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Biomedical subjects

D Yarnitsky

Publications and source records attributed to D Yarnitsky.

At least 19 recordsLinked to original sources
PubMed1997

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.

Humans↗
PubMed1997

Smooth muscle electromyography from rat urethra.

Electrical signals recorded from the penis have been suggested as reflecting electromyographic activity in the underlying smooth muscles. In order to verify this assertion, we manipulated the signal recorded from rat urethra surface. Stimulation of the pelvic nerve brought about a reduction of activity (965 +/- 826 to 166 +/- 143 microV, root mean square of the power at range 0.005-1 Hz, P = 0.008), with a significant frequency-response relationship (P = 0.0002). This effect was not altered by temporary closure of the aorta (P = 0.89), thus ruling out hemodynamic artifact as a possible cause of signal change during stimulation. Our findings support the assertion that the signal indeed reflects activity in smooth muscle.

Animals↗
PubMed1997

Vibration reduces thermal pain in adjacent dermatomes.

Spatial summation of thermal pain crosses dermatomal boundaries. In this study we examined whether a vibrational stimulus applied to adjacent or remote dermatomes affects thermal pain perception to the volar forearm. Contact heat at 2 degrees C above thermal pain threshold was applied, and a Visual Analog Scale (VAS) was used for pain assessment. We found a significant decrease in mean VAS rating when simultaneous vibratory stimuli were given to the dermatome adjacent to that receiving thermal stimulation, or to the same dermatome on the contralateral side. There was no change in VAS rating when vibration was given two or more dermatomes away. Vibration within the same dermatome also did not yield a significant change in VAS rating, possibly due to difficulty in magnitude assessment of stimuli given simultaneously within a single dermatome. The finding that vibration can reduce pain across dermatomes may allow for more flexible design of stimulation therapy for pain.

Adolescent↗
PubMed1996

[Conservative therapy in carpal tunnel syndrome].

A prospective study was designed to determine which patients with carpal tunnel would respond to conservative therapy (splinting and local injection of corticosteroids). The study included 50 hands of 34 patients, aged 25-80 years, with a mean follow-up of 18 months. Conservative therapy was effective in 82% of hands after 8 weeks, but symptoms subsequently recurred, so that by the end of a year only 20% remained asymptomatic. Failure of conservative therapy was predicted by long duration of symptoms, older age, permanent paresthesia, 2-point discrimination threshold above 6 mm, positive Phalen test within 30 seconds, and long motor and sensory distal latency.

Adrenal Cortex Hormones↗
PubMed1996

Carpal tunnel syndrome in pregnancy: indications for early surgery.

The incidence of carpal tunnel syndrome is increased during pregnancy. The common conventional therapeutic approach is conservative, as symptoms usually abate after delivery. We describe our experience with 65 hands (50 patients), who were treated initially by a conservative approach and later, when required, surgically. We found that all patients who (i) had either started having CTS symptoms during the first two trimesters or had previous history of CTS symptoms; and (ii) had both a positive Phalen test within less than 30 seconds and abnormal two point discrimination at the finger tips ( > 6 mm), were eventually operated upon, either during or after pregnancy, as conservative measures failed. We therefore recommend consideration of an early surgical approach in patients fulfilling these criteria.

Adult↗
PubMed1996

The P300 in pain evoked potentials.

Pain evoked potentials (EPs) have been used in the last two decades as means of obtaining objective measures of pain, in clinical and experimental setups. The possibility that the pain EP wave contains elements of the endogenous P300 potential rather than being a neurophysiological correlate of pain has been raised by a number of authors, but the issue has not been resolved. In this study, two experiments were performed to study the effect of nonmodality-specific factors on the laser EP: (1) a stimulus attend as opposed to a stimulus-ignore condition and (2) counterbalanced oddball and task P300 stimulus presentations. The latter was to permit full examination of the separate and combined influences of each condition on the EP. Stimuli were given to the radial hand of 10 healthy volunteers using a CO2 laser. The positive component of the laser EP was affected by both manipulations relating to (1) attention (P = 0.0146) and (2) the frequency condition (P = 0.003) in the P300 paradigm. The task condition in the second paradigm did not affect the positive wave on its own, although its effect was visible in interaction with frequency (P = 0.033). In conclusion, although the presence of a somatic component in the laser EP cannot be rules out, we suggest that the laser EP contains a definite non-modality-specific P300 component, and is not a pure neurophysiological correlate of pain intensity.

Acoustic Stimulation↗
PubMed1996

Multiple session experimental pain measurement.

