Search

The visual analogue scale (VAS) is an established, validated, self-report measure usually consisting of a 10 cm line on paper with verbal anchors labeling the ends. Palmtop computers (PTCs also known as personal digital appliances) have incorporated VAS entry by use of a touch screen. However, the validity and psychophysical properties of the electronic VAS have never been formally compared with the conventional paper VAS. The aim of this study is to determine the agreement between the electronic (eVAS) and paper (pVAS) modes. Twenty-four healthy volunteers were recruited for this study. Each study participant provided input using both measurement methods by marking the eVAS and pVAS in response to two kinds of stimuli, cognitive and sensory. A verbal rating scale of seven descriptors of intensity represented the cognitive stimuli. Participants were asked to mark the location that best corresponded to the pain intensity described by each word on scales from ‘no pain’ to ‘worst possible pain’. The sensory stimuli used were a set of test weights consisting of plastic containers ranging from 7 to 129 g. The VAS for sensory stimuli ranged from 0 (no weight) to ‘reference weight’ (the heaviest weight outside the range of test weights). There were two types of input stimuli and two modes for recording responses for a total of four experimental conditions. Two evaluators independently measured and recorded all the pVAS forms to the nearest millimeter. A total of 2016 stimuli were rated. The overall correlation for ratings of both sensory and cognitive stimuli on eVAS and pVAS was r=0.91. For paired verbal stimuli the correlation was r=0.97. For paired sensory stimuli the correlation was r=0.86. The correlation between group eVAS and pVAS ratings to common verbal stimuli was r=0.99. For common sensory stimuli the group correlation was r=0.99. The median of correlations comparing eVAS and pVAS ratings was 0.99 for verbal stimuli and 0.98 for sensory stimuli. Multivariate analyses showed equivalent stimuli to be rated much the same whether entered on paper VAS or PTC touch screen VAS (P<0.0001). Support was found for the validity of the computer version of the VAS scale. [Copyright &y& Elsevier] more...

Objectives: Semmes-Weinstein monofilaments are too long for use in parts of the oral cavity. The present study used shortened Semmes-Weinstein monofilaments to evaluate reliability and spatial differences in the intraoral tactile detection threshold (TDT) and the filament-prick pain detection threshold (FPT) in healthy volunteers., Methods: For practical purposes, classic Semmes-Weinstein monofilaments with 20 different diameters were cut to half their length (ie, 19 mm) and the bending forces were measured. Eighteen men and 18 women (age range, 20 to 33 y) were recruited to evaluate the reliability and reproducibility of measurements using half-cut monofilaments. The TDT and the FPT were measured on the labial maxillary gingiva, on the palatal maxillary gingiva, and at the anterior tip of the tongue, using a double random staircase method., Results: According to the forces needed to bend the half-cut filaments, they were renumbered from 2.55 to 6.86. There were significant differences of bending force between the half-cut and original monofilaments (P<0.001), Using half-cut filaments, the following differences could be detected; the labial maxillary gingiva had a significantly higher TDT threshold compared with the other test sites (P<0.001). By contrast, the palatal posterior maxillary gingiva had a significantly higher FPT threshold compared with the other test sites (P<0.001)., Discussions: The present study illustrated that in healthy participants, half-cut Semmes-Weinstein monofilaments reliably and easily assess TDT and FPT intraorally. A combined examination of sensory and pain thresholds using these filaments contributes to the clinical examination for orofacial pain. more...

We have demonstrated that subjects with complex regional pain syndrome (CRPS) have asymmetric venous pool plasma concentrations of norepinephrine (NE) when affected and unaffected limbs are compared, with most demonstrating decreased NE levels in the affected limb. This pilot study explored whether systemic venous plasma catecholamine levels in CRPS subjects with sympathetically maintained pain (SMP) differ from those found in healthy volunteers. We also explored whether catecholamine levels were correlated with scores on psychometric measures of depression, anxiety, and personality. Venous blood samples from 33 CRPS/SMP patients (from unaffected limbs) and 30 healthy control subjects were assayed for plasma NE and epinephrine (E) concentrations. Plasma NE levels were significantly higher in the CRPS group (P < 0.001). Statistical comparisons of E levels across groups did not achieve significance (P < 0.06), although 52% of CRPS/SMP patients had E levels exceeding the 95% confidence interval based on control data. Significant positive correlations were found between E levels and scores on the Beck Depression Inventory and Scales 1, 3, and 6 on the Minnesota Multiphasic Personality Inventory-2 (all P < 0.05). This preliminary work suggests that increased NE and E levels in CRPS/SMP patients may result from the pain of CRPS, consequent affective distress, or both. Alternatively, our findings could reflect premorbid adrenergic hyperactivity caused by affective, endocrine, or other pathology, which might predispose these individuals to develop the syndrome. Definitive studies are needed to examine these hypotheses in detail. more...

Objective: This study was designed to compare 3 commonly used methodologies for assessing clinical pain during trials involving patients diagnosed with fibromyalgia syndrome. Baseline characteristics, characteristics over time, and compliance were evaluated for each of the methods., Methods: Fourteen patients diagnosed with fibromyalgia syndrome were asked to monitor their symptoms of pain using 3 different strategies over a 12-week period: 1) real-time pain reports were collected on an electronic diary using randomly-scheduled audible prompts; 2) end-of-week reports asked patients to rate their mean pain over the past week on the electronic diary; and 3) monthly in-clinic reports asked patients to rate their mean pain for the week using a traditional paper and pencil diary., Results: Significantly different baseline values were obtained for the 3 methods. Paper and pencil produced the highest values, and real-time pain reports produced the lowest baseline values. Pain ratings were more likely to reflect decreases in the 2 methods relying on recall than the real-time strategy. The average adherence with pain monitoring using the electronic diary was 85%, which was superior to the adherence for the recall measures completed during the clinic visits., Conclusion: Pain assessment methods relying on recall might contribute to an apparent improvement in clinical trials in the absence of an intervention; such an effect has been considered a "placebo response." Future clinical trials might consider using a real-time approach to pain assessment, which in this study appeared to mitigate against seeing improvement in the absence of an intervention and demonstrated higher levels of patient adherence. more...

