Chapter 2 CLASSIFICATION OF PAIN Flashcards
KEY POINTS 1. Pain can be classified according to inferred pathophysiology, time course, location, or etiology. 2. Proper pain classification may aid in the proper treatment of the pain problem. 3. Chronic non–cancer-related pain significantly differs from acute pain in that chronic non–cancer-related pain serves no useful biologic purpose.
the most widely used classifications of pain
pain classifications depend on the following:
- Inferred pathophysiology (nociceptive vs. nonnociceptive)
- Time course (acute vs. chronic)
- Location (painful region)
- Etiology (e.g., cancer, arthritis)
What is the neurophysiologic classification of pain?
The neurophysiologic classification is based on the inferred mechanism for pain. There are
essentially two types: (1) nociceptive, which is due to injury in pain-sensitive structures, and
(2) nonnociceptive, which is neuropathic and psychogenic
Nociceptive pain can be subdivided
into
somatic and visceral (depending on which set of nociceptors is activated)
Neuropathic pain
can be subdivided into
peripheral and central (depending on the site of injury in the nervous
system believed responsible for maintaining the pain).
What is nociceptive pain?
Nociceptive pain results from the activation of nociceptors (A-delta fibers and C fibers) by
noxious stimuli that may be mechanical, thermal, or chemical.
Nociceptors may be sensitized by
endogenous chemical stimuli (algogenic substances) such as serotonin, substance P,
bradykinin, prostaglandin, and histamine.
Somatic and Visceral pain is transmitted along
Somatic pain is transmitted along sensory fibers.
Visceral pain, in comparison, is transmitted along autonomic fibers; the nervous system is intact and perceives noxious stimuli appropriately.
How do patients describe pain of somatic nociceptive origin?
Somatic nociceptive pain may be sharp or dull and is often aching in nature. It is a type of pain
that is familiar to the patient, much like a toothache. It may be exacerbated by movement
(incident pain) and relieved upon rest. It is well localized and consonant with the underlying
lesion.
Examples of somatic nociceptive pain include
metastatic bone pain, postsurgical pain,
musculoskeletal pain, and arthritic pain. These pains tend to respond well to the primary
analgesics, such as nonsteroidal antiinflammatory drugs (NSAIDs) and opioids.
How do patients describe pain of visceral nociceptive origin?
Visceral nociceptive pain arises from distention of a hollow organ. This type of pain is usually poorly localized, deep, squeezing, and crampy. It is often associated with autonomic sensations
including nausea, vomiting, and diaphoresis. There are often cutaneous referral sites (e.g., heart
to the shoulder or jaw, gallbladder to the scapula, and pancreas to the back).
Examples of visceral
nociceptive pain include
pancreatic cancer, intestinal obstruction, and intraperitoneal metastasis
How do patients describe pain of neuropathic origin?
Patients often have difficulty describing pain of neuropathic origin because it is an unfamiliar
sensation. Words used include burning, electrical, and numbing. Innocuous stimuli may be perceived as painful (allodynia). Patients often complain of paroxysms of electrical sensations
(lancinating or lightning pains).
Examples of neuropathic pain include
trigeminal neuralgia,
postherpetic neuralgia, and painful peripheral neuropathy
Clinically, how do you distinguish between paresthesia and dysesthesia?
Paresthesia is described simply as a nonpainful altered sensation, e.g., numbness. Dysesthesia
is an altered sensation that is painful, e.g., painful numbness
deafferentation pain
Deafferentation pain is a subdivision of neuropathic pain that may complicate virtually any type
of injury to the somatosensory system at any point along its course
What are examples of deafferentation pain?
Examples include welldefined
syndromes precipitated by peripheral (phantom-limb) or central (thalamic pain)
lesions. In all of these conditions, pain usually occurs in a region of clinical sensory loss.
With phantom-limb pain, the pain is actually felt in an area that no longer exists. Patients with
thalamic pain, also known as Dejerine-Roussy syndrome, report pain in all or part of the region
of clinical sensory loss
complex regional pain syndrome I (CRPS I; formerly known as reflex sympathetic dystrophy) is defined as
‘‘continuous
pain in a portion of an extremity after trauma, which may include fracture but does not
involve a major nerve, associated with sympathetic hyperactivity.’’
CRPS II
(formerly known as causalgia) as
‘‘burning pain, allodynia, and hyperpathia, usually in the foot
or hand, after partial injury of a nerve or one of its major branches.’’
