Dysautonomia · What Is It, Causes, Signs, Symptoms, Diagnosis, and More

Dysautonomia is the improper functioning of the autonomic nervous system (ANS), which controls involuntary bodily functions such as breathing, heart rate, blood pressure, digestion, body temperature, hormonal function, bladder function, and sexual function among others. Under typical conditions, the autonomic nervous system increases cardiovascular sympathetic outflow and decreases parasympathetic outflow when an individual rises from sitting to standing. The increase in sympathetic response results in peripheral vasoconstriction of blood vessels, increased cardiac rate, and increased contractile force of heart muscle, which allows for maintained perfusion to the brain and other vital organs. When dysautonomia occurs, the body’s reflexive increase in sympathetic response and decrease in parasympathetic response does not happen properly. While dysautonomia generally involves failure of the autonomic nervous system to react, excessive or overactive ANS actions can also occur. 

Overall, dysautonomia is relatively common, affecting 70 million people worldwide. It can be congenital (i.e., inherited at birth) or sporadic (i.e., arises from a mutation during an individual's lifetime). Inherited dysautonomia is more common among the Ashkenazi Jewish population. 

Familial dysautonomia is caused by a specific genetic mutation in the gene inhibitor of kappa B kinase complex-associated protein (i.e., IKBKAP, also known as ELP10). It is typically inherited in an autosomal recessive pattern, meaning that two copies of the gene must be passed down for the offspring to inherit the disease. When inherited, dysautonomia is known as familial dysautonomia, hereditary sensory neuropathy type 3, hereditary sensory and autonomic neuropathy 3, or Riley Day syndrome. 

Conversely, sporadic dysautonomia, which arises without an underlying cause, is also known as primary dysautonomia and results from a failure of the autonomic nervous system to communicate with the rest of the body. Primary dysautonomia can lead to other conditions such as neurocardiogenic syncope (i.e.,  vasovagal syncope), postural orthostatic tachycardia syndrome (POTS); multiple system atrophy; and pure autonomic failure. Neurocardiogenic syncope is the most common form of dysautonomia. It results in occasional or frequent fainting spells when the body overreacts to intense emotion or fears (e.g., the sight of blood), dehydration, or extreme pain. Heart rate and blood pressure drop suddenly, resulting in reduced blood flow to the brain, causing a brief loss of consciousness. 

On the other hand, POTS leads to tachycardia upon standing, resulting in shortness of breath, chest pain, and fainting. POTS is typically caused by a reduction in intravascular volume, which contributes to decreased venous return to the heart, reflex tachycardia, and orthostatic intolerance. On the other hand, POTS leads to tachycardia upon standing, resulting in shortness of breath, chest pain, and fainting. Multiple system atrophy causes incontinence, decreased blood pressure, and erectile dysfunction. 

The cause of multiple system atrophy is generally unknown; however, the condition has been associated with deterioration and atrophy of portions of the brain and a build-up of a protein called alpha-synuclein. The affected regions (e.g., cerebellum, basal ganglia, and brainstem) regulate internal body functions, digestion, and motor control. Symptoms include muscle stiffness, muscle weakness, blurred vision, and difficulty with bladder control.

Lastly, pure autonomic failure is a neurodegenerative disorder of the autonomic system that results in orthostatic hypotension. It is typically caused by an unusual accumulation of α-synuclein in autonomic nerves. Flare-up symptoms can be caused by various triggers such as heat, pain, stress, or overexertion. 

The primary signs and symptoms of dysautonomia include orthostatic hypotension, or a fall in blood pressure upon standing; impotence, or erectile dysfunction, in those assigned as male at birth; hypertension or hypotension; and a rapid increase in pulse rate. Other symptoms include dizziness, vertigo; lightheadedness associated with syncope or fainting; shortness of breath; heart palpitations; chest pain or discomfort, blurred vision, difficulty swallowing, nausea and vomiting, and hypoglycemia. 

Dysautonomia is diagnosed after a thorough patient history and physical exam. The healthcare professional will typically receive a detailed medication list to assess medications that might be causing the symptoms, followed by a thorough review of their medical history to assess for recent volume loss. Clinicians may also evaluate for evidence of personal neurological history and family history of dysautonomia. 

While there is currently no cure for dysautonomia, treatment is focused on managing the symptoms. To combat orthostatic hypotension, one can try a high-salt diet (e.g., adding three to five grams daily to their meals), drinking more water daily, and elevating the head of their bed. A clinician may administer bolus intravenously in emergent situations to increase blood pressure. Medications such as fludrocortisone and midodrine can increase blood pressure and be used to treat orthostatic hypotension. 

Secondary forms of dysautonomia may improve with treatment of the underlying condition. Those with chronic and progressive dysautonomia generally have a poor prognosis, as death can occur from pneumonia, acute respiratory failure, or sudden cardiopulmonary arrest.