What is Pain and Types of Pain

The English word 'pain' probably comes from Old French (peine), Latin (poena - meaning punishment pain), or Ancient Greek (poine - a word more related to penalty), or a combination of all three.

In medicine pain relates to a sensation that hurts. If you feel pain it hurts, you feel discomfort, distress and perhaps agony, depending on the severity of it. Pain can be steady and constant, in which case it may be an ache. It might be a throbbing pain - a pulsating pain. The pain could have a pinching sensation, or a stabbing one.

Only the person who is experiencing the pain can describe it properly. Pain is a very individual experience.
Types of pain
Acute pain - this can be intense and short-lived, in which case we call it acute pain. Acute pain may be an indication of an injury. When the injury heals the pain usually goes away.

Chronic pain - this sensation lasts much longer than acute pain. Chronic pain can be mild or intense (severe).

How do we classify pain?

Pain can be nociceptive, non-nociveptive, somatic, visceral, neuropathic, or sympathetic. Look at the table below.

Pain
Nociceptive Nociceptive
1)Somatic 2)Visceral 1)Neuropathic 2)Sympathetic


Nociceptive Pain - specific pain receptors are stimulated. These receptors sense temperature (hot/cold), vibration, stretch, and chemicals released from damaged cells.

Somatic Pain - a type of nociceptive pain. Pain felt on the skin, muscle, joints, bones and ligaments is called somatic pain. The term musculo-skeletal pain means somatic pain. The pain receptors are sensitive to temperature (hot/cold), vibration, and stretch (in the muscles). They are also sensitive to inflammation, as would happen if you cut yourself, sprain something that causes tissue damage. Pain as a result of lack of oxygen, as in ischemic muscle cramps, are a type of nociceptive pain. Somatic pain is generally sharp and well localized - if you touch it or move the affected area the pain will worsen.

Visceral Pain - a type of nociceptive pain. It is felt in the internal organs and main body cavities. The cavities are divided into the thorax (lungs and heart), abdomen (bowels, spleen, liver and kidneys), and the pelvis (ovaries, bladder, and the womb). The pain receptors - nociceptors - sense inflammation, stretch and ischemia (oxygen starvation).

Visceral pain is more difficult to localize than somatic pain. The sensation is more likely to be a vague deep ache. Colicky and cramping sensations are generally types of visceral pain. Visceral pain commonly refers to some type of back pain - pelvic pain generally refers to the lower back, abdominal pain to the mid-back, and thoracic pain to the upper back (see below for the meaning of referred pain).

Nerve Pain or Neuropathic Pain

Nerve pain is also known as neuropathic pain. It is a type of non-nociceptive pain. It comes from within the nervous system itself. People often refer to it as pinched nerve, or trapped nerve. The pain can originate from the nerves between the tissues and the spinal cord (peripheral nervous system) and the nerves between the spinal cord and the brain (central nervous system, or CNS).

Neuropathic pain can be caused by nerve degeneration, as might be the case in a stroke, multiple-sclerosis, or oxygen starvation. It could be due to a trapped nerve, meaning there is pressure on the nerve. A torn or slipped disc will cause nerve inflammation, which will trigger neuropathic pain. Nerve infection, such as shingles, can also cause neuropathic pain.

Pain that comes from the nervous system is called non-nociceptive because there are no specific pain receptors. Nociceptive in this text means responding to pain. When a nerve is injured it becomes unstable and its signaling system becomes muddled and haphazard. The brain interprets these abnormal signals as pain. This randomness can also cause other sensations, such as numbness, pins and needles, tingling, and hypersensitivity to temperature, vibration and touch. The pain can sometimes be unpredictable because of this.

Sympathetic Pain

The sympathetic nervous system controls our blood flow to our skin and muscles, perspiration (sweating) by the skin, and how quickly the peripheral nervous system works.

Sympathetic pain occurs generally after a fracture or a soft tissue injury of the limbs. This pain is non-nociceptive - there are no specific pain receptors. As with neuropathic pain, the nerve is injured, becomes unstable and fires off random, chaotic, abnormal signals to the brain, which interprets them as pain.

