A portable system for measuring cutaneous thresholds for warming and cooling

Cutaneous warmth and hotness thresholds to radiation heat exposure at a distance of 10 cm from 17 body regions

The purpose of the present study was to evaluate body regional differences in cutaneous warmth and hotness thresholds in relation to radiant heat exposure. Fourteen male subjects participated in this study (age: 25 ± 5 y, height: 176.6 ± 5.5 cm, body weight: 70 ± 5.8 kg). Cutaneous warmth and hotness thresholds were measured on the forehead, neck, chest, abdomen, upper back, lower back, upper arm, forearm, palm, back of hand, front thigh, shin, top of foot, buttock, back thigh, calf, and sole. The forehead (34.8 ± 0.2 °C), lower back (34.1 ± 1.2 °C) and palm (34.3 ± 0.7 °C) had the highest warmth thresholds, whereas the foot (29.8 ± 1.9 °C) and sole (28.0 ± 2.1 °C) had the lowest values among the 17 regions (P<0.001). Higher warmth thresholds were related to higher initial skin temperatures (Tsk) (r=0.972, P<0.001). Increases in Tsk for detecting warmth sensation were smaller for the lower back with a rise of 0.2 ± 0.4 °C and the abdomen (0.3 ± 0.3 °C) than for the buttock (0.9 ± 0.8 °C) and sole (0.8 ± 0.6 °C) (P<0.05). Increases in Tsk for detecting hotness sensation ranged from 0.5 to 1.5 °C. Warmth and hotness thresholds on the abdomen or sole had significant relationships with body mass index, indicating that the overweight are less sensitive to detecting radiant heat on the abdomen or sole. Thermal thresholds from radiant heat exposure of 100 cm2 were lower than the values from conductive heat exposure of 6.25 cm2, which might be explained by the effect of spatial summation.

Non-Invasive Objective Markers to Measure Pain: A Direction to Develop a Pain Device - A Narrative Review

Objective

To review the literature regarding non-invasive objective measurements of pain. Measuring pain is of uttermost importance, but it can be an inconvenient task, especially in terms of the interpretation of patient's information. Reiterating, there is no "standard" that provides the physician with a method to objectively quantify this problem of patient's pain. For assessing the pain, physician relies solely on unidimensional assessment tools or questionnaire-based pain assessment. Although pain is a subjective experience of the patient, but there is a need to measure pain sometimes in the individuals who cannot communicate their quality and severity of pain.

Material and Methods

The articles from PubMed and Google Scholar without any year and age limit were searched in the current narrative review. A total of 16 markers were searched and their relation to pain was studied.

Results

Studies have shown that these markers change in relation to pain and it can be considered a valuable tool for pain measurement but there are multiple factors like psychological and emotional factors which affect these markers.

Conclusion

There is lack of evidence to show which marker can be used for measuring pain accurately. This narrative review is an attempt to look into the various pain-related markers that can be used and it calls for further studies including clinical trials with different diseases and taking into accounts different factors affecting pain to give an accurate measurement of pain.

The effect of temporal adaptation to different temperatures and osmolarities on heat response of TRPV4 in cultured cells

Transient receptor potential vanilloid 4 (TRPV4) channel is a polymodal receptor activated by moderate heat and hypoosmolarity. TRPV4 expressed in the skin area contributes to several skin functions as a barrier to maintain internal body physiology and a transporter of external stimuli. The skin condition such as skin temperature and osmolarity varies with internal and external changes, and may influence the activity of TRPV4 contributing to skin physiology, thermal sensation, and thermoregulation. However, the combination effect of skin conditions such as temperature and osmolarity on the activity of TRPV4 has not been examined. In the current study, we investigated the effect of temporal adaptation (5-10 min) to different temperature (25-35 °C) and osmolarity (250-350 mOsm) conditions on the heat response (until 40 °C) of human TRPV4 in cultured cells using Ca²⁺ imaging. The temperature to activate TRPV4 increased with elevation of the adaptation temperature, and decreased with the adaptation to hypoosmolarity in the range of 25-35 °C. In addition, the heat response was inhibited with the adaptation to hyperosmolarity in the range of 25-35 °C. Thus, we demonstrated that the activation temperature of TRPV4 varied with the temporal sensory adaptation to different temperature and osmolarity conditions. These findings may contribute to gaining better understanding of the variation in several TRPV4-mediated skin functions.

Lower thermal sensation in normothermic and mildly hyperthermic older adults

PURPOSE

It is important to know how thermal sensation is affected by normal aging under conditions that elevate core body temperature for the prevention of heat-related illness in older people. We assessed whether thermal sensation under conditions of normothermia (NT) and mild hyperthermia (HT) is lowered in older adults.

METHODS

Seventeen younger (23 ±  3 years) and 12 older (71 ±  3 years) healthy men underwent measurements of the cold and warmth detection thresholds ( ± 0.1 °C/s) of their chest and forearm skin, and whole body warmth perception under NT (esophageal temperature, T es, ~36.5 °C) and HT (T es, ~37.3 °C; lower legs immersed in 42 °C water) conditions.

