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'''Chronic pain''' was originally defined as [[Pain and nociception|pain]] that has lasted 6 months or longer. More recently it has been defined as pain that persists longer than the temporal course of natural healing that is associated with a particular type of injury or disease process. <ref name="Shipton EA, Tait B.">{{cite journal |author=Shipton EA, Tait B |title=Flagging the pain: preventing the burden of chronic pain by identifying and treating risk factors in acute pain |journal=European journal of anaesthesiology |volume=22 |issue=6 |pages=405-12 |year=2005 |pmid=15991501}}</ref>
{{Unreferenced|date=March 2007}}
{{Expand|date=March 2007}}
{{expert-subject|Medicine}}
{{Infobox_Symptom
| Name = Chronic pain
| Background =
| Image =
| Caption =
| ICD10 = {{ICD10|R|52|1|r|50}} - {{ICD10|R|52|2|r|50}}
| ICD9 = {{ICD9|780.96}}
| ICDO =
| OMIM =
| DiseasesDB =
| MedlinePlus = 002164
| eMedicineSubj = search
| eMedicineTopic = chronic%20pain
}}
'''Chronic pain''' was originally defined as [[Pain and nociception|pain]] that has lasted 6 months or longer. It is now defined as pain that persists longer than the normal course of time associated with a particular type of injury. However, this is a rather subjective assessment.
This constant or intermittent pain has often outlived its purpose, as it does not help the body to prevent [[injury]]. On the other hand, pain does have a purpose. It is a warning to the body that something is wrong. So, even though the preventative nature of pain is absent (withdrawing your hand from a fire, to prevent a burn), pain is indicative of cellular damage. Therefore, the perception of pain, on an acute basis, occurs when heat, or chemical irritation or mechanical pressure, has created disruption of the cells, with release of certain chemical irritants to inform the brain of the tissue damage. Chronic pain, on the other hand, is often the result of ongoing irritation of the nerve fibers that carry the message of pain to the brain.


The International Association for the Study of Pain defines pain as an unpleasant sensory and affective experience induced by the exposure to noxious stimuli i.e. injury incipient or substantive in nature.<ref name="merskey">{{cite journal |author=Merskey H |title=Logic, truth and language in concepts of pain |journal=Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation |volume=3 Suppl 1 |issue= |pages=S69-76 |year=1994 |pmid=7866375}}</ref>. It is important to note that pain is subjective in nature and is defined by the person experiencing it, and the medical community's understanding of chronic pain now includes the impact that the mind has in processing and interpreting pain signals.
==Causes==
Chronic pain is transmitted to the brain [[central nervous system]] (CNS) by [[Pain and nociception|nociceptive]] impulses, which causes changes in the neural response. A nerve fiber is like an electrical wire, with insulation. The insulating material is called myelin, and it prevent electrical charges from jumping across or "shorting out" one pain nerve from the other. The more the myelin or insulation, the better protected the pain nerve fiber is from chemical, pressure, or electrical injury.


==Functional Anatomy==
There are three broad types of nerve fibers that carry the message of pain. These are the small, sparsely or totally unmyelinated fibers, called "C fibers," and the A delta and A beta pain fibers, which has more myeline surrounding them. In counter-distinction to acute pain, the chronic pain message reaches multiple areas of the brain, or central nervous system, including the reticular activating system, involved in the control of sleep, the hypothalamus, involved the the control of food intake, and emotions, the thalamus, and the sensory cortex (Hendler, N., The Anatomy and Psychopharmacology of Chronic Pain, The Jounral of Clinical Psychiatry, Vol. 43, No. 8, Sec 2:15-21, August, 1982).
The anatomy of the nociceptive system can be grossly divided into the peripheral and central nervous system. The peripheral nervous system consists of small myelinated and unmyelinated nerve fibers. These nerve fibers converge into a region of the spinal cord referred to as the dorsal horn. The dorsal horn is the first relay station in pain signal transmission. The next element of pain transmission includes nerve fibers that then travel to the thalamus. From the thalamus the next order of neurons ascend to the limbic system and sensory cortex. This accounts for the affective elements and discriminative of pain respectively.<ref name="Romanelli P, Esposito V.">{{cite journal |author=Romanelli P, Esposito V |title=The functional anatomy of neuropathic pain |journal=Neurosurg. Clin. N. Am. |volume=15 |issue=3 |pages=257-68 |year=2004 |pmid=15246335}}</ref><ref name="Vanderah TW.">{{cite journal |author=Vanderah TW |title=Pathophysiology of pain |journal=Med. Clin. North Am. |volume=91 |issue=1 |pages=1-12 |year=2007 |pmid=17164100}}</ref>
Chronic pain subsequently provokes changes in the behavior of the patient, with depression being one of the most common features after six months (Hendler, N., Depression Caused by Chronic Pain, The Journal of Clinical Psychiatry, Vol. 45, No. 3, Sec 2:30-36, March 1984). As a result, the patient may also become physically atrophied and deconditioned. However, it is important to remember that chronic pain is [[multifactorial]], with the underlying biological changes affecting [[body|physical]] and [[psychosocial]] factors.


