Encyclopedia

Encyclopedia of Pain

Adrenaline

A hormone secreted by the adrenal glands, especially in conditions of stress, increasing rates of blood circulation, breathing, and carbohydrate metabolism and preparing muscles for exertion. Also called epinephrine. Associated with emergency situations and "fight or flight" responses.

Allodynia

Allodynia is when non-painful stimuli become painful, due to increased sensitivity of the nervous system. An example is when simple touch of the skin is experienced as painful. Typical experience is of overly sensitive skin, where the individual may notice an unpleasant sensation even when being touched by clothing on the skin. Some people describe this as similar to having sunburn. It is associated with central nervous system sensitisation.

Analgesic Medicine

Medicine acting to relieve pain. Can include simple paracetamol, narcotic medicine (including tramadol) or anti-inflammatory medicine.

Arachnoiditis

Arachnoiditis is inflammation of the arachnoid, which surrounds the spinal cord and brain. It most often results from surgery, or lumbar puncture. The available literature considers non-infection and non-congenital-related arachnoiditis similar to other chronic spinal pains, and management is according to the evidence for non-specific chronic pain.

Articular cartilage

The cartilage between two bones.

Articulation

The point or type of contact between two bones.

Ascending nerves

Nerves that carry messages from the body and the outside world to the brain.

Axon

That part of the nerve that carries nerve impulses and transports chemicals to the next nerve.

Biopsychosocial Model

The biopsychosocial model acknowledges the physical, psychological and social influences on pain and disability, and focuses on increases in function. Pain management programs based on this model are reported in the research as being effective. There is moderate evidence that multimodal biopsychosocial treatments that include a cognitive-behavioural or a behavioural component are effective for chronic low back pain in the intermediate to long term.

Brainstem

The base of the brain lying between the spinal cord and the cerebral cortex.

Cartilage

A dense material that is capable of withstanding considerable pressure, found covering the surface of bones, where wear and damage results in osteoarthritis.

Causalgia

See complex regional pain syndrome. This is one of the now disused terms for this disorder.

Cell body

The enlarged portion of a neurone containing the nucleus. It is concerned more with the nuturition of the cell than with propagation of nerve impulses.

Central Nervous System

That part of the nervous system including the brain and the spinal cord (in mammals).

Central Nervous System sensitisation

Central Nervous System Sensitisation is a nervous system adaptation. This adaptation occurs because of increased signal through the central nerve cells, both from the body and also the brain, and is subject to controls that can greatly increase this signal. CNS sensitisation is contributed to in part by unhelpful beliefs, increasing attention, negative expectations, and emotions such as anxiety, depression and anger. Central nervous system sensitisation is known to occur as a response to increased activity in the nerve fibres after injury and can explain some of the diffuse symptoms in chronic pain

Complex Regional Pain Syndrome Type 1

Complex regional pain syndrome type 1 (CRPS1), also known as reflex sympathetic dystrophy (RSD), is a painful disabling disorder that occurs after stroke or limb trauma or occasionally without known incident and is difficult to both diagnose and treat. Numerous peripheral and central changes have been demonstrated in CRPS1. Peripheral abnormalities include altered activity in sympathetic neurons and increased spontaneous pain with elevated sympathetic activity. Central abnormalities include disruption of sensory cortical processing, disinhibition of the motor cortex and disrupted body schema. The available data have led to proposals that CRPS1 is a disease of the central nervous system. Modern research shows that the key to this condition is an understanding of the way the body is represented in the brain.

Cortisol

This is a chemical that works as a stress hormone. It works with adrenaline to protect you when you are threatened. However elevated levels in the long-term can negatively affect memory, normal recovery time, and can put you at risk of depression due to some of the longer term effects in the brain.

Central pain

Pain initiated or caused by a primary injury or dysfunction in the central nervous system.

Cerebral Cortex

The intricately folded outer layer of the cerebrum, making up some 40% of the brain by weight and composed of an estimated 15 thousand million neurons (grey matter). The thinking part of the brain, it reacts to a danger message from the body by locating the source of injury, assessing the damage and determining a course of action which may include a pain response.

Cerebrum

The largest and most highly developed part of the brain, situated above the brain stem. The cerebrum is responsible for the initiation and coordination of all voluntary activity in the body and for governing the functioning of lower parts of the nervous system. The outer layer of grey matter is called the cerebral cortex.

Cervical Vertebrae

The seven bones making up the neck region of the backbone.

Chronic Pain

Pain that persists over the long term, or beyond expected healing time for an injury. The source and mechanisms underlying the pain may change but the pain remains. See section on Chronic Pain.