RESULTS

Warmth detection threshold at the forearm was increased in older compared with younger participants under both NT (P = 0.006) and HT (P = 0.004) conditions. In contrast, cold detection threshold at the forearm was decreased in older compared with younger participants under NT (P = 0.001) but not HT (P = 0.16). Mild hyperthermia decreased cold detection threshold at forearm in younger participants (P = 0.001) only. There were no effects of age and condition on warmth and cold detection thresholds at chest. Whole body warmth perception increased during HT compared with NT in both groups (both, P < 0.001), and older participants had lower values than the younger group under NT (P = 0.001) and HT (P = 0.051).

CONCLUSIONS

Skin warmth detection thresholds at forearm and whole body warmth perception under NT and HT and skin cold detection thresholds at forearm under NT deteriorated with aging.

Temperature threshold testing: a systematic review

The diagnosis of small fiber neuropathy (SFN) has been recently defined as typical symptoms due to small nerve fiber dysfunction accompanied by reduced intra-epidermal nerve fiber density (IENFD) or abnormal temperature threshold testing (TTT). Guidelines have been published for the assessment of IENFD. However, international guidelines for TTT are lacking. This paper presents a systematic literature review on reported TTT methods and provides recommendations for its future use in studies evaluating patients. A total of 164 papers fulfilled pre-defined requirements and were selected for review. Over 15 types of instruments are currently being used with a variety of methodological approaches for location, stimulus application, and sensation qualities examined. Consensus is needed to standardize the use of TTT as a diagnostic and follow-up tool in patients.

OnabotulinumtoxinA improves tactile and mechanical pain perception in painful diabetic polyneuropathy

OBJECTIVES

Diabetic neuropathic pain may be relieved by onabotulinumtoxinA (BoNT/A). However, whether BoNT/A changes sensory perception in neuropathic patients remains unknown. This study used a double-blind crossover design to explore the possible effect of BoNT/A on sensory perception.

METHODS

Eighteen patients with painful diabetic polyneuropathy underwent 2 consecutive 12-week periods of treatment either in the sequence of saline (control) and then BoNT/A (SB cohort, n=9) or BoNT/A followed by saline (BS cohort, n=9). Sensory perception was assessed according to the tactile threshold [TT, logarithmized force (g) of von Frey filaments] and mechanical pain threshold [PT, logarithmized weight (g) of weighted syringes], both being averages from 4 individual measurements of bilateral medial and lateral feet obtained at baseline (before injections) and at weeks 1, 4, 8, and 12 after treatment.

RESULTS

In either the SB or the BS cohort, there was a decrease in the TT and the PT after treatment with BoNT/A but not with saline. In the analysis merging both cohorts (n=18), BoNT/A resulted in a significant decrease in TT and PT at weeks 1, 4, 8, and 12 (all Ps<0.05 vs. saline). The longitudinal effect of BoNT/A on TT and PT remained significant when baseline values, treatment sequences, and periods were controlled using generalized estimating equations.

DISCUSSION

BoNT/A may improve tactile and mechanical pain perception in painful diabetic polyneuropathy. The beneficial effects of BoNT/A deserves further study to elucidate the exact mechanism and potential for preventing insensate injuries.

Inert gas narcosis has no influence on thermo-tactile sensation

Contribution of skin thermal sensors under inert gas narcosis to the raising hypothermia is not known. Such information is vital for understanding the impact of narcosis on behavioural thermoregulation, diver safety and judgment of thermal (dis)comfort in the hyperbaric environment. So this study aimed at establishing the effects of normoxic concentration of 30% nitrous oxide (N(2)O) on thermo-tactile threshold sensation by studying 16 subjects [eight females and eight males; eight sensitive (S) and eight non-sensitive (NS) to N(2)O]. Their mean (SD) age was 22.1 (1.8) years, weight 72.8 (15.3) kg, height 1.75 (0.10) m and body mass index 23.8 (3.8) kg m(-2). Quantitative thermo-tactile sensory testing was performed on forearm, upper arm and thigh under two experimental conditions: breathing air (air trial) and breathing normoxic mixture of 30% N(2)O (N(2)O trial) in the mixed sequence. Difference in thermo-tactile sensitivity thresholds between two groups of subjects in two experimental conditions was analysed by 3-way mixed-model analysis of covariance. There were no statistically significant differences in thermo-tactile thresholds either between the Air and N(2)O trials, or between S and NS groups, or between females and males, or with respect to body mass index. Some clinically insignificant lowering of thermo-tactile thresholds occurred only for warm thermo-tactile thresholds on upper arm and thigh. The results indicated that normoxic mixture of 30% N(2)O had no influence on thermo-tactile sensation in normothermia.

Long-term neurotoxicity of chemotherapy in adolescents and young adults treated for bone and soft tissue sarcomas

Purpose. To study the long-term neurotoxicity of chemotherapy in adolescents and young adults treated for bone and soft tissue sarcomas.