==Types==
==Nociception==
The experience of pain biologically is referred to as nociception. Nociception occurs in any tissue or organ in which pain signals arise secondary to a disease process or trauma. The nociception can also occur if there is dysfunction or damage to nerves themselves.<ref name="merskey">{{cite journal |author=Merskey H |title=Logic, truth and language in concepts of pain |journal=Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation |volume=3 Suppl 1 |issue= |pages=S69-76 |year=1994 |pmid=7866375}}</ref>
This article discusses chronic pain in two categories: malignant and non-malignant.
* Pain associated with malignancy can be caused by the [[cancer]] itself or by treatment.
* Non-malignant pain includes a variety of causes: [[arthritis]], [[neuropathy]]/[[neuralgia]], [[back pain]] from injury or disorders (such as [[spinal stenosis]], [[degenerative disc disease]], [[spinal disc herniation]], etc), [[migraine]]s and other types of [[headache]]s, [[abdominal pain]] from [[chronic pancreatitis]], bowel disorders, etc; pelvic pain from various conditions ([[endometriosis]], [[interstitial cystitis]], etc); and also diffuse conditions such as [[fibromyalgia]], [[reflex sympathetic dystrophy]], [[lupus]] and other systemic autoimmune/connective tissue conditions, [[multiple sclerosis]] and some other neuromuscular conditions.


Chronic pain can occur anywhere in the body; this list includes only a few examples of conditions that can cause chronic pain. However, recent articles have suggested that between 40%-67% of chronic pain patients are misdiagnosed (Hendler, N., Kozikowski, J. Overlooked physical diagnoses in Chronic Pain Patients involved in Litigation, Psychosomatics, Vol. 34, No 6:494-501, November/December, 1993, and Hendler, N., Bergson, C., and Morrison, C. Overlooked Diagnoses in Chronic Pain Patients Involved in Litigation, Vol. 37, No 6:507-517, November/December 1996). Clearly, it is essential to obtain a proper diagnosis, because if a person is misdiagnosed, he or she will not receive the right treatment.


===Post Operative Chronic Pain===
==The Pathophysiology of Chronic Pain==
Under persistent activation nociceptive transmission to the dorsal horn may induce a wind up phenomenon. This induces pathological changes that lower the threshold for pain signals to be transmitted. In addition, it may generate nonnociceptive nerve fibers to respond to, generate and transmit pain signals. In chronic pain this process is difficult to reverse or eradicate once established.<ref name="Vadivelu N, Sinatra R.">{{cite journal |author=Vadivelu N, Sinatra R |title=Recent advances in elucidating pain mechanisms |journal=Current opinion in anaesthesiology |volume=18 |issue=5 |pages=540-7 |year=2005 |pmid=16534290}}</ref>
Post operative chronic pain is often over looked.{{Fact|date=February 2007}}. This is distinct from the initial discomfort of the surgery itself or the temporary numbness or tingling around or near where the operation was performed caused by the severing of nerves within the skin. In contrast, Post Operative Chronic Pain occurs when the nerves regenerate, but with the neurones growing back into the wrong myelin sheaths, or do not enter the sheath at all. This condition is called a neuroma. The pain nerve fibres result in messages being crossed over and sent to the wrong part of the brain. Hence a light touch may result in a perceived sense of pain or temperature change. There are no tests or scans to confirm this, as the nerves are tiny and do not show up, but it is a very real problem and can cause a person to be incapacitated with pain for which standard analgesics fail to help.


==Classification==
The most common symptoms are a tingling sensation near or around the area where the operation was performed, sharp shooting pains, severe aches after much movement, constant 'low ache' all day and sometimes a general 'weak' feeling.{{Fact|date=February 2007}} <!-- not so much as to verify this, but to provide the reader with a source to read further on the topic -->
Nociception (pain) may arise from injury or disease to visceral, somatic and neural structures in the body. More broadly pain is described as malignant or non-malignant in origin.<ref name="Vanderah TW.">{{cite journal |author=Vanderah TW |title=Pathophysiology of pain |journal=Med. Clin. North Am. |volume=91 |issue=1 |pages=1-12 |year=2007 |pmid=17164100}}</ref>

