Definition and Overview
Dysautonomia is a general term for a condition in which involuntary body functions such as cardiovascular, digestive, sweating, urination, and temperature control do not function normally due to abnormalities in the regulatory function of the autonomic nervous system. It is not a single disease, but a higher-level concept that encompasses various autonomic disorders.
The autonomic nervous system maintains homeostasis in the body's internal environment through the antagonistic actions of the sympathetic and parasympathetic nerves. When this balance is broken, symptoms appear simultaneously across multiple organs, which is a key characteristic of autonomic dysfunction.
It is estimated that various forms of autonomic dysfunction occur in approximately 1-3% of the population worldwide. Orthostatic hypotension is observed in approximately 20% of people over 65 years of age, and orthostatic tachycardia syndrome is reported to affect 500,000 to 3 million Americans.
Autonomic dysfunction is often called ‘dysautonomia’ and is also expressed in everyday language as ‘autonomic dysfunction’.
cause
The causes of autonomic dysfunction are largely divided into primary and secondary.
Primary autonomic dysfunction
This is a case where an abnormality occurs in the autonomic nervous system itself without a clear underlying disease.
- Pure autonomic failure: Occurs due to degeneration of peripheral autonomic neurons.
- Multiple system atrophy: The autonomic nervous system control center in the brain degenerates, resulting in both autonomic nervous system abnormalities and motor disorders.
- Postural orthostatic tachycardia syndrome (POTS): Heart rate increases by more than 30 beats per minute when standing up, and occurs more often in young women.
- Inappropriate sinus tachycardia: A condition in which the heart rate is abnormally fast even at rest.
Secondary autonomic dysfunction
This is a case where the autonomic nervous system is damaged by another disease.
- Diabetes: There are reports that autonomic neuropathy occurs in approximately 50% of all diabetic patients.
- Parkinson's disease: Autonomic symptoms occur in approximately 80% of patients.
- Autoimmune diseases: Includes Guillain-Barré syndrome, autoimmune autonomic ganglionopathy, etc.
- Amyloidosis: Abnormal proteins accumulate in autonomic nerve fibers, causing dysfunction.
- Autonomic dysfunction after infection: Cases of autonomic dysfunction following viral infection have been reported.
- Drugs: Antidepressants, antihypertensive drugs, antiarrhythmic drugs, etc. may affect autonomic function.
- Trauma: When a spinal cord is injured, autonomic nerve control below the damaged area is blocked.
symptoms
Symptoms of autonomic dysfunction appear in various ways depending on the organ system in which the disorder occurs.
cardiovascular system
- Orthostatic hypotension: When standing up, systolic blood pressure drops by more than 20 mmHg, causing dizziness, blurred vision, and fainting.
- Palpitations: A feeling that the heart is beating quickly or irregularly even when resting.
- Syncope or pre-syncope symptoms: sudden loss of consciousness or vision going dark occurs repeatedly.
- Supine hypertension: In some patients with autonomic failure, blood pressure actually increases when lying down.
digestive system
- Gastroparesis: The motor function of the stomach is reduced, resulting in early satiety, nausea, and vomiting.
- Constipation or diarrhea: Alternating constipation and diarrhea may occur repeatedly due to abnormal bowel movement control.
- Difficulty swallowing: Disorders of esophageal motility can make swallowing difficult.
urinary system
- Abnormalities in bladder function such as frequent urination, residual urination, and nocturia may occur.
- Decreased bladder contractility may result in incomplete urine output.
abnormal sweating
- Anhidrosis: Difficulty regulating body temperature due to lack of sweat.
- Hyperhidrosis: Excessive sweating in certain areas may occur.
- Gust sweating: Abnormal sweating on the face or neck when eating.
eyes and pupils
- Due to abnormal pupil control, glare becomes worse in bright places or adaptation to dark places becomes slower.
systemic symptoms
- Chronic fatigue: Complaints of constant fatigue regardless of activity level.
- Sleep disturbance: Poor sleep quality and frequent waking.
- Decreased concentration and cognitive function: Cognitive slowing, expressed as ‘brain fog’, may also occur.
- Exercise intolerance: Excessive heart rate or fatigue occurs even with light physical activity.
diagnosis
Diagnosis of autonomic dysfunction is made through a combination of history taking, physical examination, and autonomic nerve function tests.
History taking and physical examination
Systemically check the pattern of symptoms when standing up, sweating abnormalities, digestive symptoms, and urinary symptoms and their progress. The active orthostatic test, which measures blood pressure and heart rate when standing, is a screening test that can be easily performed in an outpatient setting.
Heart rate variability (HRV) analysis
It is a non-invasive test that evaluates the balance between the sympathetic and parasympathetic nerves by analyzing minute fluctuations in heartbeat intervals. If SDNN is less than 100ms, it suggests decreased autonomic function.
Standing tilt table inspection
After fixing the patient to the bed and tilting it at an angle of 60 to 70 degrees, changes in blood pressure and heart rate are observed continuously for 20 to 45 minutes. It is a key test for diagnosing orthostatic hypotension, orthostatic tachycardia syndrome, and vasovagal syncope.