Patients and Methods. Thirty-six adolescents and young adults (median age 17 years) were examined following chemotherapy for bone and soft tissue sarcomas. Twenty-nine (29/36) had received cisplatin (median 400 mg/m²), 15/36 ifosfamide (median 20 g/m²), and 12/36 vincristine (median 16 mg). Neurotoxicity was assessed at a median of 8 months (range, 1–54 months) after completion of chemotherapy by clinical examination, nerve conduction studies, audiograms and autonomic function tests. The same nerve conduction studies were carried out in 20 normal volunteers to define normal ranges in this age group.

Results. Sixteen patients (44%) had a significant reduction in deep tendon reflexes, and this clinical parameter correlated well with abnormalities detected in nerve conduction studies. Vibration perception threshold (VPT) was raised in 20/36 patients (55%) and this was the most sensitive single test in the assessment of neuropathy. There was a significant correlation between VPT and cumulative cisplatin dose received in mg/m^-2 (r=0.607, p<0.01). Ten of 29 patients (35%) had abnormal nerve conduction studies with a pattern characteristic of sensory axonal neuropathy. No patient complained of auditory symptoms, but minor high tone hearing loss was detected by audiograms in 5/28 patients who had received cisplatin. No patients had symptoms of autonomic neuropathy, but autonomic function tests showed minor abnormalities in 4/22 patients tested, and all had received cisplatin.

Conclusions. This study demonstrates significant, although asymptomatic, long-term neurotoxicity of cisplatin in adolescents and young adults receiving chemotherapy for bone and soft tissue sarcomas. Follow-up studies are planned to assess whether these neurological deficits improve with time.

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 and mapping: a review of nonautomated quantitative methods for examination of the patient with neuropathic pain

OBJECTIVES

Despite a growing interest in neuropathic pain, neurologists and pain specialists do not have a standard, validated, office examination for the evaluation of neuropathic pain signs to complement the neurologic, musculoskeletal, and general physical examinations. An office neuropathic pain examination focused on quantifying sensory features of neuropathic pain, ranging from deficits to allodynia and hyperalgesia, and evoked by a physiologically representative array of stimuli, will be an essential tool to monitor treatment effectiveness and for clinical investigation into the mechanisms and management of neuropathic pain. Such an examination should include mapping of areas of stimulus-evoked neuropathic pain and standardized, reproducible quantitative sensory testing (QST) of tactile, punctuate, pressure, and thermal modalities.

METHODS

We review quantitative sensory testing methodology in general and specific tests for the evaluation of neuropathic pain phenomena.

RESULTS

Numerous quantitative sensory testing techniques for dynamic mechanical, pressure, vibration, and thermal sensory testing and mapping have been described. We propose a comprehensive neuropathic pain evaluation protocol that is based upon these available techniques.

CONCLUSIONS

A comprehensive neuropathic pain evaluation protocol is essential for further advancement of clinical research in neuropathic pain. A protocol that uses tools readily available in clinical practice, when established and validated, can be used widely and thus accelerate data collection for clinical research and increase clinical awareness of the features of neuropathic pain.

Diagnosis of complex regional pain syndrome: signs, symptoms, and new empirically derived diagnostic criteria

This review will discuss the relevant history of the taxonomy and eventual development of diagnostic criteria of what is currently called complex regional pain syndrome. The authors will take their discussion through the early days (at which time the disorder was called reflex sympathetic dystrophy) through consensus-developing conferences to the current conceptualization of the criteria as published by the International Association for the Study of Pain's Task Force on Taxonomy in 1994. The authors will also mention the recent work of the closed workshop held in Budapest in 2004, where clinical and research criteria were proposed; these criteria were published in 2005. The review will also address issues of staging and subtyping the syndrome, as well as a discussion of the salient signs, symptoms, and tests appropriate for use in the diagnosis.

Site-dependent and subject-related variations in perioral thermal sensitivity

The Marstock method of limits was used to obtain thresholds for detection of cooling, warming, cold pain and heat pain for 34 young adults, upon eight spatially matched sites on the left and right sides of the face, the right ventral forearm and the scalp. Male and female subjects were tested by both a male and a female experimenter. Neither the experimenter nor the gender of the subject individually influenced the thresholds. The thermal thresholds varied greatly across facial sites: sixfold and tenfold for cool and warmth, respectively, from the most sensitive sites on the vermilion to the least sensitive facial site, the preauricular skin. Warm thresholds were 68% higher than cool thresholds, on average, and 12% higher on the left compared to the right side of the face. The mean cold pain threshold increased from 21.0 degrees C on the hairy upper lip to 17.8 degrees C on the preauricular skin. Sites on the upper lip were also most sensitive to noxious heat with pain thresholds of 42-43 degrees C. The scalp was notably insensitive to innocuous and noxious changes in temperature. For the sensations of nonpainful cool and warmth, the more sensitive a site, the less the estimates of the thresholds differed between subjects. In contrast, for heat pain, the more sensitive a site, the more the estimates differed between subjects. Subjects who were relatively more sensitive to cool tended to be relatively more sensitive to warmth. Subjects' sensitivities to nonpainful cool and warmth were less predictive of their sensitivities to painful cold and heat, respectively. Short-term within-subject variability increased with the magnitude of the thresholds. The lower the threshold, the more similar were repeated measurements of it, within a 5-25 s period.

