Pain asymbolia, also called pain dissociation, is a condition in which pain is experienced without unpleasantness. This usually results from injury to the brain, lobotomy, cingulotomy or morphine analgesia. Preexisting lesions of the insula may abolish the aversive quality of painful stimuli while preserving the location and intensity aspects. Typically, patients report that they have pain but are not bothered by it; they recognize the sensation of pain but are mostly or completely immune to suffering from it.

Pain is the main reason for visiting an emergency department in more than 50% of cases, and is present in 30% of family practice visits. Several epidemiological studies have reported widely varying prevalence rates for chronic pain, ranging from 12 to 80% of the population. It becomes more common as people approach death. A study of 4,703 patients found that 26% had pain in the last two years of life, increasing to 46% in the last month.

A survey of 6,636 children (0–18 years of age) found that, of the 5,424 respondents, 54% had experienced pain in the preceding three months. A quarter reported having experienced recurrent or continuous pain for three months or more, and a third of these reported frequent and intense pain. The intensity of chronic pain was higher for girls, and girls' reports of chronic pain increased markedly between ages 12 and 14.

The ability to experience pain is essential for protection from injury, and recognition of the presence of injury. Episodic analgesia may occur under special circumstances, such as in the excitement of sport or war: a soldier on the battlefield may feel no pain for many hours from a traumatic amputation or other severe injury.

Although unpleasantness is an essential part of the IASP definition of pain, it is possible to induce a state described as intense pain devoid of unpleasantness in some patients, with morphine injection or psychosurgery. Such patients report that they have pain but are not bothered by it; they recognize the sensation of pain but suffer little, or not at all. Indifference to pain can also rarely be present from birth; these people have normal nerves on medical investigations, and find pain unpleasant, but do not avoid repetition of the pain stimulus.

Insensitivity to pain may also result from abnormalities in the nervous system. This is usually the result of acquired damage to the nerves, such as spinal cord injury, diabetes mellitus (diabetic neuropathy), or leprosy in countries where that disease is prevalent. These individuals are at risk of tissue damage and infection due to undiscovered injuries. People with diabetes-related nerve damage, for instance, sustain poorly-healing foot ulcers as a result of decreased sensation.

A much smaller number of people are insensitive to pain due to an inborn abnormality of the nervous system, known as "congenital insensitivity to pain". Children with this condition incur carelessly-repeated damage to their tongues, eyes, joints, skin, and muscles. Some die before adulthood, and others have a reduced life expectancy. Most people with congenital insensitivity to pain have one of five hereditary sensory and autonomic neuropathies (which includes familial dysautonomia and congenital insensitivity to pain with anhidrosis). These conditions feature decreased sensitivity to pain together with other neurological abnormalities, particularly of the autonomic nervous system. A very rare syndrome with isolated congenital insensitivity to pain has been linked with mutations in the "SCN9A" gene, which codes for a sodium channel (Na1.7) necessary in conducting pain nerve stimuli.

Electroanalgesia is a form of analgesia, or pain relief, that uses electricity to ease pain. Electrical devices can be internal or external, at the site of pain (local) or delocalized throughout the whole body. It works by interfering with the electric currents of pain signals, inhibiting them from reaching the brain and inducing a response; different from traditional analgesics, such as opiates which mimic natural endorphins and NSAIDS (non-steroidal anti-inflammatory drugs) that help relieve inflammation and stop pain at the source. Electroanalgesia has a lower addictive potential and poses less health threats to the general public, but can cause serious health problems, even death, in people with other electrical devices such as pacemakers or internal hearing aids, or with heart problems.

The incidence of anesthesia awareness is higher and has more serious sequelae when muscle relaxants or neuromuscular-blocking drugs are used. This is because without relaxant the patient will move and the anesthesiologist will deepen the anesthesia.

One study has indicated this phenomenon occurs in about 1 or 2 per 1000 patients or 0.13%. There is conflicting data however as another study suggested it is a rare phenomenon, with an incidence of 0.0068% after review of their data from a patient population of 211,842 patients.

Post operative interview by an anesthetist is common practice to elucidate if awareness occurred in the case. If awareness is reported a case review is immediately performed to identify machine, medication, or operator error.

