While the exact incidence is unknown, estimates range from 33 - 57 percent of patients staying in the ICU for longer than 7 days. More exact data is difficult to obtain, since variation exists in defining the condition.

The three main risk factors for CIP and CIM are sepsis and systemic inflammatory response syndrome (SIRS), and multi-organ failure. Reported rates of CIP/CIM in people with sepsis and SIRS range from 68 to 100 percent. Additional risk factors for developing CIP/CIM include: female gender, high blood sugar (hyperglycemia), low serum albumin, and immobility. A greater severity of illness increases the risk of CIP/CIM. Such risk factors include: multi-organ dysfunction, renal failure, renal replacement therapy, duration of organ dysfunction, duration of ICU stay, low albumin, and central neurologic failure.

Certain medications are associated with CIP/CIM, such as corticosteroids, neuromuscular blocking agents, vasopressors, catecholamines, and intravenous nutrition (parenteral nutrition). Research has produced inconsistent results for the impact of hypoxia, hypotension, hyperpyrexia, and increased age on the risk of CIP/CIM. The use of aminoglycosides is "not" an independent risk for the development of CIP/CIM.

CIP/CIM can lead to difficulty weaning a person from a mechanical ventilator, and is associated with increased length of stay in the ICU and increased mortality (death). It can lead to impaired rehabilitation. Since CIP/CIM can lead to decreased mobility (movement), it increases the risk of pneumonia, deep vein thrombosis, and pulmonary embolism.

Critically ill people that are in a coma can become completely paralyzed from CIP/CIM. Improvement usually occurs in weeks to months, as the innervation to the muscles are restored. About half of patients recover fully.

Many health conditions can cause autonomic neuropathy. Some common causes of autonomic neuropathy include:

- Diabetes, which is the most common cause of autonomic neuropathy, can gradually cause nerve damage throughout the body.

- Injury to nerves caused by surgery or radiation to the neck.

- Treatment with certain medications, including some drugs used in cancer chemotherapy.

- Abnormal protein buildup in organs (amyloidosis), which affects the organs and the nervous system.

- Other chronic illnesses, such as Parkinson's disease, multiple sclerosis and some types of dementia.

- Autonomic neuropathy may also be caused by an abnormal attack by the immune system that occurs as a result of some cancers (paraneoplastic syndrome).

- Certain infectious diseases. Some viruses and bacteria, such as botulism, Lyme disease and HIV, can cause autonomic neuropathy.

- Inherited disorders. Certain hereditary disorders can cause autonomic neuropathy.

- Autoimmune diseases, in which the immune system attacks and damages parts of the body, including the nerves. Examples include Sjogren's syndrome, systemic lupus erythematosus, rheumatoid arthritis and celiac disease. Guillain-Barre syndrome is an autoimmune disease that happens rapidly and can affect autonomic nerves.

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.

Autonomic neuropathy (also AN or AAN) is a form of polyneuropathy that affects the non-voluntary, non-sensory nervous system (i.e., the autonomic nervous system), affecting mostly the internal organs such as the bladder muscles, the cardiovascular system, the digestive tract, and the genital organs. These nerves are not under a person's conscious control and function automatically. Autonomic nerve fibers form large collections in the thorax, abdomen, and pelvis outside the spinal cord. They have connections with the spinal cord and ultimately the brain, however. Most commonly autonomic neuropathy is seen in persons with long-standing diabetes mellitus type 1 and 2. In most—but not all—cases, autonomic neuropathy occurs alongside other forms of neuropathy, such as sensory neuropathy.

Autonomic neuropathy is one cause of malfunction of the autonomic nervous system (referred to as dysautonomia), but not the only one; some conditions affecting the brain or spinal cord also may cause autonomic dysfunction, such as multiple system atrophy, and therefore, may cause similar symptoms to autonomic neuropathy.

The prognosis of dysautonomia depends on several factors; individuals with chronic, progressive, generalized dysautonomia in the setting of central nervous system degeneration such as Parkinson's disease or multiple system atrophy have a generally poorer long-term prognosis. Consequently, dysautonomia could be fatal due to pneumonia, acute respiratory failure, or sudden cardiopulmonary arrest.

Autonomic dysfunction symptoms such as orthostatic hypotension, gastroparesis, and gustatory sweating are more frequently identified in mortalities.

The opioid antagonist naloxone allowed a woman with congenital insensitivity to pain to experience it for the first time. Similar effects were observed in Na1.7 null mice treated with naloxone. As such, opioid antagonists like naloxone and naltrexone may be effective in treating the condition.

The incidence of hemifacial spasm is approximately 0.8 per 100,000 persons. Hemifacial spasm is more prevalent among females over 40 years of age. The estimated prevalence for women is 14.5 per 100,000 and 7.4 per 100,000 in men. Prevalence for hemifacial spasm increase with age, reaching 39.7 per 100,000 for those aged 70 years and older. One study divided 214 hemifacial patients based on the cause of the disease. The patients who had a compression in the facial nerve at the end of the brain stem as the primary hemifacial spasm and patients who had peripheral facial palsy or nerve lesion due to tumors, demyelination, trauma, or infection as secondary hemifacial spasm. The study found that 77% of hemifacial spasm is due to primary hemifacial spasm and 23% is due to secondary hemifacial spasm. The study also found both sets of patients to share similar age at onset, male to female ratios, and similar affected side. Another study with 2050 patients presented with hemifacial spasm between 1986 and 2009, only 9 cases were caused by a cerebellopontine angle syndrome, an incidence of 0.44%.