American Academy of Disability Evaluating Physicians (AADEP) position paper: complex regional pain syndrome I (RSD): impairment and disability issues

OBJECTIVE

To provide an overview and methodology for the evaluation of impairment and functional residual capacity in complex regional pain syndrome I (CRPS I, RSD). This paper is intended to provide assistance to physicians asked to evaluate impairment- and disability-related issues and is not primarily geared to guide treatment of the CRPS I patient.

METHOD

Conference and literature review by neurology, anesthesiology, pain medicine, physiatry, and disability evaluating physicians followed by description of issues, options, and recommendations based upon the committee's deliberations and the widely used AMA Guides to the Evaluation of Permanent Impairment, fourth and fifth editions. The authors present functional criteria for assessing the severity of CRPS. These criteria were developed by committee consensus opinion based on multidisciplinary clinical experience considering daily functional issues. They can be used in conjunction with CRPS-ADL Classes of Impairment in order to categorize an individual into a specific class for purposes of permanent impairment rating. Future reliability and validity studies of this rating scale are pending future use, acceptance and, hopefully, additional studies.

RESULTS

Evaluators should perform a comprehensive assessment of patients with CRPS I to make an accurate diagnosis and exclude other conditions that could explain the symptoms and signs of the condition. While radiological, laboratory, and other diagnostic studies may be of assistance in making the diagnosis, in the final analysis, this is a clinical diagnosis. Impairment is based on objectively validated limitation in activities of daily living (ADL).

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.

Sensory recovery in a split skin graft: pinprick or a thermal sensory analyzer?

Sensory return in a split skin graft is an important factor in the protection of this graft from injury. Hence, three tests were compared: (1) the standard pain test using a simple pin, (2) the cold pain test, and (3) the hot pain test. Both the hot and cold pain tests were performed using the thermal sensory analyzer device. Thirteen patients were investigated; all had split skin grafts applied directly onto deep fascia after malignant melanoma excision on the lower limb. The period after grafting ranged from 4 to 15 years, and the mean age was 46.5 years. The normal contralateral side of each patient was used as the control for that patient. The results were collected in simple data tables and were analyzed using paired t tables for small samples with the level of significance set at p < 0.05. The standard pain test demonstrated that the split skin grafts applied on deep fascia did not recover sensation, even 15 years after surgery (p < 0.001). The hot and cold pain tests were both in agreement with the standard pain test at p < 0.001 and p < 0.03, respectively. The standard pain test is usually performed, as described in this study, using a pin, which is cheap and readily available in any plastic surgery and burn clinic. However, the cold and hot pain tests as performed here using the thermal sensory analyzer device are accurate but are costly, cumbersome, and not available in all clinics except for highly specialized units. Hence, the author would like to dispel the myth that the standard pain test is inaccurate. This might be so in testing sensation in "normal" skin but not in testing the recovery of sensation in a skin graft.

Quantitative assessment of cutaneous thermal and vibration sensation and thermal pain detection thresholds in healthy children and adolescents

Quantitative sensory testing (QST) is a noninvasive, computer-assisted method for assessing function in peripheral small and large sensory fibers. In order to use QST for clinical neurological assessment in children, it is necessary: (1) to determine whether children can reliably perform these tests and (2) to characterize normal ranges in healthy children. Values of cold sensation, warm sensation, cold pain, heat pain, and vibration sensation detection thresholds were determined in the hand and foot with the method of limits (MLI) and method of levels (MLE) in 101 healthy children aged 6-17 years using a commercially available device. Both MLI and MLE were well-accepted by children, and there was good reproducibility between two sessions. The MLE takes longer to perform but produces lower thermal detection thresholds than the MLI. In the MLI, vibration and warm sensation showed higher thresholds in the foot than hand, whereas cold pain showed lower thresholds in the foot than hand. Based on these results, QST may be used to document and monitor the clinical course of sensory abnormalities in children with neurological disorders or neuropathic pain.

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.

Quantitative sensory testing in patients with incomplete spinal cord injury

OBJECTIVE

To examine the utility of quantitative sensory testing (QST) to characterize sensory dysfunction in patients with spinal cord injury (SCI).

DESIGN

Perceptual thresholds to warm, cold, cold pain, and vibratory stimuli were investigated using a modified method of "limits."

METHOD

Three QST trials were administered to six lower leg dermatomes, on two different days, to estimate the reliability of measurement.

SETTING

Regional Spinal Cord Injury Rehabilitation Center in Ontario, Canada.

SUBJECTS

Twenty-one SCI patients with incomplete neurologic deficits and 14 able-bodied controls of similar age.

RESULTS

ANOVA revealed significantly (p < .05) reduced perceptual threshold values (hypoesthesia) for warm, cold, and vibratory sensation in the SCI group. There were no differences between group mean values for cold pain because of the inclusion of patients with hypoalgesia and hyperalgesia. Intraclass correlation coefficient estimates of reliability revealed large between-subject variability in the SCI patients associated with relatively small trial-to-trial variability within each day of testing, and appreciable between-day variances.

