Thermographic presentation of cutaneous sensory and vasomotor activity in the injured peripheral nerve

Orofacial anti-hypernociceptive effect of citral in acute and persistent inflammatory models in rats

Orofacial pain has significant psychological and physiological effects. Citral (3,7-dimethyl-2,6-octadienal) is the main component of Cymbopogon citratus (DC) Stapf, an herb with analgesic properties. Although citral has been considered a potent analgesic, its putative effects on orofacial pain are still unknown.

OBJECTIVE

The objective of this study is to test the hypothesis that citral modulates orofacial pain using two experimental models: formalin-induced hyperalgesia in the vibrissae area and during persistent temporomandibular hypernociception using Complete Freund's Adjuvant - CFA test.

METHODS

For the formalin test, citral (100 and 300 mg/kg, oral gavage) or its vehicle (Tween 80, 1 %) were given 1 h before the formalin injection subcutaneously (sc) into the vibrissae area. For the CFA model, we analyzed the prophylactic (100 mg/kg of citral by oral gavage, 1 h before CFA injection) and the chronic therapeutic (citral treatment 1-hour post-CFA injection and daily post-CFA injection) effect of citral or its vehicle in animals treated with CFA for 8 days.

RESULTS

Citral caused a decrease in formalin-induced local inflammation and the time spent performing nociceptive behavior in a dose-dependent fashion. Similarly, prophylactic and therapeutic citral treatment decreased the CFA-induced persistent mechanical hypernociception in the temporomandibular area.

CONCLUSION

Our data strengthen the notion that citral plays a powerful antinociceptive role by decreasing orofacial hypernociception in formalin and CFA models.

Reference Standard for Digital Infrared Thermography of the Surface Temperature of the Lower Limbs

Digital infrared thermographic imaging (DITI) is a supplementary diagnostic technique to visualize the surface temperature of the human body. However, there is currently no reference standard for the lower limbs for accurate diagnosis. In this study, we performed DITI on the lower limbs of 905 healthy Korean volunteers (411 males and 494 females aged between 20 and 69 years) to obtain reference standard data. Thermography was conducted on the front, back, lateral sides, and sole area, and 188 regions of interest (ROIs) were analyzed. Additionally, subgroup analysis was conducted according to the proximity of ROIs, sex, and age groups. The mean temperatures of ROIs ranged from 24.60 ± 5.06 to 28.75 ± 5.76 °C and the absolute value of the temperature difference between both sides reached up to 1.06 ± 2.75 °C. According to subgroup analysis, the sole area had a significantly lower temperature than any other areas, men had higher temperatures than women, and the elderly had higher temperatures than the young adults except for the 20s age group (p < 0.001, respectively). This result could be used as a foundation for the establishment of a reference standard for DITI. Practical patient DITI can be accurately interpreted using these data, and it can serve as a basis for further scientific research.

Complex Regional Pain Syndrome or Limb Pain: A Plea for a Critical Approach

Most frequently, complex regional pain syndrome (CRPS) develops after a trauma and affects distal parts of the limbs. Early recognition and initiation of adequate treatment is crucial for a favorable outcome. On the other hand, misdiagnosing other disorders as CRPS is detrimental because more appropriate treatment may be withheld from the patients. Despite intensive research, a specific biomarker or paraclinical measure for CRPS diagnosis is still lacking. Instead, clinical criteria approved by the International Association for the Study of Pain (IASP) and latest adapted in 2019 are central for diagnosing CPRS. Thus, the CRPS diagnosis remains challenging with the risk of a “deliberate diagnosis” for unexplained pain, while at the same time a delayed CRPS diagnosis prevents early treatment and full recovery. CRPS is a diagnosis of exclusion. To clinically diagnose CRPS, a vigorous exclusion of “other diseases that would better explain the signs and symptoms” are needed before the patients should be referred to tertiary centers for specific pain treatment. We highlight red flags that suggest “non-CRPS” limb pain despite clinical similarity to CRPS. Clinical and neurological examination and paraclinical evaluation of a probably CRPS patient are summarized. Finally, we pinpoint common differential diagnoses for CRPS. This perspective might help CRPS researchers and caregivers to reach a correct diagnosis and choose the right treatment, regardless whether for CRPS mimics or CRPS itself.

