Variance of sensory threshold measurements: discrimination of feigners from trustworthy performers

The applicability of the digit wrinkle scan to quantify sympathetic nerve function

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Normative values for stimulated skin wrinkling are age-dependent.

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Stimulated skin wrinkling has never been evaluated quantitatively.

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The clinical application of the stimulated skin wrinkling in an ordinal fashion is doubtful.

Objective

Stimulated skin wrinkling test (SSW) has been launched as a non-invasive diagnostic procedure. However, no normative age dependent values have been reported that can be applied in clinical practice. The objectives of the study were to (1) collect age-dependent normative values according to the 5-point scale assessment for the SSW, to (2) determine reliability scores for the obtained norm values, and to (3) introduce a new digital method for SSW assessment, the Digit Wrinkle Scan© (DWS©) for detection of wrinkles in a more quantitative manner.

Methods

Firstly, 82 healthy participants were included, divided in 5 age groups. The participants underwent SSW using lidocaine and prilocaine topical cream. Secondly, 35 healthy participants were included to test whether the DWS© could be a novel manner to assess the grade of wrinkling quantitatively. We determined the inter-observer reliability of both methods. Also, the intra-observer reliability was calculated for the DWS©.

Results

We found a decrease in normative values over age. The inter-observer reliability of assessment by the 5-point scale method was moderate after SSW (Cohen’s k: 0.53). Results of the DWS© indicate that total wrinkle length per mm² showed moderate to good agreement for the 4th and 5th digits after SSW, and a low agreement for the other digits.

Conclusions

Age-dependent normative values were obtained according to the 5-point scale, but its clinical application is doubtful since we found a moderate inter-observer reliability. We introduced the DWS© as a possible new method in order to quantify the grade of wrinkling.

Significance

We found unsatisfactory reliability scores, which hampers its usefulness for clinical practice.

Differential Diagnosis of Chronic Neuropathic Orofacial Pain: Role of Clinical Neurophysiology

Orofacial pain syndromes encompass several clinically defined and classified entities. The focus here is on the role of clinical neurophysiologic and psychophysical tests in the diagnosis, differential diagnosis, and pathophysiological mechanisms of definite trigeminal neuropathic pain and other chronic orofacial pain conditions (excluding headache and temporomandibular disorders). The International Classification of Headache Disorders 2018 classifies these facial pain disorders under the heading Painful cranial neuropathies and other facial pains. In addition to unambiguous painful posttraumatic or postherpetic trigeminal neuropathies, burning mouth syndrome, persistent idiopathic facial and dental pain, and trigeminal neuralgia have also been identified with neurophysiologic and quantitative sensory testing to involve the nervous system. Despite normal clinical examination, these all include clusters of patients with evidence for either peripheral or central nervous system pathology compatible with the subclinical end of a continuum of trigeminal neuropathic pain conditions. Useful tests in the diagnostic process include electroneuromyography with specific needle, neurography techniques for the inferior alveolar and infraorbital nerves, brain stem reflex recordings (blink reflex with stimulation of the supraorbital, infraorbital, mental, and lingual nerves; jaw jerk; masseter silent period), evoked potential recordings, and quantitative sensory testing. Habituation of the blink reflex and evoked potential responses to repeated stimuli evaluate top-down inhibition, and navigated transcranial magnetic stimulation allows the mapping of reorganization within the motor cortex in chronic neuropathic pain. With systematic use of neurophysiologic and quantitative sensory testing, many of the current ambiguities in the diagnosis, classification, and understanding of chronic orofacial syndromes can be clarified for clinical practice and future research.

Body regional heat pain thresholds using the method of limit and level: a comparative study

PURPOSE

The purpose of this study was to compare cutaneous heat pain thresholds using the method of limit and level.

METHODS

Sixteen young males (23.2 ± 3.2 year, 174.9 ± 4.9 cm, and 70.1 ± 8.6 kg) participated in this study. The thermode temperature increased at a constant rate of 0.1 °C s^-1 from 33 °C for the method of limit, whereas the method of level consisted of 3 s heat pulses increasing from 44 °C to 50 °C in 100 s separated by 5 s intervals. All measurements were conducted on 14 body regions (the forehead, neck, chest, abdomen, upper back, upper arm, forearm, waist, hand, palm, thigh, calf, foot, and sole) in 28 °C, 35% relative humidity.

