Quick discrimination of A(delta) and C fiber mediated pain based on three verbal descriptors.
BACKGROUND
A(δ) and C fibers are the major pain-conducting nerve fibers, activate only partly the same brain areas, and are differently involved in pain syndromes. Whether a stimulus excites predominantly A(δ) or C fibers is a commonly asked question in basic pain research but a quick test was lacking so far.


RESULTS
Of 77 verbal descriptors of pain sensations, "pricking", "dull" and "pressing" distinguished best (95% cases correctly) between A(δ) fiber mediated (punctate pressure produced by means of von Frey hairs) and C fiber mediated (blunt pressure) pain, applied to healthy volunteers in experiment 1. The sensation was assigned to A(δ) fibers when "pricking" but neither "dull" nor "pressing" were chosen, and to C fibers when the sum of the selections of "dull" or "pressing" was greater than that of the selection of "pricking". In experiment 2, with an independent cohort, the three-descriptor questionnaire achieved sensitivity and specificity above 0.95 for distinguishing fiber preferential non-mechanical induced pain (laser heat, exciting A(δ) fibers, and 5-Hz electric stimulation, exciting C fibers).


CONCLUSIONS
A three-item verbal rating test using the words "pricking", "dull", and "pressing" may provide sufficient information to characterize a pain sensation evoked by a physical stimulus as transmitted via A(δ) or via C fibers. It meets the criteria of a screening test by being easy to administer, taking little time, being comfortable in handling, and inexpensive while providing high specificity for relevant information.
Beissner
Florian
F
Clinic of Neurology, Goethe-University, Frankfurt am Main, Germany.
Brandau
Amadeus
A
Henke
Christian
C
Felden
Lisa
L
Baumgärtner
Ulf
U
Treede
Rolf-Detlef
RD
Oertel
Bruno G
BG
Lötsch
Jörn
J
D000328:Adult; D004558:Electric Stimulation; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000502:physiology*; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology*; D010146:Pain / Q000503:physiopathology*; D011795:Surveys and Questionnaires; D055815:Young Adult