Audioanalgesia (also known as audio-analgesia) is the relief of pain using white noise or music without using pharmacological agents while doing painful medical procedures such as dental treatments. It was first introduced by Gardner and Licklider in 1959.

There are many studies of this technique in dental, obstetric, and palliative care contexts. The most recent review reports mixed results for effectiveness. This questionable pain management strategy might prove useful in distraction and sensory confusion, but only when combined with actual pain relief medications. There is no research to suggest these dubious results will ever be effective other than as a means of self-distraction. This measure is similar to breathing exercises during cramps before administration of epidurals.

It has also been suggested that music may stimulate the production of endorphins and catecholamines.

Electroanalgesia poses serious health problems in those patients who need other electrical equipment in their bodies, such as pacemakers and hearing aids, because the electrical signals of the multiple devices can interfere with each other and fail. People with heart problems, such as irregular heartbeat, are also at risk because the devices can throw off the normal electrical signal of the heart.

Very rare causes of awareness include drug tolerance, or a tolerance induced by the interaction of other drugs. Some patients may be more resistant to the effects of anesthetics than others; factors such as younger age, obesity, tobacco smoking, or long-term use of certain drugs (alcohol, opiates, or amphetamines) may increase the anesthetic dose needed to produce unconsciousness but this is often used as an excuse for poor technique. There may be genetic variations that cause differences in how quickly patients clear anesthetics, and there may be differences in how the sexes react to anesthetics as well. In addition, anesthetic requirement is increased in persons with naturally red hair. Marked anxiety prior to the surgery can increase the amount of anesthesia required to prevent recall.

Preventive analgesia is a practice aimed at reducing short- and long-term post-surgery pain. Activity in the body's pain signalling system during surgery produces "sensitization"; that is, it increases the intensity of post-operative pain. Reducing activity in the body's pain-signalling system by the use of analgesics before, during and immediately after surgery is thought to reduce subsequent sensitization, and consequently the intensity of post-surgery pain. The types of nerve activity targeted in preventive analgesia include pre-surgery pain, all pain-system activity caused during surgery, and pain produced post-surgery by damage and inflammation.

A person's assessment of pain intensity from standard experimental stimuli prior to surgery is correlated with the intensity of their post-surgery pain. Pain intensity immediately post-surgery

is correlated with pain intensity on release from hospital, and correlated with the likelihood of experiencing chronic post-surgery pain.

Different medications such as pregabalin, acetaminophen, naproxen and dextromethorphan have been tried in studies about preemptive analgesia. It is not known what causes some cases of acute post-surgery pain to become chronic long term problems but pain intensity in the short- and long-term post-operative period is correlated with the amount of pain system activity during and around the time of the surgery. It is not known whether reducing post-operative sensitization by the use of preventive analgesia will affect the likelihood of acute post-operative pain becoming chronic.

Congenital insensitivity to pain is found in Vittangi, a village in Kiruna Municipality in northern Sweden, where nearly 40 cases have been reported. A few Americans also have it.

Patient-controlled analgesia (PCA) is any method of allowing a person in pain to administer their own . The infusion is programmable by the prescriber. If it is programmed and functioning as intended, the machine is unlikely to deliver an overdose of medication. Providers must always observe the first administration of any PCA medication which has not already been administered by the provider to respond to allergic reactions.

The most common form of patient-controlled analgesia is self-administration of oral over-the-counter or prescription painkillers. For example, if a headache does not resolve with a small dose of an oral analgesic, more may be taken. As pain is a combination of tissue damage and emotional state, being in control means reducing the emotional component of pain.

Physicians, Nurse Practitioners, Physician Assistants, Nurses and Midwives will typically ask for the need of relief. Women in labor have many pain relief options that work well and pose small risks when given by a trained and experienced clinician. Clinicians also can use different methods for pain relief at different stages of labor. Still, not all options are available at every hospital and birthing center. Depending on the health history of the mother, the presence of allergies or other concerns, some choices will work better than others.

