Differences In Sensory Thresholds Research Articles

(260) Effects of Surface Delay Agents on Penile Sensibility in Premature Ejaculation

Abstract Introduction The penis is an important sensory organ during sexual intercourse, transforming the sensations experienced from intercourse into neural impulses and transmitting them to the central nervous system. Our previous research has found that the sensitivity of the penis varies due to histological and neuroanatomical differences between the penile shaft and glans. We have identified hypersensitivity zones within the penis, classifying them into three subtypes，namely, glans penis, penile shaft, and whole-penis hypersensitivity. However, it remains unknown whether there are differences in sensitivity after the application of surface anesthetics to these subtypes. Objective As the hypersensitivity of the penis is not uniform throughout, with specific sensitive zones, this study aims to investigate whether there are differences in sensitivity after surface delay agents are applied to the hypersensitive and hyposensitive areas. This will aid in the precise use of surface delay agents and reduce their side effects. Methods Based on the neurophysiological results, 290 patients with primary premature ejaculation were categorized into the group with single glans penis hypersensitivity, the group with single penile shaft hypersensitivity, the group with the whole penis hypersensitivity, and the group with the whole penis being hyposensitivity. Differences in sensory thresholds, latencies, and amplitudes between the hypersensitive and hyposensitive areas of the penis were compared between patients before and after the use of delaying agents on the surface of the penis. Results The surface delay agent can indiscriminately increase the sensory threshold of both the hypersensitive and hyposensitive areas of the penis (P<0.001), but it only prolongs the latency of the hypersensitive area (P<0.001), without affecting the latency of the hyposensitive area of the penis. Conclusions The effects of the surface delay agent on the hypersensitive and hyposensitive areas of the penis are different. The delay agent only extends the latency of the hypersensitive area, suggesting that there may be differences in receptors, sensory cells, and synaptic transmission of sensory nerve fibers between the hypersensitive and hyposensitive areas of the penis. Disclosure No.

The Effects of Sex, Women’s Body Composition and Monthly Cycle Phases on the Sensory Threshold of Upper Limb to Transcutaneous Electrical Nerve Stimulation in Healthy Subjects

Neuromuscular excitability plays an essential role in electrotherapy treatment. The vast majority of these treatments are procedures that change the sensitivity to sensory stimuli, especially pain, with the use of an electric current. The aim of this study was to assess changes in the sensory threshold in response to transcutaneous electrical nerve stimulation (TENS), taking into account certain personal factors, such as sex, body composition, and phases of the menstrual cycle. The study involved 205 women and 49 men aged 19–33 years. Sensory threshold was examined by TENS stimulation (a biphasic current waveform, 100 Hz and 100 µs) and body composition using a TANITA analyzer. The mean sensitivity threshold in women was lower than in men (mean ± SD, F: 8.78 ± 2.11 mA vs. M: 11.20 ± 3.29 mA, p < 0.001). There were no significant differences in sensory threshold during the different phases of a woman’s monthly cycle. The taller the woman, the higher the sensory threshold (B ± SE, 0.15 ± 0.07, p = 0.036), while those with a higher percentage of body fat and a higher total water content had a lower sensory threshold (fat: B ± SE, −0.25 ± 0.07, p < 0.001; water: B ± SE, −0.20 ± 0.07, p = 0.003). In conclusion, the sensory threshold in women was lower than in men. In women aged 19–33 years, the phases of the monthly cycle did not affect the sensory threshold; however, being taller and having less body fat and a lower water content increased the sensory threshold.

Diferenças de sexo e idade no limiar sensitivo para estimulação elétrica transcutânea

