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Seward B Rutkove

Publications and source records attributed to Seward B Rutkove.

17 recordsLinked to original sources
PubMed2006

Electrical impedance in bovine skeletal muscle as a model for the study of neuromuscular disease.

Electrical impedance myography (EIM) consists of a set of bioimpedance methods configured for neuromuscular disease assessment, in which high-frequency electrical current is applied to a limb and the consequent surface voltage pattern over a muscle is evaluated. Prior human work has shown that the EIM parameters of resistance, reactance and phase change in different neuromuscular disease states including neurogenic and myopathic conditions. These parameters are also sensitive to the angle at which current is applied and measured relative to muscle fiber direction, a characteristic known as anisotropy. In order to obtain insights into the impedance characteristics of mammalian skeletal muscle without the confounding effects of an overlying skin-fat layer, bone and irregular muscle shape, we performed EIM on three 'nearly ideal' round 16 cm diameter, 1 cm equal thickness pieces of bovine rectus abdominis muscle. Using a standardized tetrapolar electrode array with 50 kHz electrical current, we identified strong anisotropy in the measured reactance and phase, with weaker anisotropy identified for resistance. We also found that increasing amounts of muscle maceration, a rough model of myopathic or traumatic muscle fiber injury, reduced phase and muscle anisotropy when current was injected perpendicular to the muscle fibers. These findings support that EIM parameters, including muscle anisotropy, are likely to be sensitive to the pathological changes that occur in neuromuscular disease states.

Algorithms↗
PubMed2006

Effects of age on muscle as measured by electrical impedance myography.

Electrical impedance myography (EIM) is a painless and non-invasive technique for the assessment of muscle which we apply here to the effects of normal aging. The paper presents a cross-sectional analysis of EIM data from the quadriceps and tibialis anterior of 100 healthy subjects (44 men, 56 women, ages 18-90 years). The principal EIM parameter, the spatially averaged phase theta(avg), shows a roughly quadratic reduction with increasing age, declining more steeply beyond 60 years. The correlation was stronger in men (quadriceps: r2 = 0.68 for men, 0.52 for women; tibialis anterior: r2 = 0.74 for men, 0.38 for women; p < 0.001 throughout). Additionally, four subjects (age greater than 75 years) were asked to return for repeat testing several years after their initial assessment. These longitudinal results qualitatively confirm the cross-sectional data, though with greater reductions in theta(avg) at high age. The findings of this study support the potential use of EIM as a simple and effort-independent test of muscle health in the elderly.

Adult↗
PubMed2006

Electrical impedance myography: transitioning from human to animal studies.

OBJECTIVE: To determine the feasibility of performing electrical impedance myography (EIM) in rats. METHODS: EIM was performed on the hamstring muscles of 6 healthy adult rats with applied frequencies of 2-300 kHz. Studies were performed over a 6-week period, with 3 rats having recordings made from the skin (surface EIM) and 3 with recordings directly from the muscle (direct-muscle EIM). In addition, sciatic nerve crush was performed on one rat and comparisons made pre- and post-injury. Reactance and resistance were measured and the primary outcome variable, the phase angle (theta), calculated. RESULTS: EIM patterns in the rat hamstring muscles were qualitatively similar to those observed in human subjects. This held true for both surface and direct-muscle recordings, although direct-muscle data appeared less repeatable. Sciatic nerve crush data in the single rat showed a dramatic reduction in phase and a relative loss of frequency-dependence. CONCLUSIONS: EIM data similar to that obtained from human subjects can be acquired from rat muscles with surface recordings proving more consistent and easier to obtain than direct-muscle recordings. Changes seen with sciatic nerve crush mirror those seen in patients with neurogenic injury. SIGNIFICANCE: These results support the possibility of performing EIM on rat models of neuromuscular disease.

Animals↗
PubMed2006

Test-retest reproducibility of 50 kHz linear-electrical impedance myography.