Generally with this kind of pain the skin and the area around the injury become extremely sensitive. The pain often becomes so intense that the sufferer daren't use the affected arm or leg. Lack of limb use after a time can cause other problems, such as muscle wasting, osteoporosis, and stiffness in the joints.
What is referred pain?
Also known as reflective pain. When pain is felt either next to, or at a distance from the origin of an injury it is called referred pain. For example, when a person has a heart attack, even though the affected area is the heart, the pain is sometimes felt around the shoulders, back and neck, rather than in the chest. We have known about referred pain for centuries, but we still do not know its origins and what causes it.
How do you measure pain?
It is virtually impossible to measure a person's pain objectively. Most experts say that the best way to find out how much pain a person is enduring is by a subjective pain report. A comprehensive assessment of pain should include:
The identification of all the pains. This must include the most important ones.
The site, quality, and radiation of pain
What factors aggravate and relieve the pain

When the pain occurs throughout the day

What impact the pain has on the person's function

What impact the pain has on the person's mood

The sufferers' understanding of their pain
There are many different methods for measuring pain and its severity. Health care professionals say it is important to stick to whatever system or tool you chose for a specific patient all the way through. If a patient is unable to report his pain, such as an infant, or a person with dementia, there are a number of observational pain measures a doctor can use.

Here is a list of some pain measures used today:

Numerical Rating Scales

The patient is given a form which asks him to tick from 0 to 10 what his level of pain is. 0 is no pain, 5 is moderate pain, and 10 is the worst pain imaginable.

Please rate the pain you have right now
0 2 3 4 5 6 7 8 9 10
No pain Moderate pain Worst pain imaginable


The Numerical Rating Scales are useful if you want to measure any changes in pain, as well as gauging the patient's response to pain treatment. If the patient has dyslexia, autism, or is very elderly and has dementia this may not be the best tool (see the ones below).

Verbal Descriptor Scale

This type of scale exists in many different forms. The patient is asked questions and responds verbally choosing from such terms as mild, moderate, severe, no pain, mild pain, discomforting, distressing, horrible, and excruciating.

Elderly patients with cognitive impairment, very young children, and people who respond better to verbal stimuli tend to have better completion rates with this type of scale, compared to the written numerical scale. Children respond even better to the faces scale (description below).

Faces Scale

The patient sees a series of faces. The first one is calm and happy, the second less so, etc., and the final one has an expression of extreme pain. This scale is used mainly for children, but can also be used with elderly patients with cognitive impairment. Patients with autism may respond better to this type of approach - people with autism tend to respond to visual stimuli well.

Brief Pain Inventory

This is a much more comprehensive written questionnaire. Not only does it gauge current level of pain, but also records the peaks and troughs of pain during previous days, how pain has affected mood, activity, sleep patterns, and how the pain may have affected the patient's interpersonal relationship. The questionnaire also has diagrams which the patient shades - the shaded parts being where the pain is located and where it is most severe.

McGill Pain Questionnaire

This questionnaire measures the intensity (severity) of the pain, the quality of the pain, mood, and understanding of the pain. It is also known as the McGill Pain Index. It is a scale of rating pain developed at McGill University by Melzack and Torgerson (1971).

Look at the 20 groups below.
Circle one word in each group that best describes your pain.
Circle only three words from Groups 1 to 10 that best describe your pain response.
Choose just two words in Groups 11 to 15 that best describe your pain.
Just pick the one in Group 16.
Finally, choose just one word from Groups 17-20.
You should now have seven words. Those seven words should be taken to your doctor. They will help describe both the quality and intensity of your pain.

Group 1 - Flickering, Pulsing, Quivering, Throbbing, Beating, Pounding
Group 2 - Jumping, Flashing, Shooting
Group 3 - Pricking, Boring, Drilling, Stabbing
Group 4 - Sharp, Gritting, Lacerating
Group 5 - Pinching, Pressing, Gnawing, Cramping, Crushing
Group 6 - Tugging, Pulling, Wrenching
Group 7 - Hot, Burning, Scalding, Searing
Group 8 - Tingling, Itching, Smarting, Stinging
Group 9 - Dull, Sore, Hurting, Aching, Heavy
Group 10 - Tender, Taunt, Rasping, Splitting
Group 11 - Tiring, Exhausting
Group 12 - Sickening, Suffocating
Group 13 - Fearful, Frightful, Terrifying
Group 14 - Punishing, Grueling, Cruel, Vicious, Killing
Group 15 - Wretched, Binding
Group 16 - Annoying, Troublesome, Miserable, Intense, Unbearable
Group 17 - Spreading, Radiating, Penetrating, Piercing
Group 18 - Tight, Numb, Squeezing, Drawing, Tearing
Group 19 - Cool, Cold, Freezing
Group 20 - Nagging, Nauseating, Agonizing, Dreadful, Torturing

Measuring pain when the patient is cognitively impaired

In this case doctors say that the patient's subjective pain report is the most effective and accurate way of evaluating pain. If the severely cognitively impaired patient is observed carefully it is possible to pick out clues as to the presence of pain, e.g. restlessness, crying, moaning, groaning, grimacing, resistance to care, reduced social interactions, increased wandering, not eating, and sleeping problem