Diabetic Peripheral Neuropathy (DPN) is a common and serious complication of diabetes mellitus, involving damage to the peripheral nerves that transmit information between the central nervous system and the extremities. DPN is the most frequent form of diabetic neuropathy, impacting the nerves, especially those leading to the feet and hands. It is estimated that about half of all people living with diabetes will eventually develop some form of neuropathy.
The Mechanism of Nerve Damage
The primary driver of nerve damage in DPN is the long-term exposure of nerve cells to elevated levels of glucose. This chronic high blood sugar triggers several damaging biochemical pathways, including the excessive shunting of glucose into the polyol pathway, which leads to the accumulation of substances like sorbitol and fructose inside nerve cells.
This buildup disrupts normal cell function, including reducing the activity of an enzyme called Na+/K+-ATPase, which is necessary for proper nerve signaling. High glucose also promotes the formation of advanced glycation end products (AGEs) and increases oxidative stress, accelerating cellular damage. These processes impair the structure of the nerve fibers, contributing to the breakdown of the myelin sheath and causing damage to the axon itself.
Compounding this direct nerve damage is a process called microvascular injury, which affects the tiny blood vessels supplying the nerves, known as the vasa nervorum. Damage to these small vessels restricts blood flow and oxygen delivery to the nerve tissue, further compromising nerve health and function. This combination of metabolic stress and impaired blood supply leads to the characteristic loss of sensation and motor control seen in DPN.
Recognizing the Signs and Sensations
The signs of DPN typically emerge gradually, often beginning subtly in the longest nerve fibers first, meaning symptoms usually appear in the feet and legs before the hands. This pattern of progression is commonly referred to as a “stocking-glove” distribution, as the affected areas correspond to where a stocking or glove would cover the body. The sensations experienced can be broadly categorized into sensory and motor symptoms.
Sensory symptoms are varied and can include a persistent feeling of numbness, often described as a loss of sensation to touch or temperature. Patients frequently report paresthesias, such as tingling, “pins and needles,” or an uncomfortable buzzing feeling. For many, the condition is marked by neuropathic pain, which can manifest as sharp, shooting, electric-like jolts or a deep, constant burning sensation, frequently worsening at night.
Some individuals experience hyperesthesia, an increased sensitivity where even a light touch can feel intensely painful. The most dangerous consequence of sensory loss is the inability to feel pain from injuries on the feet. This lack of protective sensation can lead to unnoticed ulcers and severe infections, major risk factors for lower-limb amputation. Motor symptoms, which are less common, include muscle weakness and loss of reflexes, affecting balance and walking.
Strategies for Symptom Management
Managing DPN requires controlling the underlying cause and preventing complications. The primary strategy for slowing the progression is maintaining strict blood glucose control. Clinicians often recommend aiming for a target HbA1c level below 7%, as tight glycemic control can help prevent the onset and worsening of nerve damage.
For managing the pain associated with DPN, pharmacological treatments are often employed, targeting the specific nature of nerve pain. These typically include certain anticonvulsants and antidepressants, which modulate pain signals in the nervous system. These drugs are selected to address the shooting or burning pain that standard over-the-counter pain relievers often cannot alleviate.
A significant focus of management is on proactive self-care, particularly concerning the feet. Daily inspection of the feet for any cuts, sores, or blisters is a fundamental practice, given the risk of unnoticed injury due to sensory loss. Wearing appropriate, protective footwear and avoiding walking barefoot are also emphasized to prevent trauma. Regular physical activity, such as walking or swimming, can also support nerve health and improve overall function.