Differential Screening of Herniated Lumbar Discs Based on Bag of Visual Words Image Classification Using Digital Infrared Thermographic Images

Doctors in primary hospitals can obtain the impression of lumbosacral radiculopathy with a physical exam and need to acquire medical images, such as an expensive MRI, for diagnosis. Then, doctors will perform a foraminal root block to the target root for pain control. However, there was insufficient screening medical image examination for precise L5 and S1 lumbosacral radiculopathy, which is most prevalent in the clinical field. Therefore, to perform differential screening of L5 and S1 lumbosacral radiculopathy, the authors applied digital infrared thermographic images (DITI) to the machine learning (ML) algorithm, which is the bag of visual words method. DITI dataset included data from the healthy population and radiculopathy patients with herniated lumbar discs (HLDs) L4/5 and L5/S1. A total of 842 patients were enrolled and the dataset was split into a 7:3 ratio as the training algorithm and test dataset to evaluate model performance. The average accuracy was 0.72 and 0.67, the average precision was 0.71 and 0.77, the average recall was 0.69 and 0.74, and the F1 score was 0.70 and 0.75 for the training and test datasets. Application of the bag of visual words algorithm to DITI classification will aid in the differential screening of lumbosacral radiculopathy and increase the therapeutic effect of primary pain interventions with economical cost.

Application of digital infrared thermography for carpal tunnel syndrome evaluation

We investigated the thermographic findings of carpal tunnel syndrome (CTS). We enrolled 304 hands with electrodiagnostically identified CTS and 88 control hands. CTS hands were assigned to duration groups (D1, < 3 months; D2, 3‒6 months; D3, 6‒12 months; D4, ≥ 12 months) and severity groups (S1, very mild; S2, mild; S3, moderate; S4, severe). The temperature difference between the median and ulnar nerve territories (ΔM-U territories) decreased as CTS duration and severity increased. Significant differences in ΔM-U territories between the D1 and D3, D1 and D4, D2 and D4, and S1 and S4 groups (P = 0.003, 0.001, 0.001, and < 0.001, respectively) were observed. Thermal anisometry increased as CTS duration and severity increased. Significant differences in thermal anisometry between the D1 and D4 as well as the D2 and D4 groups (P = 0.005 and 0.04, respectively) were noted. Thermal anisometry was higher in the S4 group than in the S1, S2, and S3 groups (P = 0.009, < 0.001, and 0.003, respectively). As CTS progresses, skin temperature tends to decrease and thermal variation tends to increase in the median nerve-innervated area. Thermographic findings reflect the physiological changes of the entrapped median nerve.

Hyperthermia associated with spinal radiculopathy as determined by digital infrared thermographic imaging

In general, in digital infrared thermographic imaging (DITI) of patients with unilateral spinal radicular pain, the thermal pattern of the extremities of the side of lesion shows hypothermia compared to the opposite, intact side. However, sometimes, DITI shows hyperthermia on the side of the lesion, and this variation can cause confusion. We compared the data of both hypothermia and hyperthermia patients to clarify the factors determining different thermal characteristics in spinal radiculopathy.We retrospectively collected data from patients who underwent DITI at a single center. The final cohort (n = 224) was allocated into 2 groups, a hypothermia group (n = 180) or a hyperthermia group (n = 44). We compared the various factors, including demographic factors and symptom-related factors, that might affect the results of DITI.Except the presence of trauma history (13.9% vs 31.8%, odds ratio 2.893, P = .008), no significant intergroup difference was found in baseline demographic factors, including age, gender, diabetes mellitus, spinal level of pathology, and intervention history. Among symptom-related factors, in the hyperthermia group, the symptom duration was shorter (10.64 weeks [95% confidence interval (CI) 8.36-13.04] vs 2.10 weeks [95% CI 1.05-3.53], P < .001) and Visual Analogue Scale (VAS) of radicular pain was higher (4.23 ± 1.29 vs 5.18 ± 1.40, P < .001) than in the hypothermia group. Also, in the regression analysis, significant factors for hyperthermia include the presence of trauma history, shorter symptom duration (cut-off value 2.50 weeks or less) and higher VAS of radicular pain (cut-off value 4.50 or more).In patients with trauma history, acute phase, and severe radicular pain, hyperthermia in DITI is not unusual and careful interpretation of the DITI results is necessary for proper diagnosis and treatment decisions in spinal radiculopathy.