RESULTS

The results are as follows. Heat pain thresholds were on average 3.2 ± 2.1 °C higher for the method of level than for the method of limit (P < 0.05). Second, the correlation coefficient between values by two methods was 0.819 (P < 0.01). Third, lower body regions (thigh, calf, and sole) had higher heat pain thresholds than upper body regions (chest) by the method of level only (P < 0.05). Fourth, body regional subcutaneous fat thickness showed no relationship with heat pain thresholds except the upper arm.

CONCLUSION

These results indicated that cutaneous heat pain thresholds vary based on the type of heat stimuli and body regions. The method of limit could be applied for predicting accumulated thermal pain starting from moderate heat, whereas the method of level may be applicable for predicting acute heat pain to flames or high heat.

Advances in diagnostics and outcome measures in peripheral neuropathies

Peripheral neuropathies are a group of acquired and hereditary disorders presenting with different distribution and nerve fiber class involvement. The overall prevalence is 2.4%, increasing to 8% in the elderly population. However, the frequency may vary depending on the underlying pathogenesis and association with systemic diseases. Distal symmetric polyneuropathy is the most common form, though multiple mononeuropathies, non-length dependent neuropathy and small fiber neuropathy can occur and may require specific diagnostic tools. The use of uniform outcome measures in peripheral neuropathies is important to improve the quality of randomized controlled trials, enabling comparison between studies. Recent developments in defining the optimal set of outcome measures in inflammatory neuropathies may serve as an example for other conditions. Diagnostic and outcome measure advances in peripheral neuropathies will be discussed.

Neuropathic pain: is quantitative sensory testing helpful?

Neuropathic pain arises as a consequence of a lesion or disease affecting the somatosensory system and is characterised by a combination of positive and negative sensory symptoms. Quantitative sensory testing (QST) examines the sensory perception after application of different mechanical and thermal stimuli of controlled intensity and the function of both large (A-beta) and small (A-delta and C) nerve fibres, including the corresponding central pathways. QST can be used to determine detection, pain thresholds and stimulus-response curves and can thus detect both negative and positive sensory signs, the second ones not being assessed by other methods. Similarly to all other psychophysical tests QST requires standardised examination, instructions and data evaluation to receive valid and reliable results. Since normative data are available, QST can contribute also to the individual diagnosis of neuropathy, especially in the case of isolated small-fibre neuropathy, in contrast to the conventional electrophysiology which assesses only large myelinated fibres. For example, detection of early stages of subclinical neuropathy in symptomatic or asymptomatic patients with diabetes mellitus can be helpful to optimise treatment and identify diabetic foot at risk of ulceration. QST assessed the individual's sensory profile and thus can be valuable to evaluate the underlying pain mechanisms which occur in different frequencies even in the same neuropathic pain syndromes. Furthermore, assessing the exact sensory phenotype by QST might be useful in the future to identify responders to certain treatments in accordance to the underlying pain mechanisms.

Guidelines and recommendations for assessment of somatosensory function in oro-facial pain conditions--a taskforce report

The goals of an international taskforce on somatosensory testing established by the Special Interest Group of Oro-facial Pain (SIG-OFP) under the International Association for the Study of Pain (IASP) were to (i) review the literature concerning assessment of somatosensory function in the oro-facial region in terms of techniques and test performance, (ii) provide guidelines for comprehensive and screening examination procedures, and (iii) give recommendations for future development of somatosensory testing specifically in the oro-facial region. Numerous qualitative and quantitative psychophysical techniques have been proposed and used in the description of oro-facial somatosensory function. The selection of technique includes time considerations because the most reliable and accurate methods require multiple repetitions of stimuli. Multiple-stimulus modalities (mechanical, thermal, electrical, chemical) have been applied to study oro-facial somatosensory function. A battery of different test stimuli is needed to obtain comprehensive information about the functional integrity of the various types of afferent nerve fibres. Based on the available literature, the German Neuropathic Pain Network test battery appears suitable for the study of somatosensory function within the oro-facial area as it is based on a wide variety of both qualitative and quantitative assessments of all cutaneous somatosensory modalities. Furthermore, these protocols have been thoroughly described and tested on multiple sites including the facial skin and intra-oral mucosa. Standardisation of both comprehensive and screening examination techniques is likely to improve the diagnostic accuracy and facilitate the understanding of neural mechanisms and somatosensory changes in different oro-facial pain conditions and may help to guide management.

