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- Neuropathic pain is defined as pain in association with primary injury or dysfunction of the nervous system, with or without ongoing tissue damage.
- Divided into 2 groups based on the location of the suspected lesion: Central vs. peripheral:
- Newer data suggest a possibility that most neuropathic syndromes have a component of both central and peripheral mechanisms.
- An important consideration with a patient with neuropathic pain is the absence of any deficit or injury. Socially, the patient appears “normal,” yet suffers from a chronic painful condition. This can lead to psychosocial distress, as the patient is labeled “drug seeking.”
- May be triggered by numerous insults, including direct nerve injury, infection, metabolic dysfunction, autoimmune disease, neoplasm, drugs, radiation, and neurovascular disorders.
- May reflect the pathologic operation of a dysfunctional nervous system rather than a manifestation of any underlying pathology itself (i.e., phantom limb pain, complex regional pain syndrome [CRPS]):
- Patients may paradoxically experience pain and hypersensitivity in an area of denervation.
- System(s) affected: Nervous; Musculoskeletal
Epidemiologic data are limited. It will also be varied, depending on the inclusion criteria: Radiculopathies, peripheral neuropathy, etc.:
- >3 million Americans suffer from painful diabetic neuropathy (PDN).
- 1 million Americans suffer from postherpetic neuralgia (PHN).
Estimated at 1.5% of the population, although recent studies in England, Germany, and France place it around 6–8% of the population.
- Polyneuropathy (diabetes mellitus, alcohol-induced, postchemotherapy, heritable neuropathies)
- Trauma (nerve entrapment, postsurgical, nerve injury)
- Infection (HIV, herpes zoster)
- Central mechanisms (stroke, multiple sclerosis [MS], spinal cord injury, limb amputation)
- Nutritional deficiencies (B12, folate)
- Medications (AIDS medications DDC and DDI, antibiotics metronidazole and isoniazid, some chemotherapeutics, amiodarone, hydralazine, phenytoin, nitrofurantoin)
- Positive symptoms due to changes in peripheral nerves, loss of inhibitory mechanisms in CNS, and central sensitization
- Negative symptoms likely due to axonal or neuronal loss
- Associated with a predisposing factor
- In addition to possible etiologies listed as risk factors above, others include:
- Demyelinating disorders (MS, Guillain-Barré)
- Neoplasm (primary/metastatic)
- Neurovascular (central post-stroke syndrome, trigeminal neuralgia)
- Autoimmune disease (Sjögren syndrome, polyarteritis nodosa)
- Structural disease (herniated disc disease)
Commonly Associated Conditions
- Sleep disturbance