Novel methods of imaging and analysis for the thermoregulatory sweat test

The thermoregulatory sweat test (TST) can be central to the identification and management of disorders affecting sudomotor function and small sensory and autonomic nerve fibers, but the cumbersome nature of the standard testing protocol has prevented its widespread adoption. A high-resolution, quantitative, clean and simple assay of sweating could significantly improve identification and management of these disorders. Images from 89 clinical TSTs were analyzed retrospectively using two novel techniques. First, using the standard indicator powder, skin surface sweat distributions were determined algorithmically for each patient. Second, a fundamentally novel method using thermal imaging of forced evaporative cooling was evaluated through comparison with the standard technique. Correlation and receiver operating characteristic analyses were used to determine the degree of match between these methods, and the potential limits of thermal imaging were examined through cumulative analysis of all studied patients. Algorithmic encoding of sweating and nonsweating regions produces a more objective analysis for clinical decision-making. Additionally, results from the forced cooling method correspond well with those from indicator powder imaging, with a correlation across spatial regions of -0.78 (confidence interval: -0.84 to -0.71). The method works similarly across body regions, and frame-by-frame analysis suggests the ability to identify sweating regions within ~1 s of imaging. Although algorithmic encoding can enhance the standard sweat testing protocol, thermal imaging with forced evaporative cooling can dramatically improve the TST by making it less time consuming and more patient friendly than the current approach. NEW & NOTEWORTHY The thermoregulatory sweat test (TST) can be central to the identification and management of several common neurological disorders, but the cumbersome nature of the standard testing protocol has prevented its widespread adoption. In this study, images from 89 clinical TSTs were analyzed retrospectively using two novel techniques. Our results suggest that these improved methods could make sweat testing more reliable and acceptable for screening and management of a range of neurological disorders.

Identification of complex regional pain syndrome in the upper limb: Skin temperature asymmetry after cold pressor test

Background

Skin temperature asymmetry (SkTA) may assist in early identification of complex regional pain syndrome (CRPS), but previous work has been limited by methodological shortcomings including failure to account for the cutaneous nerve distribution where temperature is measured and reliance on laboratory equipment not clinically available. Pilot work suggested that a cold pressor test (CPT) provided a consistent thermoregulatory stress and might increase sensitivity/specificity of SkTA measurements generated reliably by handheld infrared (IR) thermometers.

Aims

This study investigated the sensitivity, specificity, and validity of SkTA in the upper limb to identify CRPS.

Methods

This study was part of a larger clinical trial (the SARA study: www.clinicaltrials.gov NCT02070367). Using IR thermometers, we evaluated SkTA over major peripheral nerve distributions in the hands before and after immersing a single foot in 5°C water for 30 s. Participant groups included healthy volunteers, CRPS, known nerve injury, and hand fracture.

Results

SkTA was measured in 65 persons, including 17 persons with CRPS (meeting Budapest criteria). Analysis of variance for n = 378 SkTA observations supported diagnosis, CPT, and nerve distribution as significant predictors (P < 0.001) explaining 94% of the variance. Post CPT, sensitivity for a >1.5°C SkTA improved to 82.4% from 58.8%, whereas specificity dropped from 56.3% to 43.8%.

