■ Pins and needles
■ Strange painful sensations (Irving, 2005)
Typically, the pain the patient experiences from a neuropathic condition is worse at night, especially with conditions such as PDN. It is important for the health care provider to question the patient who is suspected of having a neuropathic source for their pain about the type of pain they are having; if anything causes the pain, such as movement, pressure, or differences in temperature; and if there are times of day when the pain is worse.
Physiologically, neuropathic pain has been described as pain without a braking mechanism. The pain stimulus is sustained by a collection of pain-facilitating substances, such as bradykinin, that are recruited to create the pain and continue and expand the effects of the pain stimulus. Once the nerve injury occurs, what is called an "inflammatory soup" of pain facilitators, such as substance P, hydrogen ions, interleukin-l(beta), nerve growth factor, prostaglandins, histamine, bradykinin, adenosine-5 '-triphosphate, and tumor necrosis factor, are activated to help sustain an inflammatory cycle that continues and spreads the effects of the condition (Irving, 2005).
Once the physiologic changes start, the effects on the sodium channels that are related to pain transmission take place. For a normal transmission of pain, primary sodium channels on neurons are activated. The accumulation of the pain facilitators in neuropathic pain activate secondary sodium channels on neurons that produce a slower activation and are related to pain production. When nerve damage occurs, both types of sodium channels are activated, causing a hyperexcitable neuronal state with the potential for ectopic neuronal discharge (Irving, 2005).
Two of the most common conditions associated with the hyper-excitability of the neuronal system are allodynia and hyperalgesia:
■ Allodynia is perception of pain caused by a normally nonpainful stimulus, such as light touch or hugs.
■ Hyperalgesia is an increased sensation of pain in response to a normally painful stimulus, such as intravenous needle insertion (Staats et al., 2004).
Other terms that are used to describe neuropathic pain are paresthe-sia, dysesthesia, and numbness:
■ Paresthesias are abnormal spontaneous sensations, such as burning tingling, pins, and needles.
■ Numbness is a descriptor applied by patients to a feeling of heaviness, weakness, or deadness in the affected area of the body. It is also described as painful numbness.
■ Dysesthesia is a response where an unpleasant sensation is produced by normal sensation.
Diagnosing neuropathic pain is a challenge for health care practitioners. Although the pain descriptors the patient uses are helpful is discriminating neuropathic pain from other types of pain, the patient also presents with confounding symptoms as well. Patients with neuropathic pain can also present with not only pain but also insomnia, anorexia, anxiety, depression, physical inactivity, and a diminished quality of life (Irving, 2005). Because neuropathic pain is a more complex presentation than a nocicep-tive type of pain, such as an ankle sprain, the treatment is also more complex and may take weeks or months to be effective. Making a diagnosis of neuropathic pain and selecting a treatment means that the patient with neuropathic pain will need closer follow-up and careful titration of medication with careful assessment of adverse effects, such as sedation, nausea, or constipation. However, a careful examination of the patient's pain that reveals a neuropathic component can help to ease the burden of care for both the patient and health care professional if it is identified early on in the evaluation process, and the correct medication regimen selected.
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