Neuropathic Pain

Definition

Neuropathic pain is a chronic pain condition caused by injury or dysfunction of the somatosensory nervous system, characterized by burning, shooting, or electric shock-like sensations, often accompanied by allodynia or hyperalgesia.

Epidemiology

• Prevalence: 7–10% of the general population worldwide.
• More common in adults over 50 years.
• Higher prevalence in patients with diabetes, herpes zoster, spinal cord injury, or post-stroke.
• Both sexes affected, slight female predominance.
• Often underdiagnosed due to variable presentation.

Etiology

• Peripheral neuropathy: diabetic neuropathy, post-herpetic neuralgia, traumatic nerve injury, post-surgical neuropathy.
• Central neuropathy: spinal cord injury, stroke, multiple sclerosis, brain lesions.
• Chemotherapy-induced neuropathy (e.g., platinum compounds, taxanes).
• Chronic infections (HIV-associated neuropathy), autoimmune neuropathies (Guillain-Barre syndrome, CIDP).

Pathophysiology

• Peripheral nerve injury leads to abnormal spontaneous firing and sensitization.
• Central sensitization in the spinal cord dorsal horn amplifies pain signals.
• Loss of inhibitory interneurons and increased excitatory neurotransmission.
• Upregulation of sodium channels and transient receptor potential channels in damaged nerves.
• Inflammatory mediators and glial activation contribute to chronic pain states.