8 Chronic Pain Conditions and Their Diagnostic Criteria

8. Neuropathic Pain - When Nerves Become the Problem

Neuropathic pain represents a distinct category of chronic pain resulting from disease or lesion affecting the somatosensory nervous system, characterized by unique sensory phenomena that differ markedly from nociceptive pain mechanisms. The International Association for the Study of Pain (IASP) defines neuropathic pain as pain caused by a lesion or disease of the somatosensory nervous system, requiring evidence of a relevant neurological lesion or disease affecting peripheral or central somatosensory systems and pain distribution neuroanatomically plausible for the lesion. Diagnostic criteria emphasize the presence of characteristic symptoms including burning, electric shock-like, or shooting pain qualities, along with sensory abnormalities such as allodynia (pain from normally non-painful stimuli), hyperalgesia (increased pain from painful stimuli), and hypoesthesia (decreased sensation) in the affected area. The diagnostic process involves comprehensive neurological examination, quantitative sensory testing when available, and appropriate investigations such as nerve conduction studies, electromyography, or neuroimaging to confirm the underlying neurological lesion. Common causes include diabetic neuropathy, postherpetic neuralgia, trigeminal neuralgia, spinal cord injury, stroke, and chemotherapy-induced peripheral neuropathy, each requiring specific diagnostic approaches and treatment strategies. The pathophysiology involves complex changes in ion channel expression, altered neurotransmitter function, glial cell activation, and central sensitization mechanisms that can perpetuate pain signals even in the absence of ongoing tissue damage. Screening tools such as the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) or the Douleur Neuropathique 4 (DN4) questionnaire can assist in identifying neuropathic pain characteristics, though definitive diagnosis requires correlation with clinical findings and appropriate investigations.