Experimental heat pain transients were administered to 30 normal volunteers over four weekly sessions, measuring both heat pain (HP) threshold and suprathreshold magnitude estimation through VAS. Repeatability and bias for these two factors were evaluated. Heat pain thresholds measured through the method of limits were previously shown to have inter-session bias, presumably due to a practice effect. Existence of such a bias between first and second measurement sessions casts doubt on the usefulness of this parameter for pain assessment of individuals over time. In the present study, measurements of normal HP thresholds over four sessions showed that bias exists between the first and successive sessions, but not among sessions other than the first. It is concluded that (i) HP thresholds obtained from a single session are of limited value, and should be carefully interpreted. (ii) Long-term studies that use the HP threshold should take results from the second (or later) session as their baseline. The Visual Analog Scale (VAS) is considered the 'gold standard' for assessment of clinical and suprathreshold experimental pain, and changes in VAS score are regarded as significant evidence of individual response to treatment, placebo, or experimental manipulation. Although its overall group accuracy and precision have been examined for both clinical and experimental pain, and found adequate (Price 1988), the VAS has not been rigorously assessed for repeatability. Stimuli at three pain levels, 1.5, 3 and 4.5 degrees C above each individual's heat pain threshold as determined at each session, were given. Several models of analysis of the VAS were tested and repeatabilities (r) obtained from these analyses demonstrate poor precision for each of the tested analysis models. For example, inter-session repeatabilities for the three individual pain levels ranged from r = 3.8-4.7, effectively providing a confidence interval of 7.6-9.4 for any VAS reading on a 0- to 10-point scale. An examination of intra-session VAS provided somewhat better results. Thus, use of the VAS in similar experimental settings is called into question. The use of the VAS in clinical settings, where individual assessments are necessary, is also called into question, but remains to be specifically tested.

Adolescent↗
PubMed1996

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.

Adult↗
PubMed1996

Polyneuropathy in impotence.

Three hundred and forty-one consecutive impotent patients were evaluated for the presence of polyneuropathy (PNP) by neurophysiological and psychophysical tools, including nerve conduction and quantitative sensory tests (thermal and vibratory). PNP was present in 38% of diabetics, and 10% of non diabetics. Overall, PNP was found in 19% of impotent patients. PNP is relatively common among impotent patients, and might play a causative role. Patients judged 'neurogenic' and those judged 'vasculogenic', based on nocturnal tumescence test (NPT) and vasoactive drug injection tests, had very similar rates of PNP (21 and 23%, respectively). Thus it is suggested that the vasoactive drug injection test does not serve in discriminating neurogenic from non-neurogenic impotence. NPT, however, faithfully discriminates psychogenic from organic impotence, as far as PNP is involved, since a very low percentage of patients with normal NPT had PNP.

Adolescent↗
PubMed1996

Pain-evoked potentials: what do they really measure?

Cerebral evoked potentials (EPs) in response to painful stimuli have been recorded since the 1970s. Based on the apparent relationship of the response amplitude to intensity of stimulation, these potentials are conventionally interpreted as reflecting the sensory-discriminative aspects of pain. As such, pain-EPs provide an objective measure for sensation of pain. An alternative interpretation regards the pain-EP as comprised of at least two overlapping components, one pain-specific, the other, a P300 wave. In the case of pain, the P300 may reflect the degree of discomfort or unpleasantness, thus reflecting the emotional-motivational aspect. To establish the nature of the pain-EP, mini doses of a benzodiazepine, counterbalanced with placebo, were given to 6 normal volunteers. Benzodiazepines decrease anxiety, and so diminish the emotional response to pain, but they have no analgesic effect. In all subjects, pain perception was unchanged, while the EP wave was almost completely obliterated. We conclude that the pain-EP reflects the emotional-motivational response to pain rather than the sensory-discriminative. Thus, it provides a useful neurophysiological tool for studying the emotions associated with pain.

Adult↗
PubMed1995

Paradoxical heat sensation in uremic polyneuropathy.

Sensory aspects of uremic neuropathy were studied in 36 patients using clinical assessment and quantitative sensory tests (QST). The outstanding abnormality in sensory quality was perception of heat in response to low temperature stimuli. This paradoxical heat sensation was found in the foot in 42% (15) of patients, far beyond the normal prevalence of 10%. Paradoxical sensation was positively related to cold hypoesthesia (P = 0.0004) suggesting disinhibition as a possible mechanism. Paradoxical heat sensation also positively related to creatinine level (P = 0.0012). Pruritus was present in 20 patients (56%), intensity not related to any biochemical or clinical parameter. Signs of sensory polyneuropathy (PNP), based on at least two abnormal parameters in the clinical assessment or QST, were found in 39% of patients (14), of whom 11 had paradoxical heat sensation. Thus, in 4 patients (11%), this sensory aberration preceded other signs for PNP. Paradoxical heat sensation seems to be a common and often early expression of the sensory neuropathy in uremia.

