What is diabetic neuropathy and what are its symptoms or complications?

Diabetic neuropathy is a neurological disease. It occurs in long-term poorly compensated diabetes. High blood sugar levels cause nerve damage throughout the body.

Nerves in the lower limbs and feet are most commonly affected.

However, the nerves that control the digestive tract, bladder, blood pressure, blood vessels and heart can also be damaged.

Symptoms range from a symptomless form to a very painful and disabling type of diabetic neuropathy.

Treatment consists primarily of normalising glycaemia, i.e. blood sugar levels, and controlling pain or discomfort.

Diabetic neuropathy is not a single isolated disease. It encompasses a broader spectrum of clinical syndromes that may present with different symptoms from different causes.

A common feature is dysfunction of the peripheral nervous system.

This is damage to nerve fibres, either local or diffuse. Nerves responsible for sensory perception, motor control or internal body processes, the so-called autonomic nerves, may be damaged.

The incidence of diabetic neuropathy depends on the duration and compensation of diabetes. It is estimated that up to 10% of patients already have some pathological changes in nerve fibres at the time of diagnosis of diabetes.

With a diabetes duration of 25 years, up to half of patients suffer from diabetic neuropathy.

Symptoms of diabetic neuropathy may even be the first signs of existing diabetes, leading the doctor to diagnose diabetes mellitus.

Clinically, diabetic neuropathy is divided into two types:

• the subclinical form of neuropathy.
• the clinical form of neuropathy

In the subclinical form, nerve damage is present but the patient does not experience any symptoms. The disease can be diagnosed by electrophysiological EMG and other neurological instrumentation methods.

Children and young adolescent diabetics are most commonly affected, especially those with type 1 diabetes.

Subclinical neuropathy is dangerous precisely because of its silent course. The nerve damage progresses covertly and silently. For this reason, diabetic neuropathy is only detected at a late stage of irreversible nerve damage, e.g. in the development of diabetic foot.

Early detection of diabetic neuropathy is particularly important to prevent the development of serious complications. Therapeutic intervention is still possible at an early stage of damage.

The clinical form is subjectively manifested by various symptoms and pathological findings on objective neurological examination.

The cause of nerve damage in diabetes is not yet fully understood.

It is believed that insufficient blood flow through the nerve and reduced oxygen supply to the nerve are the main contributors to the development of dysfunction.

In diabetes, too high a concentration of sugar is present in the blood, called hyperglycaemia.

With high and sustained hyperglycaemia, the blood vessel wall weakens and the lining of the blood vessels is damaged. This causes one of the common complications of diabetes, damage to small blood vessels (capillaries), called microangiopathy.

Each nerve has a small blood vessel that nourishes it (called the vasa nervorum). When this blood vessel is damaged, the nerve is imperfectly nourished and loses its proper function.

In addition, other factors contribute to nerve damage, such as:

• oxidative stress.
• genetic predisposition
• impaired fat metabolism
• immunological mechanisms

There are several risk factors that further increase the risk of diabetic neuropathy.

The most common include:

• Poorly controlled glycemia
• long-term diabetes, especially if poorly compensated
• kidney disease that has arisen as a complication of diabetes
• overweight, i.e. a BMI of 25 or more
• smoking, which itself damages and narrows blood vessels, further impairing blood and oxygen supply to nerves

Clinically, diabetic neuropathy can be divided into four main types. A patient may have symptoms of one type, but also of several types simultaneously.

All the symptoms present depend on which nerves are affected by the neuropathy. The disease is progressive in nature, so even the symptoms will gradually develop and worsen.

Symptoms can creep in unnoticed and the patient hardly notices them. This is when serious nerve damage and irreversible complications occur.

If the symptoms are accompanied by significant discomfort and pain, the patient himself seeks medical help relatively early on. This is an advantage in this case, because preventive and therapeutic intervention can still be taken in the early stages of the damage.

Peripheral neuropathy

This form of diabetic neuropathy is also called distal symmetrical peripheral polyneuropathy.

It is a very typical and common manifestation of diabetic neuropathy. The nerves in the lower limbs, specifically in the feet, are the first to be affected. The symptoms often worsen at night when the person is at rest. These unpleasant sensations disturb the patient from sleep.

