Diabetic Neuropathy

Definition

Diabetic neuropathy is a group of nerve disorders caused by chronic hyperglycemia in patients with diabetes mellitus, leading to sensory, motor, and autonomic dysfunction.

Epidemiology

• Affects approximately 50% of patients with long-standing diabetes.
• More common in type 2 diabetes due to longer asymptomatic hyperglycemia before diagnosis.
• Prevalence increases with duration of diabetes and poor glycemic control.
• Risk factors: age, smoking, hypertension, dyslipidemia, obesity, chronic hyperglycemia.
• Peripheral neuropathy is the most common form, but autonomic and focal neuropathies also occur.

Etiology

• Chronic hyperglycemia leading to metabolic and vascular injury to nerves.
• Polyol pathway activation: sorbitol accumulation causing osmotic stress.
• Advanced glycation end-products (AGEs) cause oxidative stress and inflammation.
• Microvascular damage reducing blood flow to nerves.
• Genetic susceptibility may contribute to nerve vulnerability.

Pathophysiology

• Hyperglycemia leads to oxidative stress and mitochondrial dysfunction in neurons.
• Microvascular damage causes ischemia of peripheral nerves.
• Axonal degeneration and demyelination result in impaired nerve conduction.
• Autonomic nerves may be affected leading to cardiovascular, gastrointestinal, and genitourinary dysfunction.
• Small fiber neuropathy affects pain and temperature sensation; large fiber neuropathy affects vibration, proprioception, and motor function.