What is Autonomic Dysfunction?
The autonomic nervous system (ANS) is a part of our nervous system that controls involuntary bodily functions, including blood pressure, heart rate, breathing, digestion, and sexual arousal. It is made up of three separate parts: the sympathetic, parasympathetic, and enteric nervous systems.
Both the sympathetic and parasympathetic systems contain fibers that provide sensory input and control muscle movements. In these systems, information is transmitted using two kinds of neurons: one located in the central nervous system and the other in the peripheral areas of the body, which are responsible for influencing the target tissues.
The enteric nervous system, a massive web-like structure, primarily controls the digestion process. Amazingly, it can function independently from the rest of the nervous system and contains more than a hundred million neurons of more than fifteen types.
The ANS is continuously working behind the scenes to keep us alive and well, controlling many automatic and unconscious functions in our body. Alongside the endocrine system, which controls slower, long-lasting effects on the body, the ANS has rapid, short-term effects and is responsible for maintaining things like body temperature, nutrient processing, urine flow, and eye movements.
Different functions of our body organs are regulated by either sympathetic activation or parasympathetic activation of the autonomic nervous system. For instance, sympathetic activation results in dilation of pupils, faster heart rate, and increased sweat secretion. On the other hand, parasympathetic activation leads to vision for near objects, reduced heart rate, and increased digestion, among others.
Issues with the autonomic nervous system can lead to a variety of complications. It can worsen the prognosis of other diseases when one or more subdivisions of the ANS aren’t functioning correctly. Severe cases can even cause symptoms and disabilities that require treatment themselves.
What Causes Autonomic Dysfunction?
There are numerous factors that may cause autonomic dysfunction, or problems with the automatic bodily functions. Sometimes, a patient can experience more than one of these factors at the same time. As the autonomic nervous system controls a wide range of functions, it can be impacted by an array of conditions.
Autonomic dysfunction may arise from:
Hereditary causes such as Amyloidosis, Fabry disease, hereditary sensory autonomic neuropathy, porphyrias, and genetic disorders like familial dysautonomia and dopamine-beta-hydroxylase deficiency.
It can also be acquired through various ways such as autoimmune reactions, abnormal reflex or sweating responses. This includes conditions like Guillain-Barre, rheumatoid arthritis, Sjogren, and systemic lupus erythematosus.
Metabolic conditions or nutritional deficiencies, such as diabetes and vitamin B12 deficiency, can cause autonomic dysfunction. So can certain neurological degenerative diseases like Parkinson’s or infections like HIV, leprosy, or Lyme disease.
Certain medications can also affect normal autonomic function causing symptoms. These include certain drugs like alpha blockers, and beta blockers that are known to cause low blood pressure.
Conditions like uremic neuropathy and chronic liver diseases, or injuries to the spinal cord can also lead to autonomic dysfunction.
There are several medications that can worsen a condition called Orthostatic Hypotension, which is a form of low blood pressure that occurs when standing up. These medications include diuretics, nitric oxide vasodilators, adrenergic antagonists, renin-angiotensin system inhibitors, dopamine antagonists, calcium channel blockers, selective serotonin receptor reuptake inhibitors and some antidepressants.
Risk Factors and Frequency for Autonomic Dysfunction
Autonomic dysfunction, or issues with the body’s automatic functions, is relatively common. The most frequently observed issues relate to the control of heart rate and blood pressure, leading to conditions like fainting due to abnormal vasovagal response. Other common symptoms are linked to conditions like Postural Tachycardia Syndrome (POTS), Parkinson’s disease, and its variants.
Problems with bladder control, like incontinence seen in conditions such as Multiple Sclerosis, are unspecific but not uncommon. Some symptoms, such as changes in face’s blood vessels or eye-related symptoms in some headaches, might not be the main problem but can assist in diagnosing the condition.
- Orthostatic hypotension, or sudden drop in blood pressure when standing, often occurs in people suffering from neurodegenerative disorders like Parkinson’s disease, Multiple System Atrophy, Autonomic Failure, and conditions that affect the autonomic nerves and peripheral neuropathy.
- It is more commonly seen in older people, especially those in care institutions.