A phantom limb sensation
is a nonpainful perception of the continued presence of an amputated
limb. It is part of a deafferentation syndrome, in which there is loss of sensory input
secondary to amputation
Phantom limb pain
describes painful sensations that are perceived
in the missing limb.
A phantom limb sensation vs Phantom limb pain
Phantom limb sensation is more frequent than phantom limb pain,
occurring in nearly all patients who undergo amputation. However, the sensation is time-limited
and usually dissipates over days to weeks. On occasion, these sensations may be confused
with stump pain, which is pain at the site of the amputation. Thoroughly examine the stump of any patient complaining of persistent phantom limb pain to rule out infection and neuroma
Multidimensional Pain Inventory
is a self-report questionnaire designed to assess chronic
pain patients’ adaptation to their symptoms and behavioral responses by significant others.
Section 1 includes five scales that describe pain severity and cognitive-affective responses to pain. Section 2 assesses the patient’s perceptions of how his or her significant others respond to
pain complaints. Section 3 examines various activities, such as those undertaken in the household, in society, and outdoors
Psychogenic pain
presumed to exist when no nociceptive or neuropathic mechanism can be
identified and there are sufficient psychologic symptoms to meet criteria for somatoform
pain disorder, depression, or another Diagnostic and Statistical Manual of Mental Disorders
(DSM-IV) diagnostic category commonly associated with complaints of pain.
What is the World Health Organization (WHO) ladder?
These
guidelines correlate intensity of pain to pharmacologic intervention: Mild pain (step 1) requires
nonopioid analgesics with or without adjuvant medications. If the patient does not respond
to treatment or the pain increases, the guideline suggests moving to step 2 by adding a mild
opioid to the previous therapy. If the pain continues or increases in severity, then the clinician
goes to step 3 and adds a strong opioid to the prior therapy.
Myofascial pain syndrome
defined as a regional pain syndrome characterized by the
presence of trigger points and localized areas of deep muscle tenderness in a taut band of
muscle. Pressure on a trigger point reproduces the pain.
fibromyalgia
a systemic pain disorder associated with tender points in all four quadrants of the body for at least 3 months’ duration, often with associated sleep disturbance, irritable bowel syndrome, and
depression. In myofascial pain syndrome, these associated features are significantly less
frequent.
neuropathic pain syndromes generally respond to
adjuvant
medications such as tricyclic antidepressants and to anticonvulsants
nociceptive pain
states mainstay of
treatment.
the implementation of NSAIDs alone or in combination with opioids is the mainstay of
treatment
Describe the temporal classification of pain. What is its shortcoming?
The temporal classification of pain is based on the time course of symptoms and is usually divided into acute, chronic, and recurrent. The major shortcoming is that the division between acute and chronic is arbitrary.
How is acute pain defined?
Acute pain is temporally related to injury and resolves during the appropriate healing period. There is usually no secondary gain on the patient’s part, but social, cultural, and personality
factors may play some role. Acute pain often responds to treatment with analgesic medications
and treatment of the precipitating cause. Delay or improper therapy can lead to chronic pain.
How is chronic pain defined?
Chronic pain is often defined as pain that persists for more than 3 months or that outlasts the
usual healing process. However, the cognitive-behavioral aspect, not duration, is probably
the essential criterion of the chronic nonmalignant pain syndrome. Chronic non–cancer-related
pain serves no useful biologic purpose
How is chronic pain classified in patients with cancer?
Chronic pain in patients with cancer is categorized according to whether it is tumor-related,
treatment-related, or unrelated to the cancer
Tumor-related pain may occur at
the site of
the primary tumor or at a site of metastasis
Treatment-related pain can be secondary to
the use
of chemotherapeutic agents (peripheral neuropathy), radiation therapy (radiation plexitis,
myelopathy, or secondary tumors), or surgery (postmastectomy syndrome, radical
neck syndrome, postthoracotomy syndrome).
What is meant by an etiologic classification?
An etiologic classification pays more attention to the primary disease process in which pain occurs, rather than to the pathophysiology or temporal pattern. Examples include cancer pain,
arthritis pain, and pain in sickle cell disease.
What is the basis of the regional classification of pain?
The regional classification of pain is strictly topographic and does not infer pathophysiology or
etiology. It is defined by the part of the body affected, then subdivided into acute and chronic.