The most typical symptoms include:

• decreased sensitivity or numbness to painful stimuli or temperature changes
• a tingling, tingling or burning sensation in the feet called paresthesia
• stabbing pain or cramps
• hypersensitivity to even a light touch that immediately causes pain (Sometimes the touch of a blanket or sheet on the skin is perceived as painful. This is called allodynia.)
• infectious complications such as poorly healing wounds, ulcers, bone and joint pain

Sensitivity symptoms usually spread from the toes through the foot to below the knees. Many patients have the sensation of a tight sock around the foot or later stockings. Therefore, this type of sensitivity disorder is called "stocking" or, in the upper extremities, "glove".

The painful form of diabetic neuropathy is unfortunately quite common. Approximately 40-60% of patients with diabetic neuropathy suffer from pain.

These are very uncomfortable burning sensations, electrification, pricking as if with needles, tingling, which is also associated with numbness of the limb in question, most often in the palms and soles of the hands or fingers.

Neuropathy of the gross nerve fibres

This is a painless type of the disease, but it is accompanied by an unpleasant gradual loss of position and mobility. Gradually, muscle pain is also associated, especially in large muscle groups such as the thighs.

Walking is unsteady and the patient has difficulty maintaining balance.

Autonomic neuropathy

The autonomic nervous system maintains the body's internal environment. It controls processes in the body that are not controlled by the will, such as heart rate, bladder filling, stomach and bowel emptying, genital function, and proper eye function.

Affection of these nerve endings can cause the following difficulties, for example:

• a constant feeling of cold
• thin, dry and cracked skin when sweating is disturbed
• hair loss, nail growth disorders
• swelling of the fingers
• impaired perception of their own hypoglycaemia, which is very dangerous because profound hypoglycaemia is a life-threatening condition
• impaired proper emptying of the bladder or bowels, causing urinary retention and constipation
• incomplete and slow gastric emptying (gastroparesis) associated with nausea, vomiting and inappetence
• impaired adaptation of the eyes to changes in light (narrowing and dilation of the pupils)
• impaired sexual function, e.g. erectile dysfunction
• cardiac arrhythmias

Proximal neuropathy (diabetic polyradiculopathy)

This form of diabetic neuropathy is also commonly referred to as diabetic amyotrophy. It involves damage to the nerve endings in the thigh and buttock muscles, called the lumbosacral bundle. Less commonly, the brachial bundle, i.e. the nerves in the upper limbs, is affected.

Neuropathy is associated with pain and muscle wasting. This is associated with weight loss and weakness of the limb concerned.

Symptoms are usually present on one side of the body, but not infrequently both sides are affected.

Typical symptoms include:

• hip and thigh pain, sciatic muscle pain, may mimic spinal disease
• weakened and flaccid thigh muscles, often asymmetrical
• difficulty in rising from a sitting position due to weakness of the thigh and buttock muscles

Mononeuropathy (focal neuropathy)

If the abdominal and thoracic nerves are affected, it is a thoracolumbar radiculo-neuropathy. If the head is affected, it is a cranial neuropathy. If symptoms occur in more than one place simultaneously, the disease is referred to as mononeuritis multiplex.

Mononeuropathy is the name given to damage to a specific single nerve.

The symptoms of mononeuropathy are as follows:

• difficulty focusing or double vision (optic nerve damage)
• pain behind one eye (optic nerve involvement)
• paralysis of one side of the face called Bell's palsy (damage to the facial nerve, n. facialis)
• numbness, tingling, tingling and pain in the hands and fingers
• weak and clumsy hands, inability to grasp things, difficulty with fine motor skills

Diagnosis of diabetic neuropathy includes history, objective physical neurological examination and additional examinations or laboratory blood tests.

The clinical examination is carried out by a neurologist. It includes an examination of superficial and deep sensation. It is carried out, for example, by applying a 'tuning fork', which produces vibrations, to parts of the body where the skin is close to the bone.

A patient with advanced neuropathy does not feel these vibrations. Thermal sensitivity can also be tested by applying cold and hot objects, fine sensitivity is tested with a thin thread, and so on.

