Dysautonomia


Dysautonomia, autonomic failure, or autonomic dysfunction is a condition in which the autonomic nervous system does not work properly. This condition may affect the functioning of the heart, bladder, intestines, sweat glands, pupils, and blood vessels. Dysautonomia has many causes, not all of which may be classified as neuropathic. A number of conditions can feature dysautonomia, such as Parkinson's disease, Long COVID, multiple system atrophy, dementia with Lewy bodies, Ehlers–Danlos syndromes, autoimmune autonomic ganglionopathy and autonomic neuropathy, HIV/AIDS, mitochondrial cytopathy, pure autonomic failure, autism, and postural orthostatic tachycardia syndrome.
Diagnosis is made by functional testing of the ANS, focusing on the affected organ system. Investigations may be performed to identify underlying disease processes that may have led to the development of symptoms or autonomic neuropathy. Symptomatic treatment is available for many symptoms associated with dysautonomia, and some disease processes can be directly treated. Depending on the severity of the dysfunction, dysautonomia can range from being nearly symptomless and transient to disabling and/or life-threatening.

Signs and symptoms

Dysautonomia, a complex set of conditions characterized by autonomic nervous system dysfunction, manifests clinically with a diverse array of symptoms of which postural orthostatic tachycardia syndrome stands out as the most common.
The symptoms of dysautonomia, which are numerous and vary widely for each person, are due to inefficient or unbalanced efferent signals sent via both systems. Symptoms in people with dysautonomia include:
Dysautonomia may be due to inherited or degenerative neurologic diseases or injury of the autonomic nervous system from an acquired disorder. Its most common causes include:
In the sympathetic nervous system, 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.
Mitochondrial cytopathies can have autonomic dysfunction manifesting as orthostatic intolerance, sleep-related hypoventilation, and arrhythmias.

Mechanism

The autonomic nervous system is a component of the peripheral nervous system and comprises two branches: the sympathetic nervous system and the parasympathetic nervous system. The SNS controls the more active responses, such as increasing heart rate and blood pressure. The PSNS, for example, slows down the heart rate and aids digestion. Symptoms typically arise from abnormal responses of either the sympathetic or parasympathetic systems based on situation or environment.

Diagnosis

Diagnosis of dysautonomia depends on the overall function of three autonomic functions—cardiovagal, adrenergic, and sudomotor. A diagnosis should, at a minimum, include measurements of blood pressure and heart rate while lying flat and after at least three minutes of standing. The best way to make a diagnosis includes a range of testing, notably an autonomic reflex screen, tilt table test, and testing of the sudomotor response.
Additional tests and examinations to diagnose dysautonomia include:
Tests to elucidate the cause of dysautonomia can include:
Particularly in the Soviet and post-Soviet medical literature, a subtype of dysautonomia that particularly affects the vascular system has been called vegetative-vascular dystonia. The term "vegetative" reflects an older name for the autonomic nervous system: the vegetative nervous system. While rooted in earlier concepts of neurasthenia, the diagnosis was crystallized by ’s 'neurogenic theory' to describe a functional precursor to essential hypertension: a stress-induced autonomic dysregulation that Soviet physicians observed en masse amidst the devastation of the war of annihilation on the Eastern Front.
Despite official recognition by the medical institutions in the USSR and some other Warsaw-pact countries, it has also been described as a form of culture-bound syndrome.
A similar form of this disorder has been historically noticed in various wars, including the Crimean War and American Civil War, and among British troops who colonized India. This disorder was called "irritable heart syndrome" in 1871 by American physician Jacob DaCosta.

Management

Treatment of dysautonomia can be difficult; since it is made up of many different symptoms, a combination of drug therapies is often required to manage individual symptomatic complaints. In the case of autoimmune neuropathy, treatment with immunomodulatory therapies is done. If diabetes mellitus is the cause, control of blood glucose is important. Treatment can include proton-pump inhibitors and H2 receptor antagonists used for digestive symptoms such as acid reflux.
To treat genitourinary autonomic neuropathy, medications may include sildenafil. To treat hyperhidrosis, anticholinergic agents such as trihexyphenidyl or scopolamine can be used. Intracutaneous injection of botulinum toxin type A can also be used in some cases.
Transvascular autonomic modulation, a procedure similar to balloon angioplasty, is not approved in the United States to treat autonomic dysfunction.

Prognosis

The prognosis of dysautonomia depends on several factors; people with chronic, progressive, generalized dysautonomia in the setting of central nervous system degeneration such as Parkinson's disease or multiple system atrophy generally have poorer long-term prognoses. Dysautonomia can 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.