Conclusion

This study adds further support for the accuracy of SkTA as a diagnostic indicator of CRPS. Further precision in estimates will be gained from larger studies, which should also seek to replicate our findings for SkTA in the lower limbs.

Sensory and sympathetic disorders in chronic non-specific neck pain

The signs of sympathetic and sensory nerve-related disorders are not widely investigated in chronic nonspecific neck pain (NNP) patients. Thus, we performed skin temperature (Tsk), evaporation and touch threshold (TT) measurements to reveal possible dysfunctions at the fingertips of NNP patients (n=60) compared with healthy controls (n=11). Neck pain intensity was the main modifier of Tsk, and age the main modifier of TT in a multivariate model. On comparisons of the subgroups of NNP patients with unilateral (n=26) and bilateral (n=34) symptoms and controls, TT differed and Tsk tended to differ, the unilateral pain patients being found to demonstrate higher TT values on both sides. Interrelations between the measured parameters were found in the controls, but not in the patients. The NNP patients exhibited signs of functional impairment of innervation reflected in changes in tactile sensitivity and vasoactive sympathetic function. These changes may be based on both central and peripheral mechanisms, which possibly differ in patients with unilateral and bilateral symptoms.

Thermographic evaluation of hind paw skin temperature and functional recovery of locomotion after sciatic nerve crush in rats

INTRODUCTION

Peripheral nerves are often damaged by direct mechanical injury, diseases, and tumors. The peripheral nerve injuries that result from these conditions can lead to a partial or complete loss of motor, sensory, and autonomic functions, which in turn are related to changes in skin temperature, in the involved segments of the body. The aim of this study was to evaluate the changes in hind paw skin temperature after sciatic nerve crush in rats in an attempt to determine whether changes in skin temperature correlate with the functional recovery of locomotion.

METHODS

Wistar rats were divided into three groups: control (n = 7), sham (n = 25), and crush (n = 25). All groups were subjected to thermographic, functional, and histological assessments.

RESULTS

ΔT in the crush group was different from the control and sham groups at the 1st, 3rd and 7rd postoperative days (p<0.05). The functional recovery from the crush group returned to normal values between the 3rd and 4th week post-injury, and morphological analysis of the nerve revealed incomplete regeneration at the 4th week after injury.

DISCUSSION

This study is the first demonstration that sciatic nerve crush in rats induces an increase in hind paw skin temperature and that skin temperature changes do not correlate closely with functional recovery.

NeuPSIG guidelines on neuropathic pain assessment

This is a revision of guidelines, originally published in 2004, for the assessment of patients with neuropathic pain. Neuropathic pain is defined as pain arising as a direct consequence of a lesion or disease affecting the somatosensory system either at peripheral or central level. Screening questionnaires are suitable for identifying potential patients with neuropathic pain, but further validation of them is needed for epidemiological purposes. Clinical examination, including accurate sensory examination, is the basis of neuropathic pain diagnosis. For more accurate sensory profiling, quantitative sensory testing is recommended for selected cases in clinic, including the diagnosis of small fiber neuropathies and for research purposes. Measurement of trigeminal reflexes mediated by A-beta fibers can be used to differentiate symptomatic trigeminal neuralgia from classical trigeminal neuralgia. Measurement of laser-evoked potentials is useful for assessing function of the A-delta fiber pathways in patients with neuropathic pain. Functional brain imaging is not currently useful for individual patients in clinical practice, but is an interesting research tool. Skin biopsy to measure the intraepidermal nerve fiber density should be performed in patients with clinical signs of small fiber dysfunction. The intensity of pain and treatment effect (both in clinic and trials) should be assessed with numerical rating scale or visual analog scale. For future neuropathic pain trials, pain relief scales, patient and clinician global impression of change, the proportion of responders (50% and 30% pain relief), validated neuropathic pain quality measures and assessment of sleep, mood, functional capacity and quality of life are recommended.