Thermal sensitivity in the elderly: a review

Aging is associated with a progressive decrease in thermal perception, as revealed by increased thermal detection thresholds in the elderly. This reduction in thermosensitivity follows a distal-proximal pattern, with more pronounced decrements observed in the limbs and in the perception of warmth vs. cold. The main underlying causes of this seem to be aging of the skin and subsequent reductions in thermoreceptor density and superficial skin blood flow. However, the results from some animal studies also suggest that changes in the peripheral nerve system, particularly fiber loss and decreased conduction velocity, may also be involved. In this paper, we review age-related changes in the thermal sensitivity of humans, their underlying mechanisms, and the strengths and limitations of some of the methodologies used to assess these changes.

Quantitative sensory testing: a diagnostic tool for painful neuropathy

Quantitative sensory testing (QST) analyzes sensory perceptions of external stimuli of controlled intensity. Both large and small fiber function can be evaluated by applying thermal and mechanical stimuli, thus closing the diagnostic gap for the conventional electrophysiology in the examination of thin and unmyelinated nerve fibers. Detection, pain thresholds and stimulus–response curves can be determined; therefore, QST is a valuable diagnostic tool for identifying both sensory loss (i.e., hypoesthesia and hypoalgesia) and gain (i.e., hyperalgesia and allodynia) in patients with painful or painless neuropathy. Every psychophysical approach QST requires standardized stimuli administration, instructions and data evaluation to achieve valid results. QST can be used to evaluate distinct somatosensory profiles and thus give hints to the underlying mechanisms that occur with different frequencies in different pain syndromes. This might be helpful for the future establishment of mechanism-based pharmacotherapy. Since normative data are available, QST also contributes to the individual diagnosis of neuropathy. The present article gives an outline of QST application in diagnosis and its limitations for the evaluation of neuropathic pain.

Thermal perception thresholds recorded using method of limits change over brief time intervals

Quantitative Sensory Testing (QST) of thermal perception thresholds assesses small afferent nerve function. QST has also been widely used to investigate the effects of interventions on the perception of activity within these nerve fibres, often over brief time periods. The natural variation in perception thresholds over brief time periods has not been determined, however, complicating accurate identification of induced changes. The present study therefore investigated changes in thermal perception threshold values within a 1-h period. Twenty-four healthy women volunteers aged 18-28 years (mean 20.6, SD 2.8) undertook cold sensation (CS), warm sensation (WS), cold pain (CP), and hot pain (HP) perception threshold measurements on the thenar eminence of the dominant hand during six 8-min experimental cycles. The order of stimulus presentation was randomized within pre-selected criteria. An adaptation temperature of 32 degrees C, a rate of temperature change of 0.5 degrees C/s, a 3 cm x 3 cm thermode, and a method of limits algorithm were used. Separate two-way ANOVAs with repeated measures showed statistically significant changes over time for WS, CS, and HP (p < 0.05), but not for CP (p = 0.232). The results indicate that WS, CS, and HP perception thresholds change significantly with repeated testing over a 1-h period. These results should be carefully considered when assessing the importance of observed changes in thermal perception thresholds. In research trials exclusion of a control group would be a fundamental flaw.

Streamlined classification of psychopathological hand disorders: A literature review

In the surgical hand clinic, psychopathological hand disorders can be sorted into one of the following four categories: (1) factitious wound creation and manipulation; (2) factitious edema; (3) psychopathological dystonias, and (4) psychopathological sensory abnormalities and psychopathological Complex Regional Pain Syndrome. This article introduces these four categories. Pertinent literature that includes descriptions of each category's syndromes and diseases, demographic and psychological profiles, differential diagnoses, and appropriate treatment recommendations is reviewed.