Computerized tomography (CT)

A specialized form of x ray examination in which the x ray source and detector (CT Scanner) rotate around the object to be scanned and the information obtained can be used to produce cross sectional images by computer (a CT scan). A higher radiation dose is received by the patient than with conventional x-rays, but the diagnostic information obtained is thought to outweigh the risk. CT scanning can be used for all parts of the body.

Dendrites

Part of the nerve that receives information from other neurons.

Descending nerves

Nerves that carry messages from the brain to the body based on the information that has gone up to the brain via the ascending nerves. These are the fibres that allow the nervous system to balance inhibition with excitation depending on the needs of the person at the time. This is all below consciousness

Dorsal Horn - (Dorsal means back or behind)

Located in the back of the spinal cord, cross-sectionally looking like a butterfly, it contains the cell bodies of sensory (ascending) neurons.

Dorsal Root Ganglion

Is found at each level of the spinal cord. Each one forms a swelling or nodule along the dorsal nerve root and contains cell bodies that transmit sensory information from the sensory nerves to the brain. The Dorsal Root Ganglion has been called the brain of the peripheral nervous system.

Endorphins

These are the body's natural opiates, produced in the brain in response to the stimulation of certain nerve fibres, amongst other stimuli. They are normal, natural and many times more potent than anything synthetic. The downside is that they are internally very addictive, and can cause adverse affects similar to withdrawal when they are not available. Good example: when sudden discontinuation of "hands-on" physiotherapy occurs, the individual can become much more painful than during treatment, even though there may be no overall improvement beyond a day or so each treatment.

Excitatory Neurotransmitters

These cause an increase in stimulating chemicals in a synapse between two nerves at the synapse. See inhibitory neurotransmitters, which act to balance excitatory neurotransmitters

Facet

Small flat surface on a bone, especially a surface of articulation.

Flight or fight reaction

A primitive reaction of the body to prepare it for battle (fight) or run away (flight). Usually this consists of activation of the movement muscles and increasing the supply of adrenaline. Associated with the sympathetic nervous system.

Ganglion

An aggregate of nerve cell bodies.

Grey matter

The darker coloured tissues of the central nervous system composed mainly of the cell bodies of neurons, branching dendrites of the nerve. In the brain the grey matter forms the cerebral cortex whereas in the spinal cord the grey matter lies centrally and is surrounded by white matter.

Helplessness

Where the individual feels he or she is in an environment in which some important outcome is beyond his or her control.

Herniation (of disc)

A herniated disc is a fragment of the disc nucleus that is pushed out of the outer disc margin, into the spinal canal through a tear or rupture. Sometimes produces pain and other symptoms but not necessarily.

Hyperalgesia

When normally painful stimuli become increasingly painful.

Inflammation

Usually associated with tissue damage where cell content spills and inflammatory chemicals are then released. Makes any stimulus usually painful whilst inflammation is present.

Inflammatory Soup

Chemicals that are released into the surrounding tissue and create inflammation.

Inhibitory neurotransmitters

Chemicals in the synapse which inhibit the action of other chemicals. Represents an increase in "feel good" chemicals at the synapse.

Locus of Control (in relation to pain)

The individual's sense of where control comes from, e.g., an internal locus of control is where the individual considers that pain is controlled by themselves, whereas an external locus of control is where the individual feels that pain is NOT controlled by themselves, but by factors other than themselves, e.g., medicine, doctors, events etc.

Lumbar vertebrae

The five bones of the spine that are situated between the thoracic vertebrae and the sacrum, in the lower part of the back. They are the largest vertebrae and have big lateral protrusions called "processes" for attachment of the strong muscles of the lower back.

Magnetic resonance investigation (MRI)

A diagnostic technique based on analysis of the absorption and transmission of high frequency radio waves by the water molecules in tissues placed in a strong magnetic field. Using modern high speed computers this analysis can be used to "map out" the variation in tissue signals in any plan and thus produce images of the tissues. It is particularly useful for examining the central nervous system and musculoskeletal system, and to a lesser extent the chest and abdomen. It has the potential advantage that it does not use potentially harmful ionizing radiation such as x-rays

Medicine

There are a variety of medicines prescribed to help people in pain, and it is reasonable you should try these to see whether they help you, always bearing in mind that many medications have side effects, and most make you feel "abnormal" and "out of control". If medicine takes away the pain but makes you feel "out-of-it" and incapable of normal activity, there is a danger that it will perpetuate the abnormal experience in the nervous system which leads to central nervous system sensitisation. Most evidence-based biopsychosocial multidisciplinary pain programs suggest that you need to wean yourself off analgesics before you are ready to really participate in a program. [See "Quality use of Medicine" to find out more about the medicine you have been prescribed].

