Pain

Question 1

Pain pathway: fast, localized

Answer 1

Fibers: myelinated A delta fibers
Pathway: dorsal horn, lateral STT, brainstem reticular formation and thalamus. Projections to cortex (localization and discrimination of pain)

Question 2

Pain pathway: slow

Answer 2

Fibers: unmyelinated C fibers
Pathway: spinal cord to anterior STT, brainstem reticular formation and thalamus. Projects to cortex. Excites Reticular Activating System - diffuse arousal for protective reactions.

Question 3

Intrinsic inhibition: Gate control theory

Answer 3

Balance between large (A beta, A alpha) and small (A delta, C). Large fibers can interfere with transmission of small fibers at first synapse.

Question 4

Intrinsic inhabitation: descending analgesics

Answer 4

endogenous opiates (endorphins) produced in CNS - depress pain through presynaptic inhibition.

Question 5

When is pain categorized as chronic?

Answer 5

6 months - pathology no longer identifiable

Question 6

Neurogenic Pain

Answer 6

Caused by a lesion in the CNS or PNS.
Central: post stroke (thalamic) pain, TBI, Fibromyalgia
Peripheral: CRPS, neuralgia, shingles

Question 7

CRPS

Answer 7

Complex regional pain syndrome

Characteristics: occurs after trauma and disuse, SNS involvement, disproportional pain

Question 8

CRPS stages

Answer 8

Acute: diffuse, severe burning, alloddynia, cool skin, swelling
Dystrophic/ middle: skin changes, cessation of hair and nail growth, muscle atrophy and osteoporosis
Atrophic/ late: decreased hypersensitivity, normal temperature, severe muscle atrophy, diffuse osteoporosis

Question 9

Herpes zoster

Answer 9

(Shingles)
Cause: viral, inflammation of dorsal root ganglion
Characteristics: infection can last 10 days to 5 weeks, pain can last longer

Question 10

Fibromyalgia

Answer 10

Etiology: nonarticular rheumatic disease, unknown origin
Characteristics: widespread pain and tissue tenderness