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Pain glossary

An A-Z glossary of key terms used in pain management

Acceptance and commitment therapy

A cognitive-behavioural psychological intervention that uses acceptance and mindfulness strategies, with commitment and behaviour change strategies, to increase psychological flexibility.

Acupuncture

The practice of inserting fine needles through the skin at specific points to cure disease or relieve pain (as in surgery).

Acute pain service

A multidisciplinary team including a physician trained in pain management (usually an anaesthetist), a nurse and other healthcare professionals, such as a physiotherapist and psychologist, where appropriate. Their purpose is to reduce the severity and frequency of postoperative or post-traumatic pain and to educate patients and clinical staff about the options available to treat and relieve pain. 

A-delta fibres

Myelinated nociceptor fibres which have the capacity to respond to intense heat, cold, mechanical and chemical stimuli. Activation of A-delta fibres is associated with a sharp, intense, stabbing sensation of pain and they are thought to be responsible for conducting the first pain sensation, as they conduct at 5–30 metres per second.

Adjuvant analgesics

Drugs whose primary use is not for managing pain, but in certain conditions they have analgesic properties and often will enhance the response to conventional analgesics. Examples include antidepressant and anticonvulsant drugs.

Allodynia

Pain produced by a stimulus that is normally not painful. For example, gently stroking an area may produce pain in people with complex regional pain syndrome (CRPS). Although different from referred pain it can occur in areas other than the one stimulated. Commonly seen in neuropathic pain states, it is a particular feature of postherpetic neuralgia.

Anaesthesia dolorosa

Pain occurring in an anaesthetic area, that is one where sensation is not normally perceived. Anaesthesia dolorosa is one of the complications of treatment for trigeminal neuralgia.

Anticonvulsants

Drugs that are primarily used for the treatment of epilepsy, but which have also been used for many years to reduce the severity of pain in neuropathic pain states. Their use is often limited by the development of side-effects, particularly sedation and drowsiness. 

Antidepressants

Tricyclic antidepressants (TCAs) have been used for many years in the treatment of low back pain. These drugs are particularly useful at doses lower than those used to treat depression.

Atypical facial pain

Described by the patient as a continuous pain, often having a burning or aching quality without pain-free intervals. There are no triggering factors and pain may be unilateral or bilateral and extend over several dermatomes. On examination there is rarely any sensory loss and all investigations are normal. This syndrome is often associated with significant behavioural changes and sometimes responds to behavioural therapy and TCAs. 

Balanced analgesia

The simultaneous use of drugs from different pharmacological classes to produce a greater degree of analgesia than can be achieved by using the drugs individually. In the treatment of acute postoperative pain, the combination of a local anaesthetic agent, an opioid and an anti-inflammatory drug can help to reduce pain with fewer side-effects than using the individual drugs at a higher dosage. 

Biopsychosocial pain model

A theoretical model that relies on the premise that no single dimension is adequate to understand chronic pain; consideration should be given to the interaction of biological, psychological and social factors. The model recognises that pain is rarely a phenomenon that occurs in isolation. Successful management requires attention to all components of the model.

C fibres

Unmyelinated nociceptor neurones, which conduct at a velocity of less than two metres per second and are associated with a prolonged burning sensation and dull aching pain. They are responsible for the secondary pain sensation that follows brief intense heat stimulation to the skin. The term ‘slow pain’ is often used to describe the pain caused by activation of C fibres.

Cauda equina syndrome

Compression of the nerves at the end of the spinal cord within the spinal canal.

Central pain

Pain caused by lesions or dysfunction of the CNS, within the spinal cord or brain. Commonly described as burning, aching, darting, piercing, pricking, lacerating and pressing, central pain can occur after cerebral vascular accidents either due to an infarct or haemorrhage. It is also seen in association with traumatic spinal cord and brain injury and MS. There is no universally effective treatment. 

Chronic pain

Pain associated with either a demonstrable progressive pathological process such as rheumatoid arthritis or malignancy; or pain that is present long after the immediate effects of an injury have subsided and persists beyond the healing time. Pain can be described as chronic when it exists for longer than three to six months, and is usually accompanied by a significant behavioural response and varying degrees of disability. 

Coeliac plexus block

The application of a neurolytic solution, either alcohol or phenol, to the coeliac plexus after a diagnostic block with local anaesthetic can be used to successfully treat the pain from upper abdominal tumours, particularly visceral pain due to pancreatic cancer. The injection should be performed under X-ray control, using either conventional fluoroscopy or CT scanning. Complications include hypotension due to vasodilatation of the splanchnic bed, subarachnoid injection and neurological sequelae in 1% of patients.