Of people that have a sympathectomy, it is impossible to predict who will end up with a more severe version of this disorder, as there is no link to gender, age or weight. There is no test or screening process that would enable doctors to predict who is more susceptible.

Dysautonomia may be due to inherited or degenerative neurologic diseases (primary dysautonomia) or it may occur due to injury of the autonomic nervous system from an acquired disorder (secondary dysautonomia). The most common causes of dysautonomia include

In the sympathetic nervous system (SNS), predominant dysautonomia is common along with fibromyalgia, chronic fatigue syndrome, irritable bowel syndrome, and interstitial cystitis, raising the possibility that such dysautonomia could be their common clustering underlying pathogenesis.

In addition to sometimes being a symptom of dysautonomia, anxiety can sometimes physically manifest symptoms resembling autonomic dysfunction. A thorough investigation ruling out physiological causes is crucial, but in cases where relevant tests are performed and no causes are found or symptoms do not match any known disorders, a primary anxiety disorder is possible, but should not be presumed. For such patients, the anxiety sensitivity index may have better predictivity for anxiety disorders, while the Beck anxiety inventory may misleadingly suggest anxiety for patients with dysautonomia.

The cause is generally either paraneoplastic syndrome or idiopathic. In idiopathic AAG, the body's own immune system damages a receptor in the autonomic ganglia, which is part of a peripheral nerve fibre. If the AAG is paraneoplastic, they have a form of cancer, and their immune system has produced paraneoplastic antibodies in response to the cancer.

Hemifacial spasm (HFS) is a rare neuromuscular disease characterized by irregular, involuntary muscle contractions (spasms) on one side (hemi-) of the face (-facial). The facial muscles are controlled by the facial nerve (seventh cranial nerve), which originates at the brainstem and exits the skull below the ear where it separates into five main branches.

This disease takes two forms: typical and atypical. In typical form, the twitching usually starts in the lower eyelid in orbicularis oculi muscle. As time progresses, it spreads to the whole lid, then to the orbicularis oris muscle around the lips, and buccinator muscle in the cheekbone area. The reverse process of twitching occurs in atypical hemifacial spasm; twitching starts in orbicularis oris muscle around the lips, and buccinator muscle in the cheekbone area in the lower face, then progresses up to the orbicularis oculi muscle in the eyelid as time progresses. The most common form is the typical form, and atypical form is only seen in about 2–3% of patients with hemifacial spasm. The incidence of hemifacial spasm is approximately 0.8 per 100,000 persons.

This disorder occurs in both men and women, although it affects middle-aged or elderly women more frequently. Hemifacial spasm is much more common in some Asian populations. It may be caused by a facial nerve injury, a tumor, or it may have no apparent cause. Individuals with spasm on both sides of the face are very rare.

Gustatory sweating or Frey's syndrome is another presentation of autonomic neuropathy. Gustatory sweating is brought on while eating, thinking or talking about food that produces a strong salivary stimulus. It is thought that ANS fibres to salivary glands have become connected in error with the sweat glands after nerve regeneration. Apart from sweating in the anhidriotic area of the body, it can produce flushing, goosebumps, drop of body temperature - vasoconstriction and paresthesia. Aberrant gustatory sweating follows up to 73% of surgical sympathectomies and is particularly common after bilateral procedures. Facial sweating during salivation has also been described in diabetes mellitus, cluster headache, following chorda tympani injury, and following facial herpes zoster.

Phantom sweating is another form of autonomic neuropathy. It can be observed in patients with nerve damage (following accidents), diabetes mellitus and as a result of sympathectomy. Phantom sweating is a sensation that one is sweating, while the skin remains dry. Sufferers can not distinguish whether it is real sweating or just a sensation. The phenomena is experienced in the anhidriotic, denervated area of the body, presenting an abnormal sympathetic nervous system function.

Autoimmune autonomic ganglionopathy (AAG) is an extremely rare form of dysautonomia in which the patients immune system produces ganglionic AChR antibodies, inhibiting ganglionic AChR currents and impairing transmission in autonomic ganglia. Approximately 100 Americans are diagnosed with AAG each year. Symptoms onset can be acute, subacute or gradual.

The exact incidence of Frey syndrome is unknown. The disorder most often occurs as a complication of the surgical removal of a parotid gland (parotidectomy). The percentage of individuals who develop Frey syndrome after a parotidectomy is controversial and reported estimates range from 30-50 percent. In follow-up examinations, approximately 15 percent of affected individuals rated their symptoms as severe. Frey syndrome affects males and females in equal numbers.

Currently there are no official tests or treatments for ROHHAD. Each child has the symptoms above at different ages, yet most symptoms are eventually present. Many children are misdiagnosed or are never diagnosed until alveolar hypoventilation occurs.