OBJECTIVE: Electrical impedance myography (EIM) is a method for evaluating muscle in which high-frequency, low-intensity alternating current is applied to a body region and the resulting surface voltage pattern over a muscle of interest is measured. In this study, the reproducibility for the simplest of these techniques, 50 kHz linear-EIM, was assessed for three muscles. METHODS: Fifty kilohertz linear-EIM was performed on the biceps, quadriceps, and tibialis anterior of 30 normal subjects ranging in age from 21 to 90 years, and the major outcome variable, the spatially averaged phase (thetaavg), measured. The measurements were repeated within 250 days and comparisons between the two data sets made. RESULTS: Reproducibility, as measured by the intraclass correlation coefficients for all three muscles, was very high at 0.970, 0.971, and 0.938 for biceps, quadriceps, and tibialis anterior, respectively. Variability between measurements was on average 4.2% for all muscle combined, with an upper limit of 16.8%. CONCLUSIONS: Fifty kilohertz linear-EIM demonstrates excellent test-retest reproducibility. SIGNIFICANCE: These results support the view that 50 kHz linear-EIM has the potential to be used as a simple, fast, and non-invasive measurement for the assessment of disease status, either as part of individual patient care or as a surrogate outcome measure in clinical trials work.

Adult↗
PubMed2006

Assessing neuromuscular disease with multifrequency electrical impedance myography.

Electrical impedance myography (EIM) is a noninvasive technique for neuromuscular assessment in which low-intensity alternating current is applied to a muscle and the consequent surface voltage patterns are evaluated. Previous work using a single frequency of 50 kHZ has demonstrated quantitative correlation of EIM parameters with disease status. In this investigation we examined the use of multifrequency EIM, studying a prototypical neurogenic disease (amyotrophic lateral sclerosis, ALS) and myopathic disorder (inflammatory myopathy, IM). Eleven ALS patients, 7 IM patients, and 46 normal subjects participated in the study. Although disease-specific patterns were not identified such that IM could be differentiated from ALS, impedance vs. frequency patterns for diseased subjects differed substantially from those of the age-matched normal subjects, with the greatest alterations occurring in the most severe cases. Multifrequency EIM may be well-suited to serve as an easily applied technique to assess disease severity in a variety of neuromuscular conditions.

Action Potentials↗
PubMed2005

Electrical impedance myography in the detection of radiculopathy.

Electrical impedance myography (EIM) is a new bioimpedance-based technique for neuromuscular disease assessment. Past work has focused on EIM in the evaluation of diffuse diseases (such as myopathy). In this study, the method's most basic form, linear-EIM, was used for the assessment of restricted radiculopathic disease. Ten normal subjects and 10 patients with unilateral cervical or lumbosacral radiculopathy, diagnosed by electromyography and clinical criteria, were enrolled. Linear-EIM was performed bilaterally on all individuals, and comparisons with the major outcome variable, theta(avg), were made. In normal subjects, side-to-side differences in theta(avg) averaged 0.64% and were no greater than 15.9% in magnitude. In the 10 patients with radiculopathy, theta(avg)was consistently lower in the affected extremity, with a mean side-to-side difference of 15.3%, but ranging as low as 72.3%; there was a tendency for muscles with more prominent chronic neurogenic change to show greater relative reductions in theta(avg). These findings support the potential utility of EIM in assessment of localized neuromuscular disease.

Arm↗
PubMed2005

Electrode position and size in electrical impedance myography.

OBJECTIVE: Linear-electrical impedance myography (EIM) is a non-invasive technique for the evaluation of muscle, in which high-frequency alternating current is injected into the body via two surface electrodes, and the resulting voltage pattern over a selected muscle is measured using a second, larger set of electrodes. The precise location and size of the electrodes can be critical to the data obtained, and in this study the effects of variation in these factors were evaluated. METHODS: Linear-EIM was performed in 5 subjects while varying the location of the current injecting electrodes and in an additional 8 subjects while varying the position of the voltage electrodes. RESULTS: The major outcome variable, the 'spatially averaged phase' (theta(avg)), decreased as the ipsilateral current injecting electrode was moved farther from the voltage electrodes, reaching a plateau 15-20 cm distant. As for the voltage electrode array, distal-proximal shifts resulted in the greatest changes, with variation in theta(avg) being as high as 14% per cm; circumferential shifts around the limb had more modest effects. CONCLUSIONS: Linear-EIM results depend systematically on current and voltage electrode positions, but with reasonable care variation can be minimized. SIGNIFICANCE: With proper attention to electrode placement, linear-EIM has sufficient reproducibility to become an important clinical tool in neuromuscular disease evaluation.

Adult↗
PubMed2004

Repetitive nerve stimulation for the evaluation of peripheral nerve hyperexcitability.

