However, at both frequencies of stimulation, the pain patients rated the pain
intensities of each of the ten stimuli greater than the control subjects. Furthermore,
the aftersensations lingered at 15 and 120 s after stimulation terminated, and the
aftersensation ratings predicted clinical pain ratings. Figure6.4 depicts thefindings
fromfibromyalgia patients and normal control subjects from the study by Staud
et al. ( 2007 ). It has also been demonstrated that in instances of co-morbid condi-
tions (when a patient has two coexisting pain conditions, such asfibromyalgia and
irritable bowel syndrome), temporary relief of the pain of one of the conditions
(with local anesthesia) restores“windup”ratings to be similar to controls.
Fig. 6.4 “Windup”and aftersensations infibromyalgia patients and normal controls. Group mean
responses to ten painful pressure pulses (1 kg/s and maintained for 2.5 s) delivered to the skin
every 2 s forfibromyalgia patients (dashed lines) and normal controls (solid lines). Subjects rated
the pain intensity of thefirst pulse and the tenth pulse and then the residual pain sensations at 15
and 120 s after the tenth pulse. Fibromyalgia patients rated the pressure pulses and aftersensations
as more painful than the normal controls (from Staud et al. 2007 )
6 The Challenge of Measuring Pain in Humans 111