Motor control

It has been shown that chronic pain complaints may be maintained by persistently abnormal cerebral motor control. It has been found through experimental research that pain produces differention changes in the motor control of the trunk muscles, with consistent impairment of Transverse Abdominus, the major abdominal stabiliser muscle. There are exercise protocols to assist chronic pain clients effectively return to more normal truncal control.

Motor nerves

Nerves that carry impulses outwards from the central nervous system to bring about activity in a muscle or gland.

Movement abnormalities

Scientists think that the brain controls movement at the same time that it creates experience. Therefore, if someone is experiencing pain, regardless of why, they will be moving as though they are to some extent injured. When movement disorders are really obvious they may be corrected by the individual, however, when the disorder is subtle and not as obvious it is more difficult for the individual to correct. It can set up a habitual way of moving. Rehabilitation physiotherapists who are expert in movement patterns due to pain are skilled at helping people change these patters.

Movement or motor muscles

These are long skinny muscles which reduce the angle between two bones, for example in the arm, motor muscles contract to reduce the angle between the forearm and the upper arm, by contracting. These muscles require a lot of energy in small bursts to work effectively. We are not meant to sustain motor muscle movement over the long term usually. They work closely with stabilising muscles.

Multidisciplinary approach (to pain management)

Means the inclusion of input from various health disciplines including exercise physiology, physiotherapy, counselling /psychology, medical, rehabilitation etc. Most pain management clinics describe themselves as ‘multi-disciplinary'.

Multifidis Muscle

This muscle is a deep stabilizer for the whole of the spine. It relies on activation by the Transverse Abdominus muscle. Is one of the muscles primarily responsible for maintaining the stability of the spine as a whole. With inappropriate activation of the multifidis, there can be overcompensation by the movement muscles that suddenly call for a hard contraction of these muscles beyond their capability. This then leads to strain and injury to these muscles.

Musculo-Skeletal System

The body system comprising the muscles and bones.

Myelin

A fatty substance surrounding some nerve fibres, thereby forming an insulating sheath. This sheath allows the signal to travel faster through the nerve.

Nucleus

The genetic material for the neurone is contained in the nucleus, and this is responsible for growth and nutrition. It is contained in the bulbous end of the neurone called the soma.

Neuralgia

A description of a painful sensation that often follows the course of a particular nerve.

Neurogenic or neuropathic pain

Involves the health of the nerve itself. There may have been damage due to surgery, accident, or other trauma. Equally, if you have had a sore arm, say, for a number of months, the nerves serving that arm can become "unwell", and start to behave differently. This is particularly important at the "dorsal root ganglion", just outside the dorsal horn in the spine. "An important abnormality of damaged nerve membrane is that it becomes sensitive to chemicals released by the sympathetic nervous system"

Neurolysis

A common operation on peripheral nerves. It involves a nerve trunk or its branches which may be thought to be constraining the nerve and affecting its functions. It is done with a microscope and involves cutting the nerve. Can give rise to a neuroma.

Neurone

The structural unit of the nervous system consisting of a nerve cell and its conducting dendrites and axons.

Neuroma

A tangled mass of nerve sprouts and scar tissue as a result of the nerve having been cut

Neurophysiology of pain

Looks at how pain works in the nervous system and the interactions between the nervous and other body systems to produce the experience of pain.

Neurotransmitters

Chemical substances active in the synapse which makes it possible to transmit nerve impulses between nerve cells.

Nociception

A process of responding to dangerous or potentially dangerous stimuli through the nociceptors.

Nociceptor

Free nerve endings located in most tissues of the body. They provide information regarding the location and intensity of dangerous stimuli.

Nucleus

The part of the cell that contains the genetic material (DNA).

Opiates

Group of drugs derived from opium which includes codeine, morphine and others. Opiates depress the central nervous system, they relieve pain, suppress coughing, and stimulate vomiting.

Osteoarthritis

This is about the deterioration of joints. It is associated with age but it can also be associated with overuse or incorrect positioning of joints.

Osteophyte

A projection of bone that looks like a thorn that occurs around places where cartilage has degenerated or where there has been deterioration possibly due to trauma of the joint or near the joint. It may or may not cause pain even though it can be seen on x rays.

Pain threshold

The lowest level of pain that a person can recognise.

Pain tolerance

The greatest level of pain that a person is prepared to tolerate.

