Neuropathy is the collective word for damage to nerves. Neuropathy is one of the most common diabetes related complications, with around 60-70% of people with diabetes having some level of neuropathy. There are 2 main forms of neuropathy: Peripheral neuropathy (this is damage to the nerves in the periphery, which can interfere with one’s ability to feel pain) and Diabetic Autonomic Neuropathy, often simply referred to as autonomic neuropathy, is damage to the autonomic nerves that control involuntary bodily functions and internal organs and is another serious and often overlooked complication of diabetes.
What causes diabetic autonomic neuropathy?
Hypertension and high levels of cholesterol, in particular triglycerides, can damage nerves and the small blood vessels that sustain the nerves, leading to diabetic autonomic neuropathy (DAN), which is mostly present together with other diabetes complications, such as peripheral neuropathy. However, DAN may occur on its own, or may be diagnosed before other diabetes related complications are recognised.
What are the symptoms of autonomic neuropathy?
The symptoms of autonomic neuropathy depend on which of the body’s functions are affected and can include any or a combination of the following:
Gastro-intestinal (GI) disturbances such as bloating, nausea and vomiting, gastroparesis, constipation, diarrhoea (especially at night), and faecal incontinence.
Gastroparesis can keep the body from absorbing glucose and using insulin properly and this can lead to unpredictable blood glucose levels, sometimes referred to as “brittle diabetes”.
Urinary and genital tracts (reproductive organs), including bladder problems such as recurrent urinary tract infections (UTIs), pyelonephritis, incontinence and/or sexual dysfunction.
In men, DAN may cause erectile dysfunction and/or retrograde ejaculation (sometimes called a dry orgasm). Damage to the nerves in the sex organs in women can prevent the vagina from getting lubricated in response to arousal, can reduce the feeling around the vagina and may cause trouble getting an orgasm.
Cardiovascular autonomic neuropathy (also referred to as CAN) is the most studied form of DAN. Damage to the nerves that control heart rate and blood pressure may make these nerves respond slower to changes in breathing, the body’s position, physical activity, stress, and sleep. Symptoms of CAN therefore include: tachycardia, orthostatic (or postural) hypotension and people with CAN have more than double the risk of silent myocardial ischemia and mortality.
Additionally, DAN can cause sudomotor dysfunction, which means that thermos-regulatory sweating is damaged. It tends to occur in what is commonly known as “in a glove and stocking distribution”, at least initially. Eventually it results in global anhidrosis, the inability to sweat at all. This is even more dangerous, as when one doesn’t sweat (perspire) the body can’t cool itself, which can lead to overheating and sometimes lead to heatstroke.
Some people with sudomotor dysfunction can experience excessive sweating, as the body’s way to compensate. Gustatory sweating is an abnormal production of sweat that occurs soon after eating food. The sweating begins on the forehead and then spreads to the face, scalp, and neck.
Other ways that DAN may make itself known is through:
Impaired neurovascular function
Hypoglycaemic autonomic failure, which is due to, or caused by, defective glucose counter-regulation in hypoglycaemia and hypoglycaemia unawareness.
How is DAN diagnosed?
DAN is diagnosed based on symptoms, by taking a family and medical history and by performing a physical exam which includes checking the heart rate and blood pressure (when the person is lying or sitting and on standing up), and other tests to check for different types of autonomic nerve damage. Other causes of digestive symptoms will need to be ruled out, for example through gastric emptying studies. For urinary complaints an abdominal ultrasound to check the bladder function may be performed.
How common is DAN?
It is not exactly known how many people with diabetes suffer from DAN. The numbers vary widely from one study to another depending on the assessment methods that are used. It is estimated that around 20% of people with diabetes have symptoms suggestive of DAN.
Treatments will generally focus on treating the symptoms caused by DAN include a healthy lifestyle and regular physical activity.
Over-the-counter medications to treat digestive symptoms and problems, such as constipation, diarrhoea, faecal incontinence, gastroesophageal reflux (heart burn) or gastroparesis may be recommended.
Medication may prescribed for incontinence, and regular trips to the bathroom my help. Antibiotics will be required if a UTI is present as a result of the bladder not emptying fully and it is recommend that the person drinks plenty of water to help prevent future bladder infections.
To treat sexual problems in women a referral to a gynaecologist, who may recommend lubricants for vaginal dryness, may be required. Men will often be referred to an urologist to be prescribed medications or devices to improve erectile problems.
In the case of postural (orthostatic) hypotension advise the person to get up from lying or sitting slowly to prevent light-headedness or fainting. It may be advisable for the person to increase their salt intake, to raise the head of their bed or wear compression stockings. In some cases, medications that will help the body to retain salt, medications to help raise the blood pressure or medicines that raise or lower the heart rate will be prescribed.
Often blood pressure lowering medications such as ACE inhibitors and β-blockers will be prescribed, even if the blood pressure is to target, as these treatments have been proven to be effective at reducing the cardiovascular risk factors.
If the person perspires excessively the doctor may prescribe a specific deodorant or medication to decrease the sweating. Avoiding the heat or humidity can also help. In some case surgery to cut the nerves in the sweat glands or removing the sweat glands themselves can help.
If DAN leads to hypoglycaemia unawareness increased checking of blood glucose levels is indicated. Continuous glucose monitoring can be useful in this setting, as CGM devices can sound an alarm if the blood glucose level drops too quickly or goes too low. Having smaller meals more frequently can also help in reducing the risk of hypoglycaemia.
Prevention and screening
Knowledge of early autonomic dysfunction can encourage the person to help treat autonomic neuropathy by keeping their blood glucose levels, blood pressure, and cholesterol as close to their targets as possible. Reducing alcohol intake and smoking cessation can keep nerve damage from getting worse.
It is generally recommended that a person with diabetes gets checked for any diabetes related complications on a regular bases. This should be first done at the time of diagnosis of type 2 diabetes and within 5 years after diagnosis of type 1 diabetes (unless the individual has symptoms suggestive of autonomic dysfunction earlier) and at least once every year thereafter; this is referred to as the Annual Cycle of Care.