Pressure pain thresholds asymmetry in left- and right-handers: Associations with behavioural measures of cerebral laterality

The active von Frey filament test: A new technique to evaluate hand tactile sensation in continuous variable units

The von Frey filament test (vF) is a mainstay of clinical examination. However, its results can be affected by touch speed and other potentially confounding factors. Moreover, the differences between two adjacent filament levels are too large to detect subtle changes. Active vF (AvF) was developed to induce in-depth sensory change. The present study hypothesized that AvF produces different patterns of fingertip sensation; consequently, it could be used as a new assessment tool for neural impairment. The aim of the study was to provide preliminary normative comparative vF and AvF data. This study prospectively examined 32 healthy participants, using AvF and vF. The index and the fifth finger volar pad were examined using AvF and vF, without visual stimulation. The correlation between AvF and vF measurements was evaluated. In addition, differences according to innervation zone, right versus left hand, and gender, and the correlation between AvF values and subjects' age were analyzed. Mean AvF value was significantly higher and had greater variance than vF (111.3 ± 46.9 vs. 24.1 ± 9.8; P <  0.01). The Spearman correlation coefficient between AvF and vF was 0.341. Values were similar in the index and fifth fingers and right and left hands. However, values were significantly different between women and men. The correlation between age and AvF values was 0.259. AvF provided more precise values, with continuous units for tactile sensation, excluding tester-dependent factors. Furthermore, AvF and vF values may not be correlated.

A modality selective effect of functional laterality in pain detection sensitivity

The ability to detect environmental changes is essential to determine the appropriate reaction when facing potential threats. Both detection and reaction functions are critical to survival, and the superior performance of motor reaction for the dominant hand is well recognized in humans. However, it is not clear whether there exists laterality in sensitivity to detect external changes and whether the possible laterality is associated with sensory modality and stimulus intensity. Here, we tested whether the perceptual sensitivity and electrophysiological responses elicited by graded sensory stimuli (i.e., nociceptive somatosensory, non-nociceptive somatosensory, auditory, and visual) that were delivered on/near the left and right hands would be different for right-handed individuals. We observed that perceived intensities and most brain responses were significantly larger when nociceptive stimuli were delivered to the left side (i.e., the non-dominant hand) than to the right side (i.e., the dominant hand). No significant difference was observed between the two sides for other modalities. The higher sensitivity to detect nociceptive stimuli for the non-dominant hand would be important to provide a prompt reaction to noxious events, thus compensating for its worse motor performance. This laterality phenomenon should be considered when designing experiments for pain laboratory studies and evaluating regional sensory abnormalities for pain patients.

The relationship of cortical activity induced by pain stimulation with clinical and cognitive features of somatic symptom disorder: A controlled functional near infrared spectroscopy study

OBJECTIVE

The neurobiological correlates of Somatic Symptom Disorder (SSD) introduced in the DSM-5 has been the focus of a limited investigation. We aimed to examine the cortical response to painful stimuli and its relationship to symptom severity as well as cognitive and psychological characteristics in proposed models of somatoform disorders.

METHODS

We measured hemodynamic responses by 52-channel functional near-infrared spectroscopy. We compared the cortical response to painful stimuli in index patients with SSD (N = 21) versus age, and gender matched healthy control subjects (N = 21). We used brush stimulation as the control condition. We analyzed the relationship of cortical activity with SSD symptom severity as well as somatosensory amplification (SSA), alexithymia, dysfunctional illness behaviour, worry, and neuroticism.

RESULTS

Patients with SSD had higher somatic symptom severity, SSA, alexithymia, neuroticism, illness-related worry, and behaviour. Somatic symptom severity was predicted by a model including SSA and subjective feeling of pain in the index patients. Activity in the left-angular and right-middle temporal gyri was higher in the SSD subjects than the controls during pain stimulation. Positive correlations were detected between mean pain threshold levels and left middle occipital gyrus activity, as well as between SSA-scores and right-angular gyrus activity during pain condition in the index patients with SSD.

CONCLUSION

We present the first evidence that representation of pain in terms of cortical activity is different in subjects with SSD than healthy controls. SSA has functional neuroanatomic correlates and predicts symptom severity in SSD and therefore is involved as a valid intermediate phenotype in SSD pathophysiology.