==Diagnoses==
Pain may be a response to injury or any number of disease states that provoke nociception. Advances in imaging studies and electrophysiological studies allow us to gain a deeper insight into the characteristics and properties associated with the phenomenon of chronic pain.<ref name="Dunckley P, Wise RG.">{{cite journal |author=Dunckley P, Wise RG, Fairhurst M, Hobden P, Aziz Q, Chang L, Tracey I |title=A comparison of visceral and somatic pain processing in the human brainstem using functional magnetic resonance imaging |journal=J. Neurosci. |volume=25 |issue=32 |pages=7333-41 |year=2005 |pmid=16093383 |url=http://www.jneurosci.org/cgi/content/full/25/32/7333}}</ref><ref name="Geha PY, Apkarian AV.">{{cite journal |author=Geha PY, Apkarian AV |title=Brain imaging findings in neuropathic pain |journal=Current pain and headache reports |volume=9 |issue=3 |pages=184-8 |year=2005 |pmid=15907256}}</ref><ref name="Turton AJ, McCabe CS.">{{cite journal |author=Turton AJ, McCabe CS, Harris N, Filipovic SR |title=Sensorimotor integration in Complex Regional Pain Syndrome: a transcranial magnetic stimulation study |journal=Pain |volume=127 |issue=3 |pages=270-5 |year=2007 |pmid=17011705}}</ref>

==Chronic Pain Syndrome==
Chronic pain may generate other adversities including affective symptoms of depression and anxiety. It may also contribute to decreased physical activity given the apprehension of exacerbating pain.<ref name="Pruimboom L, van Dam AC.">{{cite journal |author=Pruimboom L, van Dam AC |title=Chronic pain: a non-use disease |journal=Med. Hypotheses |volume=68 |issue=3 |pages=506-11 |year=2007 |pmid=17071012}}</ref> Conversely it may itself have psychosomatic or psychogenic component to its cause.<ref>{{cite book |author=Sarno, John et. al. |title=The Divided Mind: The Epidemic of Mindbody Disorders |year=2006 |publisher=ReganBooks |location=New York |isbn=0-06-085178-3 |pages=11-18}}</ref>


==Management==
==Management==
It is rare to completely achieve absolute and sustained relief of pain. Thus, the clinical goal is pain management. Pain management is often multidisciplinary in nature. A recent journal article by Gatchell and Okifuji recognizes the importance of comprehensive pain programs(CPPs) in the management of chronic pain. They summarize their findings as follows: "CPPs offer the most efficacious and cost-effective treatment for persons with chronic pain, relative to a host of widely used conventional medical treatment." <ref name="Henningsen P, Zipfel S.">{{cite journal |author=Henningsen P, Zipfel S, Herzog W |title=Management of functional somatic syndromes |journal=Lancet |volume=369 |issue=9565 |pages=946-55 |year=2007 |pmid=17368156}}</ref><ref name="Stanos S, Houle TT.">{{cite journal |author=Stanos S, Houle TT |title=Multidisciplinary and interdisciplinary management of chronic pain |journal=Physical medicine and rehabilitation clinics of North America |volume=17 |issue=2 |pages=435-50, vii |year=2006 |pmid=16616276}}</ref>
Chronic pain is often more difficult to treat than [[Pain and nociception|acute pain]]. Expert [[physician]] care is generally necessary to treat any pain that has become chronic and usually involves a multi-disciplinary team which may include a combination of [[physiotherapist]]s, [[psychologist]]s, [[Mental Health Counselor|counselor]]s, and specialists, such as cancer or [[palliative care]] nurses for cancer or physicians who specialize in spine medicine for back pain. [[clinical depression|Depression]] is common for patients with chronic [[back pain]], and it is important to treat both the pain and depression ([http://www.spine-health.com/topics/cd/depression/depression01.html Depression and chronic back pain]). Very often, medications called anti-depressants can help a patient in many ways, by reducing depression and anxiety, helping natural REM sleep, and reducing the perception of pain (Hendler, N, Pharmacotherapy of Chronic Pain, Chapter 9 pages 117-129, in Neurosurgical Management of Pain, (from Johns Hopkins Hospital), Edited by Richard North, MD, Ph.D, and Richard Levy, MD, Springer-Verlag, New York, 1997).


===Medications===
In managing chronic pain ([http://www.pain-management-info.com/treatment-of-pain.htm Pain Management of Chronic Pain])and in choosing which pain killers to use, beneficial analgesic effects must be balanced against any suffered drug side-effects if overall quality of life is to be improved. For example, with opioids, patients may need to adjust the dosage to reach a compromise between actual pain-killing effect and an acceptable level of nausea or constipation.