Changes to somatosensory detection and pain thresholds following high frequency repetitive TMS of the motor cortex in individuals suffering from chronic pain

Research has shown that transcranial magnetic stimulation (TMS) results in a transient reduction in the experience of chronic pain. The present research aimed to investigate whether a single session of high frequency TMS is able to change the sensory thresholds of individuals suffering from chronic pain. Detection and pain thresholds for cold and heat sensations were measured before and after 20Hz repetitive TMS (rTMS) administered over the motor cortex. A significant decrease in temperature for cold detection and pain thresholds and a significant increase in temperature for heat pain thresholds were evident following a single session of rTMS. In contrast, no change in detection and pain thresholds was obtained following sham rTMS. The finding that rTMS can have a direct effect on sensory thresholds in individuals suffering from chronic pain has implications for the therapeutic use of rTMS in the relief of chronic pain.

The evaluation of small fiber function-autonomic and quantitative sensory testing

Disorders of the autonomic and small nerve fibers comprise a wide spectrum of disease states that cross a multitude of clinical specialties.The evaluation of these disorders allows the investigator to determine the presence or absence of abnormalities in the lightly myelinated and unmyelinated nerve fibers with minimal discomfort to the patient. The severity of dysfunction also can be determined to guide therapy and aid in prognostication for individual patients.

Technology literature review: quantitative sensory testing

The development of the personal computer has simplified the process of quantitating sensory thresholds using various testing algorithms. We reviewed the technical aspects and reproducibility of different methods to determine threshold for light touch-pressure, vibration, thermal, and pain stimuli. Clinical uses and limitations of quantitative sensory testing (QST) were also reviewed. QST is a reliable psychophysical test of large- and small-fiber sensory modalities. The results of QST are highly dependent on methodology and the full cooperation of the subject. QST has been shown to be reasonably reproducible over a period of days or weeks in normal subjects. The use of QST in research and patient care should be limited to instruments and their corresponding methodologies that have been shown to be reproducible. Literature data do not allow conclusions regarding the relative merits of individual QST instruments.

Quantitative sensory testing

Quantitative sensory testing is a reliable way of assessing large and small sensory nerve fiber function. Sensory deficits may be quantified and the data used in parametric statistical analysis in research studies and drug trials. It is an important addition to the neurophysiologic armamentarium, because conventional sensory nerve conduction tests only the large fibers. QST is a psychophysical test and lacks the objectivity of NCS. The results are subject to changes owing to distraction, boredom, mental fatigue, drowsiness, or confusion. When patients are consciously or unconsciously biased toward an abnormal QST result, no psychophysical testing can reliably distinguish these patients from those with organic disease. QST tests the integrity of the entire sensory neuraxis and is of no localizing value. Dysfunction of the peripheral nerves or central nervous system may give rise to abnormalities in QST. As is true for other neurophysiologic tests, QST results should always be interpreted in light of the patient's clinical presentation. Quantitative sensory testing has been shown to be reasonably reproducible over a period of days or weeks in normal subjects. Because longitudinal QST studies of patients in drug trials are usually performed over a period of several months to a few years, reproducibility studies on the placebo-control group should be included. For individual patients, more studies are needed to determine the maximum allowable difference between two QSTs that can be attributed to experimental error. The reproducibility of thermal thresholds may not be as good as that of vibration threshold. Different commercially available QST instruments have different specifications (thermode size, stimulus characteristics), testing protocols, algorithms, and normal values. Only QST instruments and their corresponding methodologies that have been shown to be reproducible should be used for research and patient care. The data in the literature do not allow conclusions regarding the superiority of any QST instruments. The future of QST is promising; however, many factors can affect QST results. As is true for other neurophysiologic tests, QST is susceptible to many extraneous factors and to misuse when not properly interpreted by the clinician.

Quantitative sensory testing cannot differentiate simulated sensory loss from sensory neuropathy

OBJECTIVE

To differentiate the quantitative sensory testing (QST) results of subjects simulating small and large fiber sensory loss from those of normal subjects and subjects with sensory peripheral neuropathy.

BACKGROUND

QST is used to measure sensory thresholds in clinical, epidemiologic, and research studies. It is not known whether there are objective test results that characterize the subject seeking to deceive the examiner.

METHODS

The Computer Aided Sensory Examination IV 4, 2, and 1 stepping algorithm was used to determine vibration and cold perception in nine naïve subjects. Subjects were asked to simulate sensory loss (on two occasions) and to respond normally on one occasion. Test results were compared to those of subjects with diabetic sensory neuropathy. Each QST trial was performed three times.

