Your patient with severe neuropathic pain undergoes nerve conduction studies and electromyography. Her results are normal, and you decide to refer her for quantitative sensory testing (QST).
Which of the following statements about QST is true?
a. QST can be used to measure temporal summation of pain.
b. Thermal stimulation is used to measure the integrity of large myelinated nerve fibers.
c. A-beta function can only be evaluated using von Frey hair filaments.
d. QST can be used to evaluate the function of all types of nerve fibers.
Correct answer is a.
QST can be used to measure temporal summation of pain, which is a perceptual correlate of the “windup” phenomenon of pain. It is used to evaluate the function of individual nerve fibers (large and small) and to measure pain detection and tolerance thresholds. Thermal, mechanical, and vibratory stimuli can be utilized.
Heat and cold thermal stimulation can be used to measure the function of small myelinated (Ad) and unmyelinated C fibers.
The function of large myelinated A-beta fibers can be measured using both vibratory thresholds and mechanical thresholds to von Frey hair filaments.
QST cannot be used to determine the injured nerve or to localize the nerve injury. Further, QST cannot be used to assess preganglionic autonomic muscle spindle efferent nerve fiber function.
Backonja MM, Walk D, Edwards RR, et al. Quantitative sensory testing in measurement of neuropathic pain phenomena and other sensory abnormalities. Clin J Pain. 2009;25(7):641-647.
Weissman-Fogel I, Sprecher E, Granovsky Y, Yarnitsky D. Repeated noxious stimulation of the skin enhances cutaneous pain perception of migraine patients in-between attacks: clinical evidence for continuous sub-threshold increase in membrane excitability of central trigeminovascular neurons. Pain. 2003;104(3):693-700.