List of chronic pain syndromes
thumb|348x348px|Explanatory model of chronic pain.
Chronic pain is defined as reoccurring or persistent pain that lasts for over 3 months. It continues past normal healing times and therefore does not have the same function as acute pain. Acute pain serves to signal the body that there is a threat so that the body can avoid future danger. Chronic pain on the other hand does not serve this purpose. The International Association for the Study of Pain (IASP) defines pain as "An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage". Chronic pain is considered a syndrome because of the associated symptoms that develop in those experiencing chronic pain. Chronic pain is a prevalent condition that affects approximately 20% of people and accounts for 15-20% of visits to a physician.

Pain can be categorized according to its location, cause, or the anatomical system in which it affects. Pain can also defy these classifications which makes it difficult to classify chronic pain. In order to create a classification system for chronic pain, the International Association for the Study of Pain (IASP) collaborated with the World Health Organization (WHO) to form a Task Force for the Classification of Chronic Pain. The IASP Task Force was made up of those who were experts in pain and developed a new model to classify chronic pain for the ICD-11. The IASP Task Force emphasized the cause of pain, underlying mechanisms and body sites. This classification system differentiates chronic primary pain from chronic secondary pain, incorporates already existing diagnosis, and further characterizes chronic pain syndromes. The ICD-11 category for chronic pain includes the most common types of chronic pain, chronic primary pain, chronic cancer pain, chronic posttraumatic and postsurgical pain, chronic neuropathic pain, chronic secondary headache and orofacial pain, chronic secondary visceral pain, and chronic secondary musculoskeletal pain. There can also be significant overlap between several categories.

 Chronic primary pain 
Chronic primary pain is pain that affects one or more anatomical sites, reoccurs or persists for more than three months, causes emotional distress or functional disability and can't be better explained by another chronic pain condition. Emotional distress can be expressed in a number of ways such as frustration, anxiety, depression, demoralization and anger. Functional disability encompasses a large range of difficulties such as difficulties at work, difficulties with sleeping, or difficulties with social activities. Chronic primary pain can affect any body system or site and can also be widespread. Conditions within this category are further classified into chronic widespread pain, complex regional pain syndromes, chronic primary headache and orofacial pain, chronic primary visceral pain, and chronic primary musculoskeletal pain.

 Chronic widespread pain 
Chronic widespread pain is defined as diffuse musculoskeletal pain affecting at least three to four body regions and in at least three or more body quadrants and axial skeleton. Body quadrants are defined as upper, lower, left and right sides of the body. Chronic widespread pain cannot be attributed to nociceptive process in these areas.

 Fibromyalgia
 Myofascial pain syndrome

 Complex regional pain syndromes 
thumb|A 60 years old male patient suffering from type I CRPS, majorly caused by left tibial fracture. Picture taken after 6 months of the injury.
Complex regional pain syndrome is characterized by pain that is distributed regionally, usually starts in an extremity distally, occurs after a trauma, and the pain is disproportionate in severity or duration compared to the expected course of the trauma. Complex regional pain syndrome is divided into two types, type 2 requires evidence of peripheral nerve injury, while type 1 does not.

 Complex regional pain syndrome type I
 Complex regional pain syndrome type II

 Chronic primary headache and orofacial pain 
Chronic primary headache or orofacial pain is orofacial pain or headache that persists for longer than three months and occurs at least 15 days a month. When untreated the pain lasts at least two hours or can occur as many shorter episodes of pain throughout the day.

 Chronic migraine
 Chronic tension-type headache
 Trigeminal autonomic cephalalgias
 Chronic temporomandibular disorder
 Chronic burning mouth pain
 Chronic primary orofacial pain

 Chronic primary visceral pain 
Chronic primary visceral pain occurs in the head or neck viscera of the digestive system; the abdominal area from viscera of the digestive system, such as IBS; the thoracic region, such as non-cardiac chest pain; and the pelvic area from the involvement of viscera of the urinary, digestive, and genital systems, such as chronic pelvic pain. Visceral pain is caused by nociceptor activation in pelvic, thoracic or abdominal organs.

 Chronic primary chest pain syndrome
 Chronic primary epigastric pain syndrome
 Irritable bowel syndrome
 Chronic primary abdominal pain syndrome
 Chronic primary bladder pain syndrome
 Chronic primary pelvic pain syndrome

 Chronic primary musculoskeletal pain 
Chronic primary musculoskeletal pain affects the joints, muscles, bones, or tendons. Chronic primary musculoskeletal pain syndromes are classified by the location in which they affect.
 Chronic primary low back pain
 Chronic primary cervical pain
 Chronic primary thoracic pain
 Chronic primary limb pain

 Chronic secondary pain 
Chronic secondary pain syndromes are caused by other medical conditions. Pain may initially be a symptom of a disease however it can also persist after successful treatment of the underlying disorder. Chronic secondary pain can be further categorized into chronic cancer-related pain, chronic postsurgical or posttraumatic pain, chronic neuropathic pain, chronic secondary headache or orofacial pain, chronic secondary visceral pain, and chronic secondary musculoskeletal pain.