RESULTS

Reproducibility, measured by the intraclass correlation coefficient, was similar in all groups for the vibration perception test (simulation 1: 0.68 [95% CI 0.31, 0.91], simulation 2: 0.82 [95% CI 0.54, 0.95], normal response: 0.77 [95% CI 0.47, 0.94], and subjects with peripheral neuropathy: 0.76 [95% CI 0.18, 0.95]) and the cold perception test (simulation 1: 0.53 [95% CI 0.12, 0.85], simulation 2: 0.82 [95% CI 0.55, 0.95], normal subjects: 0.67 [95% CI 0.30, 0.90] and subjects with peripheral neuropathy: 0.88 [95% CI 0.57, 0.97]), all just noticeable difference units. There were no differences between performance characteristics in the two simulation trials. Responses to null stimuli did not differentiate between groups.

CONCLUSION

Test performance characteristics do not permit discrimination among subjects simulating sensory loss, subjects with normal responses, and subjects with peripheral neuropathy.

Clinical trials for drugs against diabetic neuropathy: can we combine scientific needs with clinical practicalities?

Diabetic neuropathy is a chronic progressive disease accounting for considerable morbidity and reduced quality of life among patients with diabetes. Accumulating evidence suggests that the clinical and neurophysiological markers used to assess neuropathy not only predict the development of neuropathic foot ulceration, one of the most common causes for hospital admission and lower limb amputations, but are also predictors of increased mortality in diabetic patients. In addition to metabolic control, drug treatment of both incipient and clinically manifest diabetic neuropathy will be necessary for the years to come. Because 1-2% of the whole population in western societies may be affected, the search for effective drug treatment is not only a very important goal for the patient suffering from diabetic neuropathy and for the practicing physician, but also an economic task for both the health care systems and pharmaceutical companies. The validity of inferences about the clinical consequences of the use of any given agent to induce a specific pharmacologic effect will depend not only on the extent to which it affects the targeted biological phenomenon, but also on the extent to which all of the actions of the agent have been defined and the extent to which all affect the entire organism, alone and in concert. The ultimate test of the usefulness of a drug or device depends on the determination of outcomes, ideally in randomized clinical trials (RCTs) of sufficient scope and duration. The efficacy and safety of a variety of drugs based on the different pathogenetic hypotheses proposed have been evaluated in RCTs since the 1970s. However, the quality of RCTs published between 1981 and 1992 that evaluated the effects of medical treatment in diabetic polneuropathy was poor. Adequate designs for RCTs in diabetic neuropathy must consider the following criteria: type and stage of neuropathy, homogeneity of the study population, outcome measures (neurophysiological markers, intermediate clinical end points, ultimate clinical outcomes, quality of life), natural history, sample size, study duration, reproducibility of neurophysiological and intermediate end points, nonspecific effects of treatment, measures of treatment effect, the extent to which the overall trail result applies to individual patients (external validity), and the reporting of the RCTs. Trials focusing preferentially on patients with mild or moderate early stages of neuropathy over long periods of 3-5 years aimed at slowing or prevention, rather than reversal, using end point measures that have clinical and prognostic significance are most likely to produce meaningful results.

Measurement of somatic neuropathy for clinical practice and clinical trials

Distal sensory polyneuropathy is a common and unpleasant complication of diabetes mellitus. It is the main initiating factor for foot ulceration. The increasing prevalence of diabetes has important associated health implications, both in terms of morbidity and mortality, and results in the consumption of scarce medical resources. Identification of somatic neuropathy in clinical practice is therefore important for targeted educational and other interventions. In this article, we describe methods for detecting somatic neuropathy in clinical practice and highlight those tests that are proven to be predictors of foot ulceration. The approach for detecting and characterizing somatic neuropathy for clinical trials, however, differs significantly. These methods must ideally have high levels of reproducibility, sensitivity, and specificity. Currently, several neurophysiologic tests are employed in clinical trials in order to accurately characterize diabetic neuropathy. The recent introduction of the computer-assisted programs for the measurement of sensory modalities for clinical trials has been a major advance. Due to their invasive nature and associated morbidity, nerve biopsy studies are no longer used in clinical trials. Recently, using magnetic resonance imaging (MRI), significant spinal cord atrophy has been demonstrated in established neuropathy. If this observation proves to be an early feature, then a relatively rapid, noninvasive MRI technique may be used in the future to characterize diabetic neuropathy.

