Flashcards in Chapter 8 Deck (25):
pain arising as a direct consequence of a lesion or disease affecting the somatosensory system
painless abnormal sensation in the absence of nociceptor stimulation
unpleasant abnormal sensation, either evoked or spontaneous
pain evoked by a stimulus that normally would not cause pain
excessive sensitivity to stimuli that are normally mildly painful in uninjured tissue
What are the mechanisms responsible for neuropathic pain:
1. ectopic foci
2. ephaptic transmission
3. central sensitization
4. structural reorganization
What is ectopic foci?
When myelin is damaged, signals from the exposed axon stimulate excessive production of mechanosensitive and chemosensitive ion channels, producing abnormal sensitivity to mechanical/chemical stimuli
What is ephaptic transmission?
Occurs in demyelinated regions due to a lack of insulation between neurons. An action potential in one neuron may induce an action potential in another neuron.
What is central sensitization?
is excessive responsiveness of central neurons
develops in response to ongoing nociceptive input, and yet persists after the peripheral injury has healed.
In central sensitization, the central neurons produce disproportionate neural output to incoming nociceptive signals
What is structural reorganization?
Structural changes in the dorsal horn include withdrawal of C-fiber axon terminals from the dorsal horn and growth of Aβ-fiber axons into regions of the spinal cord that normally receives only C-fiber terminals
Where can neuropathic pain arise?
CNS in response to deafferentation
What does complete nerve resection result in?
results in a lack of sensation from that nerve’s receptive field
What does partial damage result in?
allodynia and sensations similar to an electric shock
What is the central response to deafferentation?
1. phantom pain
2. central pain; SCI, CVA, MS
3. small fiber neuropathy
What is central pain caused by?
caused by a lesion of the CNS and is usually localized to the area of the body deafferented by the lesion
What does neuropathic pain refer to?
burning, shooting, aching, freezing, or tingling pain
What are the conditions that involve disturbance of top down regulation of pain?
2. episodic tension-type headache
4. chronic whiplash-associated disorder
What is fibromyalgia?
abnormal processing of pain information, resulting in the perception of pain without noxious stimuli to the nervous system.
What is treatment for fibromyalgia?
aquatic therapy with or without exercise
Criteria for ETTH (episodic tension-type headache)
-mild to moderate pain, usually bilateral
-lasting 30 mins to 7 days
-not aggravated by physical activity
-not associated with nausea or vomitting
What is the mechanism for ETTH?
supersensitivity to nitric oxide which sensitizes the nociceptive pathways in the CNS.
What are the characteristics of migraine?
-severity interfering with daily activities
-aggravation from routine physical activities
Complex regional pain syndrome:
involves the somatosensory, autonomic, and motor systems.
Chronic low back pain syndrome:
involves muscle guarding, disuse, and abnormal movements