===Opioid analgesia===
====Opioids====
[[Opioid]] medications provide short, intermediate and long acting analgesia depending upon the specific properties of the medication and whether it is formulated as an extended release drug. Opioid medications may be administered orally, by injection, via nasal mucosa or oral mucosa, rectal, transdermal, intravenously, epidurally and intrathecally. In chronic pain conditions that are opioid responsive a combination of a long acting or extended release medication is often prescribed in conjunction with a shorter acting medication for break through pain (exacerbations).
Opioids are one of the most effective treatments for chronic pain. When [[opioids]] (also called a [[narcotic]] or [[painkiller]]) are used for prolonged periods [[drug tolerance]], [[chemical dependency]] and (rarely) [[psychological addiction]] may occur. [[Chemical dependency]] is somewhat common among [[opioid]] users; however, [[psychological addiction]] rarely occurs for prescription users. Apparent [[drug tolerance]] to the pain-relieving effects of opioids may occur, although tolerance to pain reducing effects usually appears more slowly than tolerance to the euphoric effects of opioids. This may be confused with progression of the underlying disease in cancer patients, back pain patients, and other chronic pain sufferers, rather than an actual decrease in efficacy of the drug. This is normal with opioids but not with many of the other non-opiate drugs. More people die from acetaminophen (Tylenol) a common additive or stand alone [[Analgesic|pain-killer]] than from opioids.{{Fact|date=February 2007}}
Although opioids are strong analgesics, they do not provide complete analgesia regardless of whether the pain is acute or chronic in origin. Opioids are efficacious analgesics in chronic malignant pain and modestly effective nonmalignant pain management. However, there are variable associated adverse effects, especially during the commencement or change in dosing and administration. When [[opioids]] (also called a [[narcotic]]) are used for prolonged periods [[drug tolerance]], [[chemical dependency]] and (rarely) [[addiction]] may occur. [[Chemical dependency]] is ubiquitous among [[opioid]] therapy after continuous administration; however, [[drug tolerance]] is not well studied in patients on long term opioid therapy. [[ Addiction]] rarely occurs as a result of opioid prescription, but they are abused by some individuals, which can cause concern to health care providers. Diversion of opioid medications is another concern for health care providers.


====Non-steroidal anti-inflammatory drugs====
===Pain modifiers===
The other major group of analgesics are [[Non-steroidal anti-inflammatory drug]]s (NSAID). This class of medications includes acetaminophen which may be administered as a single medication or in combination with other analgesics. The alternatively prescribed NSAIDs such as ketoprofen and piroxicam, have limited benefit in chronic pain disorders and with long term use is associated with significant adverse effects. The use of selective NSAIDs designated as selective COX-2 inhibitors have significant cardiovascular and cerebrovascular risks which have limited their utilization.<ref name="Munir MA, Enany N.">{{cite journal |author=Munir MA, Enany N, Zhang JM |title=Nonopioid analgesics |journal=Med. Clin. North Am. |volume=91 |issue=1 |pages=97-111 |year=2007 |pmid=17164106}}</ref><ref name="Ballantyne JC.">{{cite journal |author=Ballantyne JC |title=Opioids for chronic nonterminal pain |journal=South. Med. J. |volume=99 |issue=11 |pages=1245-55 |year=2006 |pmid=17195420}}</ref>
Drugs within this class act centrally on the brain to down regulate the perceived painful stimulus. Drugs having this effect were fortuitously identified whilst being used to treat unrelated conditions. The first such group were the [[tricyclic antidepressants]] (in particular [[amitriptyline]]) and the dose required is far lower than that used to treat depression. Similarly some of the [[anticonvulsant]] drugs are used for this (in particular [[carbamazepine]] [[sodium valproate]] and [[gabapentin]]). For most of these drugs, their use in chronic pain management is [[off-label use|off-label]].


====Antidepressants and Antiepileptic drugs====
===Trigger Point Injections / Core Blocks===
Some [[antidepressant]] and [[antiepileptic]] drugs are used in chronic pain management and act primarily within the pain pathways of the central nervous system, though peripheral mechanisms have been attributed as well. These mechanisms vary and in general are more effective in [[neuropathy|neuropathic]] pain disorders as well as [[complex regional pain syndrome]].<ref name="Jackson KC 2nd.">{{cite journal |author=Jackson KC |title=Pharmacotherapy for neuropathic pain |journal=Pain practice : the official journal of World Institute of Pain |volume=6 |issue=1 |pages=27-33 |year=2006 |pmid=17309706}}</ref>
(Excerpt from [http://pippensqueak.blogspot.com/2005/06/chronic-pain.html Chronic Pain] written by patient undergoing this treatment)
Only recently has research been undertaken to try and find more permanent solutions for these debilitating conditions. One method that has been formulated is Trigger Point Injections which are also sometimes referred to. This involves the injection of a mixture of steroid and anaesthetic into the specific pressure points in the body where the pain is located in an attempt to disburse contracted tissue that could be causing the disturbance.