- POTS is more frequently seen in women.
- Fainting is very common in the general population, and it is most often due to reflex syncope – an overreaction of the body’s normal mechanisms causing an individual to faint.
- The frequency of reflex syncope is higher during adolescence and in people over 55 years old.
- Carotid sinus hypersensitivity, defecation, and cough syncope – types of conditions causing fainting, are almost exclusive to the elderly population.
Signs and Symptoms of Autonomic Dysfunction
When investigating diseases tied to autonomic dysfunction, it’s important to consider symptoms in each area and conduct thorough examinations. To suspect cardiovascular autonomic dysfunction, symptoms such as fainting or near-fainting, as well as the full disease manifestation, should be closely looked at. The common symptoms when standing up can include feelings of light-headedness, blurred or narrowed vision, neck pain, nausea, heart palpitations, shakiness, weakness, and dizziness. There may also be signs of exercise intolerance, fatigue, breathlessness, chest pain, anxiety, hyperventilation, coldness or pain in hands and feet, difficulty concentrating, and headaches.
Sweating intensity alternation on different body parts, particularly lessened sweating on distant parts of the body while the palms and soles are unaffected, can suggest a sudomotor autonomic lesion. Lastly, urgency and incontinence are generally linked to a neurogenic bladder more than retention.
- Feeling of light-headedness
- Blurred or narrowed vision
- Neck pain
- Nausea
- Heart palpitations
- Shakiness
- Weakness
- Dizziness
- Exercise intolerance
- Fatigue
- Breathlessness
- Chest pain
- Anxiety
- Hyperventilation
- Coldness or pain in hands and feet
- Difficulty concentrating
- Headaches
Testing for Autonomic Dysfunction
If doctors suspect that a patient has issues with their automatic nervous system (ANS), they may conduct various tests. These tests help in confirming the diagnosis and deciding the treatment plan.
Simple tests that can be done in a doctor’s office include checking cardiovascular reactions, casual sweat patterns, and changes in the pupils. Especially common are blood pressure and heart rate checks, both lying flat and standing for three minutes.
When these basic tests don’t provide enough information but there’s still high suspicion of a problem, a tilt table test might be necessary. In this test, the patient’s body position is changed while monitoring their cardiovascular reactions to maneuvers like the Valsalva (forceful exhalation against a closed airway), hyperventilation, or exposure to cold.
Other tests, like the sympathetic skin response and thermoregulatory sweat test, offer added information. For example, if a patient reports unusual sweating, a sweat test could be a good choice. Bladder ultrasound and urodynamic studies can help if urinary problems are present. Other tests may not affect treatment decisions, but they can offer more information about a patient’s symptoms or help narrow down the diagnosis.
A positive result for specific autoantibodies, such as those against alfa-3-acetylcholine receptors, can lead to immunosuppressive therapy, a treatment that reduces the body’s immune response.
A tilt table test is often recommended when there’s a high likelihood of conditions like orthostatic hypotension, commonly associated with Parkinson’s disease, or if the patient has a significant motor impairment which makes standard tests difficult. It’s also used to monitor the progression of an autonomic disorder and see how it responds to treatment.
Normal responses to a tilt table test include a small increase in heart rate and diastolic blood pressure. However, identifying an autonomic disorder often includes unexpected drops in blood pressure or heart rate that don’t compensate for each other. Other conditions like neurogenic syncope, orthostatic hypotension, and postural orthostatic tachycardia syndrome have their own specific responses to the test.
Treatment Options for Autonomic Dysfunction
Treatment options for health issues can usually be grouped into three areas. First, they may aim to address the symptoms. Non-drug treatments and medication can both be used. For example, physical activities like exercising or physiotherapy can help with some heart-related problems caused by issues with the nervous system. Sunglasses can ease eye problems.
Second, some treatments focus on the root causes of the symptoms. For instance, if the immune system is involved, treatments could include steroids and other drugs to suppress the immune response, as well as intravenous immunoglobulins and plasma replacement therapy.
Last but not least, the underlying causes of the health problems have to be addressed. Sometimes, it’s a serious condition like cancer that triggers other issues with the nervous system. In other cases, the problem can be a result of certain drugs interacting with the nervous system.
