TYPES OF PAIN
Treatment modalities are dictated not only by the cause of pain but also
by the type of pain. Pain can be divided into two broad categories:
nociceptive and neuropathic (non-nociceptive). These types of pain differ
in their causes, symptoms, and responses to analgesics.
Nociceptive or somatic pain results from direct stimulation of
nociceptive, intact (uninjured) afferent nerve endings. Descriptors for
this type of pain are usually "dull," "sharp," and/or "aching," or a
combination of these, and the intensity of the pain varies from mild to
severe. In general, somatic pain can be well controlled if the cause of
the stimulation can be removed or otherwise treated (surgery, radiation
therapy, chemotherapy, etc.), or somatic pain can be treated with
analgesics. Response to analgesics is usually good.
Neuropathic pain, on the other hand, is caused by nervous system
dysfunction rather than stimulation of intact afferent nerve endings. It
is characterized by burning, shooting, and tingling pain, associated with
allodynia, hyperpathia, paresthesias and dysesthesias. The most frequent
causes of neuropathic pain in cancer patients are tumor or
treatment-related nerve damage, acute herpes zoster (shingles),
post-herpetic neuralgia, and phantom limb pain. Neuropathic pain may be
accompanied by sympathetic nervous system dysfunction, e.g., causalgia or
reflex sympathetic dystrophy, currently termed Complex Regional Pain
Syndrome. Compared with nociceptive pain, neuropathic pain usually
requires more complex pharmaco therapy (See Table I).
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