===Interventional therapy===
There has been some success treating cases of migraines, back pain, and other muscular associated situations with this procedure.{{Fact|date=February 2007}} If they are able to isolate the centers that are the focal points of the pain then a series of treatments are started. In theory as the treatment progresses the nerves are released from the pressure that is causing the continual transmission of the pain signal to the memory centre of the brain. This in turn should allow the brain to forget the pain.
[[Injection]]s, [[Neuromodulation]] and Neuroablative Therapy may be used to target either the tissue structures and organ/systems responsible for persistent [[nociception]] or the nerves conveying nociception from the structures implicated as the source of chronic pain.<ref name="Varrassi G, Paladini A">{{cite journal |author=Varrassi G, Paladini A, Marinangeli F, Racz G |title=Neural modulation by blocks and infusions |journal=Pain practice : the official journal of World Institute of Pain |volume=6 |issue=1 |pages=34-8 |year=2006 |pmid=17309707}}</ref><ref name="Meglio M.">{{cite journal |author=Meglio M |title=Spinal cord stimulation in chronic pain management |journal=Neurosurg. Clin. N. Am. |volume=15 |issue=3 |pages=297-306 |year=2004 |pmid=15246338}}</ref><ref>{{cite journal |author=Rasche D, Ruppolt M, Stippich C, Unterberg A, Tronnier VM |title=Motor cortex stimulation for long-term relief of chronic neuropathic pain: a 10 year experience |journal=Pain |volume=121 |issue=1-2 |pages=43-52 |year=2006 |pmid=16480828}}</ref><ref name="Boswell MV, Trescott AM">{{cite journal |author=Boswell MV, Trescot AM, Datta S, Schultz DM, Hansen HC, Abdi S, Sehgal N, Shah RV, Singh V, Benyamin RM, Patel VB, Buenaventura RM, Colson JD, Cordner HJ, Epter RS, Jasper JF, Dunbar EE, Atluri SL, Bowman RC, Deer TR, Swicegood JR, Staats PS, Smith HS, Burton AW, Kloth DS, Giordano J, Manchikanti L |title=Interventional techniques: evidence-based practice guidelines in the management of chronic spinal pain |journal=Pain physician |volume=10 |issue=1 |pages=7-111 |year=2007 |pmid=17256025|url=http://www.painphysicianjournal.com/2007/january/2007;10;7-111.pdf?PHPSESSID=ea188711febadee5420f1c9061ebd249 |format=PDF}}</ref><ref name="Romanelli P, Esposito V">{{cite journal |author=Romanelli P, Esposito V, Adler J |title=Ablative procedures for chronic pain |journal=Neurosurg. Clin. N. Am. |volume=15 |issue=3 |pages=335-42 |year=2004 |pmid=15246341}}</ref>


===Rehabilitation===
At this time these procedures are starting to become readily available in North America. In the United States these procedures are showing very promising results with patients according to the Chronic Pain Association of America.{{Fact|date=February 2007}} Insurance companies are gradually starting to cover the costs of the procedures because the government has recognized their validity, based from the outcome of many completed studies and regimens of injections. This also means that the procedures are now regulated so you do have a guarantee that the standards of the Core Block are being maintained.
{{see|Physical medicine and rehabilitation}}
As alluded to earlier there are other modalities used in the treatment of chronic pain. These include: physical modalities such as thermal agents and [[electrotherapy]]. Complementary and alternative medicine, therapeutic exercise and behavioral therapy are also utilized autonomously or in tandem with interventional techniques and conventional pharmacotherapy. This is most often structured in a multidisciplinary or interdisciplinary program.<ref name="Geertzen JH, Van Wilgen CP.">{{cite journal |author=Geertzen JH, Van Wilgen CP, Schrier E, Dijkstra PU |title=Chronic pain in rehabilitation medicine |journal=Disability and rehabilitation |volume=28 |issue=6 |pages=363-7 |year=2006 |pmid=16492632}}</ref>


==References==
Although the procedure is covered by provincial health programs in Canada it can only be done by anaesthesiologists in a hospital situation. Since not all doctors in that field even perform this procedure, the wait time to get into a pain clinic in Canada can be as high as sixteen months.
* Carol A. Warfield: ''Principles & Practice of Pain Management '' 1st edition, McGraw-Hill Professional 2004<b/>
* John D. Loeser: ''Bonica's Management of Pain'' 3rd edition, Lippincott Williams & Wilkins 2001

