Anesthesia dolorosa or anaesthesia dolorosa or deafferentation pain is pain felt in an area (usually of the face) which is completely numb to touch. The pain is described as constant, burning, aching or severe. It can be a side effect of surgery involving any part of the trigeminal system, and occurs after 1–4% of peripheral surgery for trigeminal neuralgia. No effective medical therapy has yet been found. Several surgical techniques have been tried, with modest or mixed results. The value of surgical interventions is difficult to assess because published studies involve small numbers of mixed patient types and little long term follow-up.

- Gasserian ganglion stimulation is stimulation of the gasserian ganglion with electric pulses from a small generator implanted beneath the skin. There are mixed reports, including some reports of marked, some of moderate and some of no improvement. Further studies of more patients with longer follow-up are required to determine the efficacy of this treatment.

- Deep brain stimulation was found in one review to produce good results in forty-five percent of 106 cases. Though relief may not be permanent, several years of relief may be achieved with this technique.

- Mesencephalotomy is the damaging of the junction of the trigeminal tract and the periaqueductal gray in the brain, and has produced pain relief in a group of patients with cancer pain; but when applied to six anesthesia dolorosa patients, no pain relief was achieved, and the unpleasant sensation was in fact increased.

- Dorsal root entry zone lesioning, damaging the point where sensory nerve fibers meet spinal cord fibers, produced favorable results in some patients and poor results in others, with incidence of ataxia at 40%. Patient numbers were small, follow-up was short and existing evidence does not indicate long term efficacy.

- One surgeon treated thirty-five patients using trigeminal nucleotomy, damaging the nucleus caudalis, and reported 66% "abolition of allodynia and a marked reduction in or (less frequently) complete abolition of deep background pain."

This disorder is characterized by episodes of severe facial pain along the trigeminal nerve divisions. The trigeminal nerve is a paired cranial nerve that has three major branches: the ophthalmic nerve (V), the maxillary nerve (V), and the mandibular nerve (V). One, two, or all three branches of the nerve may be affected. Trigeminal neuralgia most commonly involves the middle branch (the maxillary nerve or V) and lower branch (mandibular nerve or V) of the trigeminal nerve.

An individual attack usually lasts from a few seconds to several minutes or hours, but these can repeat for hours with very short intervals between attacks. In other instances, only 4-10 attacks are experienced daily. The episodes of intense pain may occur paroxysmally. To describe the pain sensation, people often describe a trigger area on the face so sensitive that touching or even air currents can trigger an episode; however, in many people, the pain is generated spontaneously without any apparent stimulation. It affects lifestyle as it can be triggered by common activities such as eating, talking, shaving and brushing teeth. The wind, chewing, and talking can aggravate the condition in many patients. The attacks are said by those affected to feel like stabbing electric shocks, burning, sharp, pressing, crushing, exploding or shooting pain that becomes intractable.

The pain also tends to occur in cycles with remissions lasting months or even years. 1–6% of cases occur on both sides of the face but extremely rare for both to be affected at the same time. This normally indicates problems with both trigeminal nerves, since one serves strictly the left side of the face and the other serves the right side. Pain attacks are known to worsen in frequency or severity over time, in some people. Pain may migrate to other branches over time but in some people remains very stable.

Rapid spreading of the pain, bilateral involvement or simultaneous participation with other major nerve trunks (such as Painful Tic Convulsif of nerves V & VII or occurrence of symptoms in the V and IX nerves) may suggest a systemic cause. Systemic causes could include multiple sclerosis or expanding cranial tumors.

The severity of the pain makes it difficult to wash the face, shave, and perform good oral hygiene. The pain has a significant impact on activities of daily living especially as people live in fear of when they are going to get their next attack of pain and how severe it will be. It can lead to severe depression and anxiety.

