Diabetic foot is one of the most important complications of diabetes mellitus and is primarily associated with diabetic peripheral neuropathy, impaired blood circulation to the lower limbs, and, in many cases, a combination of both. Damage to the peripheral nerves can gradually reduce the ability to feel pain, temperature, and pressure in the feet. As a result, a minor injury, blister, burn, or pressure from unsuitable footwear may go unnoticed. When impaired blood circulation is also present, healing may be more difficult, increasing the risk of developing a diabetic foot ulcer, infection, and other serious complications. For this reason, the early identification of diabetic neuropathy and loss of protective sensation is an essential part of diabetic foot prevention.

Diabetic Neuropathy and Diabetic Foot

Diabetic peripheral neuropathy is a common complication of diabetes mellitus and primarily affects the nerves of the lower limbs. Symptoms usually begin in the soles of the feet and toes and may gradually progress upwards.

Patients may experience:

• numbness in the feet
• tingling
• burning sensations
• prickling or electric shock-like sensations
• neuropathic pain
• increased sensitivity to touch
• reduced temperature sensation
• reduced pain sensation
• loss of sensation in the soles of the feet
• balance problems, particularly when neuropathy is more advanced

Symptoms of neuropathic pain may be more pronounced at night and can significantly affect sleep and quality of life.

Loss of Protective Sensation

One of the most important consequences of diabetic polyneuropathy is the loss of protective sensation in the feet. Under normal circumstances, pain acts as a warning signal. It causes us to move the foot away from a source of heat, change footwear when it causes injury, or become aware of a wound.

When sensation is reduced, the patient may not notice:

• a small wound
• a blister
• a cut
• a burn
• a foreign object inside the shoe
• prolonged pressure on a specific area of the sole

As a result, a small and initially painless injury may progress into a more significant wound or ulcer.

Symptoms of Diabetic Neuropathy in the Feet

Diabetic neuropathy does not always cause pain. Some patients experience severe burning or pain, while others may have significant peripheral nerve damage without obvious symptoms.

Possible symptoms include:

• numbness in the toes or soles of the feet
• burning sensations in the feet
• pain, particularly at night
• tingling
• pins-and-needles sensations
• increased sensitivity even to light touch
• reduced ability to distinguish between hot and cold
• reduced awareness of the position of the feet
• unsteadiness while walking

The absence of pain does not necessarily mean that the nerves are functioning normally.

Neuropathic, Ischemic and Neuroischemic Foot

Depending on the predominant underlying mechanism, diabetic foot may present with different characteristics.

Neuropathic Foot

In a neuropathic diabetic foot, peripheral nerve damage is the predominant problem. Reduced sensation increases the risk of repeated minor injuries and the development of ulcers in areas exposed to increased pressure.

Ischemic Foot

In an ischemic foot, there is reduced arterial blood flow to the lower limbs due to peripheral arterial disease. Patients may experience pain while walking, pain at rest in more advanced cases, coldness of the affected limb, changes in skin color, or delayed wound healing.

Neuroischemic Foot

In a neuroischemic diabetic foot, neuropathy and impaired arterial circulation occur together. The combination of reduced sensation and inadequate blood supply significantly increases the risk of complications.

Diagnosis of Diabetic Peripheral Neuropathy

Diagnosis is based on the patient’s medical history and neurological examination.

The assessment may include evaluation of:

• sensation to touch
• pain perception
• temperature sensation
• vibration sensation
• reflexes
• muscle strength
• balance and gait
• the presence of loss of protective sensation

Testing with a 10-g monofilament is particularly important for assessing protective sensation in the foot.

Electromyography and Peripheral Nerve Assessment

In selected cases, electromyography and nerve conduction studies may be performed to assess peripheral nerve function.

Neurophysiological testing can help with:

• confirming and assessing polyneuropathy
• evaluating the severity and distribution of nerve damage
• investigating atypical symptoms
• differentiating diabetic neuropathy from other peripheral nerve disorders

The presence of diabetes mellitus does not necessarily mean that every episode of numbness or pain in the feet is caused by diabetic neuropathy. Other causes of peripheral neuropathy should be investigated when indicated by the clinical presentation.