Pressure Algometry for the Detection of Mechanical Nociceptive Thresholds in Horses

Simple Summary

It is difficult to measure pain in horses. As animals are not able to verbalize what they feel, we are left with trying to interpret the different signs that they display when they are in pain. Many of these signs are vague (e.g., not eating their food), but some are more readily identified if the animal moves away or lifts their leg when pressure is applied to a sensitive area. Pressure algometry is a tool used to detect responses to applied mechanical stimuli within painful and nonpainful tissues. Pressure algometry has been used in many different studies, but there is no consensus on how to synthesize this information to better diagnose and treat pain in horses. The purpose of this study was to summarize the results of these studies. Based on that review, we conclude that there is good evidence that pressure algometry is a reliable and objective method to measure pain responses. This information will help to improve the diagnosis and treatment of pain in horses.

Abstract

The clinical assessment of pain is subjective; therefore, variations exist between practitioners in their ability to identify and localize pain. Due to differing interpretations of the signs or severity of pain equine practitioners may assign varying levels of clinical significance and treatment options. There is a critical need to develop better tools to qualify and quantify pain in horses. Palpation is the most common method to detect local tenderness or sensitivity. To quantify this applied pressure, pressure algometry has been used to gradually apply pressure over specified landmarks until an avoidance response is noted, which is defined as the mechanical nociceptive threshold (MNT). Numerous studies have used pressure algometry in different applications to measure MNTs in horses. There is an acute need to establish normative values within different body regions and to develop standardized methods of testing MNTs to better guide practitioners in the diagnosis and treatment of pain. The aim of this systematic review was to summarize the evidence for the use of pressure algometry in horses. There is good evidence that pressure algometry is a repeatable, semi-objective method that can be used in a wide array of clinical and research applications to assess MNTs in horses.

Migraine Pain Location and Measures of Healthcare Use and Distress: An Observational Study

Introduction

Lateralized pain is a core diagnostic feature of migraine. In previous research, left-sided spinal pain was more frequent and associated with greater emotional distress and healthcare use than right-sided pain. We hypothesized therefore that patients with left-sided head pain might experience higher levels of distress or healthcare use than those with right-sided or bilateral pain.

Methods

Medical record information was extracted for 477 randomly selected patients with migraine seen in 2011 in a tertiary headache clinic. This included demographic data, pain location, handedness, comorbid psychiatric diagnoses, medical and emergency department visits, and use of selected headache medications.

Results and Discussion

Two hundred twenty-eight of four hundred seventy-seven (47.8%) patients reported lateralized pain, of which 107 (47.9%) patients were right sided compared with 65 (28.5%) left-sided patients (p=0.001), while 56 (24.5%) reported unilateral pain with no side predominance. Contrary to expectations, with the exception of self-reported posttraumatic stress disorder, there were no statistically significant differences between left and right in measures of psychiatric distress, emergency department visits, or healthcare use.

Conclusion

Although unilateral pain location can be helpful in making a migraine diagnosis, it does not appear to have additional clinical implications. Additionally, its absence does not rule out a diagnosis of migraine since more than half of migraineurs have bilateral head pain.

Differential efficiency of transcutaneous electrical nerve stimulation in dominant versus nondominant hands in fibromyalgia: placebo-controlled functional near-infrared spectroscopy study

Using functional near-infrared spectroscopy (fNIRS), modulation of hemodynamic responses by transcutaneous electrical nerve stimulation (TENS) during delivery of nociceptive stimulation was investigated in fibromyalgia (FM) patients and healthy controls for both hands. Two experiments were conducted: (1) median nerve stimulation with TENS and (2) painful stimulation using electronic von Frey filaments with TENS/placebo TENS. Mean [Formula: see text] brain activity was compared across groups and conditions using factorial ANOVA. Dominant (right) hand stimulation indicated significant interactions between group and condition in both hemispheres. Post hoc results revealed that FM patients showed an increased activation in "pain + TENS" condition compared to the "pain + placebo TENS" condition while the brain activity patterns for these conditions in controls were reversed. Left-hand stimulation resulted in similar TENS effects (reduced activation for "pain + TENS" than "pain + placebo TENS") in both groups. TENS effects in FM patients might be manipulated by the stimulation side. While the nondominant hand was responsive to TENS treatment, the dominant hand was not. These results indicate that stimulation side might be an effective factor in FM treatment by using TENS. Future studies are needed to clarify the underlying mechanism for these findings.

