What are the symptoms of autonomic dysfunction?

When describing the symptoms of autonomic nervous system dysfunction it is easiest to divide it in to the particular systems (for example the heart or cardiovascular system, the bladder or urinary system etc). This is because each system in the body has an autonomic nerve supply and when there is a problem each system produces its own distinct set of symptoms. The heart or cardiovascular system has the largest autonomic supply and is the most likely to cause symptoms because of this.

Cardiovascular system

The most common symptoms that are caused by a dysfunction of the autonomic nervous system are lightheadedness and dizziness or fainting episodes. There can be other symptoms like the sensation that your heart is beating far too fast especially on standing up. These symptoms primarily occur in the standing up position. This is because on standing up blood pools below the diaphragm. Then the autonomic nerves in the legs compensate for this by constricting and pushing blood back up to the heart and at the same time the heart rate increases which also allows more blood to get back to the heart. The blood pressure then normalises. This takes only a few seconds and this is something that happens without you even knowing it- this happens in everybody.

When there is a dysfunction of the autonomic nervous system this compensation is sluggish or simply does not occur and this is what leads to the symptoms (lightheadedness, dizziness) described above. All of these symptoms are referred to as symptoms of “orthostatic intolerance”. Other common symptoms would be excessive fatigue or a feeling of “mental fogginess”.

Similarly, when we lie down to go to sleep there is a natural but slight increase in blood pressure that reaches a point and does not increase anymore. Then as we fall asleep there is a natural dip in blood pressure over night. Patients who suffer from problems in the autonomic nervous system have problems with both of these. This can lead to what is referred to as “supine hypertension” which just means high blood pressure in the lying down position. Also, when this dip in blood pressure that is supposed to occur at night doesn’t this is referred to as “non-dipping” and this has been shown to be associated with an increased risk of heart attacks at night.

Another common cardiovascular symptom of autonomic dysfunction is exercise intolerance. This occurs because the heart no longer has the ability to adjust to what is needed to be able to exercise- primarily this is an increase in both heart rate and blood pressure that is needed to supply the muscles with adequate blood supply in order to exercise.

Gastro-intestinal symptoms

People who have a dysfunction of the autonomic nervous system commonly experience gastro-intestinal related symptoms. The most common symptom is constipation that often alternates with diarrhoea. Another symptom would be bloating after eating and getting full after eating only a small few bites of a meal. This can lead to a loss of appetite and nausea and vomiting. A lot of these symptoms are generated by “gastroparesis”. This essentially means that transit of food through the gastrointestinal system is either slowed down considerably or stopped altogether. A big problem in patients with gastroparesis is variable absorption of medications.

Urinary symptoms

There can be difficulty starting urination, incontinence, difficulty knowing that your bladder is full and difficulty emptying your bladder fully which can lead to urinary tract infections.

Sexual dysfunction

This can involve problems achieving an erection or with ejaculation in men. In women this can involve vaginal dryness.

Impaired sweating

This can be either sweating too much or actually even more problematic is sweating too little. Both of these symptoms can be quite uncomfortable. Patients who sweat too much find that even minimal exertion will cause so much sweating to make it not worth it. However, people who cannot sweat enough are in a more precarious situation as they lose the ability to reduce their temperature and have abnormal temperature regulation.

Pupillary abnormalities

Our pupils have an autonomic nerve supply that controls the ability of the pupil to constrict and dilate in response to changes in the amount of light. This can manifest as the pupils being sluggish and having difficulty adjusting from light to dark. This can cause problems being able to see when driving at night.