Degeneration of nociceptive nerve terminals in human peripheral neuropathy

Patients with peripheral neuropathy have symptoms involving small-diameter nociceptive nerves and elevated thermal thresholds. Nociceptive nerves terminate in the epidermis of the skin and are readily demonstrated with the neuronal marker, protein gene product 9.5 (PGP 9.5). To investigate the pathological characteristics of elevated thermal thresholds, we performed PGP 9.5 immunocytochemistry on 3 mm punch skin biopsies (the forearm and the leg) from 55 normal subjects and 35 neuropathic patients. Skin innervation was evaluated by quantifying epidermal nerve densities. Epidermal nerve densities were reduced in neuropathic patients compared to normal subjects. Epidermal nerve densities were variably correlated with thermal thresholds. The proportion of neuropathic patients with reduced epidermal nerve densities was larger than the proportion of neuropathic patients with elevated thermal thresholds. These results indicated that degeneration of epidermal nerve terminals preceded the elevation of thermal thresholds. Skin biopsy together with immunocytochemical demonstration of epidermal innervation offers a new approach to evaluate small-fiber sensory neuropathy.

Thermal thresholds in complex regional pain syndrome type I: sensitivity and repeatability of the methods of limits and levels

OBJECTIVES

To study whether the method of levels (MLE) or the method of limits (MLI) is preferable as a method of measuring thermal perception thresholds in patients with complex regional pain syndrome type I (CRPS I).

METHODS

Perception thresholds for warmth and cold were measured twice, with both MLE and MLI, at a 1 month interval, both at unaffected and affected wrists (n=33) or feet (n=20) of patients with CRPS I of one extremity.

RESULTS

(1) Sensitivity for pathology was equal for both methods. (2) The agreement between thresholds measured by both methods was low at all locations, except for the unaffected wrist. Since thresholds measured with the MLI always contain reaction time artefacts, this lack of agreement favours the MLE. (3) At both unaffected and affected wrists, the MLE showed significantly better coefficients of repeatability as compared to the MLI for both sensations. However, at both unaffected and affected feet, there was no preference for either method as far as threshold measurement repeatability was concerned.

CONCLUSIONS

Abnormal thermal perception thresholds occurred in 20% (foot) to 36% (wrist) of the CRPS I patients on the affected side and in 15% (foot, wrist) on the unaffected side. The MLE is considered to be the preferable method to assess thermal perception thresholds in CRPS I.

Antiretroviral therapy may improve sensory function in HIV-infected patients: a pilot study

OBJECTIVE

To evaluate thermal and nociceptive function in a prospective, longitudinal study of 49 consecutive HIV-1-infected patients before and at 1, 4, and 8 months after initiation of highly active antiretroviral therapy.

METHODS

Quantitative assessments of thermal perception thresholds for warmth (dWT), cold (dCT), and heat pain (HPT) were performed. CD4+ cell levels in blood and HIV-1 RNA levels in plasma were determined. Depending on the virologic response to treatment, the patients were divided into two groups: responders (37 of 49, 76%) and nonresponders (12 of 49, 24%).

RESULTS

Before treatment, impairment of dWT was found in 26 of 49 patients, of dCT in 33 of 49 patients, and of HPT in 19 of 49 patients. Improvements of perception thresholds for dWT (p < 0.0001), dCT (p < 0.001), and HPT (p < 0.01) were observed after 8 months of treatment in the responder group but not in the nonresponders. Within the responder group, improved thermal perception thresholds was associated with higher pretreatment CD4+ levels than in patients without improvement.

CONCLUSIONS

Virologically successful antiretroviral combination therapy of HIV-1-infected patients has a capacity to improve function of the thermal and nociceptive systems, especially in patients with less advanced immunodeficiency.