CONCLUSIONS

With QST in SCI there is a need for repeated measurements across days to establish stable baseline measures or outcomes following intervention. QST is a useful adjunct to clinical examination for assessment of preserved sensation.

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.

Reliability of cephalic thermal thresholds in healthy subjects

Reproducibility and normal variation of cephalic warm and cold detection thresholds were investigated in three healthy subject groups. The face, the mastoid process, and the hands were studied. No significant intra-observer test-retest difference (n = 20) was found. Good reliability (intra-class correlation coefficient [ICC] > 0.4) was found for 13 of 14 measurements. A small significant inter-observer difference (n = 20) was found for cold thresholds. Good reliability (ICC > 0.4) was observed for both cold and warm thresholds in most of the test locations (6 of 8). In general, the largest variability was found in the mastoid and frontal lateral regions. Thermal thresholds varied with investigation site in 56 controls (ANOVA, p < 0.0005). No significant gender differences were found for cephalic warm and cold thresholds. Most cold thresholds (4 of 5) but also some warm thresholds (2 of 5) increased with age at the cephalic sites. Our results reveal the frontal medial, the maxillar medial, and lateral regions as the most reliable cephalic test locations. The mastoid region may also be useful for investigating the upper cervical small-fiber function.

Central nervous system abnormalities in complex regional pain syndrome (CRPS): clinical and quantitative evidence of medullary dysfunction

OBJECTIVE

Sensory and motor abnormalities are common among patients with complex regional pain syndrome (CRPS). The purpose of the present study was to define and characterize these abnormalities and to develop a hypothesis regarding the area of the central nervous system from which they derive.

DESIGN

Data were acquired from study subjects using clinical examination and quantitative assessment of neurological function. Subjects were divided into four groups. CRPS patients were differentiated into two groups based on the presence or absence of sensory deficit on the face to clinical examination. The other two groups were composed of patients with other chronic pain syndromes and normal individuals without chronic pain or disability. Clinical and quantitative data were compared between groups.

PATIENTS

One hundred forty-five CRPS patients, 69 patients with other pain conditions, and 26 normal individuals were studied.

RESULTS

A high incidence of trigeminal hypoesthesia was observed in CRPS patients. CRPS patients with trigeminal hypoesthesia manifested bilateral deficits of sensory function, with a predominant hemilateral pattern. These patients also manifested bilateral motor weakness with a more prominent hemiparetic pattern. Both sensory and motor deficits were greatest ipsilateral to the painful side of the body. These features differed significantly from those of CRPS patients lacking clinical trigeminal deficit, other pain patients, and normals. A lower cranial nerve abnormality (sternocleidomastoid weakness) and a myelopathic feature (Hoffman's reflex) were more common in CRPS patients with trigeminal hypoesthesia.

CONCLUSIONS

Nearly half of CRPS patients had abnormalities of spinothalamic, trigeminothalamic, and corticospinal function that may represent dysfunction of the medulla. One-third of the remaining CRPS patients had neuroimaging evidence of spinal cord or brain pathology. The majority of CRPS patients in this study have measurable abnormalities of the sensory and motor systems or neuroimaging evidence of spinal cord or brain dysfunction.

Normal distributions of thermal and vibration sensory thresholds

The distributions of sensory thresholds were estimated in a healthy population while controlling for potential covariates. Using the method of levels and the two-alternative forced choice, thermal and vibration thresholds respectively were measured in the hand and foot of 148 subjects. Age was uniformly distributed between 20 and 86 years. Independent effects of age, gender, height, and skin temperature were estimated using multiple linear regression. Parametric and nonparametric methods were used to estimate the distributions of interest. Significant age-related increases were observed for all vibration thresholds (P < 0.0001), and for thermal thresholds in the foot (P < 0.0002). Percentiles were estimated for thermal thresholds in the hand and age-adjusted continuous distributions were calculated for all other thresholds. Height was positively associated with vibration thresholds in the foot (P < 0.003), and appropriate corrections were made. Our results provide reference values for thermal and vibration sensory thresholds in a healthy population, allowing for the accurate diagnosis of disordered sensory function.

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.

Penile thermal sensation

PURPOSE

To our knowledge no direct measurement of autonomic failure in the penis is currently available. Indirect techniques in clinical use, such as bulbocavernosus reflex, genital somatosensory evoked potentials and biothesiometry, all rely on large nerve fiber function. Since micturition and potency depend on small fibers of the peripheral system, tests of these fibers might be more relevant in the clinical diagnostic evaluation. We provide upper normal limits and demonstrate repeatability of small fiber mediated sensations of warm and cold sensory thresholds on penile skin.

MATERIALS AND METHODS

Penile warm and cold sensory thresholds were measured in 35 healthy volunteers (at 2 sessions in 27) via 2 methods.

RESULTS

Upper normal values, expressed as 95% confidence limits for warm and cold thresholds, through methods of limits and levels as well as inter-session repeatability are given.

CONCLUSIONS

Penile thermal thresholds are repeatable and can be used as a valid diagnostic tool to assess somatic small fiber function in patients with lower urinary tract disorders.

