Neurology
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Postherpetic neuralgia, when defined as neuropathic pain persisting 1 month or longer after herpes zoster infection, affects about 10% of all patients who have contracted the disease. The incidence of postherpetic neuralgia increases with age; at age 60, about 50% of herpes zoster patients will suffer significant pain, and this proportion grows with subsequent decades. If therapy is carefully chosen and monitored, it is possible to give satisfactory relief, taking pain from severe to mild, to between 60 and 70% of patients. This article will review current treatment and focus on antidepressant drugs, treatments that are contentious and of current interest such as topical agents, and the use of opioids for this type of chronic neuropathic pain.
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The neurologist is an important part of the pain management team. Factors that can alter presentation and complicate establishing a diagnosis are reviewed. ⋯ Treatment planning consists of addressing potential sources of failure of pain management, setting appropriate goals, and using the diagnostic assessment to plan pharmacologic and nonpharmacologic interventions based on pain mechanisms. Even if pharmacologic interventions do not alter pain, an education-oriented behavioral pain program integrated with physical therapy can improve function and foster self-reliance in controlling pain.
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A variety of mechanisms may generate pain resulting from injury to the peripheral nervous system. None of these mechanisms is disease-specific, and several different pain mechanisms may be simultaneously present in any one patient, independent of diagnosis. Diagnosis of neuropathic pain is often easily made from information gathered on neurologic examination and from patient history. ⋯ An adequate trial for each agent tried is key to pharmacologic treatment of neuropathic pain. Tricyclic antidepressants are first-line agents, although other drugs, including anticonvulsants, local anesthetic antiarrhythmics, clonidine, opioids, and certain topical agents, also offer pain relief in some patient populations. The novel antidepressants venlafaxine and nefazodone are potentially useful new drugs that are better tolerated than tricyclic antidepressants.
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Spinal epidural lipomatosis (SEL) is a rare complication of iatrogenic Cushing's syndrome (CS). There is only one case reported of symptomatic SEL in association with endogenous CS. We present a patient with compressive myeloradiculopathy due to SEL and Cushing's disease and suggest that in SEL of hypercortisolism, the excess of corticosteroids is the stimulus for the growth of adipose tissue in the spinal canal and that treatment should be aimed at correcting the endocrine abnormality.
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In 12 zoster patients who had developed postherpetic neuralgia with dynamic mechanical allodynia and in six zoster patients who had recovered without pain, the functional role of nociceptive C-fibers in allodynia was assessed by quantifying axon reflex reactions induced by histamine iontophoresis within allodynic regions and in their contralateral sites. In patients with postherpetic neuralgia, histamine responses were reduced or abolished within allodynic areas, indicating degeneration of nociceptive C-fibers. ⋯ These results demonstrate that sensitized nociceptive C-fibers are not involved in signaling and maintenance of allodynia. Alteration in CNS processing may reorganize synaptic ties between central pain-signaling pathways and mechanoreceptive A beta-fibers depending on afferent C-fiber degeneration rather than ongoing C-fiber input.