However, not all people will have the symptoms described above and there are variants of TN. One of which is atypical trigeminal neuralgia ("trigeminal neuralgia, type 2" or trigeminal neuralgia with concomitant pain ), based on a recent classification of facial pain. In these instances there is also a more prolonged lower severity background pain that can be present for over 50% of the time and is described more as a burning or prickling, rather than a shock.

Trigeminal neuropathic pain is similar to TN2 but can have the electric pulses associated with classic TN. The pain is usually constant and can also give off a tingling, numbness sensation. This pain is due to unintentional damage to one or more of the trigeminal nerves from trauma, oral surgery, dentistry work, etc. It is difficult to treat but sufferers are usually given the same anticonvulsant and tricyclics antidepressant medicines as with the other types of neuralgias. Surgical options are DREZ (dorsal root entry zone) lesion and MCS or Motor Cortex Stimulation.

TN needs to be distinguished from other forms of unilateral pain which are related to damage to the trigeminal nerve by trauma to the face or dental treatments. This is often termed painful trigeminal neuropathy or post-traumatic neuropathy as some sensory changes can be noted e.g. decrease in pain sensation or temperature. This is important as different care pathways are used. Trigeminal pain can also occur after an attack of herpes zoster, and post-herpetic neuralgia has the same manifestations as in other parts of the body. Trigeminal deafferentation pain (TDP), also termed anesthesia dolorosa, is from intentional damage to a trigeminal nerve following attempts to surgically fix a nerve problem. This pain is usually constant with a burning sensation and numbness. TDP is very difficult to treat as further surgeries are usually ineffective and possibly detrimental to the person.

Signs and symptoms include erythema (redness/flushing) and sweating in the cutaneous distribution of the auriculotemporal nerve, usually in response to gustatory stimuli. There is sometimes pain in the same area, often of a burning nature. Between attacks of pain there is sometimes numbness or other alterred sensations (anesthesia or paresthesia). This is sometimes termed "gustatory neuralgia".

Trigeminal neuralgia (TN or TGN) is a chronic pain disorder that affects the trigeminal nerve. There are two main types: typical and atypical trigeminal neuralgia. The typical form results in episodes of severe, sudden, shock-like pain in one side of the face that lasts for seconds to a few minutes. Groups of these episodes can occur over a few hours. The atypical form results in a constant burning pain that is less severe. Episodes may be triggered by any touch to the face. Both forms may occur in the same person. It is one of the most painful conditions and can result in depression.

The exact cause is unclear but believed to involve loss of the myelin around the trigeminal nerve. This may occur due to compression from a blood vessel as the nerve exits the brain stem, multiple sclerosis, stroke, or trauma. Less common causes include a tumor or arteriovenous malformation. It is a type of nerve pain. Diagnosis is typically based on the symptoms after ruling out other possible causes such as postherpetic neuralgia.

Treatment includes medication or surgery. The anticonvulsant carbamazepine or oxcarbazepine is the usual initial treatment and is effective in about 80% of people. Other options include lamotrigine, baclofen, gabapentin, and pimozide. Amitriptyline may help with the pain but opioids are not usually effective in the typical form. In those who do not improve or become resistant to other measures, a number of types of surgery may be tried.

It is estimated that 1 in 8,000 people develop trigeminal neuralgia a year. It usually begins in people over 50 years old, but can occur at any age. Women are more commonly affected than men. The condition was first described in detail in 1773 by John Fothergill.

Frey's syndrome (also known as Baillarger’s syndrome, Dupuy’s syndrome, auriculotemporal syndrome, or Frey-Baillarger syndrome) is a rare neurological disorder resulting from damage to or near the parotid glands responsible for making saliva, and from damage to the auriculotemporal nerve often from surgery.

The symptoms of Frey's syndrome are redness and sweating on the cheek area adjacent to the ear (see focal hyperhidrosis). They can appear when the affected person eats, sees, dreams, thinks about or talks about certain kinds of food which produce strong salivation. Observing sweating in the region after eating a lemon wedge may be diagnostic.