Thermometric diagnosis of peripheral nerve injuries. Assessment of the diagnostic accuracy of a new practical technique

The diagnosis of nerve injury using thermotropic liquid crystal temperature strips was compared blindly and prospectively against operative findings in 36 patients requiring surgical exploration for unilateral upper limb lacerations with suspected nerve injury. Thermotropic liquid crystal strips were applied to affected and non-affected segments in both hands in all subjects. A pilot study showed that a simple unilateral laceration without nerve injury results in a cutaneous temperature difference between limbs, but not within each limb. Thus, for detection of a nerve injury, comparison was made against the unaffected nerve distribution in the same hand. Receiver operating characteristic curve analysis showed that an absolute temperature difference > or = 1.0 degrees C was diagnostic of a nerve injury (area under the curve = 0.985, sensitivity = 100%, specificity = 93.8%). Thermotropic liquid crystal strip assessment is a new, reliable and objective method for the diagnosis of traumatic peripheral nerve injuries. If implemented in the acute setting, it could improve the reliability of clinical assessment and reduce the number of negative surgical explorations.

Thermographic assessment of inferior alveolar nerve injury in patients with dentofacial deformity

PURPOSE

The purpose of this study was to evaluate the injury and recovery of the inferior alveolar nerve in orthognathic patients at 1 and 4 weeks after surgery using electronic thermography.

MATERIALS AND METHODS

Twenty subjects with Class III dentofacial deformity were studied. All patients underwent bilateral sagittal split ramus osteotomy. To image the temperature of the face, 1 anteroposterior view and 1 lateral view were taken from both the right and left sides. Similar images were taken at 1 and 4 weeks after surgery. The control was the presurgical temperature of the 20 patients who showed unilateral or bilateral nerve damage after surgery.

RESULTS

In the patients with unilateral nerve damage (n = 14), on the anteroposterior views, the temperatures of the mentum on the 2 sides differed by 0.64 degrees C at 1 week after surgery, and the difference decreased to 0.23 degrees C at 4 weeks after surgery. On the lateral images, the differences in temperature between the mentum areas were 0.10 degrees C at 1 week and 0.27 degrees C at 4 weeks after surgery. In the patients with bilateral nerve injury (n = 6), on the anteroposterior views, the temperatures of the mentum on the 2 sides differed by 0.20 degrees C at 1 week after surgery and 0.13 degrees C after 4 weeks. On the lateral views, the differences were 0.18 degrees C at 1 week and 0.34 degrees C at 4 weeks after surgery. Using the repeated measurement analysis method, the anteroposterior view showed statistically significant results in the patients with unilateral nerve damage.

CONCLUSION

The infrared body temperature method is an objective method that can be applied as a supplemental diagnostic method for inferior alveolar nerve injury.

Sympathetic pathology evidenced by hand thermal anomalies in carpal tunnel syndrome

OBJECTIVE

To clarify sympathetic pathology in carpal tunnel syndrome and the usefulness of digital infrared thermography as a diagnostic aid.

MATERIAL AND METHODS

38 clinically diagnosed carpal tunnel syndrome hands from 30 patients (confirmed by the standard nerve conduction studies) and 41 hands from 22 healthy volunteers (the hands having current finger inflammation were excluded) were studied. A series of hand infrared photos of each subject were taken and stored by using the technique of digital infrared thermography. We studied the infrared pictures and measured the temperatures of finger tips from digit 1 (D1) to digit 5 (D5), the center point of thenar (Th) and hypothenar eminences (Ht), then we calculated the temperature differences (absolute values) between each two of the 7 points, and median index (MI): (D1-D2)+(D2-D3)+(D1-D3). The means of D2 and Th (MD2+Th), D5 and Ht (MD5+Ht) were also calculated.