Cognitive-behavioural therapy

An approach to the management of chronic pain directed towards considering how the person relates to their pain and addressing the patient’s understanding of their painful condition. The treatment focuses on understanding the person’s thoughts about their condition and modifying any abnormal beliefs and misconceptions. Acceptance and commitment therapy is a recent variant.

Complex regional pain syndrome

Referring to two conditions previously known as reflex sympathetic dystrophy (type 1 CRPS) and causalgia (type 2 CRPS), CRPS encompasses a range of painful conditions, which usually occur after injury. It is usually confined to the extremities, although may occur in low back pain. The magnitude and duration of symptoms appear to be out of proportion to the event that caused the injury, and ranging from mild swelling with trophic changes in the skin, to gross swelling and deformity necessitating amputation. Treatment is focussed on encouraging early mobilisation and facilitating active mobilisation using local anaesthetic nerve blocks, the use of anticonvulsants and other co-analgesics. 

Deafferentation pain

Pain due to a lesion or dysfunction in the nervous system resulting from loss of sensory input into the CNS. This can occur with peripheral nerve lesions, such as brachial plexus avulsion, or in association with pathology in the CNS.

Epidural abscess

An uncommon complication of epidural analgesia (<0.01%), it occurs more commonly in the absence of epidural analgesia and is associated with type 1 diabetes, cancer, degenerative disease of the spine and spinal surgery. Four clinical phases are described in the development of an epidural abscess. Initially there is back pain occurring within 24 hours of the abscess development, followed by root pain, fever, sphincter and muscular weakness and finally paralysis.

Epidural analgesia

The infusion of local anaesthetic drugs, with or without the addition of opioids, into the epidural space. It is useful in reducing acute postsurgical pain, acute pain from causes such as labour and trauma, and sometimes in the management of cancer-related pain. Complications include hypotension, dural puncture headache, pruritus and urinary retention. Some evidence suggests that continuous use may reduce postoperative hospital stay.

Epidural steroids

Injections of steroids into the epidural space to treat radicular pain have been used for four decades; they are mainly indicated for conditions of nerve root irritation and inflammation. The most common combination injected is a weak local anaesthetic solution such as bupivacaine and triamcinolone. A variation uses saline rather than a local anaesthetic.

Fibromyalgia

A common clinical condition in which reproducible tenderness is elicited in specified areas of the body associated with widespread pain and symptoms of stiffness, fatigue, altered sleep pattern and depression of mood. It is most commonly seen in females aged between 20 and 50. Fibromyalgia is associated with irritable bowel syndrome, migraine, Raynaud’s disease, non-dermatomal paraesthesia and considerable disability.

Gate theory of pain

In 1965 Melzack and Wall suggested that it was possible to modulate noxious impulses at spinal cord level. Stimulation of large diameter A-beta fibres, which are non-nociceptive, inhibits the response to painful stimuli of wide dynamic range neurones in the dorsal horn of the spinal cord. Descending inputs are also thought to modulate activity in the dorsal horn, which helps to explain how cognitive and emotional factors influence nociceptive processing.

Guanethidine block

Also known as IV regional analgesia, this technique was first described by Hannington-Kiff in 1974 and involves applying a tourniquet to the affected limb, after which a mixture of local anaesthetic, usually prilocaine and guanethidine, is injected into a cannula placed in the affected limb. After 20 minutes the tourniquet is deflated. The technique has been used to treat pain associated with sympathetic hyperactivity and is also used for the treatment of type 1 CRPS.

Hyperaesthesia

Increased sensitivity to stimulation excluding the special senses. 

Hyperalgesia

Increased sensitivity to painful stimuli.

Hyperpathia

A painful syndrome characterised by an increased reaction to a stimulus, especially a repeated stimulus, as well as a decreased pain threshold. Dermatomal spread may also occur.

McGill Pain Questionnaire

A pain assessment tool developed by Melzack and Torgerson to measure the quality of pain the patient experiences. Patients are presented with a list of 102 words grouped into 20 different categories. The categories are divided into sensory qualities of pain, affective qualities including emotional aspects and fear associated with painful experiences, and an evaluative summary of the intensity of the overall pain experienced. The questionnaire can be analysed and a pain rating index is obtained. A simpler version of the tool, the Short-Form McGill Questionnaire, was devised in 1987.

Mindfulness-based cognitive therapy

A psychological therapy that blends features of cognitive therapy with mindfulness techniques.

Myofascial pain syndrome

A regional pain syndrome accompanied by trigger points. It is distinguished from fibromyalgia in that in the latter there is generalised pain. Trigger points are characterised by localised tenderness, the presence of a taut band, referred pain on palpation over a trigger point site and a twitch response. 