Paresthesia is an abnormal sensation such as tingling, tickling, pricking, numbness or burning of a person's skin with no apparent physical cause. The manifestation of a paresthesia may be transient or chronic, and may have any of dozens of possible underlying causes.

The most familiar kind of paresthesia is the sensation known as "pins and needles" or of a limb "falling asleep". A less well-known and uncommon but important paresthesia is formication, the sensation of bugs crawling underneath the skin.

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.

Paresthesias of the hands, feet, legs and arms are common, transient symptoms. The briefest, electric shock type of paresthesia can be caused by tweaking the ulnar nerve near the elbow. Similar brief shocks can be experienced when any other nerve is tweaked (a tweaked neck nerve may cause a brief shock-like paresthesia toward the scalp). In the older age group, spinal column irregularities may tweak the spinal cord briefly when the head or back is turned, flexed, or extended into brief uncommon positions (Lhermitte's sign). The most common, everyday cause is temporary restriction of nerve impulses to an area of nerves, commonly caused by leaning or resting on parts of the body such as the legs (often followed by a pins and needles tingling sensation). Other causes include conditions such as hyperventilation syndrome and panic attacks. A cold sore outside the mouth (not a canker sore inside the mouth) can be preceded by tingling because a cold sore is caused by herpes simplex virus. The Varicella zoster virus (Shingles) also notably may cause recurring pain and tingling in skin or tissue along the distribution path of that nerve (most commonly in skin, along a dermatome pattern, but sometimes feeling like headache, chest or abdominal pain, or pelvic pain).

Other common examples occur when sustained pressure has been applied over a nerve, inhibiting or stimulating its function. Removing the pressure typically results in gradual relief of these paresthesias. Most pressure-induced paraesthesia results from awkward posture, such as engaging in cross-legged sitting for prolonged periods of time.

Saddle anesthesia is a loss of sensation (anesthesia) restricted to the area of the buttocks, perineum and inner surfaces of the thighs.

It is frequently associated with the spine-related injury cauda equina syndrome. It is also seen in conus medullaris, the difference is that it is symmetrical in conus medullaris and asymmetric in cauda equina.It may also occur as a temporary side-effect of a sacral extra-dural injection:

Four cardinal symptoms have sometimes been used as diagnostic criteria:

1. painful, fatty lipomas (benign fatty tumors) across anatomy

2. obesity, frequently in menopausal age

3. weakness and fatigue

4. emotional instability, depression, epilepsy, confusion, and dementia.

There are also potential signs of the disease which are identified as the following:

However, as it is unclear which symptoms are cardinal and which symptoms are minor signs in Dercum's disease, it is unclear which should be used as diagnostic criteria. Researchers have proposed a 'minimal definition' based on symptoms most often part of Dercum's disease: 1) Generalized overweight or obesity. 2) Chronic pain in the adipose tissue. The associated symptoms in Dercum's disease include obesity, fatty deposits, easy bruisability, sleep disturbances, impaired memory, depression, difficulty concentrating, anxiety, rapid heartbeat, shortness of breath, diabetes, bloating, constipation, fatigue, weakness and joint and muscle aches. Regarding the associated symptoms in Dercum's disease, only case reports have been published. No study involving medical examinations has been performed in a large group of patients.

Hypokalemic sensory overstimulation is characterized by a subjective experience of sensory overload and a relative resistance to lidocaine local anesthesia. The sensory overload is treatable with oral potassium gluconate. The phenotype overlaps with that of attention deficit disorder, raising the possibility of subtypes of attention deficit disorder that have a peripheral sensory cause and possible new forms of therapy.

Anaphia, also known as tactile anesthesia, is a medical symptom in which there is a total or partial absence of the sense of touch.

Anaphia is a common symptom of spinal cord injury and neuropathy.