RESULTS

The results showed that the temperatures of median nerve distribution area in the hands were highly significantly different (Th-Ht, p < 0.001, MI, p < 0.001) between carpal tunnel syndrome (CTS) and the control group. The differences between the median and ulnar nerve distribution area were also highly significantly different in CTS hands (MD2+Th compared to MD5+Ht, p < 0.01). The sensitivity and specificity of digital infrared thermography were 84 and 91%, respectively.

CONCLUSION

Digital infrared thermography suggests sympathetic neural pathology in carpal tunnel syndrome. It may also be useful as an additional non-invasive tool in the diagnosis of CTS especially in the early stage.

Segmental regulation pattern of body surface temperature in the rat hindlimb

Body surface zones or 'thermatomes', whose temperature is regulated by a single spinal segment, were investigated by thermography in the rat hindlimb. First, the spatial relation between the dermatome delineated by dye extravasation and the corresponding thermatome was investigated in rats pretreated with intravenous application of Evans blue. Electrical stimulation of the spinal nerves and sympathetic trunk segments at L3 and L5 induced a distal dominant temperature decrease. In contrast, Evans blue extravasation appeared in the medial (in L3) and lateral (in L5) paw only by electrical stimulation of the spinal nerves. Second, thermatomes L1-L5 were determined in other rats. Electrical stimulation of the sympathetic trunk segments L1-L6 produced a temperature decrease in the abdomen, hindlimb, and tail. However, the hindlimb temperature was regulated mainly by L2-L5 levels, particularly by L4 and L5. The abdomen was regulated uniformly by L1-L6, and the tail by L6. It was demonstrated that thermatomes are manifested differently from the corresponding dermatomes in the rat hindlimb.

Role of thermography in the assessment of infraorbital nerve injury after malar fractures

We studied 45 patients with malar fractures who had some degree of infraorbital nerve deficit. Thermographic facial images failed to show any substantial changes in the temperature profiles of the affected and the normal control sides in relation to reco very of their facial sensation. Although some patients who had thermography on the day of injury showed significant temperature differences between the affected and the normal sides, these differences were probably the result of the acute inflammatory ch anges caused by the injury. We suggest that infrared thermography has little place in the assessment of infraorbital nerve deficits.

Computerised infrared imaging system for studying thermal activation on the skull following somatic stimulation in small animals

A computerised infrared imaging system has been developed to measure infrared radiation as a means of functionally mapping the cerebral cortex. In two species of small mammal, rat and gerbil, the authors localised the thermal changes at the skull overlying the somatic sensory cortex following somatic stimulation of the mystacial vibrissae. Though typically small in magnitude, a thermal response could be detected through the skull. To enhance detection sensitivity, a number of measures were taken to improve various aspects of data acquisition, stimulus delivery and control of experimental conditions. Regarding data analysis, a coordinate system based on skull landmarks was adopted to localise thermally-active regions for comparison across animals of the same species. To extract the region of weak temperature changes, a coarse-to-fine detection strategy was developed, which searched automatically for clusters of temporally- and spatially-correlated pixels above a data-driven threshold. Thus, the dynamic aspect of the thermal changes at any region of interest on the skull could be studied efficiently. The detection algorithm was tested against simulated responses in addition to empirical data obtained from animals. All of the above software was integrated in a user-friendly package.

Electronic thermography for the assessment of inferior alveolar nerve deficit

Neurosensory deficit is one of the major complications encountered in oral and maxillofacial surgery. OBJECTIVES. To determine the efficacy of electronic thermography in objectively assessing neurosensory deficits of the inferior alveolar nerve. STUDY DESIGN. Three studies were conducted measuring skin temperature over the chin region of the face at 0.1 degree C accuracy. RESULTS. (1) Thermal symmetry of the chin region in normal subjects (delta T = 0.2 degree C, SD = 0.02 degree C); (2) Induction of transient thermal asymmetry by local anesthetic injection (delta T = +0.4 degree C, SD = 0.2 degree C); (3) nine subjects with neurologic alterations of the inferior alveolar nerve (delta T = +0.5 degree C, SD = 0.2 degree C). Statistically significant differences were found between control group and experimental groups at p < 0.001 with the use of the Student's t test. CONCLUSIONS. These studies indicate that electronic thermography is capable of detecting sensory changes caused by inferior alveolar nerve injury or by pharmacologic nerve block.