Neuropathic pain

Pain arising from abnormalities within the central or peripheral nervous system, associated with injury, damage or dysfunction of the nervous system, such as pain after brachial plexus avulsion, postherpetic neuralgia, complex regional pain syndrome and Pancoast syndrome. Stimuli that are not normally considered to be noxious may produce pain, for example, lightly touching or stroking of the affected area.

Oligoanalgesia

The under-treatment of pain in patients presenting to A&E due to a fear of masking symptoms and a preoccupation with the diagnosis of underlying conditions. 

Opioid analgesics

A diverse group of drugs with a broadly similar pharmacology. Opioids work by binding to mu, kappa and delta receptors in the CNS. Opioids are commonly prescribed for moderate to severe pain, particularly for palliative care, cancer pain and chronic non-cancer pain. They can also be used in mild to moderate pain that cannot be controlled adequately by NSAIDs, such as postoperative or dental pain.

Pain

The International Association for the Study of Pain (IASP) defines pain as ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage’.

Pain behaviour

A descriptive term used specifically to refer to how people respond to pain. There is a wide range of pain behaviours and they may be helpful and adaptive or unhelpful and maladaptive. Often contrasted with pain beliefs and emotional responses to pain.

Pain management programme

A multidisciplinary method of helping those with chronic pain; usually, but not exclusively, back pain. This requires the input of physiotherapists, psychologists, occupational therapists, nurses and pain clinicians. The purpose is to focus on the effects of pain on behaviour, mood, function and activity, rather than reducing the intensity of pain. Although the pain is not cured, the programme will help to reduce fear avoidance behaviour in those with chronic pain.

Patient-controlled analgesia 

A method of administering a variety of analgesics where the patient has control over how much of the drug they receive, up to a predetermined limit, and how often they receive the drug. It enables the patient to feel more in control of their pain management and reduces nursing time. It is most commonly used in acute postoperative pain and is sometimes used in cancer pain. 

Phantom pain

An unpleasant painful sensation referred to a surgically removed limb or portion thereof. Pain persisting beyond six months after amputation is notoriously difficult to treat. It is important not to attribute all pain in amputees to phantom pain and a careful history is necessary to elicit the exact cause. Other causes include stump pain, neuromata and ill-fitting prosthetic limbs.

Postherpetic neuralgia

One of the most common complications of zoster virus infection. Pain persists after the rash has healed. People over the age of 60 are particularly at risk. The most common sites are in the mid-thoracic dermatomes and in the ophthalmic division of the trigeminal nerve. Around 30 per cent of patients still suffer from postherpetic neuralgia 12 months after the onset. In some cases pain persists for many years.

Pre-emptive analgesia

It is suggested that by using analgesic techniques before surgery it may be possible to reduce the intensity and duration of postoperative pain, based on the hypothesis that if it is possible to prevent nociceptive impulses reaching the spinal cord then it may be possible to reduce hyperexcitability and other changes occurring in the dorsal horn.

Radiculopathy

Damage to the nerve roots that enter or leave the spinal cord, caused by disc prolapse, spinal arthritis, diabetes mellitus or ingestion of heavy metals.

Spinal cord stimulation

A technique whereby an electrode is inserted either percutaneously or via a surgical laminotomy into the epidural space, enabling an electric current to be applied to the spinal cord via either an internal or external pulse generator; it is used to treat pain arising from a variety of conditions. 

Stump pain

Pain occurring in the residual stump occurs in up to 50 per cent of cases in the first weeks after amputation. The quality of the pain can be described as soreness or a stabbing sensation; in addition a burning sensation in the stump can occur. It is important to carefully assess the patient as there can be a variety of causes including neuromata, progression of ischaemic pain in cases of peripheral vascular disease, poorly fitting prostheses or bony spurs.

Trigeminal neuralgia (tic douloureux)

A chronic painful condition characterised by severe pain, usually stabbing or like an electric shock in the distribution of the trigeminal nerve. Pain can last from seconds to minutes, is almost always unilateral, and can be triggered by brushing teeth, face washing or a cold wind. On physical examination there are no sensory defects. Between the episodes of pain there is no background discomfort. Often the cause can be a tortuous blood vessel compressing the nerve root. 

Transcutaneous electrical nerve stimulation (TENS)

Stimulation of the sensory myelinated A-beta fibres to produce a pleasant, gentle tingling sensation. A pulse generator delivers current to the skin via electrodes, usually placed proximal to the painful area. The patient is able to control the amplitude or intensity of the impulse, the frequency and the pulse width. TENS should not be used on the anterior part of the neck, in pregnancy or in the presence of a cardiac pacemaker.

Date of preparation: September 2015; MINT/PAEU-14003




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