==Footnotes==
<div class="references-small"><references/></div>


==See also==
==See also==
{{col-begin|width=95%}}
* [[Transcutaneous Electrical Nerve Stimulator]]
|-
|
;Conditions related to [[Pain]]:
* [[Arthritis]]
* [[Back pain]]
* [[Back pain]]
* [[Cancer]]
* [[Cancer]]
* [[Complex Regional Pain Syndrome]]
* [[Migraine]]
* [[Depression]]
* [[Fibromyalgia]]
* [[Headache]]
* [[Sciatica]]
* [[Tension myositis syndrome]]


;Drugs:
* [[Analgesia]]
* [[Antiepileptics]]
** [[Gabapentin]]
** [[Pregabalin]]
** [[Levetiracetam]]
** [[Topiramate]]
** [[Lamotrigine]]
** [[Zonisamide]]
* [[Antidepressants]]
* [[Local anesthetics]]
** [[Ketamine]]
* [[NSAIDs]]
* [[Opioids]]
* Other agents:
**[[Clonidine]]
** [[Ziconotide]]
|
;Other approaches in [[Physical medicine and rehabilitation]] (Physiatry):
* [[Cryotherapy]]
* [[Exercise]]
* [[Hot pack]]
* [[Occupational therapy]]
* [[Physical therapy]]
* [[TENS]]

;Alternative therapies:
* [[Accupuncture]]
* [[Behavioral therapy]]
* [[Chiropractic]]
* [[Massage therapy]]
* [[Prolotherapy]]


;Surgery:
* [[Spinal cord stimulation]]
|}


==External links==
==External links==
* [http://www.spine-health.com/chronicpain/index.html Chronic Pain Health Hub]
* [http://www.chronicpainsolutions.com Chronic Pain Solutions]
* [http://www.stoppain.org/ StopPain.org]
* [http://www.theacpa.org/ American Chronic Pain Association]
* [http://www.theacpa.org/ American Chronic Pain Association]
* [http://www.spine-health.com/topics/cd/chronic_pain/chronicpain01.html Chronic Pain as a Disease: Why does it still hurt?]
* [http://www.spine-health.com/topics/cd/chronic_pain/chronicpain01.html Chronic Pain as a Disease: Why does it still hurt?]
* [http://www.spine-health.com/Topics/cd/stress/str01.html Stress Related Chronic Pain]
* [http://www.spine-health.com/topics/cd/stress/str01.html Psycho-physiological Pain]
* [http://www.pain.com/ Pain.com]
* [http://www.painknowledge.org/ NIPC- PainKnowledge.org]
* [http://www.ampainsoc.org/people/ Patient consumer web page sponsored by the APS]
* [http://www.painfoundation.org/ American Pain Foundation]
* [http://www.painfoundation.org/ American Pain Foundation]
* [http://www.pain-management-info.com/types-of-pain.htm/ Pain Management Information-Discusses Conventional & Alternative Treatment of Pain]
* [http://www.pain-management-info.com/types-of-pain.htm/ Pain Management Information-Discusses Conventional & Alternative Treatment of Pain]
* [http://www.iasp-pain.org/ International Association for the Study of Pain- IASP]


{{external links|May 2007}}


[[Category:Nociception]]
[[Category:Nociception]]

Revision as of 00:53, 16 June 2007

Chronic pain was originally defined as pain that has lasted 6 months or longer. More recently it has been defined as pain that persists longer than the temporal course of natural healing that is associated with a particular type of injury or disease process. [1]

The International Association for the Study of Pain defines pain as an unpleasant sensory and affective experience induced by the exposure to noxious stimuli i.e. injury incipient or substantive in nature.[2]. It is important to note that pain is subjective in nature and is defined by the person experiencing it, and the medical community's understanding of chronic pain now includes the impact that the mind has in processing and interpreting pain signals.