Abstract Introduction Pain is one of the main symptoms prevalent in most pathologies. Transcutaneous Electrical Nerve Stimulation (TENS) represents not only a therapeutic measure, but also a mean to quantify the neurosensory and pain perception in patients with chronic pain. Objective To evaluate the relationship between sex and age with neurosensory thresholds (sensory threshold and tolerance threshold) in the application of therapeutic current in patients with chronic pain. Methods Forty-five patients with chronic pain (30 women and 15 men) aged between 24 and 87 years were selected. Each patient answered the Individual Questionnaire, McGill Pain Questionnaire (MPQ) and Beck Depression Inventory (BDI). Subsequently, the electric current was applied, through which the sensory and pain thresholds were analyzed, as well as the perception of activation of the neurosensory pathways for each individual. Data were analyzed using the SPSS 24.0 for Windows. Results There was no significant correlation (p > 0.05) between a possible depressive diagnosis and the perception of current by the sensory and pain thresholds. Regarding sex, there was a significant difference in sensory thresholds (p = 0.003) between men and women, while no statistical differences were observed between sexes for pain complaint and pain threshold (p > 0.05). For the correlational analysis, a significant correlation (p = 0.05) was identified between the variables BMI and pain tolerance threshold (r = 0.68) for females and age and sensory threshold (r = 0.65) for males. Conclusion The sex and age variables are important in the measurement of TENS parameters because they lead to significant differences in sensory and pain thresholds.

Sex and age differences in sensory threshold for transcutaneous electrical stimulation

Resumo Introdução A dor é um dos principais sintomas preva-lentes na maioria das patologias. A estimulação elétrica ervosa transcutânea (TENS) se apresenta não apenas como medida terapêutica, como também um meio de quantificar a percepção neurossensitiva e dolorosa em pacientes com dores crônicas. Objetivo Avaliar a relação entre sexo e idade com os limiares neurossensitivos (limiar sensitivo e limiar de tolerância) na aplicação da corrente terapêutica TENS, em pacientes com dores crônicas. Métodos Foram selecionados 45 pacientes com dores crônicas (30 mulheres), com idade entre 24 e 87 anos. Cada paciente respondeu ao Questionário Individual, ao Questionário McGill de Dor (MPQ) e ao Inventário de Depressão de Beck (BDI). Posteriormente, aplicou-se a corrente elétrica TENS, pela qual foram analisados o limiar sensitivo e doloroso, bem como a percepção de acionamento das vias neurossensitivas para cada indivíduo. Os dados foram analisados pelo pacote SPSS 24.0 for Windows. Resultados Não houve correlação significativa (p > 0,05) entre possível diagnós-tico depressivo e a percepção da corrente pelos limiares de sensibilidade e dor. Em relação ao sexo, houve diferença significativa nos limiares sensitivos (p = 0,003) entre homens e mulheres. Já para a queixa de dor e limiar de dor, não foram observadas diferenças estatísticas entre os sexos (p > 0,05). Para as análises correlacionais, identificou-se correlação significativa (p = 0,05) entre as variáveis de índice de massa corporal e limiar de tolerância à dor (r = 0,68) para o sexo feminino e idade e limiar sensitivo (r = 0,65) paro o sexo masculino. Conclusão As diferenças identificadas entre os limiares de sensibilidade entre os sexos, onde as mulheres identificaram o estímulo elétrico significativamente primeiro que os homens, podem auxiliar nas doses de intensidade ou tipo de corrente terapêutica dos pacientes.

An Observational Study Comparing Fibromyalgia and Chronic Low Back Pain in Somatosensory Sensitivity, Motor Function and Balance.

Fibromyalgia (FM) and chronic low back pain (CLBP) have shared pathophysiology and have a considerable impact on patients’ daily activities and quality of life. The main objective of this study was to compare pain impact, somatosensory sensitivity, motor functionality, and balance among 60 patients with FM, 60 patients with CLBP, and 60 pain-free controls aged between 30 and 65 years. It is essential to know the possible differences existing in symptomatology of two of the major chronic pain processes that most affect the population, such as FM and CLBP. The fact of establishing possible differences in sensory thresholds, motor function, and proprioceptive measures among patients with FM and CLBP could bring us closer to a greater knowledge of the chronic pain process. Through an observational study, a comparison was made between the three groups (FM, CLBP, and pain-free controls) evaluating functional performance, postural balance, kinematic gait parameters, strength, depression, fatigue, and sensitivity to pain and vibration. Patients with chronic pain showed worse somatosensory sensitivity (p < 0.001) and motor function (p < 0.001) than pain-free controls. Moreover, patients with FM showed greater pain impact (p < 0.001) and bigger somatosensory (p < 0.001) and motor deficiencies (p < 0.001) than patients with CLBP. Further research should explore the possible reasons for the greater deterioration in patients with FM in comparison with other chronic pain conditions. Our results, showing the multiple areas susceptible of deterioration, make it necessary to adopt interdisciplinary interventions focused both on physical and emotional dysfunction.