 Chronic cancer-related pain 
Pain is the most common symptom of cancer at the time of diagnosis. Cancer-related pain can be caused by metastases, the tumour itself, inflamed or eroding bone viscera or nerves, or pain related to cancer treatments. The term “cancer-related pain” only indicates that pain is related to cancer and doesn't imply the exact cause of the pain.

 Chronic cancer pain 
Chronic cancer pain is caused by metastases or primary cancer. It has neuropathic and inflammatory mechanisms that are caused by how tissue responds to tumours or metastases. Neuropathic pain is caused by damage to the somatosensory nervous system. Signs and symptoms of neuropathic pain include allodynia (pain caused by non-painful stimuli), hyperalgesia (an increase in pain perception due to painful stimuli), and paresthesia (abnormal sensations such as needle bites, tingling, itching, decreased or loss of sensitivity).

 Chronic visceral cancer pain
 Chronic bone cancer pain
 Chronic neuropathic cancer pain

 Chronic post cancer treatment pain 
Cancer treatments can also contribute to chronic pain. Cancer treatments include chemotherapy, surgery, and radiotherapy, which are known to cause chronic pain.
 Chronic post cancer medicine pain
 Chronic painful chemotherapy-induced polyneuropathy
 Chronic post radiotherapy pain
 Chronic painful radiation-induced neuropathy
 Chronic postcancer surgery pain

 Chronic postsurgical or posttraumatic pain 
Chronic postsurgical or posttraumatic pain is pain that develops of becomes more severe following surgery or an injury. Chronic postsurgical or posttraumatic pain continues past the expected timeframe for healing (typically three months). The pain is localized to the site of injury or surgery.

 Chronic post traumatic pain 
thumb|Hyperextension and hyperflexion in whiplash injury.
Chronic post traumatic pain is pain that develops are worsens after an injury. The pain is either localized to the injured region, referred to a dermatomal region, or innervation territory of the nerves in the area.

 Chronic pain after burns injury
 Chronic whiplash injury associated pain
 Chronic pain after musculoskeletal injury
 Chronic pain after peripheral nerve injury or chronic pain after central nervous system injury

 Chronic postsurgical pain 
Chronic postsurgical pain refers to pain that develops or becomes more severe after a surgical procedure.

 Chronic pain after spinal surgery
 Chronic pain after herniotomy
 Chronic pain after hysterectomy
 Chronic pain after amputation
 Chronic pain after thoracotomy
 Chronic pain after breast surgery
 Chronic pain after arthroplasty

 Chronic neuropathic pain 
Chronic neuropathic pain is caused by a disease or lesion of the somatosensory nervous system. Chronic neuropathic pain requires a history of nervous system injury or disease as well as a distribution of pain that makes sense in the context of neuroanatomy.

 Chronic central neuropathic pain 
Chronic central neuropathic pain is caused by a lesion or disease of the central somatosensory nervous system.

 Chronic central neuropathic pain associated with spinal cord injury
 Chronic central neuropathic pain associated with brain injury
 Chronic central post stroke pain
 Chronic central neuropathic pain associated with multiple sclerosis

 Chronic peripheral neuropathic pain 
Chronic central neuropathic pain is caused by a lesion or disease of the peripheral somatosensory nervous system.

 Chronic neuropathic pain after peripheral nerve injury
 Chronic painful polyneuropathy
 Chronic painful radiculopathy
 Postherpetic neuralgia
 Trigeminal neuralgia

 Chronic secondary headache or orofacial pain 
thumb|A T2-weighted sagittal MRI scan, from a patient with Chiari-like symptomatology, demonstrating tonsillar herniation less than 3 mm
Chronic secondary headache or orofacial pain is a result of an underlying disorder. Chronic secondary headache or orofacial pain can be caused by ischemic stroke, nontraumatic intracranial hemorrhage, arteritis, cervical carotid or vertebral artery disorder, unruptured vascular malformation, pituitary apoplexy, genetic vasculopathy, increased cerebrospinal fluid pressure, Chiari malformation type I, low cerebrospinal fluid pressure, intracranial neoplasms, intrathecal injection, noninfectious inflammatory intracranial disease, epileptic seizure, substance withdrawal, bacterial meningitis, subdural empyema, meningoencephalitis, viral meningitis or encephalitis, brain abscess, intracranial fungal or other parasitic infections, hypoxia, hypercapnia, cardiac cephalalgia, dialysis, fasting, arterial hypertension, and hypothyroidism.