Abnormal movements in complex regional pain syndrome: assessment of their nature

Abnormal movements may be a clinical feature in complex regional pain syndrome (CRPS), but their basic nature is unclear. Between August 1989 and September 1998, patients fulfilling diagnostic criteria for CRPS (I or II) and displaying abnormal movements were entered into a prospective study. Fifty-eight patients, 39 women and 19 men, met entry criteria; 47 had sustained a minor physical injury at work. The patients exhibited various combinations of dystonic spasms, coarse postural or action tremor, irregular jerks, and, in one case, choreiform movements. Patients underwent rigorous clinical and laboratory evaluation aimed at characterizing their neurological disturbance. Surprisingly, no case of CRPS II but only cases of CRPS type I displayed abnormal movements. In addition to an absence of evidence of structural nerve, spinal cord, or intracranial damage, all CRPS I patients with abnormal movements typically exhibited pseudoneurological (nonorganic) signs. In some cases, malingering was documented by secret surveillance. This study highlights abnormal movements in CRPS as constituting a key clinical feature that differentiates CRPS I from CRPS II. They are consistently of somatoform or malingered origin, signaling an underlying psychoneurological disorder responsible for the entire CRPS profile.

Quantitative sensory testing: effect of site and skin temperature on thermal thresholds

OBJECTIVE

To determine the effect of different sites and local skin temperature on thermal thresholds.

METHODS

Cool and warm detection and cold and heat pain thresholds were compared in 46 normal volunteers at the thenar eminence (TE), dorsum of the hand (DH), volar surface of the wrist (VW) and dorsum of the foot (DF).

RESULTS

The hand is more sensitive than the foot for cool and warm. TE is more sensitive for warm than DH and VW but the difference is clinically negligible. DH and VW are equally sensitive to warm. TE, DH, and VW are equally sensitive to cool. Inter-individual variance is smallest at TE. Warm and cool thresholds are independent of local skin temperature (range of 27-37 degrees C). TE is less sensitive for cold pain but otherwise the hand and the foot are equally sensitive to thermal pain.

CONCLUSION

Testing of thermal thresholds in normal subjects can be adequately conducted at several sites at the hand, however, TE is preferred given the small inter-individual variability. TE may be preferred for evaluating hyperalgesia to cold given its higher threshold. Warming or cooling of the skin is unnecessary within the range normally encountered in routine clinical evaluation.

Chronic pain disability exaggeration/malingering and submaximal effort research

OBJECTIVE

This is the first review of chronic pain (CP) malingering/disease simulation research. The purpose of this review was to determine the prevalence of malingering within CP patients (CPPs), whether evidence exists that malingering can be detected within CPPs, and to suggest some avenues of research for this topic.

DESIGN

A computer and manual literature search produced 328 references related to malingering, disease simulation, dissimulation, symptom magnification syndrome, and submaximal effort. Of these, 68 related to one of these topics and to pain. The references were reviewed in detail, sorted into 12 topic areas, and placed into tabular form. These 12 topic areas addressed the following: existence of malingering within the CP setting; dissimulation, identification simulated (faked) facial expressions of pain; identification of malingering by questionnaire; identification of malingered sensory impairment; identification of malingered loss of hand grip strength; identification of submaximal effort by isometric strength testing; identification of submaximal or malingered effort by isokinetic strength testing; identification of submaximal or malingered effort by the method of coefficient of variation; self-deception; symptom magnification syndrome; and miscellaneous malingering identification studies. Each report, in each topic area, was rated for scientific quality according to guidelines developed by the Agency for Health Care, Policy and Research (AHCPR) for rating the level of evidence presented in the reviewed study. The AHCPR guidelines were then used to rate the strength and consistency of the research evidence in each topic area based on the type of evidence the reports represented. All review conclusions were based on the results of these ratings.

SETTING

Any medical setting reporting on either malingering or disease simulation, or dissimulation, or submaximal effort and pain.

PATIENTS

Normal volunteers, CPPs, or any group asked to produce a submaximal or malingered effort or a malingered test profile.

RESULTS

The reviewed studies indicated that malingering and dissimulation do occur within the CP setting. Malingering may be present in 1.25-10.4% of CPPs. However, because of poor study quality, these prevalence percentages are not reliable. The study evidence also indicated that malingering cannot be reliably identified by facial expression testing, questionnaire, sensory testing, or clinical examination. There was no acceptable scientific information on symptom magnification syndrome. Hand grip testing using the Jamar dynamometer and other types of isometric strength testing did not reliably discriminate between a submaximal/malingering effort and a maximal/best effort. However, isokinetic strength testing appeared to have potential for discriminating between maximal and submaximal effort and between best and malingered efforts. Repetitive testing with the coefficient of variation was not a reliable method for discriminating a real/best effort from a malingered effort.