Assessment of Gastric Sensitivity and Symptom Patterns in Patients With Functional Dyspepsia With or Without Bile Gastropathy

Introduction: The pathophysiology of patients with functional dyspepsia remains unclear. Our aim was to evaluate the effects of bile gastropathy on gastric sensation in dyspeptic patients compared with those without bile gastropathy and healthy controls. Methods: Patients presenting with symptoms (>1 year) of functional dyspepsia (Rome III) completed an abdominal symptom assessment on a 0-3 point Likert scale assessing the intensity, duration and frequency prior to gastric barostat study. A 3-sensor manometry probe with compliant balloon was placed through the mouth into the stomach. Stepwise graded balloon distensions were performed in 3-mmHg increments until maximum tolerable pressure or 24 mmHg was reached. Gastric sensory responses were evaluated in fasting and post-prandial states after infusion of a liquid meal. Gastric sensory responses were compared with healthy controls. All subjects underwent endoscopies with biopsies for bile gastropathy. Results: Based on endoscopy and biopsies, patients were categorized as bile gastropathy (BG; n=15; f=13; age=37.5yrs) or no bile gastropathy (NBG; n= 15; f=10; age=36.7). Control data was obtained from 12 asymptomatic controls (n=12; f=6; age=32.3yrs). Mean symptoms scores of belching (4.1 vs 2.9), indigestion (7.1 vs 5.1) and gas (5.4 vs 3.9) were not significantly different in BG and NBG groups. In pre-prandial states, both BG (2.79 mmHg, 5.67 mmHg, 7.77 mmHg; all p<0.05) and NBG groups (3.27mmHg, 7.00 mmHg, 10.7 mmHg; all p<0.05) demonstrated lower thresholds for first sensation, moderate sensation, and discomfort compared to healthy controls (9.5 mmHg, 15.5mmHg, 18.5mmHg), respectively, as shown in Table 1. In post-prandial states, both BG (1.50 mmHg, 4.00 mmHg, 5.79 mmHg; p<0.05) and NBG groups (1.67mmHg, 3.20 mm Hg, 6.13 mmHg, all p<0.05) demonstrated lower thresholds for first sensation, moderate sensation, and discomfort compared to healthy controls (9.75 mmHg, 16.25mmHg, 20.25mmHg). While most sensory thresholds in the BG group were lower in pre or post-prandial states compared to NBG, these differences were not significant (p=NS). Conclusion: Functional dyspepsia is associated with significant gastric visceral hypersensitivity in both the fasting and post-prandial state when compared to healthy subjects. However, our study did not reveal significant differences in sensory thresholds amongst dyspeptic patients with or without bile gastropathy.433 Figure 1. Mean pressure thresholds (mmHg) for first, moderate and discomfort sensations in patients with bile gastritis (BG), no bile gastritis (NBG), and controls, *indicates significant difference (p<0.05) in sensory thresholds between respective groups and controls.

A low dose of three local anesthetic solutions for interscalene blockade tested by thermal quantitative sensory testing: a randomized controlled trial.

This randomized double-blind controlled trial compared the block characteristics of three low-dose local anesthetics at different roots in an ultrasound-guided interscalene block, using thermal quantitative sensory testing for assessing the functioning of cutaneous small nerve fibres. A total of 37 adults scheduled to undergo shoulder arthroscopy were randomized to receive 5mL of either 0.5% levobupivacaine with and without epinephrine 1/200,000 or 0.75% ropivacaine in a single-shot interscalene block. Thermal quantitative sensory testing was performed in the C4, C5, C6 and C7 dermatomes. Detection thresholds for cold/warm sensation and cold/heat pain were measured before and at 30min, 6, 10 and 24h after infiltration around C5. The need for rescue medication was recorded. No significant differences between groups were found for any sensation (lowest P = 0.28). At 6h, the largest differences in sensory thresholds were observed for the C5 dermatome. The increase in thresholds were less in C4 and C6 and minimal in C7 for all sensations. The analgesic effect lasted the longest in C5 (time × location mixed model P < 0.001 for all sensory tests). The time to rescue analgesia was significantly shorter with 0.75% ropivacaine (P = 0.02). The quantitative sensory findings showed no difference in intensity between the local anesthetics tested. A decrease in block intensity, with minimal changes in pain detection thresholds, was observed in the roots adjacent to C5, with the lowest block intensity in C7. A clinically relevant shorter duration was found with 0.75% ropivacaine compared to the other groups. Trial registration NCT 02691442.