People tend to gain weight in lipedematous areas and lose it in non-lipedematous areas, though there are cases where weight loss has resulted in improvement of the condition. Obese lipedema patients who undergo bariatric surgery lose fat primarily from the waist up. While lipedema presents itself in various ways, diagnosis is possible as early as pre-puberty when inner thigh pads present and at any age when fat gathers and drapes at knees.

Symptoms of lipedema include disproportionately large, column-like legs, legs unusually large to the knees, disproportionate hips, stomach or buttocks. As lipedema progresses, patients become increasingly heavy in the lower body. The additional, expanding fat cells interfere with the pathways of lymphatic vessels, and patients can develop secondary lymphedema, a condition known as lipo-lymphedema. Many lipedema patients cannot tolerate the compression garments associated with conventional lymphedema treatment because the underlying lipedematous fat is very painful, and those patients therefore are at risk for the side effects of uncontrolled lymphedema, including recurring blood infections and fibrosis. If not kept in check through a healthy lifestyle, lipo-lymphedema can worsen, and patients will become progressively less mobile.

Postoperative residual curarization (PORC) is a residual paresis after emergence from general anesthesia with neuromuscular-blocking drugs.

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.

Hypokalemic sensory overstimulation is a term coined by MM Segal to describe a syndrome that has been reported in a single case-study by his group. Segal describes the syndrome as a form of neurological disorder that has similarities to attention deficit hyperactivity disorder and has several similarities to disorders of ion channels, in particular to the muscle disorder hypokalemic periodic paralysis.

It is medically related to disorders of ion channels, in particular to the muscle disorder hypokalemic periodic paralysis and is similar in nature to ADHD, as the prominent feature of hypokalemic sensory overstimulation is the feeling of sensory overstimulation that is also characteristic of attention deficit disorder and the over stimulation of the nervous system.. It may also be connected with premenstrual syndrome and the body's natural sodium levels.

Adiposis dolorosa, also known as Dercum's disease or Anders disease, is a rare condition characterized by generalized obesity and fatty tumors in the adipose tissue. The tumors are normally painful and found in multiples on the extremities. The cause and mechanism of Dercum's disease remains unknown. Possible causes include nervous system dysfunction, mechanical pressure on nerves, adipose tissue dysfunction, and trauma.

Dercum's disease was first described at Jefferson Medical College by neurologist Francis Xavier Dercum in 1892.

Lipedema is a disorder where there is enlargement of both legs due to deposits of fat under the skin. Typically it gets worse over time, pain may be present, and people bruise easily. In severe cases the trunk and upper body may be involved.

The cause is unknown but is believed to involve genetics and hormonal factors. It often runs in families. Risk factors include being overweight or obese. Other conditions that may present similarly include obesity, lipohypertrophy, chronic venous insufficiency, and lymphedema.

A number of treatments may be useful including physiotherapy and exercise. While surgery can remove fat tissue it can also damage lymphatic vessels. Treatment does not typically result in complete resolution. It is estimated to affect up to 11% of women. Onset is typically during puberty, pregnancy, or menopause.

Trigger fingers is a common disorder characterized by catching, snapping or locking of the involved finger flexor tendon, associated with dysfunction and pain. It is a sub-set of stenosing tenosynovitis.

A disparity in size between the flexor tendon and the surrounding retinacular pulley system, most commonly at the level of the first annular (A1) pulley, results in difficulty flexing or extending the finger and the "triggering" phenomenon. The label of trigger finger is used because when the finger unlocks, it pops back suddenly, as if releasing a trigger on a gun.

Diagnosis is made almost exclusively by history and physical examination alone. More than one finger may be affected at a time, though it usually affects the index, thumb, middle, or ring finger. The triggering is usually more pronounced late at night and into the morning, or while gripping an object firmly.

Nitrous oxide, desflurane, and isoflurane are most the most commonly used anesthetic gases. They may cause some complications due to their leakage and storage failure.