If you suffer from Orthostatic Hypotension, a condition in which your blood pressure drops when you stand up from a sitting or lying position, there are ways to manage it.
Non-medication methods include stopping medicines that could be making your symptoms worse, using compression stockings and abdominal binders, drinking a lot of water and increasing your salt intake. Lifestyle changes can also help, like slowly changing your body position, staying out of hot and humid weather, or switching to exercises that don’t need you to stand up.
If these changes don’t provide relief, medication may be required. Two drugs approved by the FDA for treating low blood pressure when standing up are midodrine and droxidopa. Another drug, fludrocortisone, which is a synthetic corticosteroid, can be used to increase blood volume and to relieve symptoms.
Several other options are available for patients who don’t respond to the initial treatment. These include caffeine, anti-inflammatory drugs, and several other medications.
If you have Parkinson’s disease and experiencing issues related to nervous system dysfunction, various treatment options are also available. For constipation, you could use certain remedies which have been proven to be more effective than a placebo. For excessive drooling, chewing gum or hard candy could help. More severe cases might benefit from botulinum toxin injections into the salivary glands or the use of medication called glycopyrrolate. For a runny nose, a nasal spray called Ipratropium may work. And for sexual dysfunction, men can use sildenafil an hour before sex while women can use vaginal lubricants.
Finally, you could also experience low blood pressure when standing up. This can either be a feature of Parkinson’s itself, or it could be a side effect of the medications used to treat it. In such cases, specific treatment will be needed.
What else can Autonomic Dysfunction be?
When diagnosing a condition called orthostatic hypotension, which is a form of low blood pressure that happens when you stand up from sitting or lying down, doctors consider a number of possible causes. These include:
- Heart problems like anemia, irregular heart beat, congestive heart failure, heart attack, inflammation of the heart muscle or the sac that surrounds the heart, problems with the heart valves, and poor vein function.
- Use of certain medications or substances, such as alcohol, heart disease medications, antidepressants, blood pressure drugs, Parkinson’s disease meds, diuretics, pain killers, antipsychotics, and sedatives.
- Hormonal problems like adrenal insufficiency, diabetes insipidus, hypoaldosteronism, high blood sugar, low potassium levels, and underactive thyroid.
- Low volume of blood within your blood vessels, which could be due to blood loss, dehydration, shock, or changes during and after pregnancy.
- Other factors, including aids, anxiety or panic disorders, eating disorders, or prolonged bed rest.
Each condition may present similar symptoms, therefore, doctors have to conduct thorough tests and observations to accurately diagnose the problem.
What to expect with Autonomic Dysfunction
Autonomic dysfunction can become significant because of its link to the outlook of the main disease, the intensity of symptoms, such as feeling lightheaded when standing up, and how it responds to treatment. Unfortunately, the basic types of autonomic dysfunction, whether they’re affecting your peripheral or central nervous system, tend to have a bad outlook. This is especially true if they’re combined with symptoms related to Parkinson’s disease or problems with body movement.
These primary forms of autonomic dysfunction typically begin to appear around the age of 60. Sadly, survival rates five years after the neurological symptoms appear are less than 50%.
Possible Complications When Diagnosed with Autonomic Dysfunction
Orthostatic hypotension, which is the medical term for low blood pressure when standing up, can result in falls, especially in elderly people. These falls can lead to other health issues. Studies have shown that orthostatic hypotension increases the risk of heart problems and death from various causes, primarily because of related diseases and underlying health problems.
Interestingly, there also seems to be a link between orthostatic hypotension and the development of dementia and cognitive impairment. But the exact reasons behind this are not clear. The repeated episodes of low blood pressure and the resulting lack of blood flow to the brain could potentially result in nerve cell damage. Orthostatic hypotension is also connected with a particular type of brain lesion, typically seen in people with vascular cognitive impairment.
It is also important to note that cognitive impairment and orthostatic hypotension can both be early signs of an underlying neurodegenerative disease, for example, dementia with Lewy bodies, which is a type of dementia linked to Parkinson’s disease.