Fear extinction learning ability predicts neuropathic pain behaviors and amygdala activity in male rats.

BackgroundThe amygdala plays a key role in fear learning and extinction and has emerged as an important node of emotional-affective aspects of pain and pain modulation. Impaired fear extinction learning, which involves prefrontal cortical control of amygdala processing, has been linked to neuropsychiatric disorders. Here, we tested the hypothesis that fear extinction learning ability can predict the magnitude of neuropathic pain.ResultsWe correlated fear extinction learning in naive adult male rats with sensory and affective behavioral outcome measures (mechanical thresholds, vocalizations, and anxiety- and depression-like behaviors) before and after the induction of the spinal nerve ligation model of neuropathic pain compared to sham controls. Auditory fear conditioning, extinction learning, and extinction retention tests were conducted after baseline testing. All rats showed increased freezing responses after fear conditioning. During extinction training, the majority (75%) of rats showed a decline in freezing level to 50% in 5 min (fear extinction+), whereas 25% of the rats maintained a high freezing level (>50%, fear extinction−). Fear extinction− rats showed decreased open-arm preference in the elevated plus maze, reflecting anxiety-like behavior, but there were no significant differences in sensory thresholds, vocalizations, or depression-like behavior (forced swim test) between fear extinction+ and fear extinction− types. In the neuropathic pain model (four weeks after spinal nerve ligation), fear extinction− rats showed a greater increase in vocalizations and anxiety-like behavior than fear extinction+ rats. Fear extinction− rats, but not fear extinction+ rats, also developed depression-like behavior. Extracellular single unit recordings of amygdala (central nucleus) neurons in behaviorally tested rats (anesthetized with isoflurane) found greater increases in background activity, bursting, and evoked activity in fear extinction− rats than fear extinction+ rats in the spinal nerve ligation model compared to sham controls.ConclusionThe data may suggest that fear extinction learning ability predicts the magnitude of neuropathic pain-related affective rather than sensory behaviors, which correlates with differences in amygdala activity changes.

Treatment of Allodynia by Occipital Nerve Stimulation in Chronic Migraine Rodent

Occipital nerve stimulation (ONS) is a therapy that benefits one-third of medically refractory chronic migraine (CM) patients. How ONS affects sensory thresholds and whether modulation of thresholds could predict which patients respond to the therapy remains unclear. To examine the effects of ONS on mechanical and thermal thresholds in a rodent CM model to better elucidate its mechanism of action. Male Sprague-Dawley rats were implanted bilaterally with electrodes to produce ONS. The CM cohort was infused with inflammatory media epidurally based on a validated model, whereas shams were not. Thresholds were evaluated with von Frey filaments and hot plate and thermode tests. No baseline differences in sensory thresholds were found between the sham (n = 16) and CM (n = 16) groups. After headache induction, CM animals demonstrated mechanical allodynia in the occiput, periorbital region, forepaws, and hind paws (P < .05). In CM animals, ONS increased mechanical thresholds in all regions (P < .001), whereas in shams, it did not. ONS did not affect thermal thresholds in either group. We show that ONS improves mechanical thresholds in a rodent CM model, but not in shams. Our finding that mechanical but not thermal thresholds are altered with ONS suggests a more significant modulation of A-α/β fibers than of C fibers. Assessing the ability of ONS to reduce mechanical thresholds during a trial period could potentially be used to predict which patients respond.