There are many methods of relieving pain used for labor. Rare and unpredictable, serious complications sometimes occur. Also, most medicines used to manage pain during labor pass freely into the placenta to the baby. Asking questions about the procedures and medications might affect the baby are valid questions.

More and more women in the United States are using water to find comfort during labor. This is called hydrotherapy. Laboring in a tub of warm water helps women feel physically supported, and keeps them warm and relaxed. Plus, it is easier for laboring women to move and find comfortable positions in the water.

In waterbirthing, a woman remains in the water for delivery. The American Academy of Pediatrics has expressed concerns about delivering in water because of a lack of studies showing its safety and because of the rare but reported chance of complications. Ask your doctor or midwife if you want to know more about waterbirthing.

Congenital insensitivity to pain (CIP), also known as congenital analgesia, is one or more rare conditions in which a person cannot feel (and has never felt) physical pain. The conditions described here are separate from the HSAN group of disorders, which have more specific signs and cause. Because feeling physical pain is vital for survival, CIP is an extremely dangerous condition. It is common for people with the condition to die in childhood due to injuries or illnesses going unnoticed. Burn injuries are one of the more common injuries.

There are not a lot of studies that have investigated the prevalence of EM, so far only four have been conducted.

The mean of all the studies combined results in an EM estimation incidence of 4.7/100,000 with a mean of 1 : 3.7 of the male to female ratio, respectively.

In 1997 there was a study conducted in Norway that estimated that the annual incidence of 2/100,000, with a 1 : 2.4 male to female ratio in this study

population, respectively. In 2009 there was a population-based study of EM in the USA (Olmsted County, Minnesota), that reported that the annual incidence was 1.3/100,000, with a 1 : 5.6 male to female ratio in this study population, respectively.

The incidence in this study of primary and secondary EM was 1.1 : 0.2 per 100 000 people per year, respectively.

A study of a single centre in the south of Sweden in 2012, showed the overall annual population-based incidence was 0.36/100,000.

In New Zealand (Dunedin) a study estimated that in 2013 the incidence of EM is 15/100,000, with a 1 : 3 male to female ratio in this study

population, respectively. This last study has an estimation that is at least ten times higher than the prevalence previously reported. This study recruited individuals based on self-identification of symptoms (after self-identification, patients where invited for an assessment of an EM diagnosis), instead of participants that are identified through secondary and tertiary referrals that was conducted by the other studies.

Several medications, including verapamil and nifedipine, as well as ergot derivatives such as bromocriptine and pergolide, have been associated with medication-induced erythromelalgia.

CES is often concurrent with congenital or degenerative diseases and represents a high cost of care to those admitted to the hospital for surgery. Hospital stays generally last 4 to 5 days, and cost an average of $100,000 to $150,000, unless the patient lives in a country where healthcare is free at the point of delivery.

One of the defining characteristics of minimally conscious state is the more continuous improvement and significantly more favorable outcomes post injury when compared with vegetative state. One study looked at 100 patients with severe brain injury. At the beginning of the study, all the patients were unable to follow commands consistently or communicate reliably. These patients were diagnosed with either MCS or vegetative state based on performance on the JFK Coma Recovery Scale and the diagnostic criteria for MCS as recommended by the Aspen Consensus Conference Work-group. Both patient groups were further separated into those that suffered from traumatic brain injury and those that suffered from non-traumatic brain injures (anoxia, tumor, hydrocephalus, infection). The patients were assessed multiple times over a period of 12 months post injury using the Disability Rating Scale (DRS) which ranges from a score of 30=dead to 0=no disabilities. The results show that the DRS scores for the MCS subgroups showed the most improvement and predicted the most favorable outcomes 12 months post injury. Amongst those diagnosed with MCS, DRS scores were significantly lower for those with non-traumatic brain injuries in comparison to the vegetative state patients with traumatic brain injury. DRS scores were also significantly lower for the MCS non-traumatic brain injury group compared to the MCS traumatic brain injury group. Pairwise comparisons showed that DRS scores were significantly higher for those that suffered from non-tramuatic brain injuries than those with traumatic brain injuries. For the patients in vegetative states there were no significant differences between patients with non-traumatic brain injury and those with traumatic brain injuries. Out of the 100 patients studied, 3 patients fully recovered (had a DRS score of 0). These 3 patients were diagnosed with MCS and had suffered from traumatic brain injuries.

