning and hurting sensations extending into the legs, which are called sciatiae and are of neuropathic origin.
But whatever the type of pain, you feel your pain. It can only last a short while or can hang on for months, or even longer. Pain may go beyond the pure physical sensation of hurting (see "What are the symptoms of pain?"): it may also affect your mood, work and social life. Pain may entail you into a spiral downwards to feeling bad, isolation, despair or even depression.
Managing pain aims at providing a continued suppression of pain and maximising the patient’s quality of life – both by gaining autonomy and participation in work and social life. The World Health Organisation’s (WHO) guidelines for chronic cancer pain management recommend a three-step approach to drug therapy (see also "FAQ"). These guidelines are based on the premise that all pain can be treated with drugs. Your healthcare advisor (doctor or nurse) will be fully aware of the available range of medications from the different drug agent categories.
Advances in pain treatment have resulted in a wide variety of safe and effective options for the control of pain. If one type of drug does not bring relief, there are many others available. However, no medication should be taken without the knowledge of your doctor or nurse.
Make sure you fully understand what type of medicine you are being prescribed, how to take it and what possible side effects you may experience.
