Diabetic neuropathy – a common complication of diabetes

Prevalence of Diabetic Neuropathy

It is estimated that approximately 2-8% of the world’s population suffers from neuropathy, with diabetes mellitus (DZ) being the main cause in Western countries. Distal symmetric polyneuropathy (DSP) is the most common neuropathic complication of diabetes and the most common form of neuropathy worldwide. Pirart J. mentioned that in 8% of cases, signs of neuropathy can be detected at the time of diagnosis of diabetes mellitus, and about 50% of patients will develop neuropathy after 25 years of diabetes mellitus, in addition to nephropathy and retinopathy. Dyck P.J. found that 66% of type 1 diabetics and 59% of type 2 diabetics have neuropathy.

Diabetic neuropathy is a late complication of diabetes that can affect any part of the nervous system. Although rarely a direct cause of death, it is a major cause of morbidity and early disability, affecting 50-60% of diabetic patients. A substantial body of evidence indicates that approximately 30-40% of individuals with diabetes experience symptoms of diabetic peripheral neuropathy. This prevalence is observed to increase with age, reaching approximately 44% among diabetic patients over the age of 70.

What is diabetic neuropathy?

Diabetic neuropathy is the most common complication of diabetes. It affects patients with type 1 and type 2 diabetes in equal proportions of both sexes. Different types of neuropathy can occur in the same patient. This involves symptoms triggered by damage to the peripheral nervous system caused by prolonged hyperglycemia.

In patients with type 2 diabetes mellitus, neuropathy may be present at the time of diagnosis. Therefore, a neurological consultation is recommended to confirm or deny the presence of the disease. In contrast, in type 1 diabetes mellitus, neuropathy may occur later, depending on glycemic control. In such cases, a neurological evaluation is recommended in five years after the diagnosis.

There are different types of diabetic neuropathy, depending on the peripheral nerve damage. The symptoms become progressively more severe, and in the early stages, they may go unnoticed.

Causes and Risk Factors

Diabetic neuropathy is a condition that results from damage to the peripheral nervous system. The underlying cause of this damage can be attributed to some factors, including metabolic disorders, infections, malignant tumors, inflammation, vitamin deficiencies, toxin accumulation, or hereditary conditions.

Among these potential causes, diabetes is a particularly prevalent contributor to neuropathy. Uncontrolled diabetes leads to elevated blood sugar levels, which in turn cause damage to nerve endings and, over time, even large nerves. Additionally, neuropathy can be caused by prolonged pressure or compression of a nerve.

The development of diabetic neuropathy is influenced by many factors that may increase the risk of damage to the peripheral nerves. These factors include:

• poor glycemic control;
• elevated LDL (bad cholesterol) and triglyceride levels;
• obesity;
• eye and kidney damage caused by diabetes;
• high blood pressure;
• smoking and alcohol consumption;
• old age;
• duration of onset of diabetes or glycemic imbalance (prediabetes);
• frequent hypoglycemia;
• local ischemia;
• sedentary lifestyle;
• common metabolic disorders in children and adolescents.

Types and symptoms of diabetic neuropathy

Diabetic neuropathy can be classified into four main categories: peripheral, autonomic, proximal, and focal. The symptoms associated with each type of neuropathy vary depending on the nerves affected and the underlying pathology. Diabetics may develop one or more forms of neuropathy, and the symptoms of this complication often manifest and progress gradually. In some cases, patients may only begin to notice the problems after the nerve damage becomes significant.

The symptoms of each form of diabetic neuropathy are unique and described in detail below.

1. Diabetic Peripheral Neuropathy

Also referred to as distal symmetric peripheral neuropathy, this represents the most prevalent form of diabetic neuropathy. Initially, it affects the soles and feet, and can subsequently disseminate to the hands and arms. The symptoms, which are typically more pronounced at night, include:

• numbness or diminished sensation to pain or temperature fluctuations;
• tingling or burning sensation;
• sharp pains or cramps;
• muscle weakness;
• loss of balance and coordination;
• extreme sensitivity to touch (for some patients, even the weight of bedding can cause discomfort);
• loss of reflexes, particularly in the ankle;
• serious foot problems include ulcers, infections, and bone and joint damage.

2. Autonomic neuropathy

Autonomic neuropathy refers to damage to the autonomic nervous system, which regulates many vital bodily functions. These include blood pressure, heart rate, sweating, eye functions, bladder control, digestive processes, and the functioning of the sex organs. Diabetes can damage nerves in these areas of the body, resulting in the following symptoms:

• impaired ability to perceive hypoglycemia (low blood sugar);
  • decreased blood pressure upon rising from a seated or supine position, which can precipitate dizziness or syncope (orthostatic hypotension);
  • gastrointestinal disturbances, including constipation, uncontrolled diarrhea, or alternating between the two;
  • urinary tract infections, urinary retention, or incontinence;
  • slow emptying of the stomach (gastroparesis), which causes nausea, vomiting, feelings of fullness, and loss of appetite;
  • difficulty swallowing (dysphagia);
  • difficulty adjusting vision from light to dark or from far to near;
  • profuse sweating;
  • increased resting heart rate;
  • disorders of sexual function, such as vaginal dryness in women and erectile dysfunction in men.