Functional Anatomy

The anatomy of the nociceptive system can be grossly divided into the peripheral and central nervous system. The peripheral nervous system consists of small myelinated and unmyelinated nerve fibers. These nerve fibers converge into a region of the spinal cord referred to as the dorsal horn. The dorsal horn is the first relay station in pain signal transmission. The next element of pain transmission includes nerve fibers that then travel to the thalamus. From the thalamus the next order of neurons ascend to the limbic system and sensory cortex. This accounts for the affective elements and discriminative of pain respectively.[3][4]

Nociception

The experience of pain biologically is referred to as nociception. Nociception occurs in any tissue or organ in which pain signals arise secondary to a disease process or trauma. The nociception can also occur if there is dysfunction or damage to nerves themselves.[2]


The Pathophysiology of Chronic Pain

Under persistent activation nociceptive transmission to the dorsal horn may induce a wind up phenomenon. This induces pathological changes that lower the threshold for pain signals to be transmitted. In addition, it may generate nonnociceptive nerve fibers to respond to, generate and transmit pain signals. In chronic pain this process is difficult to reverse or eradicate once established.[5]

Classification

Nociception (pain) may arise from injury or disease to visceral, somatic and neural structures in the body. More broadly pain is described as malignant or non-malignant in origin.[4]

Diagnoses

Pain may be a response to injury or any number of disease states that provoke nociception. Advances in imaging studies and electrophysiological studies allow us to gain a deeper insight into the characteristics and properties associated with the phenomenon of chronic pain.[6][7][8]

Chronic Pain Syndrome

Chronic pain may generate other adversities including affective symptoms of depression and anxiety. It may also contribute to decreased physical activity given the apprehension of exacerbating pain.[9] Conversely it may itself have psychosomatic or psychogenic component to its cause.[10]

Management

It is rare to completely achieve absolute and sustained relief of pain. Thus, the clinical goal is pain management. Pain management is often multidisciplinary in nature. A recent journal article by Gatchell and Okifuji recognizes the importance of comprehensive pain programs(CPPs) in the management of chronic pain. They summarize their findings as follows: "CPPs offer the most efficacious and cost-effective treatment for persons with chronic pain, relative to a host of widely used conventional medical treatment." [11][12]

Medications

Opioids

Opioid medications provide short, intermediate and long acting analgesia depending upon the specific properties of the medication and whether it is formulated as an extended release drug. Opioid medications may be administered orally, by injection, via nasal mucosa or oral mucosa, rectal, transdermal, intravenously, epidurally and intrathecally. In chronic pain conditions that are opioid responsive a combination of a long acting or extended release medication is often prescribed in conjunction with a shorter acting medication for break through pain (exacerbations). Although opioids are strong analgesics, they do not provide complete analgesia regardless of whether the pain is acute or chronic in origin. Opioids are efficacious analgesics in chronic malignant pain and modestly effective nonmalignant pain management. However, there are variable associated adverse effects, especially during the commencement or change in dosing and administration. When opioids (also called a narcotic) are used for prolonged periods drug tolerance, chemical dependency and (rarely) addiction may occur. Chemical dependency is ubiquitous among opioid therapy after continuous administration; however, drug tolerance is not well studied in patients on long term opioid therapy. Addiction rarely occurs as a result of opioid prescription, but they are abused by some individuals, which can cause concern to health care providers. Diversion of opioid medications is another concern for health care providers.

Non-steroidal anti-inflammatory drugs

The other major group of analgesics are Non-steroidal anti-inflammatory drugs (NSAID). This class of medications includes acetaminophen which may be administered as a single medication or in combination with other analgesics. The alternatively prescribed NSAIDs such as ketoprofen and piroxicam, have limited benefit in chronic pain disorders and with long term use is associated with significant adverse effects. The use of selective NSAIDs designated as selective COX-2 inhibitors have significant cardiovascular and cerebrovascular risks which have limited their utilization.[13][14]

Antidepressants and Antiepileptic drugs

Some antidepressant and antiepileptic drugs are used in chronic pain management and act primarily within the pain pathways of the central nervous system, though peripheral mechanisms have been attributed as well. These mechanisms vary and in general are more effective in neuropathic pain disorders as well as complex regional pain syndrome.[15]

Interventional therapy

Injections, Neuromodulation and Neuroablative Therapy may be used to target either the tissue structures and organ/systems responsible for persistent nociception or the nerves conveying nociception from the structures implicated as the source of chronic pain.[16][17][18][19][20]

Rehabilitation

Further information: Physical medicine and rehabilitation

As alluded to earlier there are other modalities used in the treatment of chronic pain. These include: physical modalities such as thermal agents and electrotherapy. Complementary and alternative medicine, therapeutic exercise and behavioral therapy are also utilized autonomously or in tandem with interventional techniques and conventional pharmacotherapy. This is most often structured in a multidisciplinary or interdisciplinary program.[21]

References

  • Carol A. Warfield: Principles & Practice of Pain Management 1st edition, McGraw-Hill Professional 2004
  • John D. Loeser: Bonica's Management of Pain 3rd edition, Lippincott Williams & Wilkins 2001