Left/Right Pain Asymmetry With Injectable Cosmetic Treatments for the Face

BACKGROUND

Pain is processed and experienced differently on the left (L) and right (R) sides of the body; however, L/R pain asymmetry with cosmetic treatments of the face has not been evaluated.

OBJECTIVES

The authors compared patient ratings of L/R facial pain during and immediately after injectable cosmetic treatments.

METHODS

In this cross-sectional multicenter pragmatic study, pain levels were evaluated for 302 patients who underwent facial treatments with botulinum toxin (BTX) and/or impermanent soft-tissue filler (STF). Patients indicated pain intensity on each side of the face with a visual analogue scale (VAS; 0, no pain; 10, worst pain).

RESULTS

Combined mean VAS scores for BTX and STF treatments (L, 3.79 vs R, 3.42), and individual scores for BTX (L, 3.60 vs R, 3.30) or STF (L, 4.22 vs R, 3.69) treatments were significantly different, with pain rated as worse on the L side of the face (all P < 0.01). When treatments were performed first on the L side, patients rated the overall experience as significantly less painful than when treatments were begun on the R side. BTX treatments with a 29-gauge (G) needle were significantly more painful than with a 33-G needle.

CONCLUSIONS

To lessen pain with injectable facial treatments, the authors recommend placing the first injection on the L side of the face and, when possible, employing a high-G needle.

LEVEL OF EVIDENCE 2

A SCN10A SNP biases human pain sensitivity

Background:

Nav1.8 sodium channels, encoded by SCN10A, are preferentially expressed in nociceptive neurons and play an important role in human pain. Although rare gain-of-function variants in SCN10A have been identified in individuals with painful peripheral neuropathies, whether more common variants in SCN10A can have an effect at the channel level and at the dorsal root ganglion, neuronal level leading to a pain disorder or an altered normal pain threshold has not been determined.

Results:

Candidate single nucleotide polymorphism association approach together with experimental pain testing in human subjects was used to explore possible common SCN10A missense variants that might affect human pain sensitivity. We demonstrated an association between rs6795970 (G > A; p.Ala1073Val) and higher thresholds for mechanical pain in a discovery cohort (496 subjects) and confirmed it in a larger replication cohort (1005 female subjects). Functional assessments showed that although the minor allele shifts channel activation by −4.3 mV, a proexcitatory attribute, it accelerates inactivation, an antiexcitatory attribute, with the net effect being reduced repetitive firing of dorsal root ganglion neurons, consistent with lower mechanical pain sensitivity.

Conclusions:

At the association and mechanistic levels, the SCN10A single nucleotide polymorphism rs6795970 biases human pain sensitivity.

Fasting and acquired capability for suicide: a test of the interpersonal-psychological theory of suicide in an undergraduate sample

Though some preliminary research within the framework of the interpersonal-psychological theory of suicide (IPTS; Joiner, 2005) has postulated that restrictive eating may contribute to increased risk for suicide through its effect on the acquired capability for suicide (ACS; i.e., increased fearlessness about death and heightened physical pain tolerance), existing studies have not conducted direct tests of this relationship. To enhance understanding of this relationship, we compared undergraduates who endorsed one form of restrictive eating, fasting, (n = 99) to controls endorsing no forms of eating pathology over the lifetime (n = 94). We hypothesized that the fasting group would have higher ACS and higher likelihood of suicide attempt history. Contrary to hypotheses, no differences emerged between groups on ACS, and frequency of fasting within the fasting group was not significantly associated with ACS. Consistent with hypotheses, the fasting group was more likely to have suicide attempt history. Though results were not entirely consistent with hypotheses, the current study represents the first attempt at isolating and examining one form of restrictive eating (i.e., fasting) within the context of the IPTS. Results suggest that, in isolation, fasting may not be directly contributing to increases in ACS.