The effects of electroacupuncture on analgesia and peripheral sensory thresholds in patients with burn scar pain

The aim of this study is to observe if the effects of electro-acupuncture (EA) on analgesia and peripheral sensory thresholds are transposable from the model of heat pain in volunteers to the clinical setting of burn scar pain.After severe burns, pathological burn scars (PPBS) may occur with excruciating pain that respond poorly to treatment and prevent patients from wearing their pressure garments, thereby leading to unesthetic and function-limiting scars. EA might be of greater benefit in terms of analgesia and functional recovery, should it interrupt this vicious circle by counteracting the peripheral hyperalgesia characterizing PPBS.Therefore we enrolled 32 patients (22 males/10 females) aged of 46±11 years with clinical signs of PPBS and of neuropathic pain despite treatment. The study protocol consisted in 3 weekly 30-min sessions of standardized EA with extra individual needles in accordance to Traditional Chinese Medicine, in addition of previous treatments. We assessed VAS for pain and quantitative sensory testing (QST) twice: one week before and one after protocol. QST measured electrical thresholds for non-nociceptive A-beta fibers, nociceptive A-delta and C fibers in 2 dermatomes, respectively from the PPBS and from the contralateral pain-free areas. Based on heat pain studies, EA consisted in sessions at the extremity points of the main meridian flowing through PPBS (0.300s, 5Hz, sub noxious intensity, 15min) and at the bilateral paravertebral points corresponding to the same metameric level, 15min. VAS reduction of 3 points or below 3 on a 10 points scale was considered clinically relevant. Paired t-test compared thresholds (mean [SD]) and Wilcoxon test compared VAS (median [IQR]) pre and after treatment, significant p<0.05.The reduction of VAS for pain reached statistical but not clinical relevance (6.8 [3] vs. 4.5 [3.6]). This was due to a large subgroup of 14 non-responders whose VAS did not change after treatment (6.6 [2.7] vs. 7.2 [3.8]). That subgroup exhibited significant differences in sensory thresholds when compared to the 18 responders (VAS from 7 [3] to 3 [1]).First, responders’ thresholds for A-delta and C fibers in the PPBS area were significantly lower than those in the pain-free area before treatment but corrected after acupuncture (from respectively 60 [30] and 63 [10]% to 91 [11] and 106 [36]%). That might account for a nociceptive hypersensitivity in the PPBS that corrected after treatment. On the contrary, in non-responders nociceptive thresholds were similar in both the PPBS and the pain-free areas before treatment and did not change after EA. However, absolute values for thresholds in the pain-free areas where significantly lower for non-responders than for responders. The fact that non-responders had significant pain scores while presenting with lowered nociceptive thresholds even in the pain-free areas might evoke the possibility of a generalized supra-spinal hyperalgesia. The fact that acupuncture did not correct the pain nor the nociceptive thresholds in this subgroup requires further investigation.We also observed a statistically and clinically relevant reduction in VAS for pruritus for all patients – even those from the subgroup of non-responders to pain – that is worth to be mentioned and requires further studies to be confirmed.This observational study is the first that confirms the effects of acupuncture on analgesia and nociceptive thresholds in the clinical setting of burn pain only for patients presenting with a burn-localized but not a generalized hyperalgesia.

Epicritic Sensation in Cervical Spinal Cord Injury: Diagnostic Gains Beyond Testing Light Touch

Abstract Applied as a bedside test of gross dorsal column function, the testing of light touch (LT) sensation is of high clinical value in the diagnosis of human spinal cord injury (SCI). However, the assessment of overall dorsal column deficit by testing only LT may be limited, because the dorsal column pathway conveys several large diameter afferent modalities (e.g., sensation of touch, two-point discrimination, and proprioception). Therefore, the objective of this study was to compare the epicritic sensation assessed by LT, Semmes-Weinstein monofilament (SWM), and electrical perception threshold (EPT) across cervical dermatomes (C3-C8) in individuals with cervical SCI. A multicenter cross-sectional study was performed at 6 months after cervical SCI, applying combined measures of LT, SWM, and EPT, bilaterally over predefined key sensory points (C3-C8). A total of 300 left- and right-sided dermatomes were tested for each outcome measure in 25 participants. The percentage agreement between classifications according to LT and SWM/EPT testing for all dermatomes between C3 and C8 ranged from 95.5% to 36.2%. The degree of agreement showed considerably variable κ coefficients (-0.1≥kw≤0.7) for each dermatome between C3 and C8. The additional measurements of epicritic sensation by SWM and EPT increased sensitivity by detecting and quantifying differences in sensory thresholds above, at, and below the LT level of injury. This is relevant for early clinical trials (phase 1/2), in which disclosing any biological activity of an intervention may be revealed by subtle sensory changes that might gain a clinical relevance.

