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Biomedical subjects

S B Rutkove

Publications and source records attributed to S B Rutkove.

At least 19 recordsLinked to original sources
PubMed2002

A pilot randomized trial of oxandrolone in inclusion body myositis.

BACKGROUND: Inclusion body myositis (IBM) remains without effective therapy. As anabolic steroids have myotrophic properties, the authors studied whether a synthetic androgen, oxandrolone, would have efficacy in IBM. METHODS: A double-blind, placebo-controlled, crossover design was used. Patients received oxandrolone or placebo for 12 weeks followed by a minimum 2-month washout period, followed by 12 weeks of the alternative treatment. Maximal voluntary isometric contraction testing (MVICT), manual muscle testing (MMT), and functional performance testing were obtained before and after each treatment period, with the whole-body MVICT score as the primary outcome measure. RESULTS: Of 19 patients enrolled, 16 (14 men, 2 women; median age 68.5 years) had complete data for at least the first treatment period, with 13 completing the entire study. Whole-body MVICT improved by a median of 15.5 kg with drug and 4.1 kg with placebo (p = 0.06), whereas MMT demonstrated a median increase of 2.0 Medical Research Council points with drug and 0.9 point with placebo (p = 0.33). Upper-extremity MVICT demonstrated a significant treatment effect, with strength increasing a median 6.3 kg with drug vs 2.5 kg with placebo (p = 0.006). Stair climbing also increased a median of 1 step on average with drug versus no change with placebo (p < 0.001). Minimal adverse effects occurred. CONCLUSIONS: Oxandrolone had a borderline significant effect in improving whole-body strength and a significant effect in improving upper-extremity strength as measured by MVICT. Given these findings, further study of this drug, possibly in combination with an immunomodulating agent, is warranted.

Aged↗
PubMed2001

Effects of temperature on neuromuscular electrophysiology.

Like nearly all biologic structures, the peripheral nervous system is remarkably temperature sensitive. Clinical neurophysiologists are most aware of the untoward effects of cooling on nerve conduction studies, including reduced conduction velocity, prolonged distal latency, and increased response amplitude and duration. However, familiarity with the effects of temperature variation on the peripheral nervous system can also provide a deeper understanding of the physiological mechanisms underlying the function of nerve, muscle, and neuromuscular junction in health and disease. Intentional temperature alteration can also improve the diagnostic accuracy of certain electrophysiologic tests, such as the use of heat when performing repetitive nerve stimulation in myasthenia gravis or the use of cold during needle electromyography in some of the myotonic disorders. Finally, extremes of temperature have long been known to produce permanent neuronal dysfunction; recent investigations are beginning to elucidate the mechanisms of such injury.

Body Temperature↗
PubMed2001

Focal cooling improves neuronal conduction in peroneal neuropathy at the fibular neck.

Heat can induce conduction block (CB) in demyelinated neurons; whether cooling can reverse CB and increase strength is uncertain. In six patients with electrophysiologic evidence of peroneal neuropathy at the fibular neck with definite motor CB, standard motor nerve conduction studies were performed at 32 degrees C and then after the fibular neck region was cooled with an ice pack to 8 degrees -12 degrees C. In all patients, cooling increased the amplitude and area of the compound motor action potential obtained with popliteal fossa stimulation, decreasing the relative amplitude drop across the fibular neck from a mean of 78% to 55%. A concomitant increase in foot dorsiflexor strength was clearly observed in three of the six patients. Both the electrophysiologic and clinical changes readily reversed upon rewarming. These data support the belief that, in compressive neuropathies, cooling relieves conduction block in selected motor neurons, improving strength.

Action Potentials↗
PubMed2001

Heat-sensitive conduction block in ulnar neuropathy at the elbow.