OBJECTIVE: To examine the utility of repetitive nerve stimulation (RNS) in the evaluation of peripheral nerve hyperexcitability (PNH). BACKGROUND: PNH describes a group of disorders characterized by muscle cramps, twitching and stiffness. When severe, PNH may be characterized by the presence of continuous muscle fiber activity on routine needle electromyography (EMG). In milder forms of the disease, nerve hyperexcitability may be evidenced by the presence of after-discharges or cramp potentials following RNS. METHODS: Fifty-four patients were prospectively recruited and classified into one of three groups-PNH, other neuromuscular disease and controls. We recorded and quantified the after-discharges and cramp potentials following RNS at 1, 5, 10 and 30 Hz. RESULTS: The proportion of nerves with after-discharges and/or cramp potentials was significantly greater in the PNH group than the control group at both 5 Hz (p=0.03) and 10 Hz (p=0.01), as well as in the neuromuscular disease group compared to controls at 5 Hz (p=0.02). There was also a significant concordance between complaints of muscle cramps and fasciculations and the finding of after-discharges and/or cramp potentials at both 5 Hz (p=0.005) and 10 Hz (p=0.004). At a stimulation frequency of 10 Hz, the sensitivity of RNS for the diagnosis of PNH (primary or secondary) was 79% and the specificity was 88%. CONCLUSION: Our findings suggest that RNS at or below a stimulation frequency of 10 Hz (when positive) is a useful test for the diagnosis of PNH, whether it is primary or secondary.

Adult↗
PubMed2003

Pattern recognition.

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Attitude of Health Personnel↗
PubMed2003

Ambulatory foot temperature measurement: a new technique in polyneuropathy evaluation.

Complaints of abnormal foot temperature are common among patients with polyneuropathy. However, there is no published method of ambulatory foot temperature measurement to identify possible thermoregulatory disturbances in these patients. We configured a digital electronic thermometer and thermocouple to measure and record distal foot and ambient temperatures simultaneously every minute for 24 to 48 h. Sixteen patients with polyneuropathy and 5 normal subjects were studied; 12 patients with polyneuropathy and 4 normal subjects had at least 24 h of successful recording. The data obtained from these patients were consistent and easily summarized by standard statistical methods. In the others, technical difficulties produced nonphysiological readings. In the patients with polyneuropathy, changes in foot temperature mirrored ambient temperature fluctuations more closely than in normal subjects. This technique shows promise in studying temperature regulation in the feet and may provide new insights into neuropathy-associated pain and the pathogenesis of polyneuropathy.

Adult↗
PubMed2003

Ulnar neuropathy in the forearm: A possible complication of diabetes mellitus.

Ulnar neuropathy in the forearm is an unusual cause of hand weakness and sensory loss that is most often attributed to compression of the nerve distally within the humero-ulnar arcade (cubital tunnel). An association with diabetes mellitus, however, has not been reported. We identified four patients with type I diabetes mellitus and clinical findings suggestive of ulnar neuropathy in whom electrophysiologic testing revealed partial conduction block or abnormal temporal dispersion within the forearm segment of the ulnar nerve. Although evidence for a mild underlying polyneuropathy was present in three patients, the ulnar nerve abnormalities were disproportionately severe. In all cases, a Martin-Grüber anastomosis was excluded. Whether this lesion is due to an increased propensity to focal compression of the ulnar nerve within the humero-ulnar arcade or whether it represents a localized manifestation of the generalized polyneuropathy remains to be determined.

Diabetes Mellitus, Type 1↗
PubMed2003

Electrical impedance of muscle during isometric contraction.

Non-invasive measurements of the 50 kHz impedance of the anterior forearm show that the resistance and reactance increase under voluntary isometric contraction of the finger flexor muscles. The relationship between impedance and force is nonlinear, dependent on the type of test, the history of prior exercise, and the health status of the subject. Nevertheless, useful dynamic response parameters betaR = deltaR/R0deltaF and betax = deltaX/X0deltaF can be defined, typically a few hundredths of a per cent per newton. Evidence is presented for the view that these effects reflect dominantly physiological as opposed to morphological changes in the muscle. In particular, (a) the impedance changes many milliseconds before the force is generated, (b) betaR and betaX change substantially during a series of repetitions of the same exercise, and (c) the impedance does not return to its original value following relaxation of the muscle. Supporting data are presented for six healthy men and women, with ages ranging from 19 to 70 years. A preliminary study of patients with various neuromuscular diseases was also performed, amongst whom marked quantitative and qualitative contrasts with the healthy group were found. Further research aimed at assessing the clinical potential of such measurements is discussed, as are studies to elucidate the underlying mechanisms for the impedance changes. We propose the name 'dynamic electrical impedance myography' for this new technique.