The results of two experiments suggest that sensory and affective verbal descriptors provide a valid scaling method which discriminates between the sensory intensity and the affect, or unpleasantness, of electrocutaneous stimuli. Twenty-four subjects judged the sensory intensity and affect of noxious electrocutaneous stimuli by choosing verbal descriptors from randomized lists and by cross-modality matching to time duration and to handgrip force. The psychophysical functions for sensory intensity generated by the descriptor and the cross-modality functions for sensory intensity generated by the descriptor and the cross-modality methods are the same. Psychophysical functions for affect generated by thedescriptor and the cross-modality methods are different. However, only the descriptor method produces psychophysical functions for affect that are significantly different from all the sensory functions. This result suggest that only the descriptor method distinguishes between sensory intensity and affect. The discriminative power of the descriptor method is demonstrated further in an experiment in which 32 subjects rated either the sensory intensity or the affect of the electrocutaneous stimuli immediately before and after an i.v. administration of 5 mg diazepam. This common minor tranquilizer significantly lowered affective descriptor responses (P less than 0.005) without altering sensory descriptor and sensory and affective handgrip responses. These experiments indicate that sensory and affective verbal pain descriptors may be used as a valid and sensitive tool for the evaluation of pain and pain control methods. more...

Twenty-nine subjects used quantified verbal descriptors of sensory intensity (i.e., weak, mild, intense) or unpleasantness (i.e., annoying, unpleasant, distressing) to assess the intensity or unpleasantness of sensations evoked by painful electrical stimulation of the tooth pulp over a broad stimulus range, and by a natural thermal tooth pulp stimulus, cold spray applied to exposed dentin. In addition, subjects matched the intensity or unpleasantness of the sensations evoked by the natural stimulus to that of the electrical stimuli by both the Method of Limits and the Method of Constant Stimuli. Quantified verbal descriptor values of either the sensory intensity or unpleasantness of the electrical stimuli were linearly related to stimulus intensity on a log scale, indicating that the relationships can be described by power functions. The quantified verbal description of the natural thermal stimulus and the intensity of the electrical stimulus directly matched to the thermal stimulus determined the coordinates of the clinical stimulus data point. This point was close to the experimental stimulus power function, indicating that the verbal magnitude of the clinical stimulus is predicted by the verbal magnitude of the specific electrical stimulus intensity that was matched to the clinical stimulus. This consistency supports the validity of the use of quantified verbal descriptors for the assessment of both experimentally controlled noxious stimulation and uncontrolled clinical pain sensations. It also supports the validity of direct matches between clinical and experimental pain sensations and the unpleasantness of these sensations. This procedure provides a useful independent validational paradigm for clinical pain assessment. more...

The Descriptor Differential Scale (DDS) applies psychophysical principles to clinical pain assessment. It contains 12 descriptor items for each pain dimension assessed. For each item, subjects indicate if their pain either is equal in magnitude to that implied by the anchoring descriptor, or how much greater or lesser on a 10-point graphic scale. The method permits collection of multiple responses, reducing scaling error, and assess both pain magnitude and scaling consistency. Ninety-one patients completed the sensory intensity and unpleasantness forms of the DDS at both 1 and 2 h after surgical extraction of a lower third molar. Results show that the DDS satisfies standard psychometric criteria for reliability, objectivity and item homogeneity. The coefficients found satisfy standard psychometric criteria and improve after elimination of inconsistent profiles. more...

Psychophysical experiments were carried out on 6 huma subjects to determine how first and second pain are influenced by peripheral receptor mechanisms and by central nervous system inhibitory and facilitatory mechanisms. For these experiments, brief natural painful stimuli delivered to the hand were a train of 4-8 constant waveform heat pulses generated by a contact thermode (peak temp. = 51-5% C). The magnitude of first and second pain sensations was estimated using cross-modality matching procedures and reaction times were determined. The latter confirmed the relationship between first and second pain and impulse conduction in Adelta and C noxious heat afferents, respectively. The intensity of first pain decreased with each successive heat pulse when the interpulse interval was 80 sec or less. This decrease was most likely the result of heat induced suppression of Adelta heat nociceptors since it did not occur if the probe location changed between successive heat pulses. In contrast, second pain increased in intensity with each successive heat pulse if the interval was 3 sec or less. This summation was most likely due to central nervous system summation mechanisms since it also occurred after blockage of first pain by ulnar nerve compression and when the location of the thermode changed between heat pulses. These observations and their interpretations are supported by our recording of responses of singlt Adelta heat nociceptive afferents, C polymodal nociceptive afferents, and "warm" afferents of rhsus monkeys to similar trains of noxious heat pulses. Their responses to these heat pulses show a progressive suppression. Furthermore, previous studies have shown that wide dynamic range dorsal horn neurons show summated responses to repeated volleys in C fibers (greater than 1/3 sec). These spinal cord summation mechanisms could account for the summation of second pain. more...