Masticatory muscle myositis (MMM) is an inflammatory disease in dogs affecting the muscles of mastication (chewing). It is also known as atrophic myositis or eosinophilic myositis. MMM is the most common inflammatory myopathy in dogs. The disease mainly affects large breed dogs. German Shepherd Dogs and Cavalier King Charles Spaniels may be predisposed. There is a similar disease of the eye muscles found in Golden Retrievers. Symptoms of acute MMM include swelling of the jaw muscles, drooling, and pain on opening the mouth. Ophthalmic signs may include third eyelid protrusion, red eyes, and exophthalmos (protruding eyeballs). In chronic MMM there is atrophy of the jaw muscles, and scarring of the masticatory muscles due to fibrosis may result in inability to open the mouth (trismus). The affected muscles include the temporalis, masseter, and pterygoid muscles. The disease is usually bilateral.

MMM is caused by the presence of 2M fibers in the muscles of the jaw. 2M fibers are not found elsewhere in the body. The immune system recognizes these proteins as foreign to the body and attacks them, resulting in inflammation. Diagnosis of MMM is through either biopsy of the temporalis or masseter muscles or the 2M antibody assay, in which blood serum of the possible MMM-dog is reacted with temporalis tissue of a normal dog, or both. False negatives by the 2M antibody assay may be obtained if MMM is end-stage with destruction of type 2M fibers and marked fibrosis. Treatment is usually with corticosteroids such as prednisone, often with decreasing doses for up to 4–6 months, and in the case of trismus, manual opening of the mouth under anesthesia. Feeding very soft or liquid food during this time is usually necessary. The ultimate degree of recovery of jaw function and muscle mass will depend upon the extent of damage to the muscle tissue. Recurrence of MMM may occur. Misdiagnosis of MMM as a retroorbital abscess based on physical examination and finding of trismus leads to inappropriate treatment with antibiotics, which will not impede the progress of MMM.

Anesthesia awareness, also referred to as accidental awareness during general anaesthesia (AAGA) or unintended intra-operative awareness, is a potential complication occurring during general anesthesia where the intended state of complete unconsciousness is not maintained throughout the whole procedure. It can occur either because of failure to deliver sufficient anesthetic medication to the patient's body, or because of individual patient factors that mean the patient is resistant to what would normally be an adequate dose of anesthetic medication.

Typically, Dupuytren's contracture first presents as a thickening or nodule in the palm, which initially can be with or without pain. Later in the disease process, there is painless increasing loss of range of motion of the affected fingers. The earliest sign of a contracture is a triangular “puckering” of the skin of the palm as it passes over the flexor tendon just before the flexor crease of the finger, at the metacarpophalangeal (MCP) joint. Generally, the cords or contractures are painless, but, rarely, tenosynovitis can occur and produce pain. The most common finger to be affected is the ring finger; the thumb and index finger are much less often affected. The disease begins in the palm and moves towards the fingers, with the metacarpophalangeal (MCP) joints affected before the proximal interphalangeal (PIP) joints.

In Dupuytren's contracture, the palmar fascia within the hand becomes abnormally thick, which can cause the fingers to curl and can impair finger function. The main function of the palmar fascia is to increase grip strength; thus, over time, Dupuytren's contracture decreases a person's ability to hold objects. People may report pain, aching and itching with the contractions. Normally, the palmar fascia consists of collagen type I, but in Dupuytren sufferers, the collagen changes to collagen type III, which is significantly thicker than collagen type I.

People with severe involvement often show lumps on the back of their finger joints (called “Garrod's pads”, “knuckle pads”, or “dorsal Dupuytren nodules”) and lumps in the arch of the feet (plantar fibromatosis or Ledderhose disease). In severe cases, the area where the palm meets the wrist may develop lumps. Severe Dupuytren disease may also be associated with frozen shoulder (adhesive capsulitis of shoulder), Peyronie's disease of the penis, increased risk of several types of cancer, and risk of early death, but more research is needed to clarify these relationships.