Assessment of Blood Circulation in the Foot

Neurological assessment represents only one part of the evaluation of diabetic foot. The arterial circulation of the lower limbs should also be assessed, particularly when symptoms or signs of peripheral arterial disease are present. Depending on the individual case, vascular or vascular surgical assessment and specialized testing of the circulation may be required.

Diabetic Foot Ulcer

A diabetic foot ulcer may begin with an apparently minor injury or repeated pressure on a particular area of the foot. Because of neuropathy, the patient may not experience pain and may continue placing pressure on the affected area. If reduced blood circulation is also present, healing may become even more difficult.

Management of a diabetic foot ulcer may require:

• relieving pressure from the affected area
• appropriate wound care
• removal of non-viable tissue when indicated
• assessment and treatment of possible infection
• assessment of arterial circulation
• appropriate footwear or orthotic devices
• optimization of diabetes control

The management of diabetic foot ulcers often requires a multidisciplinary approach.

Diabetic Foot Infection

A foot ulcer may become infected, and the infection can spread to deeper tissues or even to the bones. Particular attention is required because neuropathy can reduce pain sensation, meaning that the severity of an injury or infection may be underestimated.

Signs may include:

• redness
• swelling
• increased warmth of the foot
• discharge from a wound
• changes in skin color
• unpleasant odor
• fever or general malaise

These symptoms require prompt medical assessment.

Signs Requiring Immediate Medical Assessment

A patient with diabetes mellitus should seek immediate medical assessment if they develop:

• a new wound or ulcer on the foot
• significant redness or swelling
• a suddenly warm and swollen foot
• discharge from a wound
• a change in the color of a toe or part of the foot
• an area of blackened skin
• fever associated with a foot wound
• rapid deterioration of an existing wound

Early treatment can significantly reduce the risk of serious complications.

Treatment of Painful Diabetic Neuropathy

The treatment of painful diabetic neuropathy aims to reduce neuropathic pain and improve sleep, mobility, and quality of life. Depending on the individual patient, pharmacological and non-pharmacological interventions specifically targeting neuropathic pain may be used. Good control of diabetes is also important, together with management of other modifiable risk factors such as blood pressure, lipid levels, body weight, and smoking. Treatment can significantly reduce symptoms, although established loss of nerve fibers is generally not reversible.

Prevention of Diabetic Foot

Prevention is a fundamental part of diabetic foot management. People with diabetes should regularly inspect their feet, particularly when reduced sensation is present.

Important preventive measures include:

• daily inspection of the soles and toes
• checking for wounds, blisters, redness, or changes in the skin
• wearing appropriate footwear
• avoiding walking barefoot when sensation is reduced
• taking care with very hot water or heating devices
• appropriate skin and nail care
• regular medical examination of the feet

Prevention is particularly important because a patient with severe neuropathy may injure the foot without being aware of it.

Regular Foot Assessment in Diabetes

People with diabetes mellitus should undergo regular assessment for diabetic peripheral neuropathy and the risk of diabetic foot complications.

More frequent assessment may be required when there is:

• loss of protective sensation
• peripheral arterial disease
• foot deformity
• a previous diabetic foot ulcer
• previous amputation
• Charcot neuroarthropathy
• renal failure or other significant risk factors

Early identification of a high-risk foot allows preventive measures to be introduced before an ulcer or another serious complication develops.

Neurological Follow-Up of Diabetic Neuropathy

Neurological follow-up is particularly important when numbness, burning sensations, neuropathic pain, sensory impairment, or balance problems are present. Assessment of peripheral nerve function can help identify neuropathy before more serious complications develop. Early diagnosis of diabetic peripheral neuropathy, appropriate foot care, good diabetes management, and collaboration between different medical specialties when necessary are essential components in preventing ulcers, infections, and serious complications of diabetic foot.