Sensory nerve disturbance following Le Fort I osteotomy

This study assessed sensory nerve disturbance after Le Fort I osteotomy using the electric pulp test, pin-prick sensation, fine touch, and cold sensation. After 6 months, 78% of teeth positive preoperatively to an electric pulp tester regained sensitivity. Return of palatal sensation was affected by whether or not the greater palatine nerve (GPN) was divided during surgery. After 6 months, where the GPN was intact, all patients had fine touch sensation (88% at the preoperative level), and all had pin-prick sensation (97% at preoperative level). When the GPN was divided, all patients had fine touch sensation (13% at preoperative level), and all had pin-prick sensation (63% at preoperative level). The differences in the return to preoperative sensation were significant for fine touch (P=0.0001++) and for pin-prick (P-0.03) by chi-square analysis. Sensation returned more quickly and more completely in the two cases where the contralateral GPN was intact. In the buccal mucosa, 95% of patients regained some fine touch sensation after 6 months, but none returned to the preoperative level. Similarly, 85% regained some pin-prick sensation, but none achieved preoperative levels. Cold sensation, pin-prick sensation, and fine touch on the face returned to the preoperative level in all patients by 6 weeks postoperatively.

Influence of age, temperature, sex, height and diazepam on vibration perception

Vibration perception was quantitatively examined in 92 healthy volunteers (46 females, 36 males, aged 10-71 years). Vibration perception thresholds, vibration disappearance thresholds and vibration thresholds were assessed at the second metacarpal bone, styloid process of ulna, lateral epicondyle of humerus, first phalanx of the big toe, first metatarsal bone, medial malleolus and proximal part of the tibia bilaterally. Vibration sensitivity was found to be age-dependent. Under the age of 60, the correlation was linear. Vibration thresholds depended on body site but they were not related to sex or body side. Temperature and diazepam affect the perception of vibration considerably. Small interindividual variability was found in measurements repeated in 3 consecutive days, after 4 weeks and after a year.

Components of variance for vibratory and thermal threshold testing in normal and diabetic subjects

Quantitative sensory testing (QST) is commonly used in the assessment of diabetic neuropathy. However, little data are available on the reliability of tactile and thermal testing devices. Reproducibility of QST measures between centers has not been previously reported. This study was designed to validate QST testing procedures and determine if these devices are suitable for large scale multicenter clinical trials. Finger and toe vibratory (Vf, Vt) and thermal (Tf, Tt) thresholds were determined for ten normal individuals by a two-alternative forced-choice procedure using the Optacon Tactile Tester (OTT) and Thermal Sensitivity Tester (TST). Threshold measurements were reproducible between technologists and had a day-to-day coefficient of variation of Vf 20%, Vt 23%, Tf 41%, and Tt 95%. Thresholds were determined for 140 normal individuals at six centers. Mean threshold values between centers were not significantly different. Center-to-center coefficients of variation (CV) were Vf 44%, Vt 45%, Tf 47%, and Tt 87%. There was no significant difference in threshold measures with regard to sex, side studied, presence of calluses, or skin temperature. Vf thresholds significantly correlated with age (p < 0.01). There was no correlation between either vibratory or thermal thresholds in normal individuals, and nerve conduction velocities (NCV). Thermal and vibratory thresholds were determined for 98 diabetic patients. Diabetic subjects without clinical evidence of neuropathy were not significantly different from normal individuals, but diabetic patients with neuropathy had increased thresholds compared to normals (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative measurement of cutaneous perception in diabetic neuropathy

To determine the diagnostic value of various cutaneous sensory modalities in diabetic neuropathy, we studied cutaneous perception at the dominant hallux of 113 subjects (32 normal healthy controls and 81 diabetic subjects). The cutaneous sensory perception tests included warm and cold thermal perception, vibration, touch-pressure sensation, and current perception testing (CPT). The sensitivity of each modality when specificity is held greater than 90% was as follows: warm = 78%, cold = 77%, vibration = 88%, tactile-pressure = 77%, 5-Hz CPT = 52%, 250-Hz CPT = 48%, and 2000-Hz CPT = 56%. Combination thermal and vibratory gave optimum sensitivity (92-95%) and specificity (77-86%). We conclude that vibratory and thermal testing should be the primary screening tests for diabetic peripheral neuropathy. Other modalities may be of use only in specific situations.

Cerebrospinal fluid levels of beta endorphin in painful and painless diabetic polyneuropathy

beta endorphin (beta-EP) is an important modulator of central pain pathways. To examine whether changes in central production of beta-EP contribute to the pathogenesis of diabetic neuropathic pain, we compared the cerebrospinal fluid (CSF) levels of beta-EP and its precursor proopiomelanocortin (POMC) between 15 diabetic patients with chronic painful diabetic polyneuropathy, eight patients with severe painless diabetic neuropathy, and ten nondiabetic controls. Both peptides were measured by specific monoclonal antibody-based two-site immunoradiometric assays (IRMAs). In the diabetic patients with painful neuropathy, mean +/- SD CSF beta-EP concentrations (5.7 +/- 2.2 pmol/L) were comparable to those of the diabetic patients with painless neuropathy (6.0 +/- 2.3 pmol/L) and did not correlate with the severity of neuropathic pain. CSF beta-EP, but not POMC, concentrations were lower in the diabetic neuropathic patients overall (5.8 +/- 1.9 pmol/L) compared to the control subjects (7.6 +/- 2.2 pmol/L) (p < 0.05). CSF POMC showed no intergroup differences. However, POMC levels were 80-fold higher than those of beta-EP and should always be considered when interpreting immunoreactive beta-EP or other derivative peptide levels in CSF. We conclude that CSF beta-EP levels appear to be reduced in diabetic polyneuropathy but they do not relate to the presence of neuropathic pain. This might explain why opioid analgesics are of little, if any, help in alleviating diabetic neuropathic pain.