 Chronic dental pain
 Chronic neuropathic orofacial pain
 Headache or orofacial pain associated with chronic secondary temporomandibular disorders
 Chronic headache or orofacial pain associated with disorders of homoeostasis or their nonpharmacological treatment
 Chronic headache or orofacial pain associated with cranial or cervical vascular disorder
 Chronic headache or orofacial pain associated with non-vascular intracranial disorder
 Chronic headache associated with a substance or its withdrawal
 Chronic headache or orofacial pain attributed to trauma or injury to the head and/or neck
 Chronic headache or orofacial pain attributed to infection

 Chronic secondary visceral pain 
Chronic secondary visceral pain refers to reoccurring or persisting pain caused by organs in the thoracic, abdominal, and pelvic cavities.

 Chronic visceral pain from mechanical factors 
thumb|Bronchial stenosis after surgery in a patient with complete disruption of the right bronchus.
Chronic visceral pain from mechanical factors is caused by external compression of internal organs, internal organ traction involving ligaments and vessels, or internal obstructions, such as stones or stenosis, which can block hollow viscera and cause dilation above the obstruction.

 Chronic visceral pain from mechanical factors in the head or neck region
 Chronic visceral pain from mechanical factors in the thoracic region
 Chronic visceral pain from mechanical factors in the abdominal region
 Chronic visceral pain from mechanical factors in the pelvic region

 Chronic visceral pain from vascular mechanisms 
Chronic visceral pain from vascular mechanisms is caused by changes in the arterial or venous blood vessels that supply blood to the viscera of the thoracic, abdominal and pelvic cavities and the head or neck region. It can also be caused by a disorder of the vascular system that causes pain in other areas of the body.

 Chronic visceral pain from vascular mechanisms in the head or neck region
 Chronic visceral pain from vascular mechanisms in the thoracic region
 Chronic visceral pain from vascular mechanisms in the abdominal region
 Chronic visceral pain from vascular mechanisms in the pelvic region

 Chronic visceral pain from persistent inflammation 
Chronic visceral pain from persistent inflammation is pain caused by chronic inflammation of internal organs. This inflammation can be caused by noninfectious, infectious, or autoimmune mechanisms.

 Chronic visceral pain from persistent inflammation in the head or neck region
 Chronic visceral pain from persistent inflammation in the thoracic region
 Chronic visceral pain from persistent inflammation in the abdominal region
 Chronic visceral pain from persistent inflammation in the pelvic region

 Chronic secondary musculoskeletal pain 
Chronic secondary musculoskeletal pain can be caused by a variety of conditions, including chronic nociception in the vertebral column, joints, bones, muscles, tendons, and soft tissues, as well as deep somatic lesions.

 Chronic secondary musculoskeletal pain from persistent inflammation 
thumb|Tophaceous gout affecting the right great toe and finger interphalangeal joints.
One of the main causes of many musculoskeletal disorders is inflammation. Similarly, one of the main causes of persistent musculoskeletal pain is ongoing inflammation. Inflammation-related pain symptoms include heightened sensitivity to stimuli in the afflicted area. In rheumatological disorders with inflammation as the principal pathophysiological mechanism, chronic secondary musculoskeletal pain can be the main symptom.

 Chronic secondary musculoskeletal pain from persistent inflammation due to infection
 Chronic secondary musculoskeletal pain from persistent inflammation due to crystal deposition
 Chronic secondary musculoskeletal pain from persistent inflammation due to autoimmune and auto-inflammatory disorders

 Chronic secondary musculoskeletal pain associated with structural changes 
Chronic secondary musculoskeletal pain associated with structural changes can be attributed to modifications in the structure of a joint, bone, or tendon. The structural alteration can be seen on imaging or determined from a clinical assessment.

 Chronic secondary musculoskeletal pain associated with osteoarthritis
 Chronic secondary musculoskeletal pain associated with spondylosis
 Chronic pain after musculoskeletal injury

 Chronic secondary musculoskeletal pain due to disease of the nervous system 
Chronic secondary musculoskeletal pain due to disease of the nervous system is associated with central or peripheral nervous system conditions that are categorized elsewhere. It involves pain brought on by changes in sensory and motor function.

 Chronic secondary musculoskeletal pain associated with Parkinson's disease
 Chronic secondary musculoskeletal pain associated with multiple sclerosis
 Chronic secondary musculoskeletal pain associated with peripheral neurologic disease

 Referances 
 Citations 

 Sources 

 
 
 
 
 
 
 
 
 
 
 
 
 
 

 Further reading 
 
 

 External links 
 
 

Category:Chronic pain syndromes
Category:Lists of diseases