Pathophysiology
Clinical meaning
Neuropathic pain results from damage to or dysfunction of the somatosensory nervous system, producing pain that is mechanistically different from nociceptive (tissue damage) pain. Peripheral nerve injury causes ectopic firing of damaged neurons, upregulation of sodium and calcium channels, and sensitization of dorsal horn neurons (central sensitization). Characteristic descriptors include burning, shooting, stabbing, electric shock-like, tingling, and numbness - often described as pins and needles or fire. Allodynia (pain from normally non-painful stimuli like light touch) and hyperalgesia (exaggerated pain response to mildly painful stimuli) are hallmark features. Common conditions include diabetic peripheral neuropathy, postherpetic neuralgia (after shingles), trigeminal neuralgia, phantom limb pain, chemotherapy-induced peripheral neuropathy, and complex regional pain syndrome. Traditional analgesics (acetaminophen, NSAIDs) are largely ineffective for neuropathic pain. First-line treatments include anticonvulsants (gabapentin, pregabalin), SNRIs (duloxetine), and tricyclic antidepressants (amitriptyline), which modulate the neuronal ion channels and neurotransmitters involved in pain signal processing.