Quantitative assessment of thermal and pain sensitivity

Values for thermal specific and thermal pain thresholds were determined in 150 healthy volunteers, 67 women and 83 men, aged from 10 to 73 years. Warm-cold difference limen, heat pain and cold pain thresholds were assessed at the face, thenar, medial surface of the upper- and forearm, lateral mammary, lateral umbilical, anterior thigh and lateral leg regions, and lateral aspect of the dorsum of the foot. Temperature and pain sensitivity were assessed by the Marstock method. Temperature sensitivity was found obviously age-dependent. The correlation is linear. Women showed greater sensitivity for small temperature changes, reflected as warm-cold difference limen, and for heat pain and cold pain. Great variation of thermal and pain sensitivity of different body parts was significant in all volunteers, irrespective of age and sex. Interindividual variation was also considerable. Small intraindividual variability was found in measurements repeated in 4 consecutive days and after 4 weeks. Body length did not influence thermal and pain perception thresholds. There were no differences found in thermal and pain sensitivity between the left and the right side of the body.

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

Sensory threshold measurements are criticized as subjective and therefore not to be relied upon in clinical diagnostic practice, particularly when deliberate deception by the patient is suspected. In an attempt to devise a method which permits dependable sensory threshold interpretation, individual variability of thresholds was examined in normal and neuropathic subjects. Normals were also instructed to feign sensory impairment resulting from hypothetical injury. For each subject, a number of threshold readings were averaged, yielding individual means and variances. Feigning normal subjects evidenced a larger variance compared to trustworthy normal and neuropathic subjects. Thus, alertness to variance reinforces the psychophysical analysis: small variance values suggest trustworthy normal or pathological results, whereas large variance calls the interpreter's attention to feigned results or inattentive test performance.

Thermal testing: normative data and repeatability for various test algorithms

Measurement of thresholds for warm and cold sensation was performed on 106 normal subjects, at thenar eminence and foot dorsum. Three test algorithms were used, the reaction-time-inclusive method of limits, and reaction-time-exclusive methods of levels and staircase. Tests were repeated 2 weeks following the first for most of the subjects, and after elimination of 5 outlying subject data points, and determination of no systematic relationship between magnitude and variability of test scores, data from between 72 and 76 subjects were used to derive repeatability coefficients, by ANOVA-based procedures which extend standard repeatability assessment methods. Normative data tables are presented, with measures of repeatability for the various algorithms and modalities. Method of limits tests exhibited inter-session bias, and large repeatability coefficients, compared with methods of levels and staircase, which exhibited no bias and had better (lower) repeatability coefficients. All three methods had similar test durations. We conclude that on the basis of these data, the reaction-time-exclusive methods of levels and staircase have a definite advantage over the method of limits.

Cardiorespiratory reflexes, vibratory and thermal thresholds, sensory and motor conduction in diabetic patients with end-stage nephropathy

The neuropathic profile was studied in 26 patients with long-standing, insulin-dependent diabetes mellitus and end-stage nephropathy using tests to evaluate large and small nerve fibres and autonomic function. Clinically, 18 patients (69%) has symptoms and signs of peripheral neuropathy, 9 (35%) had symptoms of autonomic involvement. Vibratory sensation was impaired in 20 patients (77%) in the lower limbs and in 6 (22%) in the upper limbs; cold and warm sensation was equally often impaired in the feet and in the hands with no significant difference between patients with and without neuropathy. Heart rate variation was abnormal in 23 patients at rest (88%), in 24 (92%) during deep breathing and during the orthostatic test. Conduction studies revealed abnormalities in two or more nerves in all patients regardless of whether or not they had overt neuropathy clinically. Thus, the applied multimodal tests revealed evidence of impaired function in large or small nerve fibres or both in all patients independent of clinical findings.

Capillary filtration coefficient in type II (non-insulin-dependent) diabetes

Changes in microvascular permeability may be important in the pathogenesis of diabetic microangiopathy. In order to assess microvascular fluid permeability, the capillary filtration coefficient was determined in the forearm of 24 normotensive type II diabetic patients with minimal evidence of microangiopathy and satisfactory glycemic control, and 24 age- and sex-matched control subjects, using a sensitive strain gauge plethysmographic system. The median capillary filtration coefficient was not significantly different in the type II diabetic patients and control subjects [5.3 (3.2 - 9.1) x 10(-3) mL.min-1.100 g tissue-1.mm Hg-1 versus 5.4 (3.5 - 8.0) x 10(-3) mL.min-1.100 g tissue-1.mm Hg-1, p = 0.98)]. There were no correlations between capillary filtration coefficient and age, blood pressure, body mass index, duration of diabetes, glycemic control, or the presence of microvascular complications. These findings contrast with type I diabetes, where capillary filtration coefficient is elevated at an early stage in the disease, and lend support to the theory that there are differences in early microvascular functional abnormalities between type I and type II diabetes.