CONCLUSIONS

Current data on the prevalence of malingering within CPPs is not consistent, and no conclusions can be drawn from these data. As yet, there is no reliable method for detecting malingering within CPPs, although isokinetic testing shows promise. Claims by professionals that such a determination can be made should be viewed with caution.

Quantitative thermal perception testing in adults

In 225 adults aged 18 to 80 years, normative warm and cold perception thresholds were assessed at the volar distal forearm, thenar eminence, lower medial calf, and lateral dorsal foot using the method of limits and a Thermotest (Somedic, Stockholm, Sweden). A 1.5-cm x 2.5-cm thermode, a 1 degrees C/s stimulus change rate, and a 32 degrees C baseline temperature were applied. Thresholds of five consecutive stimuli were averaged. At the thenar eminence a 3 degrees C/s stimulation was applied in addition to the 1 degree C/s stimulation. Effects of spatial summation were studied at the calf and forearm by additional testing with a 2.5-cm x 5.0-cm thermode. To evaluate the influence of skin temperature, thresholds were correlated with the pretest skin temperature at the tested sites. Reproducibility of stimulus perception was determined by comparing the lowest to the highest response to five consecutive stimuli. Results showed sufficient accuracy of thermal perception thresholds. Thresholds were higher with the 3 degrees C/s stimulation than with the 1 degree C/s stimulation. Thresholds were lower with the large than with the small probe. Skin temperature had only minimal influence on thresholds. The use of a 32 degrees C baseline temperature and a 1 degree C/s stimulus change rate is recommended. The large probe should be used at body sites where the entire thermode surface adjusts planely to the skin. Warming up the tested skin area is not necessary before thermotesting.

Prevalence of malingering in inpatient suicide ideators and attempters

The purpose of the present study was to ascertain the prevalence of malingering by inpatients admitted to an urban hospital for suicidal ideation or attempt. Fifty-eight consecutively hospitalized suicidal patients were asked to participate, and of these 40 (70%) agreed to do so. Each patient was given an anonymous questionnaire asking whether they had lied or purposely exaggerated suicidal ideation to gain admission. A psychiatrist and masters-level psychologist, both blind to the patient responses, then rated each patient for suspicion of malingering. Each patient was also administered the MMPI-2 F, L, and K validity scales. Four patients (10%) indicated they had malingered and indicated that external incentives had motivated them to feign either suicidal ideation or a suicide attempt. None of the MMPI-2 validity scales correlated with self-reported malingering. The clinicians detected malingerers with 100% sensitivity, but the specificity rates were only 58% for the psychiatrist and 32% for the psychologist. The results indicate that some inpatients malinger about the extent of their suicidal intentions. The data demonstrate the difficulty inherent in detecting malingering by clinical interviewing and psychological testing.

Painful neuropathies

Pain following peripheral nerve lesion appears to be a paradox because damage of primary afferent nerve fibres carrying nociceptive information should result in hypoalgesia. The very existence of neuropathic pain therefore implies fundamental changes of nociceptive processing and there have been considerable advances in the understanding of factors that precipitate neuropathic pain. This knowledge has already been harnessed for the development of novel analgesic therapies to supplement traditional treatment with anticonvulsant and antidepressants drugs which has shown clear effectiveness in systematic reviews of randomised controlled trials.

Clinical applications of quantitative sensory testing (QST)

Quantitative sensory testing (QST) has been used clinically for the last two decades, yielding a substantial number of publications regarding these applications. In this review we tried to amass together the major findings of these publications into one monograph, excluding those dealing with pain. This was done with the aim of assisting clinicians in the better use of QST techniques for the benefit of their patients.

Quantitative sensory testing

Quantitative sensory testing has become commonplace in clinical neurophysiology units. Measurement of the thermal and vibratory senses provides an estimate on function of sensory small and large fibers, respectively. Being psychophysical parameters, sensory threshold values are not objective, and various test algorithms have been developed aiming at optimized results. In this review the various test algorithms are screened, and their relative advantages and disadvantages are discussed. Considerations of quality control are reviewed, and the main fields of clinical application are described.