Late sensory changes following chest drain insertion during thoracotomy

It is well known that chest drains are associated with severe movement-related acute pain. These noxious stimuli could play a significant role in development and maintenance of persistent post-operative pain. Therefore we studied chest drain sites in post-thoracotomy pain syndrome (PTPS) patients, in regard to pain and sensory dysfunction. We quantified thermal and pressure thresholds on both the chest drain side and the contralateral side in 11 PTPS patients and 10 pain-free post-thoracotomy patients 33 months after the thoracotomy. On average, each patient had two chest drains inserted during surgery. At follow up, two patients experienced pain at the chest drain sites, but had maximal pain near or at the thoracotomy scar. Comparison between chest drain side and control side for all 21 patients demonstrated significantly elevated thresholds for warmth detection and heat pain on the chest drain side (P < 0.01), but not for cool detection or pressure. No significant differences between chest drain side and control side were observed within PTPS or pain-free patients. Comparing PTPS and pain-free patients (chest drain-to-control side), no significant differences in thresholds were found. Although all 11 PTPS patients suffered from incisional pain, only two patients had pain from chest drains. Increased thresholds for thermal detection suggest that chest drain insertion is associated with late nerve injury. Because no significant differences in sensory thresholds between PTPS and pain-free patients were found, the pathophysiological role of small fibre nerve injury from chest drains in relation to PTPS remains unclear.

Changing the sensory threshold of elderly people through low-frequency, high-voltage acupoint electrical stimulation

It is widely known that acupoint of electrotherapy decreases the threshold of pain and release of catecholamine by mechanical and chemical stimulation. However, there have been no studies to find the change in the sensory threshold and time-dependent stimulus generated by acupoint electrical stimulation (AES) on the different body regions. The present study was conducted to examine the differences in sensory threshold between elderly and youthful subjects, as well as the sensory threshold by electrical stimulation in the lower back, shoulder, and knee joint regions in the elderly. The sensory threshold was increased in subjects over age 60 compared with 20 year olds. In relation to age, the sensory threshold was increased in the 60 s, 70 s, and 80 s, respectively, compared with during the 20 s. The sensory threshold was significantly increased in the lower back region compared with the shoulder and knee joint regions. The result of the analysis of the sensory threshold in response to the application of electrical stimulation revealed a time-dependent response, with the sensory threshold little changed. However, the change in the sensory threshold was significantly associated with time, increasing after AES from 10 and 15 min compared with 0 min for all ages. It was most pronounced in both the shoulder and knee joint region. Therefore, these results at least partially suggest that the change in sensory threshold is associated with age, and suggest the need to develop specialized physiotherapy to enable seniors to lead healthy lives.

Influence of aging on thermal and vibratory thresholds of quantitative sensory testing

