C h a p t e r 3 5
Somatosensory Function, Pain, and Headache
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result from partial or complete loss of descending inhib-
itory pathways or spontaneous firing of regenerated
nerve fibers. They include conditions such as causalgia,
phantom limb pain, and postherpetic neuralgia. Central
pain, which is associated with disease or injury of the
CNS, is characterized by burning, aching, hyperalgesia,
dysesthesia, and other abnormal sensations, and is expe-
rienced as superficial (skin) or deep (bone or muscle)
pain. It is associated with conditions such as thalamic
lesions, spinal cord injury, surgical interruption of pain
pathways, and multiple sclerosis.
Unlike acute pain, chronic pain serves no useful pur-
pose. It imposes physiologic, psychological, interper-
sonal, and economic stresses and may exhaust a person’s
resources. It is often associated with loss of appetite,
sleep disturbances, and depression, which commonly is
relieved once the pain is removed.
Chronic pain management is complex and treatment
depends on the cause of the pain, the natural history
of the underlying health problem, and the life expec-
tancy of the individual.
20,21
If the organic illness causing
the pain cannot be cured, then noncurative methods
of pain control become the cornerstone of treatment.
Chronic pain is best handled by a multidisciplinary
team that includes specialists in areas such as anesthe-
siology, nursing, physical therapy, social services, and
surgery.
Cancer is a common cause of chronic pain.
23–25
The
goal of chronic cancer pain management should be pain
alleviation and prevention. Preemptive therapy tends to
reduce sensitization of pain pathways and provides for
more effective pain control. Pharmacologic and non-
pharmacologic interventions are the same as those used
for other types of chronic pain. Depending on the form
and stage of the cancer, other treatments such as pal-
liative radiation, antineoplastic therapies, and palliative
surgery may help to control the pain. In 1986, the World
Health Organization (WHO) developed a three-step
ladder that assists clinicians in choosing the appropri-
ate analgesic medications.
26
Step 1 involves the use of
nonopioid analgesics, and steps 2 and 3 involve the use
of opioid analgesics.
Pain Management
Careful assessment of pain assists clinicians in diagnos-
ing, managing, and relieving the patient’s pain. As with
other disease states, eliminating the cause of the pain is
preferable to simply treating the symptom.
Assessment
Assessment includes such things as the nature, sever-
ity, location, and radiation of the pain. Reports of pain
are almost entirely subjective. A careful history often
provides information about the triggering factors (i.e.,
injury, infection, or disease) and the site of nociceptive
stimuli (i.e., peripheral receptor or visceral organ).
21
A
comprehensive pain history should include pain onset;
description, localization, radiation, intensity, quality, and
pattern of the pain; anything that relieves or exacerbates
it; and the individual’s personal reaction to the pain.
The single most reliable indicator of the existence and
intensity of acute pain is probably the person’s self-report.
Unlike many other bodily responses, such as tem-
perature and blood pressure, the nature, severity, and
distress of pain cannot be measured objectively. To over-
come this problem, various methods have been devel-
oped for quantifying pain based on the person’s report.
They include numeric pain intensity, visual analog, and
verbal descriptor scales. Most pain questionnaires assess
a single aspect of pain such as pain intensity. For exam-
ple, a
numeric pain intensity
scale would have patients
select which number best represents the intensity of their
pain, where 0 represents no pain and 10 represents the
most intense pain imaginable. A
visual analog
scale also
can be used; it is a straight line, often 10 cm in length,
with a word description (e.g., “no pain” and “the most
intense pain imaginable”) at each of the ends of the line
representing the continuum of pain intensity.
Nonpharmacologic Interventions
A number of nonpharmacologic methods of pain control
are used in pain management. These include cognitive-
behavioral interventions (e.g., relaxation, distraction,
imagery, and biofeedback), physical agents (e.g., heat and
cold), electroanalgesia (transcutaneous electrical nerve
stimulation [TENS]), and acupuncture. Often these meth-
ods are used in addition to analgesics rather than as the
sole form of pain management.
PharmacologicTreatment
Pharmacologic treatment involves the use of drugs in the
management of pain. It includes the use of nonnarcotic
and narcotic analgesics, as well as adjuvant medications,
such as antidepressants, anticonvulsants, and muscle
relaxants. Topical medications (e.g., fentanyl patch) are
a new aspect of pain management, whose full potential
has yet to be determined.
An analgesic drug is a medication that acts on the
nervous system to decrease or eliminate pain without
inducing unconsciousness. Analgesic drugs do not cure
the underlying cause of the pain, but their appropriate
use makes the pain more tolerable and, in the case of
acute pain, may prevent it from progressing to chronic
pain. The ideal analgesic would be effective and nonad-
dictive and produce minimal adverse effects. Although
long-term treatment with opioids can result in opioid
tolerance (i.e., increasingly greater drug dosages being
needed to achieve the same effect) and physical depen-
dence, this should not be confused with addiction.
Long-term drug-seeking behavior is rare in persons who
are treated with opioids only during the time that they
require pain relief. The unique needs and circumstances
presented by each person in pain must be addressed to
achieve satisfactory pain management.
Nonnarcotic Analgesics.
Nonnarcotic oral analgesic
medications include aspirin, other NSAIDs, and acet-
aminophen. Aspirin (acetylsalicylic acid) acts periph-
erally and centrally to block the transmission of pain
impulses. It also has antipyretic and anti-inflammatory
properties. The action of aspirin and other NSAIDs is