Parasympathetic nervous system

Frequently works to oppose the sympathetic nervous system, associated with the phrase "rest and digest", keeps the body balanced. See Sympathetic nervous system.

Pars Defect or Spondylolysis

The pars defect may be related to trauma (some people who play cricket experience it) but may also be the result of an abnormality of the pars from birth. The pars is the bone that connects the superior (above) and inferior (below) facets of a vertebral body. In some people (usually manifests with symptoms sometime in mid-late childhood) there is a congenital elongation and thinning of the pars that makes it susceptible to fracture. There may be a combination of trauma and congenital predisposition.

Peripheral Sensitisation

Often due to long term inflammation in the peripheral nervous system. Gives rise to increased sensitivity to signals through the nervous system.

Peripheral Nervous System

Nerves that communicate information about the outside of the body including the arms and legs with the central nervous system, includes the dorsal root ganglion but not the dorsal horn.

Radicular Pain

Radicular pain is to do with pressure on nerves. This pain will correspond pretty well to patterns associated with different spinal nerves.

Receptors

There are other nerves that sit right next to the synapse and they have special openings that are designed specifically to receive the chemicals that have just been released by the previous nerve. Receptors are easily visualized if you think of them as like ports into the hard drive on your computer, or little doors or openings that admit chemicals from the surrounding environment. Different receptors are specific to different substances.

Red Flags

Biomedical signs associated with pain which indicate that further investigation is required because there may be a potentially serious problem.

Reflex Sympathetic Dystrophy

See Complex Regional Pain Syndrome - This is the old expression for this disorder involving the brain's representation of the body.

Sacrum

<

The continuation of the backbone below the lumbar vertebrae consisting of several vertebrae joined together.

Self Efficacy

The confidence a person has to do things while they are still experiencing pain.

Sensory nerves

Nerves that carry information inwards and upwards to the brain from the body Different sensory nerves convey information about temperature pain, touch, taste etc to the brain where the brain interprets the chemical signals to have a sensory experience.

Spinal cord

The portion of the central nervous system enclosed in the vertebral column, consisting of nerve cells and bundles of nerves connecting all parts of the body with the brain. It contains a core of grey matter surrounded by white matter. From it arises 31 pairs of spinal nerves.

Spondylolysis

See pars defect.

Spondylolisthesis

A forward movement of one vertebra upon another, because of a defect in the bone or in the joints that normally hold the spine together. This may be present at birth or it may develop after injury.

Stabilisers

Deep muscles important in supporting the skeleton. They require a small amount of energy over a long period of time. They do not create movement in the skeleton, they hold the skeleton firm so that the movement or motor muscles can do the work of moving the body.

Stenosis

A narrowing of the spinal canal. It can mean that there is a resulting pressure on the spinal cord or nerves.

Substantia gelatinosa

A region found throughout the length of the spinal cord on each side, of short densely packed nerve fibres that are diffusely interconnected.

Sympathetic Nervous System

This is the part of the nervous system that is associated with the concept of ‘fight or flight' or the emergency response. It has fibres that reach into organs, blood vessels and glands to enable it to send signals quickly to activate for example the uptake of oxygen, which allows muscles to move fast, and for fast responses all round. It works in conjunction with the parasympathetic nervous system which balances the body after this response by allowing it to rest and recover.

Synapse

When a nerve is stimulated, it sends a signal that runs all the way along its length (axon), and along each branch if the nerve divides or has a few ends. When the signal reaches the end of a nerve, it has nowhere to go, so the nerve releases chemicals (neurotransmitters) into the space at the end of the nerve. This space is called a "synapse".

Thoracic Vertebrae

The twelve bones of the backbone to which the ribs are attached. They lie between the cervical and lumbar vertebrae and are characterized by the presence of facets for articulation with the ribs.

Transverse Abdominus

A large stabilizing muscle of the abdomen, which has been found to be abnormally inactive in those experiencing long term pain. Associated with the functioning of the multifidis in the abdomen.

Ventral Horn

Two arms located at the front of the spinal cord, are called ventral horns. They contain the cell bodies of the descending nerve fibres.

Vertebra/e

One of the 33 bones of which the backbone is composed. Each vertebra typically consists of a body from the back of which arises an arch of bone (the neural arch) enclosing a cavity (the vertebral canal, or foramen) through which the spinal canal passes. The neural arch bears one spinal process and two transverse processes, providing anchorage for muscles and four articular processes with which adjacent vertebra articulate (join). Individual vertebrae are bound together by ligaments and intervertebral discs.