Valsalva maneuver test
Analyze the response patterns of blood pressure and heart rate after holding your breath and pressing your stomach. Loss of a specific stage among the four stages of blood pressure response suggests sympathetic or parasympathetic nerve dysfunction.
deep breathing test
Heart rate fluctuations are measured while taking 6 deep breaths per minute. If the difference between the increase in heart rate during inhalation and decrease in heart rate during exhalation decreases, it indicates a decrease in parasympathetic (vagus) nerve function.
Sweating function test
Sweat secretion ability and distribution are evaluated through quantitative sweat axon reflex testing (QSART). The extent of autonomic nerve damage is estimated based on the area and pattern of sweating abnormality.
Differential test for cause
To determine the cause of autonomic dysfunction, blood sugar, glycated hemoglobin, thyroid function, autoantibodies, and nerve conduction tests may be additionally performed.
treatment
Treatment of autonomic dysfunction involves management of the cause of the disease and symptomatic treatment for each symptom.
Non-drug treatment
- Water intake: Drink 2 to 3 liters of water per day.
- Salt intake: Salt intake of 6 to 10 g per day may help relieve orthostatic hypotension (if there is no contraindication disease such as heart failure).
- Compression stockings and belly bands: Help maintain blood pressure when standing by reducing blood retention in the lower extremities and abdomen.
- Posture management: Sleeping with the head of the bed raised 10 to 15 degrees can relieve nocturnal diuresis and morning orthostatic hypotension.
- Exercise therapy: Start with aerobic exercise (swimming, cycling) performed in a lying or sitting position and gradually increase the intensity.
medication
- Midodrine: An alpha-1 agonist that improves orthostatic hypotension by constricting blood vessels.
- Fludrocortisone: Increases sodium and water retention in the body.
- Droxidopa: A norepinephrine precursor used to treat orthostatic hypotension.
- Pyridostigmine: A cholinesterase inhibitor used for mild orthostatic hypotension.
- Beta blockers: May be used to control rapid heart rate in orthostatic tachycardia syndrome.
Neuromodulation treatment
- Stellate ganglion block: Local anesthetic is injected into the sympathetic ganglion in the neck to suppress hyperactivation of the sympathetic nerves.
- Transcranial Magnetic Stimulation (TMS): Improves the function of the autonomic nervous system control center through non-invasive brain stimulation.
- Transcranial Direct Current Stimulation (tDCS): Helps restore autonomic balance by controlling brain cortex activity with microcurrent.
Cause of disease Treatment
In autonomic neuropathy caused by diabetes, blood sugar control is key. Immunotherapy can be effective for autoimmune autonomic disorders. If it is drug-induced, the causative drug needs to be adjusted.
Progress and Complications
The course of autonomic dysfunction varies greatly depending on the cause and type.
Symptoms of orthostatic tachycardia syndrome often improve with appropriate management, and in some patients, natural recovery is observed over several years. On the other hand, symptoms of multiple system atrophy or progressive autonomic dysfunction tend to worsen over time.
The main complications are as follows:
- Falls and fractures: Orthostatic hypotension or syncope increases the risk of falls.
- Nutritional deficiencies: Disorders of gastrointestinal motility may reduce food intake and nutrient absorption.
- Decreased quality of life: Chronic fatigue, exercise intolerance, and cognitive decline limit daily life.
- Cardiovascular complications: Persistent orthostatic hypotension can be a risk factor for stroke and myocardial infarction.
- Recumbent hypertension: Caution is needed as medications used to treat orthostatic hypotension can excessively increase blood pressure in the supine position.
life guide
For patients with autonomic dysfunction, daily management is very important in controlling symptoms.
fluids and salt
- Drink 2 to 3 liters of water a day, often in small portions.
- Consume an appropriate amount of salt according to your doctor's instructions.
- Drinking a glass of water (approximately 500 mL) immediately after waking up and before a meal can help relieve orthostatic symptoms.
exercise
- Perform regular aerobic exercise 3 to 5 times a week.
- In the early stages of severe orthostatic symptoms, lying down on a bicycle or swimming are safe.
- Increase exercise intensity gradually, but do not overdo it.
posture management
- When getting up from sitting or lying down, move slowly and step by step.
- When you have to stand for a long time, cross your legs or raise your toes to contract your lower extremity muscles.
- Adjust your sleeping position by raising the head of your bed by 10 to 15 cm.
environmental management
- Hot environments, hot baths, and saunas can dilate blood vessels and worsen symptoms.
- Limit excessive caffeine and alcohol intake.
- Maintain regular sleep habits and ensure 7 to 8 hours of sleep per day.
Symptom monitoring
- Measure and record your blood pressure and heart rate regularly at home.
- Keeping a symptom diary can help identify triggers and provide treatment.
- If new symptoms appear or existing symptoms suddenly worsen, visit a specialist early.