Pain and cooperation in patients having dominant-side or nondominant-side phacoemulsification

PURPOSE

To evaluate the relationship between laterality and perceived pain and cooperation during phacoemulsification under combined topical and intracameral anesthesia.

SETTING

University ophthalmology clinic and eye hospital, Kahramanmaraş, Turkey.

DESIGN

Cohort study.

METHODS

Seventy-eight patients with senile cataracts who had ocular surgery were included prospectively. The dominant side was determined with the Edinburg Handedness Inventory. Phacoemulsification and intraocular lens implantation were performed. The surgeon graded the patient's cooperation from 0 (best) to 3 (worst). The duration of surgery was recorded. Another researcher rated perceived pain from 0 (no pain) to 10 (unbearable pain) using a visual analogue scale (VAS). Pain scores and the degree of cooperation for dominant-side and nondominant-side surgery were the primary outcomes.

RESULTS

Forty-six patients had surgery in the dominant eye and 32 in the nondominant eye. The 2 groups were similar in age, sex, and severity and type of cataract. The mean VAS score was significantly higher in patients having dominant-side surgery than in those having nondominant-side surgery (P<.01). Similarly, the mean cooperation score was significantly poorer in the patients having dominant-side surgery (P<.05). Visual analogue scores were correlated with patient cooperation (r = 0.890, P<.0001).

CONCLUSION

Pain scores were higher in dominant-side surgery for cataract under topical and intracameral anesthesia, which should be kept in mind when selecting anesthesia and in studies in which pain is scored.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

The pain experience and cooperation of patients in consecutive cataract surgery

PURPOSE

The aim of this study was to investigate the pain experience and the cooperation of patients during consecutive cataract surgery.

METHODS

In this prospective, randomized study, 60 consecutive adult patients with bilateral senile cataracts were recruited. All operations were performed with clear corneal phacoemulsification (phaco) technique under topical and intracameral anesthesia without sedation. The first surgery was performed in the eye with high-grade cataract. The other eye was operated within 3 months. Every patient was graded using a visual analogue scale (VAS) from 0 (no pain) to 10 (unbearable pain) after the surgery. The cooperation of the patient was graded from 0 (no event) to 3 (marked eye and head movement and lid squeezing) by the surgeon. The VAS scores and cooperation of patients were the main outcome measurements.

RESULTS

The mean VAS score was 1.50± 0.81 in the first surgery and 2.15±0.79 in the other eye surgery (p<0.001). The patient cooperation score was 1.50±0.81 in the first surgery and 2.18±0.77 in the other eye surgery (p<0.001). The VAS and patient cooperation scores were positively correlated (r=0.633, p<0.001) in the study group. The VAS and patient cooperation scores were similar based on sex and laterality.

CONCLUSIONS

Patients who previously underwent phaco surgery in one eye experience more pain and have worse cooperation during the other eye phaco surgery.

Stoicism and Sensation Seeking: Male Vulnerabilities for the Acquired Capability for Suicide

Our aim was to investigate two personality traits (i.e., stoicism and sensation seeking) that may account for well-established gender differences in suicide, within the framework of the interpersonal theory of suicide. This theory proposes that acquired capability for suicide, a construct comprised of pain insensitivity and fearlessness about death, explains gender differences in suicide. Across two samples of undergraduates (N = 185 and N = 363), men demonstrated significantly greater levels of both facets of acquired capability than women. Further, we found that stoicism accounted for the relationship between gender and pain insensitivity, and sensation seeking accounted for the relationship between gender and fearlessness about death. Thus, personality may be one psychological mechanism accounting for gender differences in suicidal behavior.

