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Diabetic Neuropathy

What is diabetic neuropathy?

Diabetic neuropathy is the damage to the nerves that occur because of diabetes. The nerves are bundles of fibres in the body that are responsible for communicating and co-ordinating actions between the brain and the rest of the body. There are different types of neuropathies, depending on the function of the nerve that is damaged. The most common form of diabetic neuropathy is Diabetic Peripheral Neuropathy (DPN), which affects the nerves in the arms and legs.

How does diabetic neuropathy occur?

Diabetes is the inability to control blood sugar levels due to the inability to produce insulin or the resistance to it. A high level of blood sugar leads to the sugars to stick to the cells in the blood. These cells in turn stick to the side of the blood vessels and build up, causing narrowing of the blood vessels, very much like limescale building up in pipes and causing blockages and reducing the flexibility of the blood vessels, causing the blood pressure to go up. Also, the lack or resistance to insulin can change the way the body processes cholesterol, a fatty substance that is found in the blood. In diabetic patients, the amount of cholesterol in the blood also increases and this too can build up in the blood vessels, forming a plaque and contribute towards the narrowing of the arteries.

The nerves are supplied by small arteries. The fundamental unit of a nerve is known as the neuron. Each individual neuron is responsible for relaying electrical signals between each other. There are different types of nerves, sensory nerves are nerves that are responsible for relaying information that is to do with touch and pain. Motor nerves are nerves that are responsible for relaying information to the muscles to perform an action. Autonomic nerves are nerves that oversee and control the internal organs such as the gut, the bladder, and the sex organs. Autonomic nerves also control the blood pressure and heart rate. In diabetes, as we can see from above, these small vessels can become clogged up with deposits, which can reduce blood supply to the nerves and thus the supply of oxygen and nutrients. Due to the reduced amount of nutrients supplied to the nerve cells, the neurons can start to break down and thus the nerve can start to degenerate. This in turn can affect the electrical signals transmitted normally through these nerves – the side effects of which are dependent on the type of nerves affected.

The risk factors for diabetic neuropathy include poorly controlled blood sugar levels and uncontrolled blood pressure. Other risk factors include:

1. Smoking

2. High cholesterol

3. Height (longer nerve fibres are more likely to be affected)

Healthy Nerves
Nerves in diabetic neuropathy

How is diabetic neuropathy diagnosed?

Since the relationship between diabetes and neuropathy has been well established, checking the extent of retinal damage is part of any regular diabetes check-ups that one undergoes. The initial way of assessing for any eye disease is to take a photo of the back of the eye. Further investigations include fluorescein angiography, where a die is injected into the veins in your arms which then quickly reaches the eyes, where images of the back of the eye are taken. The dye enables to visualise all the small blood vessels in the eye and investigate the source of leakage of fluid. Another investigation that can be used to assess for any macular oedema is called an optical coherence tomography scan, which produces a cross sectional scan of the retina.

How common is diabetic neuropathy?

It is estimated that around 1 in 2 people with diabetes will develop diabetic neuropathy in their lifetime. There are no major differences in the type of nerves affected between type 1 diabetes and type 2 diabetes. 

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