Clinical Abnormalities of Pain and Other Somatic Sensations
Some Clinical Abnormalities of Pain and Other Somatic Sensations Hyperalgesia A pain nervous pathway sometimes becomes excessively excitable; this gives rise to hyperalgesia, which means hypersensitivity to pain. Possible causes of hyperalgesia are (1) excessive sensitivity of the pain receptors themselves;, whichhis called primary hyperalgesia, andn (2) facilitation of sensory transmission, which is callede secondary hyperalgesiaa. An example of primary hyperalgesia is the extreme sensitivity of sunburned skin, which results from sensitization of the skin pain endings by local tissueue products from the burn-perhaps histamine, perhaps prostaglandins, perhaps others. Secondary hyperalgesiais frequently results from lesions in the spinal cord or the he thalamus. Several of these desions are discussed in sub-sequent sections. Herpes Zoster (Shingles) Occasionally herpesvirus infects a dorsal root ganglion. This causes severe pain in the dermatomal segment sub-serve...