Quantitative sensory testing has become a common approach to evaluate thermal and vibratory thresholds in various types of neuropathies. To understand the effect of aging on sensory perception, we measured warm, cold, and vibratory thresholds by performing quantitative sensory testing on a population of 484 normal subjects (175 males and 309 females), aged 48.61 +/- 14.10 (range 20-86) years. Sensory thresholds of the hand and foot were measured with two algorithms: the method of limits (Limits) and the method of level (Level). Thresholds measured by Limits are reaction-time-dependent, while those measured by Level are independent of reaction time. In addition, we explored (1) the correlations of thresholds between these two algorithms, (2) the effect of age on differences in thresholds between algorithms, and (3) differences in sensory thresholds between the two test sites. Age was consistently and significantly correlated with sensory thresholds of all tested modalities measured by both algorithms on multivariate regression analysis compared with other factors, including gender, body height, body weight, and body mass index. When thresholds were plotted against age, slopes differed between sensory thresholds of the hand and those of the foot: for the foot, slopes were steeper compared with those for the hand for each sensory modality. Sensory thresholds of both test sites measured by Level were highly correlated with those measured by Limits, and thresholds measured by Limits were higher than those measured by Level. Differences in sensory thresholds between the two algorithms were also correlated with age: thresholds of the foot were higher than those of the hand for each sensory modality. This difference in thresholds (measured with both Level and Limits) between the hand and foot was also correlated with age. These findings suggest that age is the most significant factor in determining sensory thresholds compared with the other factors of gender and anthropometric parameters, and this provides a foundation for investigating the neurobiologic significance of aging on the processing of sensory stimuli.

Differences in Sensory Thresholds in the Skin of Women with Fibromyalgia Syndrome: A Comparison Between Ketamine Responders and Ketamine Non-Responders

Objectives: To compare detection and pain thresholds in the skin of female fibromyalgia patients who were either ketamine responders or ketamine nonresponders.Methods: Detection thresholds to innocuous warmth, of cold, heat or cold pain, and touch and dynamic touch sensation were determined in the skin. Pressure pain thresholds, local and widespread pain intensity, and pain duration were also registered.Results: Ketamine nonresponse was associated with more pronounced hypersensitivity for thermal pain [especially cold pain] than ketamine response.Conclusions: Blockade of N-metyl-D-aspartic acid receptors by ketamine and the recording of pain thresholds in the skin, especially for cold pain, might reveal different mechanisms of allodynia.

Gender Differences in Neuroselective Current Perception Thresholds of the Trigeminal and Median Nerves

Purpose : The goal of this study was to ascertain gender differences in sensory thresholds by measuring current perception threshold (CPT) values of the trigeminal and median nerves in healthy individuals.Materials and Methods : CPT values were measured using a Neurometer® (Neurotoron, Baltimore, MD, USA) when electrical stimulation of 2, 000, 250, or 5 Hz was applied to the left preauricular (trigeminal nerve) and thenar eminence (median nerve) regions in 20 healthy volunteers (10 males and 10 females with a mean age of 24.4 years). The day-to-day reliability of CPT was first verified in the trigeminal region by a test-retest method using an interclass correlation coefficient (ICC). The CPT values were then measured and statistically analyzed to evaluate whether the values were influenced by the electrical stimulation frequency and gender difference.Results : Irrespective of the stimulation frequency, the ICC values were high (2, 000 Hz : 0.62, 250 Hz : 0.80, 5 Hz : 0.86), showing the high day-to-day reliability of CPT. The electrical frequency of the stimulation significantly influenced the CPT (ANOVA : p<0.0001) ; the mean CPT value during 2, 000 Hz stimulation was significantly higher than the value during 250 and 5 Hz stimulation (Bonferroni test : p<0.001). For median nerve stimulation, the mean CPT was lower for women than for men, but no significant gender difference was identified (ANOVA : p=0.11). Conversely, gender exerted significant effects on CPTs (ANOVA : p=0.02) for trigeminal nerve simulation. As to stimulation frequency, the mean CPT following 2, 000 Hz stimulation of the trigeminal nerve was significantly lower for women than for men (Bonferroni test : p<0.001).Conclusion : The results suggest that healthy women are more sensitive to tactile or pressure sensations compared to healthy men, and that the effects of gender differences on the sensory threshold can be ignored with pain-related nerve fibers such as Aδ and C fibers.

Anorectal dysfunction after surgical treatment for cervical cancer.