Thermographic observations in unilateral carpal tunnel syndrome: report of 61 cases

This study was undertaken to assess the sensitivity and specificity of thermographic diagnosis of unilateral carpal tunnel syndrome in a patient population large enough to permit meaningful statistical analysis. Sixty-one persons with clinical diagnoses of unilateral carpal tunnel syndrome confirmed by electrodiagnostic examination and 40 symptom-free volunteers underwent standard thermographic examinations. The thermographic images were then randomly sorted and interpreted by an experienced physician thermographer. Fifty-seven of the 61 patients with carpal tunnel syndrome were found to have thermographic abnormalities, while only one of the control group was found to have such an abnormality. Individual area sensitivity was highest in the dorsal area, but addition of other regions increased this measure; specificity ranged between 98% and 100%. These findings would appear to confirm the value of thermography in the diagnosis of unilateral carpal tunnel syndrome.

Future applications of electronic thermography

The dental literature does not yet indicate the full range of facial thermographic findings in health and disease. Thermography is not useful in assessing some common dental problems, such as periapical granuloma. Promising reports, however, support its use in the diagnosis of neuralgias and atypical odontalgia, TMJ, nerve damage and repair after oral surgery, and in evaluating local dental anesthesia. Unfortunately, few if any of these studies were properly designed or conducted, limiting current attempts to define the value of thermography in dentistry. Until this situation resolves, ET of the face, for use in dentistry, can only be considered an investigational procedure. More research will clarify the precise contribution of thermography to dental problems.

Quantification of thermal asymmetry. Part 2: Application in low-back pain and sciatica

Temperature differences between the lower extremities were measured using a computerized thermometric scanning system in order to compare the degree of thermal asymmetry in 144 patients with low-back pain. The patients displayed highly significant thermal asymmetries, with the involved limb being cooler (p less than 0.001). When asymmetries exceeded 1 standard deviation from the mean temperature of homologous regions measured in 90 normal control subjects, the positive predictive value of thermometry in detecting root impingement was 94.7% and the specificity was 87.5%. These values indicate that calculation of temperature asymmetry is particularly effective in evaluating reported pain in psychosocially affected patient populations in whom the chance of positive myelography or impaired root function is low. In this group of patients, thermometric study provides physicians with important information for proper decision making. The test can be performed to avoid more invasive and probably less revealing diagnostic or exploratory surgical procedures.

Assessment of myocardial blood flow by real-time infrared imaging

In order to evaluate the applicability of infrared imaging for the assessment of myocardial perfusion, 10 open-chested dogs were studied by a real-time infrared imaging system. The left anterior descending coronary artery was occluded for 90 min followed by 210 min of reperfusion. During the experiment, myocardial surface temperature was mapped by an infrared imaging system with a thermal resolution power of 0.1 degree C and correlated with regional myocardial blood flow measured using radiolabeled microspheres. Following the experiment, acute myocardial injury was evaluated using triphenyltetrazolium chloride staining. After 90 min of ischemia, there was a significant correlation between myocardial blood flow and myocardial surface temperature (R = 0.694, P less than 0.001). After reperfusion, temperature did not correlate with blood flow, but there was a significant correlation between temperature and ischemic myocardial injury (R = 0.551, P less than 0.05). Temperature changes during acute regional ischemia and reperfusion may be regulated by the changes in myocardial blood flow and myocardial metabolism. Temperature analysis using real-time infrared imaging may be a useful means for the evaluation of myocardial blood flow and myocardial injury during ischemia and reperfusion.

