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Name of Symptom/Sign:
Chronic pain
Classifications and external resources

ICD-10	R52.1-R52.2
ICD-9

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, 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 emotional experience associated with actual or potential tissue damage, or described in terms of such damage."^[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.

Contents 1 Functional Anatomy 2 Nociception 3 The Pathophysiology of Chronic Pain 4 Classification 5 Diagnoses 6 Chronic Pain Syndrome 7 Management 7.1 Medications 7.1.1 Opioids 7.1.2 Non-steroidal anti-inflammatory drugs 7.1.3 Antidepressants and Antiepileptic drugs 7.2 Interventional therapy 7.3 Rehabilitation 8 References 9 Footnotes 10 See also 11 External links

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]

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]

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 pain signals. Nonnociceptive nerve fibers may also be able to generate and transmit pain signals. In chronic pain this process is difficult to reverse or eradicate once established.^[5]

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]

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 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]

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]

Prof/Dr Brian Rothbart has linked chronic pain to the feet. He was the first to discover and publish on two very common and previously unrecognized embryological foot structures that he links to postural distortions and the development of chronic pain (Primus Metatarsus Supinatus and the Preclinical Clubfoot Deformity. Using Proprioceptive insoles (referred to as Rothbarts Proprioceptive Insoles), these foot structures and posture are stabilized, which in turn, eliminates the chronic pain (foot to jaw).

"Because patients with chronic pain suffer many consequences of their illness, any treatment with the potential to improve their symptoms should be prescribed and the results carefully studied." conclusion of the Johns Hopkins Arthritis Center.

In the treatment of chronic pain, whether due to malignant or benign processes, the three-step WHO Analgesic Ladder is often used.[1][2][3] This provides guidelines for stepping up the amount of analgesia and maintains a general basis that is used in a number of countries around the world to manage chronic pain conditions. The exact medications recommended will vary with the country and the individual treatment centre, but the following gives an example of the approach to treating chronic pain with medications. If, at any point, treatment fails to provide adequate pain relief, then the doctor and patient move onto the next step.

1. Mild Pain - Non-Opioid ± Adjuvents:
   • paracetamol (acetaminophen), or
   • a non steroidal anti-inflammatory drug (NSAID) such as ibuprofen.

For a number of patients, these simple analgesics can control chronic pain when taken on a regular basis, either alone or with other non-medication methods. Some patients may also be offered atypical or adjuvent medications including tricyclic antidepressants and some anticonvulsants, and topical agents such as lidocaine and capsaicin.

2. Mild to Moderate Pain - Weak Opioid ± Non-Opioid ± Adjuvents:
   • paracetamol and an NSAID, or
   • paracetamol in a combination product with a weak opioid such as codeine, or
   • a paracetamol and weak opioid combination, and an NSAID.

Using two or more analgesics in combination often provides greater analgesia, at lower doses, than using the individual medications alone. Some patients may also be prescribed other medications, such as tramadol, and any adjuvents listed in step 1.

3. Moderate to Severe Pain - Strong Opioid ± Non-Opioid ± Adjuvents:
   First line choices:
   • Morphine is the gold standard choice.
   Second line choices:
   • Oxycodone although this has received bad press in certain countries and is less popular,
   • Fentanyl in the form of a transdermal patch designed for chronic pain management,
   • Diamorphine, hydromorphone or methadone are used less frequently.
   Not recommended for chronic pain management:
   • Pethidine (meperidine) is not regularly used due to its low potency, short duration of action, and toxicity associated with repeated use.

Opioid medications can provide a short, intermediate or 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).

Most opioid treatment is oral (tablet, capsule or liquid), but suppositories and skin patches can be prescribed. An opioid injection is rarely needed for patients with chronic pain.

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 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.

The other major group of analgesics are Non-steroidal anti-inflammatory drugs (NSAID). This class of medications does not include acetaminophen, which has minimal anti-inflammatory properties. However, acetaminophen may be administered as a single medication or in combination with other analgesics (both NSAIDs and opioids). 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]

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] Drugs such as Gabapentin have been widely prescribed for the off-label use of pain control. The list of side effects for these classes of drugs are typically much longer than opiate or NSAID treatments for chronic pain, and many antiepileptics cannot be suddenly stopped without the risk of seizure.

pulsed radiofrequency, 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]}

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]

• 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

Suffering Conditions related to pain Arthritis Back pain Cancer Complex Regional Pain Syndrome Clinical depression Fibromyalgia Headache Sciatica Drugs Analgesia Antiepileptics Gabapentin Pregabalin Levetiracetam Topiramate Lamotrigine Zonisamide Antidepressants Local anesthetics Ketamine Acetaminophen (Paracetamol) 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 Acupuncture Behavioral therapy Chiropractic Massage therapy Prolotherapy Surgery Spinal cord stimulation

• American Chronic Pain Association
• American Pain Foundation
• International Association for the Study of Pain- IASP
• Patient consumer web page sponsored by the APS

v • d • e Symptoms and signs (R00-R69, 780-789)
Circulatory and respiratory systems	Tachycardia - Bradycardia - Palpitation - Heart murmur - Epistaxis - Hemoptysis - Cough - abnormalities of breathing (Dyspnea, Orthopnoea, Stridor, Wheeze, Cheyne-Stokes respiration, Hyperventilation, Mouth breathing, Hiccup, Bradypnea, Hypoventilation) - Chest pain - Asphyxia - Pleurisy - Respiratory arrest - Sputum - Bruit/Carotid bruit - Rales
Digestive system and abdomen	Abdominal pain (Acute abdomen) - Nausea/Vomiting - Heartburn - Dysphagia - flatulence and related (Abdominal distension, Bloating, Burping, Tympanites) - Fecal incontinence (Encopresis) - hepatosplenomegaly (Hepatomegaly, Splenomegaly) - Jaundice - Ascites - Fecal occult blood - Halitosis
Skin and subcutaneous tissue	disturbances of skin sensation (Hypoesthesia, Paresthesia, Hyperesthesia) - Rash - Cyanosis - Pallor - Flushing - Petechia - Desquamation - Induration - Diaphoresis
Nervous and musculoskeletal systems	abnormal involuntary movements (Tremor, Spasm, Fasciculation, Athetosis) - Gait abnormality - lack of coordination (Ataxia, Dysmetria, Dysdiadochokinesia, Hypotonia) - Tetany - Meningism - Hyperreflexia
Urinary system	Dysuria - Vesical tenesmus - Urinary incontinence - Urinary retention - Oliguria - Polyuria - Nocturia - Extravasation of urine
Cognition, perception, emotional state and behaviour	Anxiety - Somnolence - Coma - Amnesia (Anterograde amnesia, Retrograde amnesia) - Dizziness/Vertigo - smell and taste (Anosmia, Ageusia, Parosmia, Parageusia)
Speech and voice	speech disturbances (Dysphasia, Aphasia, Dysarthria) - symbolic dysfunctions (Dyslexia, Alexia, Agnosia, Apraxia, Acalculia, Agraphia) - voice disturbances (Dysphonia, Aphonia)
General symptoms and signs	Fever (Hyperpyrexia) - Headache - Chronic pain - Malaise/Fatigue (Asthenia, Debility) - Fainting (Vasovagal syncope) - Febrile seizure - Shock (Cardiogenic shock) - Lymphadenopathy - Edema (Peripheral edema, Anasarca) - Hyperhidrosis (Sleep hyperhidrosis) - Delayed milestone - Failure to thrive - Short stature (Idiopathic) - food and fluid intake (Anorexia, Polydipsia, Polyphagia) - Cachexia - Xerostomia - Clubbing