3. Proximal Neuropathy

This form of diabetic neuropathy, also referred to as diabetic polyradiculopathy, predominantly affects the nerves in the thighs, hips, buttocks, and legs. However, it can also involve the abdominal and thoracic regions. The symptoms typically manifest on one side of the body but may subsequently extend to the other side over time. Proximal neuropathy is a more prevalent condition among individuals with type 2 diabetes and the elderly. People with proximal neuropathy may experience:

• severe pain in the buttocks, hip, or thigh that emerges abruptly within a few days;
• weakness in the thigh muscles and loss of thigh muscle mass;
• difficulty rising from a seated position;
• weight loss;
• pain in the chest or abdominal wall.

In most instances, the condition shows signs of improvement over time, albeit to a limited degree. However, it bears noting that the severity of symptoms may fluctuate before exhibiting a discernible recovery.

1. Mononeuropathy

Also referred to as focal neuropathy, this form of diabetic neuropathy entails damage to a singular nerve. The affected nerve may be situated in the face, trunk, arm, or leg. It is most prevalent in the elderly, manifests abruptly, and induces acute discomfort, yet does not result in long-term complications. Mononeuropathy can lead to:

• difficulty in concentrating or double vision;
• difficulty focusing the eyes;
• pain behind one eye;
• paralysis on one side of the face;
• numbness or tingling in one hand or a finger;
• weakening of the hand muscles, which may lead to dropping objects;
• pain in the shin or leg area;
• muscle weakness that limits the ability to lift the front of the foot (drop foot phenomenon);
• localized pain on the front of the thigh.

Mononeuropathy may result from nerve compression. In patients with diabetes, carpal tunnel syndrome represents a prevalent form of neuropathy resulting from compression. This can manifest as numbness or tingling in the hands and fingers, as well as a sensation of muscle weakness, which may culminate in the inadvertent dropping of objects from the hand.

Symptoms of neuropathy usually occur depending on the course of the condition and the type of neuropathy.

Diagnosis of Diabetic Neuropathy

The diagnosis of diabetic neuropathy is made at the time of diagnosis of type 2 diabetes or, in the case of type 1 diabetes, five years after the onset of symptoms. Thereafter, annual testing is conducted. All studies have demonstrated that neuropathy-specific changes manifest at an early stage, namely at the prediabetes stage. The diagnosis of diabetic neuropathy entails a series of steps, including:

• history of the patient’s symptoms;
• annual sensitivity testing, encompassing pain, vibration, pressure and heat;
• electromyography, which gauges the nerve conduction velocity in skeletal muscles.

The neurologist establishes the definitive diagnosis.

Treatment of diabetic neuropathy

The treatment of diabetic neuropathy is contingent upon the specific symptoms and the underlying etiology of the neuropathy. There is currently no cure for diabetic neuropathy. The treatment plan is centered on secondary prophylaxis (the removal of aggravating factors) and the maintenance of blood glucose levels at a target value. This can be maintained by:

• treatment with insulin or oral antidiabetic drugs as the treating physician prescribes;
• smoking cessation;
• following an adequate diet;
• taking daily light exercise;
• regular medical check-ups.

Examination of the feet plays an important role because people with diabetes, especially those with diabetic neuropathy, have impaired sensation. A foot lesion can go unnoticed, become infected, and increase the risk of amputation if the infection spreads to the bone.

Prevention

The primary objective of preventing diabetic neuropathy is to achieve optimal metabolic balance, which should be initiated during the prediabetic period.

Modifications to lifestyle, including strict glycemic control, weight loss, a balanced diet, and regular exercise, have been shown to have a beneficial impact on the progression of neuropathy, reduce the severity of symptoms, and may even facilitate regeneration of nerve fibers.

It is important to note that when type 1 diabetes is first diagnosed, it is not advisable to lower the blood sugar level excessively immediately.

There is evidence that sufficient physical activity has a beneficial effect on nerve damage in the autonomic nervous system and on symptoms of peripheral nerve damage. This is observed in individuals with type 1 and type 2 diabetes.

Conclusion

It can be concluded that neuropathy represents one of the most significant complications associated with diabetes. Given its high prevalence and early onset, the diagnosis of neuropathy should be a priority. The long-term subclinical course and unfavorable long-term prognosis (in the absence of treatment) of the most common forms (diffuse sensorimotor neuropathy and autonomic neuropathy) result in complications with high treatment costs and an elevated risk of disability or even death.

The relative underdiagnosis of autonomic impairment increases the risks, particularly for cardiovascular neuropathy, which has been demonstrated to be a significant predictor of adverse cardiac events. The treatment of diabetic patients should encompass education and training on the necessity of maintaining optimal glycemic control, the importance of early recognition of complications, and the pivotal role of self-care measures.

The most effective method for the prevention and treatment of neuropathy is the control of glycemic levels. Current studies indicate that future treatments may include medications with the potential to reverse neuronal damage. Diabetic foot ulcers and infections should be prevented as much as possible and treated promptly once they have occurred, given the high risk of amputation.

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