In summary, those with minimally conscious state and non-traumatic brain injuries will not progress as well as those with traumatic brain injuries while those in vegetative states have an all around lower to minimal chance of recovery.

Because of the major differences in prognosis described in this study, this makes it crucial that MCS be diagnosed correctly. Incorrectly diagnosing MCS as vegetative state may lead to serious repercussions related to clinical management.

Plexopathy symptoms often resemble spinal cord disorders. A neurosurgical consultation is usually undertaken to ensure proper diagnosis, management, and treatment. Patients with chronic symptoms will likely be advised to follow up with outpatient care from either their health care provider or specialist.

Various etiologies of CES include fractures, abscesses, hematomas, and any compression of the relevant nerve roots. Injuries to the thoracolumbar spine will not necessarily result in a clinical diagnosis of CES, but in all such cases it is necessary to consider. Few epidemiological studies of CES have been done in the United States, owing to difficulties such as amassing sufficient cases as well as defining the affected population, therefore this is an area deserving of additional scrutiny.

Traumatic spinal cord injuries occur in approximately 40 people per million annually in the United States, resulting from traumas due to motor vehicle accidents, sporting injuries, falls, and other factors. An estimated 10 to 25% of vertebral fractures will result in injury to the spinal cord. Thorough physical examinations are required, as 5 to 15% of trauma patients have fractures that initially go undiagnosed.

The most frequent injuries of the thoracolumbar region are to the conus medullaris and the cauda equina, particularly between T12 and L2. Of these two syndromes, CES is the more common. CES mainly affects middle-aged individuals, particularly those in their forties and fifties, and presents more often in men. It is not a typical diagnosis, developing in only 4 to 7 out of every 10,000 to 100,000 patients, and is more likely to occur proximally. Disc herniation is reportedly the most common cause of CES, and it is thought that 1 to 2% of all surgical disc herniation cases result in CES.

Plexopathy is a disorder affecting a of nerves, blood vessels, or lymph vessels. The region of nerves it affects are at the brachial or lumbosacral plexus. Symptoms include pain, loss of motor control, and sensory deficits.

There are two main types of plexopathy: brachial plexopathy and lumbosacral plexopathy. They are usually caused from some sort of localized trauma such as a dislocated shoulder. The disorder can also be caused secondary to a compression, co-morbid vascular disease, infection, or may be idiopathic with an unknown cause. Both plexopathies can also occur as a consequence of radiation therapy, sometimes after 30 or more years have passed, in conditions known as Radiation-induced Brachial Plexopathy (RIBP) and Radiation-induced Lumbosacral Plexopathy (RILP).

A minimally conscious state (MCS) is a disorder of consciousness distinct from persistent vegetative state and locked-in syndrome. Unlike persistent vegetative state, patients with MCS have partial preservation of conscious awareness. MCS is a relatively new category of disorders of consciousness. The natural history and longer term outcome of MCS have not yet been thoroughly studied. The prevalence of MCS was estimated to be 112,000 to 280,000 adult and pediatric cases.

Post-polio syndrome occurs in approximately 25 to 50 percent of people who survive a poliomyelitis infection. On average, it occurs 30–35 years afterwards; however, delays of between 8–71 years have been recorded. The disease occurs sooner in persons with more severe initial infection. Other factors that increase the risk of postpolio syndrome include increasing length of time since acute poliovirus infection, presence of permanent residual impairment after recovery from the acute illness, and being female.

Post-polio syndrome is documented to occur in cases of nonparalytic polio (NPP). One review states late-onset weakness and fatigue occurs in 14 to 42 percent of NPP patients.

Lameness is an abnormal gait or stance of an animal that is the result of dysfunction of the locomotor system. In the horse, it is most commonly caused by pain, but can be due to neurologic or mechanical dysfunction. Lameness is a common veterinary problem in racehorses, sport horses, and pleasure horses. It is one of the most costly health problems for the equine industry, both monetarily for the cost of diagnosis and treatment, and for the cost of time off resulting in loss-of-use.