Diabetic Neuropathy

Definition

Diabetic neuropathy is nerve damage caused by long-standing diabetes mellitus. It results directly from prolonged high blood sugar levels.

Pathophysiology

The pathophysiology of diabetic neuropathy involves both metabolic and vascular disturbances triggered by chronic hyperglycemia.

• Metabolic injury: Elevated glucose levels activate the polyol pathway within nerve cells, leading to the accumulation of sorbitol and fructose. This increases oxidative stress, disrupts normal nerve signaling, and damages structural proteins. Advanced glycation end products (AGEs) further modify proteins and lipids, which impairs repair mechanisms and speeds up degeneration.

   

• Vascular injury: Diabetes also causes microvascular disease. Thickening of basement membranes and narrowing of small vessels reduce blood flow to the vasa nervorum. This deprives nerves of oxygen and nutrients. The resulting ischemia intensifies metabolic damage and worsens nerve dysfunction.

   

• Structural changes: These combined effects lead to demyelination, axonal loss, and impaired regeneration. As a result, conduction velocity slows, and communication between nerves and target tissues becomes increasingly ineffective.

• Functional consequences: Sensory nerve involvement is most prominent. This leads to the loss of pain, temperature, and vibration sensation, usually beginning in the feet and moving upward. Motor nerve damage causes weakness, muscle wasting, and foot deformities. Autonomic nerve damage results in cardiovascular instability, gastrointestinal motility disorders, bladder dysfunction, sexual dysfunction, and abnormal sweating.