Aged↗
PubMed2002

Localized bioimpedance analysis in the evaluation of neuromuscular disease.

Localized bioimpedance analysis is a novel, noninvasive technique with potential application to neuromuscular disease. In this procedure, high-frequency alternating current is passed through muscle, and parameters related to the consequent voltage pattern are evaluated. Currents flowing perpendicular to muscle fibers encounter many more cell membranes than do currents flowing parallel to them, producing surface voltage patterns that are altered by disease. Using this technique, 45 normal subjects and 25 patients with various neuromuscular diseases were studied, including 4 with amyotrophic lateral sclerosis, 4 with inflammatory myopathy, and 11 with inclusion-body myositis. Two parameters, the spatially averaged phase and the effective longitudinal resistivity, were altered in patients with neuromuscular disease. Reductions in phase correlated to disease progression, whereas normalization of phase correlated with disease remission. In patients with inclusion-body myositis, a unique pattern of reduced phase and elevated resistivity was identified. These findings suggest that localized bioimpedance analysis has the potential of playing a substantial role in the diagnostic and therapeutic evaluation of neuromuscular disease.

Adult↗
PubMed2002

Diagnostic accuracy of electrodiagnostic testing in the evaluation of weakness.

Electrodiagnostic testing is often used in the evaluation of patients presenting with weakness, but the diagnostic accuracy of the test in this setting is unknown. We prospectively identified 100 patients presenting to our electromyography (EMG) laboratory with the chief complaint of weakness, and compared their referring diagnosis with the electrophysiological diagnosis reached after electrodiagnostic testing. We reviewed each patient's medical record 9 months after EMG to yield a final diagnosis. Electrodiagnostic testing led to a single diagnosis in 79% of the cases; in 31%, this diagnosis was unsuspected by the referring clinician. Adequate follow-up was available for 79% of the patients. The electrodiagnostic testing resulted in a single, correct diagnosis in 73% of the patients and provided more than one possible diagnosis, one of which was correct, in an additional 18%, for an overall diagnostic accuracy of 91% in this group of patients presenting with weakness.

Adolescent↗
PubMedDate not supplied

Induction of myasthenia gravis, myositis, and insulin-dependent diabetes mellitus by high-dose interleukin-2 in a patient with renal cell cancer.

Interleukin-2 is an effective agent against renal cell carcinoma and melanoma, but it has been associated with autoimmune sequelae such as hypothyroidism and vitiligo. A 64-year-old man with non-insulin-dependent diabetes and metastatic renal cell carcinoma developed insulin-dependent diabetes after his first cycle of therapy with high-dose (HD) interleukin-2. After additional therapy with interleukin-2, the patient developed generalized myasthenia gravis (MG) and polymyositis, both of which responded to treatment with corticosteroids and plasmapheresis. To investigate the role of IL-2 in the development of these autoimmune complications, autoantibody titers were assayed from serum obtained before and after IL-2 treatment and after treatment with corticosteroids plus plasmapheresis. Before IL-2 treatment, the patient had antibodies directed against insulin, islet cell antigens, and striated muscle. Acetylcholine receptor antibody levels were normal before starting IL-2. After treatment with IL-2, the patient developed acetylcholine receptor binding antibodies and exhibited an increase in the striated muscle antibody titer from 1:40 to 1:160. Recovery from the MG and polymyositis was associated with substantial decreases in the acetylcholine receptor and striated muscle antibody titers. These findings suggest that HD IL-2 accelerated the progression of latent autoimmune diabetes and myositis in this patient whose tolerance to islet cell antigens and striated muscle had already been broken and precipitated a break in tolerance to the acetylcholine receptor resulting in the development of MG. This case demonstrates the importance of prompt recognition of IL-2-induced MG and shows how this complication can be successfully managed with aggressive therapy.

Carcinoma, Renal Cell↗