Congenital sensory neuropathy in association with ichthyosis and anterior chamber cleavage syndrome

Two patients with a congenital neuropathy are described. Both had atypical features including: ichthyosis and a mild anterior chamber cleavage syndrome. Both had severely reduced, or absent, sensation for light touch, vibration, position and temperature. Pain sensation was mildly reduced. There was some evidence of motor involvement but this was relatively minor compared with the sensory involvement. Nerve action potentials were small or absent and sural nerve biopsies showed almost complete absence of myelinated nerve fibres with multiple bundles of abnormally arranged axons and Schwann cell processes. These patients appear to have an undescribed syndrome in which the large sensory neurons and the anterior chamber of the eye did not develop properly. This may reflect a failure of migration, differentiation or proliferation of neural crest cells.

Peripheral nerve function in chronic venous insufficiency

Abnormalities of vasomotion, impairment of the venoarteriolar reflex and increased skin blood flow reported in the liposclerotic skin of patients with chronic venous insufficiency (CVI) suggest altered nervous control of the skin microcirculation. The aim of this study was to determine whether patients with CVI have a peripheral neuropathy. Forty patients with CVI and lipodermatosclerosis (LDS) and 35 age and sex-matched controls were examined for neuropathy using three modalities of testing. Threshold to warming was used to assess unmyelinated fibres, and threshold to cooling and vibration to assess myelinated fibres. Warming and cooling thresholds were measured on the sole of the foot by a purpose built, computer controlled instrument. The threshold to vibration was measured on the big toe using the Ohio Bio-thesiometer. A significantly raised threshold to warming and vibration was found in the CVI group compared to the normal controls [median threshold to warming (interquartile range) in CVI group = 5.3 (0.1-9.1) median threshold to warming (interquartile range) in controls = 1.21 (0.17-3.5), p = 0.005 and median threshold to vibration (interquartile range) in CVI group = 22 (13-31) median threshold to vibration (interquartile range) in controls = 12 (8.5-27.5), p = 0.024]. The thresholds to cooling was not statistically different in the two groups. This study demonstrates the presence of a peripheral neuropathy in patients with chronic venous insufficiency, and this may be important in the pathogenesis of venous ulceration.

Discrimination between painful and painless diabetic neuropathy based on testing of large somatic nerve and sympathetic nerve function

The syndromes of painful diabetic neuropathy and painless foot ulceration are distinct clinical entities. To investigate whether there is a pattern of nerve fibre involvement that could clearly discriminate between them, we have studied three groups of diabetic patients, 19 with painful neuropathy, 14 with painless foot ulceration, and 19 with no clinical neuropathy. Large somatic nerve fibre function was assessed by nerve conduction studies and vibration thresholds, small somatic nerve function by cooling and warming thresholds, the parasympathetic system by heart-rate dependent cardiac autonomic reflexes, and the sympathetic system by postural drop in blood pressure and plasma noradrenaline (supine and erect). Normal ranges were obtained from 25 age-matched healthy subjects. Painful neuropathy was characterized by uniform dysfunction of small somatic fibres and preserved sympathetic nerve activity (plasma noradrenaline) with a wide range of large somatic fibre and autonomic reflex abnormalities. By contrast, in painless foot ulceration there was universal severe dysfunction of all nerve fibre populations. Discriminant analysis identified peroneal motor conduction velocity as the best single variable for distinguishing between painful and painless neuropathy (81% of cases). A combination of peroneal motor conduction velocity with vibration threshold and plasma noradrenaline discriminated completely between the two clinical syndromes. These findings suggest that the key differences between painful and painless diabetic neuropathy are in large somatic and sympathetic fibre function.

The function of large and small nerve fibers in renal failure

Previous clinical and neurophysiological studies of uremic neuropathy have focused almost exclusively on the function of large sensory and motor axons. The sensations of heat and cold depend on the function of unmyelinated afferents and small myelinated afferents, respectively, and these sensations can be quantified using a standardized psychophysical technique. Thermal thresholds were measured in 20 patients with end-stage renal failure to determine the extent of small afferent fiber involvement and to compare this with the clinical and electrophysiological evidence of large fiber involvement. Whereas abnormalities of standard nerve conduction studies were found in 16 patients, abnormal thermal thresholds were found in only 6 patients. In the nerve conduction studies, the amplitudes of nerve potentials were reduced more than their conduction velocities, consistent with an axonopathy. This study found little evidence of significant dysfunction of small afferent fibers in end-stage renal failure and, when such changes occurred, they did not correlate with the clinical evidence of polyneuropathy. The functional sparing of axons of small diameter is consistent with the relative sparing of these axons in pathological studies.