Altered processing of pain-related information in patients with fibromyalgia

Pressure pain thresholds (PPTs) and event-related potentials (ERPs) elicited by emotional words were analyzed in 12 patients with fibromyalgia (FM) and 12 matched healthy subjects. PPTs were assessed at the middle finger of both hands, before and after the experiment. Overall, FM patients and healthy subjects did not differ in PPT. Nevertheless, FM patients as compared with healthy controls were characterized by a significant enhancement of pain sensitivity from the beginning to the end of the experiment indicating a long lasting sensitization due to repeated stimulation. ERPs were recorded during a language decision task where subjects had to react to unpleasant pain-related and emotionally neutral words depending on syntactic or orthographic cues. An emotional category effect was observed on N400 and P300 components of the ERP, indicating that unpleasant words elicited more positive amplitudes than neutral words. A significant group effect was observed on P200 amplitudes, showing reduced amplitudes in FM patients as compared to healthy controls. Furthermore, unpleasant pain-related compared to neutral words triggered significantly enhanced late positive slow waves in healthy controls, while a comparable effect was not found in FM patients. The ERP and PPT data suggest that FM patients are characterized by an altered cognitive processing of pain-related information and by an abnormal adaptation to mechanical pain stimuli, respectively.

Localization of pain-related brain activation: a meta-analysis of neuroimaging data

A meta-analysis of 140 neuroimaging studies was performed using the activation-likelihood-estimate (ALE) method to explore the location and extent of activation in the brain in response to noxious stimuli in healthy volunteers. The first analysis involved the creation of a likelihood map illustrating brain activation common across studies using noxious stimuli. The left thalamus, right anterior cingulate cortex (ACC), bilateral anterior insulae, and left dorsal posterior insula had the highest likelihood of being activated. The second analysis contrasted noxious cold with noxious heat stimulation and revealed higher likelihood of activation to noxious cold in the subgenual ACC and the amygdala. The third analysis assessed the implications of using either a warm stimulus or a resting baseline as the control condition to reveal activation attributed to noxious heat. Comparing noxious heat to warm stimulation led to peak ALE values that were restricted to cortical regions with known nociceptive input. The fourth analysis tested for a hemispheric dominance in pain processing and showed the importance of the right hemisphere, with the strongest ALE peaks and clusters found in the right insula and ACC. The fifth analysis compared noxious muscle with cutaneous stimuli and the former type was more likely to evoke activation in the posterior and anterior cingulate cortices, precuneus, dorsolateral prefrontal cortex, and cerebellum. In general, results indicate that some brain regions such as the thalamus, insula and ACC have a significant likelihood of activation regardless of the type of noxious stimuli, while other brain regions show a stimulus-specific likelihood of being activated.

Social exclusion and pain sensitivity: why exclusion sometimes hurts and sometimes numbs

Some research indicates that social exclusion leads to increased emotional- and physical-pain sensitivity, whereas other work indicates that exclusion causes emotional- and physical-pain numbing. This research sought to examine what causes these opposing outcomes. In Study 1, the paradigm used to instantiate social exclusion was found to moderate the social exclusion-physical pain relation: Future-life exclusion led to a numbing of physical pain whereas Cyberball exclusion led to hypersensitivity. Study 2 examined the underlying mechanism, which was hypothesized to be the severity of the "social injury." Participants were subjected to either the standard future-life exclusion manipulation (purported to be a highly severe social injury) or a newly created, less-severe version. Supporting our hypothesis, the standard (highly severe) future-life exclusion led to physical-pain numbing, whereas the less-severe future-life exclusion resulted in hypersensitivity. Implications of these results for understanding the exclusion-pain relation and other exclusion effects are discussed.

Effect of gender and hand laterality on pain processing in human neonates

BACKGROUND

Previous studies in adults have reported that handedness and gender can affect pain perception. However, it is currently unclear when these differences emerge in human development. Therefore, we examined prefrontal responses to pain stimulation among newborns during their first acute pain experience after birth.

METHODS

Forty newborns at 4-6 days postnatal age were observed during clinically required blood sampling while prefrontal activation was measured with near infrared spectroscopy. Blood sampling in this study was the first experience of a procedure involving skin breaking for these infants. We divided subjects into a right-hand stimulation group (n=21) and a left-hand stimulation group (n=19), depending on whether blood was sampled from the right or the left hand. A three-way analysis of variance (ANOVA) was conducted to examine the effects of several variables on the magnitude of the oxy-Hb value in response to pain stimulus, including stimulus side (right hand or left hand), gender (male or female), recording side (right prefrontal area or left prefrontal area) and interactions between these variables.

