Autonomic neuropathy: symptoms, causes, tests and treatment

The autonomic nervous system looks after functions your body carries out automatically. Diabetes UK explains that autonomic neuropathy is damage to the nerves that carry information to your organs and glands, which help to control functions such as how your stomach empties, how regularly your heart beats and how your sexual organs work.

Diabetes UK lists it as one of the main types of diabetic neuropathy (it says there are four). It also occurs without diabetes. Patient.info says autonomic nerve fibres are affected in most symmetrical peripheral neuropathies, although the involvement is often mild or does not cause obvious symptoms.

The symptoms depend on which organs are affected, and one person may have just one or several. Diabetes UK and Patient.info describe the following.

• Dizziness, light-headedness or fainting on moving from lying to standing (orthostatic or postural hypotension), which Patient.info says is the most commonly recognised symptom and may be worse after eating, with exercise or in heat.

• Irregular heartbeat or palpitations, and (in cardiovascular autonomic neuropathy) an inability to exercise for more than a short time, according to the NHS.

• Gastroparesis, where food moves through the stomach slowly, with bloating, constipation or diarrhoea (Diabetes UK).

• Loss of bladder control and incontinence (Diabetes UK).

• Sweating problems: being unable to sweat properly and intolerance to heat, or sweating related to eating food (Diabetes UK).

• Erectile problems in men (Diabetes UK); Patient.info also describes genital autonomic neuropathy in women, for which vaginal lubricants and oestrogen creams may help.

• Supine hypertension (high blood pressure when lying flat), listed by Patient.info.

Patient.info lists a wide range of causes. The most common is likely to be diabetes, where over time high blood sugar damages the nerves. The NHS says diabetes (type 1 and type 2) is the most common cause of peripheral neuropathy in the UK.

Patient.info says it is important to recognise and correctly diagnose autonomic neuropathy because successful treatment and management can be offered. A family history and drug history may be important. Onset is usually slow, but can occasionally be acute.

Which tests are used depends on the presentation. Patient.info lists heart rate variability with breathing and the Valsalva manoeuvre (a variation in heart rate with breathing of fewer than 10 beats per minute is abnormal), blood pressure response lying and standing, tilt-table testing, sweat tests such as the quantitative sudomotor axon reflex test and thermoregulatory sweat test, blood tests (full blood count, glucose, HIV, antibodies, amyloid investigation, genetic testing), cystometry and urodynamics for the bladder, and gastric investigations. Nerve conduction studies are often normal because the affected fibres are small.

If you have diabetes, regular check-ups matter. The NHS says people at highest risk of peripheral neuropathy, such as those with diabetes, are recommended to have regular check-ups.

Patient.info describes treatment as education about the condition, treatment of the underlying cause, and management of each affected system.

Patient.info lists the most severe complications as cardiac arrest, dangerous heart rhythms and sudden cardiac death, and blood pressure fluctuations with a risk of cerebral and cardiac ischaemia. The NHS notes that in cardiovascular autonomic neuropathy the heart may suddenly develop an abnormal pattern of beating (arrhythmia), which could lead to cardiac arrest, and that people with it will probably need to have their condition monitored.

The outlook depends on the cause. Patient.info says that in most cases the course is gradual progression, and that in diabetes the outlook is improved with good control of diabetes. Other measures may halt progression, such as abstaining from alcohol or treating a correctable syndrome.

See a GP if you have fainted, even if it seems nothing serious. The NHS says to get your blood pressure checked if you keep getting dizziness, light-headedness, blurred vision, weakness, confusion or fainting. People with diabetes who notice numbness, bladder, gut, sweating or erectile changes should tell their diabetes team.

The NHS says to call 999 if someone who has fainted is not breathing, cannot be woken within 1 minute, has not fully recovered or has difficulty speaking or moving, has chest pain or a pounding, fluttering or irregular heartbeat, has seriously hurt themselves, is having a seizure, or fainted while exercising or lying down.

Driving: the NHS fainting page notes you must not drive if your GP has referred you to a specialist and you are waiting to be assessed. Check DVLA rules if you have blackouts.

On the NHS, your GP or diabetes team is the usual starting point. Simple tests such as lying and standing blood pressure can be done in primary care; formal autonomic function testing is done in specialist neurology, cardiology or diabetes services, and availability varies. Referral to specialists such as cardiology, gastroenterology, urology or neurology depends on which systems are affected.

Private autonomic testing and specialist consultations are available in some centres and may shorten waits. The tests and treatments described above are the same in either setting. Ask what tests are included and who will coordinate the follow-up, and keep your GP and diabetes team informed.