MCAS is a relatively new diagnosis, being unnamed until 2007, and is believed to be very under-diagnosed. New findings are revealing that MCAS is much more prevalent than previously thought.

Central hypoventilation syndrome is a heterogeneous group of seemingly overlapping diseases. Paired-like homeobox 2B (PHOX2B) was confirmed in 2009 as the disease-causing gene in patients with congenital central hypoventilation syndrome (CCHS), a condition present in newborns. This genetic mutation is not present though in those with late-onset central hypoventilation syndrome and hypothalamic dysfunction.

There are no known causes, but the condition appears to be inherited in some patients. Symptoms of MCAS are caused by excessive chemical mediators inappropriately released by mast cells. Mediators include leukotrienes and histamines. The condition may be mild until exacerbated by stressful life events, or symptoms may develop and slowly trend worse with time.

Frey's syndrome often results as a side effect of surgeries of or near the parotid gland or due to injury to the auriculotemporal nerve, which passes through the parotid gland in the early part of its course. The Auriculotemporal branch of the Trigeminal nerve carries parasympathetic fibers to the sweat glands of the scalp and the parotid salivary gland. As a result of severance and inappropriate regeneration, the parasympathetic nerve fibers may switch course, resulting in "gustatory Sweating" or sweating in the anticipation of eating, instead of the normal salivatory response.

It is often seen with patients who have undergone endoscopic thoracic sympathectomy, a surgical procedure wherein part of the sympathetic trunk is cut or clamped to treat sweating of the hands or blushing. The subsequent regeneration or nerve sprouting leads to abnormal sweating and salivating. It can also include discharge from the nose when smelling certain food.

Rarely, Frey's syndrome can result from causes other than surgery, including accidental trauma, local infections, sympathetic dysfunction and pathologic lesions within the parotid gland.

An example of such, rare trauma or localized infection; can be seen in situations where a hair follicle has become ingrown and is causing trauma or localized infection near or over one of the branches of the auriculotemporal nerve.

Hypohidrosis is diminished sweating in response to appropriate stimuli. While hyperhidrosis is a socially troubling but benign condition, hypohidrosis can lead to hyperthermia, heat exhaustion, heat stroke and potentially death. An extreme case of hypohydrosis in which there is a complete absence of sweating and the skin is dry is termed anhidrosis.

Antibodies against voltage-gated potassium channels (VGKC), which are detectable in about 40% of patients with acquired neuromytonia, have been implicated in Morvan’s pathophysiology. Raised serum levels of antibodies to VGKCs have been reported in three patients with Morvan’s Syndrome. Binding of serum from a patient with Morvan’s Syndrome to the hippocampus in a similar pattern of antibodies to known VGKC suggest that these antibodies can also cause CNS dysfunction. Additional antibodies against neuromuscular junction channels and receptors have also been described. Experimental evidence exists that these anti-VGKC antibodies cause nerve hyperexcitability by suppression of voltage gated K+ outward currents, whereas other, yet undefined humoral factors have been implicated in anti-VGKC antibody negative neuromyotonia. It is believed that antibodies to the Shaker-type K+ channels (the Kv1 family) are the type of potassium channel most strongly associated with acquired neuromyotonia and Morvan’s Syndrome.

Whether VGKC antibodies play a pathogenic role in the encephalopathy as they do in the peripheral nervous system is as yet unclear. It has been suggested that the VGKC antibodies may cross the blood–brain barrier and act centrally, binding predominantly to thalamic and striatal neurons causing encephalopathic and autonomic features.

Idiopathic craniofacial erythema is a medical condition characterised by severe, uncontrollable, and frequently unprovoked, facial blushing.

Blushing can occur at any time and is frequently triggered by even mundane events, such as, talking to friends, paying for goods in a shop, asking for directions or even simply making eye contact with another person.

For many years, the cause of the condition was thought to be an anxiety problem, caused by a mental health disorder. However, in recent years experts in the field of the disorder believe it to be caused by an overactive sympathetic nervous system, an automatic response which sufferers have no mental control over. It is related to focal hyperhidrosis, more commonly known as excessive sweating, as it is caused by the same overactive nerves which cause excessive sweating. Sufferers of severe facial blushing commonly experience focal hyperhidrosis. Studies have also shown that patients with severe facial blushing or focal hyperhidrosis commonly have family members with one or both of the related disorders.

Life expectancy with Fabry disease for males was 58.2 years, compared with 74.7 years in the general population, and for females 75.4 years compared with 80.0 years in the general population, according to registry data from 2001 to 2008. The most common cause of death was cardiovascular disease, and most of those had received kidney replacements.

In one case, a patient was diagnosed with both Morvan's syndrome and pulmonary hyalinizing granulomas (PHG). PHG are rare fibrosing lesions of the lung, which have central whorled deposits of lamellar collagen. How these two diseases relate to one another is still unclear.

Thymoma, prostate adenoma, and in situ carcinoma of the sigmoid colon have also been found in patients with Morvan’s Syndrome.