RESULTS

The data revealed a significant effect of stimulus side (F (1, 72)=9.892, P=0.002), showing that the right-hand stimulation induced a greater prefrontal activation than the left-hand stimulation. No significant gender difference or interactions were found.

CONCLUSION

Our findings suggest that hand laterality affects pain perception even in neonates. However, gender differences in pain perception did not appear to occur during the neonatal period. Further investigations using brain-imaging techniques are required to identify laterality- or gender-related differences in pain processing in humans.

Determination and use of mechanical nociceptive thresholds of the thoracic limb to assess pain associated with induced osteoarthritis of the middle carpal joint in horses

OBJECTIVES

To establish reference mechanical nociceptive threshold (MNT) values of the equine thoracic limb and to assess the use of MNT values to detect pain associated with induced osteoarthritis in the middle carpal joint.

ANIMALS

24 adult horses.

PROCEDURES

MNT values were evoked by a pressure algometer at 17 sites within each thoracic limb during 2 baseline sessions conducted an average of 5 days apart. Effects of age, sex, weight, and wither height on MNT values were assessed separately for each site. Tolerance of horses to the procedure was graded subjectively and correlated with MNT values. Synovitis and osteoarthritis were induced arthroscopically in the middle carpal joint of 1 randomly selected thoracic limb. The opposite limb served as a sham-operated control limb. Mechanical nociceptive threshold values were recorded weekly and correlated with clinical, radiographic, and necropsy scores measured over 10 weeks. Lower MNT values corresponded with increased pain, whereas higher MNT values indicated reduced pain.

RESULTS

A gradual increase in MNT values was detected from proximal-to-distal sites of the thoracic limbs. High MNT values were recorded for geldings and tall horses. In general, tolerance to procedure scores was positively correlated with overall pooled MNT values within each thoracic limb. From 2 to 6 weeks after surgery, the osteoarthritic limb had significantly reduced MNT values within the carpal region. The osteoarthritic limb also had significant changes in clinical examination, radiographic, and necropsy scores, which were poorly correlated with MNT values.

CONCLUSIONS AND CLINICAL RELEVANCE

Pressure algometry provided objective assessment of nociception of the thoracic limb; however, MNT values were poorly correlated with clinical variables used to assess osteoarthritis.

Affective pain modulation in fibromyalgia, somatoform pain disorder, back pain, and healthy controls

Previous research suggested that patients with fibromyalgia (FM) experience a higher pain intensity (clinical pain) than do patients with musculoskeletal pain after negative emotional priming compared to positive priming. To further examine affective pain modulation in FM, we applied an experimental pain induction to compare 30 patients with FM with 30 healthy (pain-free) participants (HC), and 30 patients with back pain (BP). For another group of 30 patients with somatoform pain disorder (SF), we predicted the same pain modulation as for FM. As primes we presented positive, neutral, negative, and pain-related pictures and assessed pain intensity in response to a fixed pressure weight. Overall, picture valence modulated pain intensities (in the order of pain-related > negative pictures > neutral), but the pain intensities between neutral and positive pictures did not differ significantly. SF reported significantly higher pain intensities than did BP and HC; FM were in between, but did not differ significantly from the three other groups. There was no interaction of priming and group. Affective modulation of pain was not specifically altered in FM and SF, but SF were more sensitive to pressure pain than BP and HC.

Emotion and Pain: A Functional Cerebral Systems Integration

Emotion and pain are psychological constructs that have received extensive attention in neuropsychological research. However, neuropsychological models of emotional processing have made more progress in describing how brain regions interact to process emotion. Theories of emotional processing can describe inter-hemispheric and intra-hemispheric interactions during emotional processing. Due to similarities between emotion and pain, it is thought that emotional models can be applied to pain. The following review examines the neuropsychology of emotion and pain using a functional cerebral systems approach. Specific comparisons are made between pain and anger. Attention is given to differences in cerebral function and physiology that may contribute to the processing of emotion and pain. Suggestions for future research in emotion and pain are given.