In addition to the objective examination, the patient can fill in special questionnaires that focus on his subjective feelings, e.g. a description of his pain.

Of the auxiliary examinations, the most useful is the EMG examination, i.e. electrophysiological tests. The EMG examination determines the speed of conduction through the nerve. Pathological curves and blocks in conduction are a sign of nerve damage.

Skin biopsy is a relatively invasive examination. It is used primarily to diagnose the painful form of diabetic neuropathy. We observe a reduction in the density of intraepidermal nerve fibres.

There are also various patches that are applied to the foot. If they change color while being worn, it indicates the presence of nerve fiber damage.

The course of diabetic neuropathy depends on the form of diabetes that the patient has (DM 1 and DM 2), the form of diabetic neuropathy (painful form, peripheral, subclinical, etc.) and last but not least on the effectiveness of treatment, glycaemic control, lifestyle and other associated diseases that may complicate the course.

Poorly treated diabetics suffer from a higher risk of serious complications and higher mortality.

Some of the most serious complications include:

• skin breakdown
• infection of small skin tears
• formation of skin ulcers
• 'salami amputations' of the limbs
• myocardial infarction
• ischaemic stroke, stroke

Prevention of complications and proper organ function

When organ function is impaired, examination by many other specialists is necessary. For example, a urologist is necessary for urinary tract disorders, a gastroenterologist for digestive problems, a cardiologist for heart rhythm disorders, etc.

• For urinary and urinary tract problems, a strict urination schedule or timed urination, i.e. urinating at a certain hour, can help.
  • Pressure on the lower abdominal area where the bladder is located also helps patients.
  • A common complication is incomplete emptying, where residual urine remains in the bladder. This predisposes to urinary tract infections, which are already increased in diabetics due to the higher concentration of glucose in the urine.
  • Catheterisation, i.e. the insertion of a thin tube into the bladder to drain the urine, helps with residual urine.
• For symptoms of gastroparesis (i.e. indigestion, frequent burping, nausea and vomiting), eating more frequent small portions of food helps.
• In disorders of the autonomic nervous system, there are fluctuations in blood pressure. If blood pressure is low when standing, this is orthostatic hypotension. It is dangerous because standing for long periods or sudden changes in position cause disturbances in consciousness and fainting. It is treated by drinking more fluids, slowly changing position from sitting to standing and sleeping with the head raised at least 10 cm.

Lifestyle changes

A high risk of complications arises if the patient has both diabetes and high blood pressure. It is therefore important to compensate not only for high glycaemia but also for high blood pressure. At least basic medical treatment is necessary for values above 130/90 mmHg.

A balanced, healthy diet, especially vegetables and whole grains, is also important. If the patient is overweight, he or she should try to achieve optimal BMI values. An active lifestyle and regular exercise are helpful.

Physical activity helps to lower blood sugar levels.

In addition, it improves blood flow in the blood vessels and maintains a healthy cardiovascular system.

Smoking or any other tobacco use further narrows the blood vessels and impairs blood flow to the nerves. Therefore, diabetics should try to get rid of this habit.

Supplements to basic treatment

Some dietary supplements can improve the patient's condition quite effectively, for example, by blood supply to the tissue, improving blood circulation, promoting nerve regeneration, affecting swelling, and so on.

It is essential to consult a doctor before taking any supplement. This will avoid unwanted drug interactions or side effects.

Topically on the skin, capsaicin cream is popular. This is applied to the skin in areas where there is burning, tingling or pain, such as the soles of the feet. The most common side effect is skin irritation, redness and intolerance to the burning heat that the cream naturally produces.

Alpha-lipoic acid is a powerful antioxidant found naturally in some foods, such as potatoes and fruits, and in various dietary supplements. Because oxidative stress is a major factor in damage to blood vessels and subsequently nerves, all antioxidants are very effective in preventing these complications. Alpha-lipoic acid is the most effective of these.

In Europe, alpha-lipoic acid is an officially approved drug for the treatment of diabetic neuropathy.

Acupuncture is a method that generally helps with various types of chronic pain. Neuropathic pain is no exception. Its effect requires several sessions. When performed professionally, it has no serious side effects.