Thermography in posttraumatic pain

Posttraumatic pain is often associated with complex disturbances of the sympathetic nervous system which also controls microcirculation of the skin. Circulatory skin changes are in turn reflected by altered superficial thermal emission, which can be reliably imaged by thermography. Examples of classic thermographic patterns associated with commonly occurring injuries and detected along cutaneous distributions of peripheral nerves or spinal root dermatomes are presented. Thermographic abnormalities may also occur in ondermatomal distributions to involve an entire hand, foot, or extremity as observed in reflex sympathetic dystrophy. Such thermographic findings often appear before skin or roentgenographic changes become manifest and lead to earlier diagnosis. Prompt and more effective treatment, particularly in reflex sympathetic dystrophy, may thereby be initiated so that full blown, difficult to manage, chronic disability may be averted. The diagnosis of malingering may also be strengthened or suspected if thermographic studies together with other examinations are normal.

Rett syndrome: new observations

Two elderly females with Rett syndrome are reported with evidence of a slowly progressive central and distal peripheral nervous system involvement. Thermography in 4 girls confirmed distal hypothermia of the extremities in a glove and stocking distribution. Unilateral sympathectomy during surgery for scoliosis in one of them resulted in increased warmth and physical growth of the foot and nails, compared to the uninjured side. This suggests increased sympathetic tone as the probable cause of distal hypothermia, vasomotor instability and dystrophy of the feet in this disorder. In an attempt to identify a marker, girls with clinically classical Rett syndrome had plasma and urinary cell evaluation for an unusual glycolipid. A blind study using a small number of patients failed to prove absolute specificity and additional studies are required to evaluate its validity as a marker for Rett syndrome.

Computerized thermography. The emergence of a new diagnostic imaging modality

Medical thermology is a relatively new diagnostic imaging modality that is based on thermography and has just recently gained acceptance by the medical community at large. In fact, the first comprehensive book on thermology appeared in press just a few months ago (2). Thermography is the recording and displaying of images that depict the distribution of temperature on the skin surface of patients. Thermology is the systematic interpretation of clinical thermograms. The leading thermographic technique is now based on remote infrared sensing. using digitizing techniques and microcomputers, the images can be processed to facilitate better thermological interpretation. This paper presents a brief account of the evolvement of this imaging modality, its current technology and medical uses, and its potential to become a major diagnostic tool in a large number of clinical situations. Finally, we will attempt to assess the overall role and place of thermology in medicine while also pointing out the need for fundamental thermological research to support the current empirical diagnostic applications.

Precision thermal imaging of the extremities

Precision thermal imaging can give valuable physiological information which is not obtainable by any other means. It is particularly useful for follow up because it is painless and noninvasive. Meticulous attention to technique is necessary. A strict pre-examination protocol must be adhered to. Proper equilibration with ambient temperature is essential. The parts to be imaged must be insulated from other parts of the body. Standard views must be obtained. Adherence to good technique will yield repeatable accurate images.

Thermographic imaging of cutaneous sensory segment in patients with peripheral nerve injury. Skin-temperature stability between sides of the body

Sensory examination based on the patient's subjective assessment of symptoms may raise difficult questions about whether the individual's expressed complaint is based on organic nerve damage, psychogenic factors, or even malingering. A prototype computerized telethermograph has allowed clinical quantification of peripheral nerve injury. The system makes possible mapping and imaging of the damaged area, as well as skin temperature measurements. In normal persons, the skin temperature difference between sides of the body was only 0.24 degree +/- 0.073 degree C. In contrast, in patients with peripheral nerve injury, the temperature of the skin innervated by the damaged nerve deviated an average of 1.55 degrees C (p less than 0.001). The new technique requires further refinement, but it appears that use of this method may be cost-effective in helping to resolve medicolegal conflicts concerning peripheral nerve injury.