Adolescent↗
PubMed1995

Heat pain thresholds: normative data and repeatability.

Measurement of thresholds for heat-induced pain was performed on 106 normal subjects, at thenar eminence and foot dorsum, using the reaction time-inclusive method of limits. Tests were repeated 2 weeks following the first test for most of the subjects. After determination that there were no outlying data points and that there was no systematic relationship between magnitude and variability of test scores, data from between 72 and 76 subjects were used to define normal upper and lower ranges by age, as well as repeatability coefficients. This was done through ANOVA-based procedures that extend standard repeatability assessment methods. Normative data tables are presented, with measures of repeatability for the various sites and modalities. For the conventional test range, reaching 55 degrees C, measurement of heat pain thresholds can define both hyper- and hypoalgesia. Application of repeatability coefficients allows for intra-individual inter-session comparison in longitudinal studies.

Adult↗
PubMed1995

Sweat secretion, stratum corneum hydration, small nerve function and pruritus in patients with advanced chronic renal failure.

Sweat secretion, stratum corneum hydration and small nerve fibre function were measured in 40 patients with advanced chronic renal failure (CRF), using pilocarpine iontophoresis, electrical capacitance and a thermal sensory analyser which measures the thresholds of warm and heat pain sensation. Correlations were sought between these parameters, and the presence and severity of pruritus and skin xerosis were compared with 45 healthy control subjects. The mean sweat secretion and stratum corneum hydration of CRF patients were significantly lower than in controls. Thirteen patients had pathological thresholds to warm sensation on the foot, and eight on the hand. None had pathological thresholds to heat-pain. The presence of pruritus did not correlate with any of the following: xerosis, stratum corneum hydration, sweat secretion or the results of thermal testing.

Aged↗
PubMed1995

Corpus cavernosum electromyogram: spontaneous and evoked electrical activities.

Sympathetic skin responses recorded from the surfaces of limbs and the penis resemble the waveforms recorded by needle from the corpora cavernosa. Thus, corpus cavernosum electromyography might reflect a systemic sympathetic response rather than unique smooth muscle corporeal activity. We recorded electrical activity simultaneously from the corpora and limbs of 10 subjects. Spontaneous activity was unique to the corpora, while electrical activity in response to sympathetic activating maneuvers was found simultaneously in the corpora and limbs (Fisher's exact test, p < 0.001). It is concluded that 2 types of electrical activity can be recorded from the corpora--spontaneous activity, which might reflect specific smooth muscle activity, and response activity, which is part of the systemic response to sympathetic stimulation.

Adult↗
PubMed1994

Full dose vincristine (without 2-mg dose limit) in the treatment of lymphomas.

BACKGROUND: Most current lymphoma protocols limit vincristine dose to 2 mg per single dose. Because a lower dose of vincristine may be associated with poorer outcome, there is some rationale to increase the dose of vincristine. METHODS: The feasibility of full dose vincristine (i.e., 1.4 mg/m2 without 2-mg dose limit) was prospectively evaluated in lymphoma patients treated with various combinations. After an initial dose of 1.4 mg/m2, patients were carefully monitored, and dose was modified according to toxicity. RESULTS: One hundred and four consecutive patients (31 with Hodgkin's disease and 73 with non-Hodgkin's lymphoma), aged 18-78 years were evaluated. The first dose was greater than 2 mg in 90% of the patients. The mean actual dose (percent of projected dose) was 100% in the first course and gradually decreased to 64% in the eighth course. The mean actual dose intensity of vincristine (percent of projected dose intensity) during the initial six cycles of prednisone, methotrexate, calcium leucovorin, doxorubicin, cyclophosphamide, etoposide, and mechlorethamine, vincristine, procarbazine, prednisone (ProMACE/MOPP), cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP), and MOPP/doxorubicin, bleomycin, and vinblastine (MOPP/ABV) was 82% and MOPP/doxorubicin, bleomycin, and vinblastine was 82%, 83%, and 87%, respectively. Symptoms of neuropathy developed in 92% of the patients and were usually of mild or moderate severity. Toxicity included World Health Organization (WHO) Grades 3 and 4 constipation in 10 (10%), and WHO Grade 3 peripheral neurotoxicity in 16 (15%) patients. Rapid improvement was usually noticed within a few weeks after withdrawal of vincristine. The median duration of symptoms from discontinuation of vincristine was 3 months for paresthesiae and motor weakness and 5 months for muscle cramps. CONCLUSIONS: Full dose vincristine in lymphoma protocols is feasible but is associated with increased toxicity. The therapeutic advantage of full dose vincristine has yet to be proven.

Adolescent↗
PubMed1994

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.

Cold Temperature↗
PubMed1994

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.

Adult↗