Sensory and motor effects of experimental muscle pain in patients with lateral epicondylalgia and controls with delayed onset muscle soreness

This study compares the effect of experimental muscle pain on deep tissue sensitivity and force attenuation in the wrist extensors of patients with lateral epicondylalgia (n=20), and healthy controls (n=20) with experimentally induced sensori-motor characteristics simulating lateral epicondylalgia. Delayed onset muscle soreness (DOMS) in wrist extensors of healthy controls was induced by eccentric exercise in one arm 24h prior to injection (Day 0). Saline-induced pain intensity (visual analogue scale, VAS), distribution, and quality were assessed quantitatively in both arms for both groups. Pressure pain thresholds (PPT) were assessed at three different sites in the wrist extensors. Maximal grip force and wrist extension force were recorded. In response to saline-induced pain in the extensor carpi radialis brevis, regardless of arm, the patient group demonstrated a significantly quicker pain onset (P<0.01), mapped larger pain areas and more referred pain areas, compared to healthy controls (P<0.03). Pain persisted significantly longer in the sore arm of the patient group, compared with all other arms (P<0.02). Patients demonstrated significant bilateral hyperalgesia at extensor carpi radialis brevis during and post saline-induced pain compared to pre-injection and healthy controls (P<0.04). The sore arm in patients and the DOMS arms in healthy subjects showed significantly reduced maximal force (P<0.0001), at all Day 1 times compared with the control arms. In patients, the bilateral increase in deep tissue sensitivity and enlarged referred pain areas during saline-induced pain might suggest involvement of central sensitisation.

Comparison of pressure pain threshold, grip strength,dexterity and touch pressure of dominant and non-dominant hands within and between right-and left-handed subjects

This study was done to evaluate differences in pressure pain threshold, grip strength, manual dexterity and touch pressure threshold in the dominant and non-dominant hands of right- and left-handed subjects, and to compare findings within and between these groups. Thirty-nine right-handed and twenty-one left-handed subjects participated in the study. Pressure pain threshold was assessed using a dolorimeter, grip strength was assessed with a hand-grip dynamometer, manual dexterity was evaluated using the VALPAR Component Work Sample-4 system, and touch pressure threshold was determined using Semmes Weinstein monofilaments. Results for the dominant and non-dominant hands were compared within and between the groups. In the right-handed subjects, the dominant hand was significantly faster with the VALPAR Component Work Sample-4, showed significantly greater grip strength, and had a significantly higher pressure pain threshold than the non-dominant hand. The corresponding results for the two hands were similar in the left-handed subjects. The study revealed asymmetrical manual performance in grip strength, manual dexterity and pressure pain threshold in right-handed subjects, but no such asymmetries in left-handed subjects.

Pain thresholds as a putative functional test for cerebral laterality in major depressive disorder and panic disorder

OBJECTIVE

Both major depressive disorder (MDD) and panic disorder (PD) exhibit an illness-related functional cerebral laterality with a frontal right/left asymmetry. Using experimental pain lateralization as a putative indicator of functional cerebral laterality, we assessed body side differences in pressure, cold and heat pain thresholds in patients with MDD and PD as well as in healthy control subjects (HC). To control for an attentional bias in perception, reaction times for selective attention were also measured for both visual fields.

METHOD

21 inpatients with MDD, 21 inpatients with PD (DSM-IV diagnosis) and 20 HC subjects, all right-handed, were investigated drug free. Pain thresholds for pressure, cold and heat were assessed at the right and left forearm or hand. A neuropsychological standard test was used to measure selective attention (signal detection, Wiener Testsystem), which allows for the discrimination between left and right visual field stimulus processing.

RESULTS

In all participants, a left-sided increased pain sensitivity could be verified by using pressure pain, but not by thermal pain (cold, heat). The diagnosis of MDD or PD had no influence on pain threshold lateralization. There were no differences in reaction times of selective attention between the groups of patients and the HC. Neither did stimulus presentation in the left or right visual field affect reaction time differently.

CONCLUSION

Body side asymmetry of pain perception was only found for pressure pain targeting mainly deep tissue (muscle) nociception. This asymmetry, however, cannot be regarded as an indicator of a pathological functional cerebral laterality in MDD and PD.