Although bowel symptoms and complaints are common after radical hysterectomy, the effects of operation on anorectal function are incompletely understood. In this prospective pilot study we evaluated the incidence of bowel symptoms, changes in anorectal physiology, and quality of life after radical hysterectomy. Eleven women undergoing radical hysterectomy for early-stage cervical cancer completed bowel function symptom surveys and cancer-specific quality-of-life scales before operation and at 6 weeks and 6 months after operation. The bowel function symptom survey was also repeated at 18 months postoperation. Anorectal manometry, balloon defecation, and pudendal nerve latency tests were performed before the operation and 6 months postoperatively. The mean age was 45.3 years (range 34 to 56 years), and four of the patients were postmenopausal. Resting and squeeze sphincter pressures, volume of saline infused at first leak, total volume retained, and threshold volume for maximum tolerable volume were all decreased significantly (p < 0.05) after operation. Pudendal nerve terminal motor latency increased (p < 0.05) bilaterally. There were no significant differences in sensory thresholds. At 18 months, two women reported constipation, six reported flatus incontinence, and two reported fecal incontinence. The total quality-of-life score declined at 6 weeks but then improved significantly by 6 months (p = 0.02). Bowel dysfunction is common after radical hysterectomy. Many women exhibit manometric and subjective changes compatible with fecal incontinence.

Lowered oesophageal sensory thresholds in patients with symptomatic but not excess gastro-oesophageal reflux: evidence for a spectrum of visceral sensitivity in GORD.

Some patients undergoing ambulatory oesophageal pH monitoring to investigate symptoms suggestive of gastro-oesophageal reflux disease (GORD) are found to have oesophageal acid exposure within the physiological range but show a close correlation between their symptoms and individual reflux episodes. It is suggested that these patients might exhibit enhanced oesophageal sensation, akin to the heightened perception of both physiological and provocative stimuli in the gut that has been described in patients with functional gastrointestinal disorders. This study tested the hypothesis by measuring the sensory thresholds for oesophageal balloon distension and discomfort in 20 patients with symptoms of GORD, in whom ambulatory pH monitoring had shown normal acid exposure times, but in whom the symptom index for reflux events was 50% or greater, and compared these with 15 healthy volunteer controls, and with control groups with confirmed excess reflux. The study group showed lower thresholds both for initial perception of oesophageal distension, and for discomfort, compared with healthy controls (median ml (range)); 7.5 (2-19) v 12 (6-30) (p = 0.002) and 10 (5-20) v 16 (8-30) (p < 0.0001), respectively. Sensory thresholds in the study group were also significantly lower than in patients with excess reflux, and than patients with Barrett's oesophagus, who also exhibited significantly higher sensory thresholds than healthy controls. No differences in sensory thresholds for somatic nerve stimulation were found between the study group and health controls. The results show a spectrum of visceral sensitivity in GORD, with enhanced oesophageal sensation in patients with symptomatic but not excess gastro-oesophageal reflux, suggesting that their symptoms result from a heightened perception of normal reflux events.

Individual differences in sensory threshold for aroma chemicals added to beer

The flavor impression made by a given product on different people can be judged from the variation in flavor thresholds for its principal flavor constituents. Perception threshols were determined for 25 compounds. The compounds were purified to constant flavor and threshold. Twenty-two laboratories and a total of 400 tasters each examined from 1 to 18 of the compounds. These were added to bland beers, and Best-Estimate Thresholds (BET) were determined by ASTM Method E679, the Ascending Method of Limits. Several training sessions were given before any main test. Panel thresholds varied from a high of 17 g/liter for ethanol, to a low of 0.1 μg/liter for geosmin and 2-nonenal. The difference between panels as a rule was less than threefold and rarely exceeded fivefold. Those oftenquoted differences of 100-fold or more were rarely seen, and it is tempting to conclude that many of them are artifacts due to misflavoring by impurities or confusion on the part of untrained tasters. Individual differences in sensory threshold for a given compound can be described by the log standard deviation from the geometric mean of the panel. The log s.d. averaged 0.53 ± 0.15 (3.4-fold) over 60 panels. The log s.d. varied from the most uniform at 0.26 (1.8-fold) for SO 2 to the least uniform at 0.95 (8.9-fold) for geraniol. The variability was least for simple flavors such as sweet, salty, butyric and alcoholic, and highest for complex yet distinct flavors such as hop oil, geraniol, vanillin and 2-nonenal. Results pointed towards the existence of a bimodal distribution of thresholds for geraniol and vanillin. No taster was highly sensitive to more than a few compounds nor was any taster insensitive to more than half of the compounds.