Footnotes

  1. ^ Shipton EA, Tait B (2005). "Flagging the pain: preventing the burden of chronic pain by identifying and treating risk factors in acute pain". European journal of anaesthesiology. 22 (6): 405–12. PMID 15991501.
  2. ^ a b Merskey H (1994). "Logic, truth and language in concepts of pain". Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation. 3 Suppl 1: S69-76. PMID 7866375.
  3. ^ Romanelli P, Esposito V (2004). "The functional anatomy of neuropathic pain". Neurosurg. Clin. N. Am. 15 (3): 257–68. PMID 15246335.
  4. ^ a b Vanderah TW (2007). "Pathophysiology of pain". Med. Clin. North Am. 91 (1): 1–12. PMID 17164100.
  5. ^ Vadivelu N, Sinatra R (2005). "Recent advances in elucidating pain mechanisms". Current opinion in anaesthesiology. 18 (5): 540–7. PMID 16534290.
  6. ^ Dunckley P, Wise RG, Fairhurst M, Hobden P, Aziz Q, Chang L, Tracey I (2005). "A comparison of visceral and somatic pain processing in the human brainstem using functional magnetic resonance imaging". J. Neurosci. 25 (32): 7333–41. PMID 16093383.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. ^ Geha PY, Apkarian AV (2005). "Brain imaging findings in neuropathic pain". Current pain and headache reports. 9 (3): 184–8. PMID 15907256.
  8. ^ Turton AJ, McCabe CS, Harris N, Filipovic SR (2007). "Sensorimotor integration in Complex Regional Pain Syndrome: a transcranial magnetic stimulation study". Pain. 127 (3): 270–5. PMID 17011705.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  9. ^ Pruimboom L, van Dam AC (2007). "Chronic pain: a non-use disease". Med. Hypotheses. 68 (3): 506–11. PMID 17071012.
  10. ^ Sarno, John; et al. (2006). The Divided Mind: The Epidemic of Mindbody Disorders. New York: ReganBooks. pp. 11–18. ISBN 0-06-085178-3. {{cite book}}: Explicit use of et al. in: |author= (help)
  11. ^ Henningsen P, Zipfel S, Herzog W (2007). "Management of functional somatic syndromes". Lancet. 369 (9565): 946–55. PMID 17368156.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  12. ^ Stanos S, Houle TT (2006). "Multidisciplinary and interdisciplinary management of chronic pain". Physical medicine and rehabilitation clinics of North America. 17 (2): 435–50, vii. PMID 16616276.
  13. ^ Munir MA, Enany N, Zhang JM (2007). "Nonopioid analgesics". Med. Clin. North Am. 91 (1): 97–111. PMID 17164106.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  14. ^ Ballantyne JC (2006). "Opioids for chronic nonterminal pain". South. Med. J. 99 (11): 1245–55. PMID 17195420.
  15. ^ Jackson KC (2006). "Pharmacotherapy for neuropathic pain". Pain practice : the official journal of World Institute of Pain. 6 (1): 27–33. PMID 17309706.
  16. ^ Varrassi G, Paladini A, Marinangeli F, Racz G (2006). "Neural modulation by blocks and infusions". Pain practice : the official journal of World Institute of Pain. 6 (1): 34–8. PMID 17309707.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  17. ^ Meglio M (2004). "Spinal cord stimulation in chronic pain management". Neurosurg. Clin. N. Am. 15 (3): 297–306. PMID 15246338.
  18. ^ Rasche D, Ruppolt M, Stippich C, Unterberg A, Tronnier VM (2006). "Motor cortex stimulation for long-term relief of chronic neuropathic pain: a 10 year experience". Pain. 121 (1–2): 43–52. PMID 16480828.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  19. ^ Boswell MV, Trescot AM, Datta S, Schultz DM, Hansen HC, Abdi S, Sehgal N, Shah RV, Singh V, Benyamin RM, Patel VB, Buenaventura RM, Colson JD, Cordner HJ, Epter RS, Jasper JF, Dunbar EE, Atluri SL, Bowman RC, Deer TR, Swicegood JR, Staats PS, Smith HS, Burton AW, Kloth DS, Giordano J, Manchikanti L (2007). "Interventional techniques: evidence-based practice guidelines in the management of chronic spinal pain" (PDF). Pain physician. 10 (1): 7–111. PMID 17256025.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  20. ^ Romanelli P, Esposito V, Adler J (2004). "Ablative procedures for chronic pain". Neurosurg. Clin. N. Am. 15 (3): 335–42. PMID 15246341.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  21. ^ Geertzen JH, Van Wilgen CP, Schrier E, Dijkstra PU (2006). "Chronic pain in rehabilitation medicine". Disability and rehabilitation. 28 (6): 363–7. PMID 16492632.{{cite journal}}: CS1 maint: multiple names: authors list (link)

See also

External links

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