OBJECTIVES: To study the effects of elbow heating on conduction block (CB) and across-elbow conduction velocity (CV) in patients with ulnar neuropathy at the elbow (UNE). METHODS: We studied 15 patients with UNE, performing motor nerve conduction studies at 32 degrees C and after heating the elbow to 42 degrees C. RESULTS: At 32 degrees C, mean response amplitude and area with above-elbow (AE) stimulation were 20.4 and 16.0% lower than with below-elbow (BE) stimulation, respectively. With heating the elbow to 42 degrees C, these differences increased significantly to 28.9 and 26.9% (P=0.019 and 0.029), respectively. The mean CV reduction in the across-elbow segment relative to the forearm segment also increased from 20.5 m/s at 32 degrees C to 25.6 m/s at 42 degrees C (P=0.0010). Across-elbow CV at 32 degrees C correlated with increased CB (as measured by amplitude) with heating (r=0.53, P=0.048) and approached significance for area (r=0.48, P=0.068) Likewise, baseline CB at 32 degrees C correlated with the likelihood of increased CB for amplitude (r=0.77, P<0.001), and approached significance for area (r=0.47, P=0.079). CONCLUSIONS: Elbow heating in UNE increases the relative drop in across-elbow CV and the degree of across-elbow CB; absolute across-elbow CV and the presence of baseline CB at 32 degrees C are good predictors of this latter effect.

Adult↗
PubMed2000

Pseudofacilitation: A temperature-sensitive phenomenon.

With sustained isometric exercise, compound muscle action potential (CMAP) amplitude of normal subjects may increase, a phenomenon known as pseudofacilitation. To explore the mechanism of pseudofacilitation, the effect of exercise combined with focal heating and cooling of abductor pollicis brevis was examined in 10 normal subjects. After 10 s of isometric exercise, CMAP amplitude increased by 3.6% (median value) at 32 degrees C and 6.4% at 40 degrees C, and decreased by 9.1% at 20 degrees C. Duration decreased by 12.6% at 32 degrees C and 11.7% at 42 degrees C, but increased by 12.4% at 20 degrees C. Area decreased by 9.8% at 32 degrees C and 8. 6% at 42 degrees C, and increased by 1.1% at 20 degrees C. Changes with cooling were significant (P < 0.01) as compared to baseline (32 degrees C); changes with heating were not. Thus, cooling reverses the expected increase in CMAP amplitude normally seen with exercise. Although providing only indirect evidence, these findings are consistent with the hypothesis that increased activity of muscle Na(+),K(+)-pump plays a role in producing pseudofacilitation.

Action Potentials↗
PubMed1999

Heat sensitivity of sensory fibers in carpal tunnel syndrome.

Elevations in temperature may produce conduction block in demyelinated neurons. A well-described phenomenon in multiple sclerosis, it has also been reported in some patients with inflammatory demyelinating polyneuropathies. We used carpal tunnel syndrome (CTS) as a model to study the effect of heat on nerves with focal demyelination secondary to chronic compression. Compound motor and sensory responses were measured in 12 CTS patients and 12 normal subjects at 32 degrees C and with heating to 42 degrees C. Changes in relative motor response amplitude and area were similar for both normal subjects and CTS patients. In CTS patients, however, sensory response amplitude and area decreased 34.3% and 48.9%, significantly more than the 25.2% and 39.1% reductions in normal subjects (P=0.021 and P=0.018 respectively). We hypothesize that these reductions in response amplitude are secondary to the occurrence of heat-induced conduction block in demyelinated sensory neurons.

Adult↗
PubMed1999

Electromyography and magnetic resonance imaging in the evaluation of radiculopathy.

Electromyography (EMG) and magnetic resonance imaging (MRI) are commonly used in the diagnosis of cervical and lumbosacral radiculopathy, but the agreement between the two studies is unknown. We retrospectively studied 47 patients with a clinical history compatible with either cervical or lumbosacral radiculopathy who were evaluated with both an EMG and a spine MRI within 2 months of each other. Among these patients, 55% had an EMG abnormality and 57% had an MRI abnormality that correlated with the clinically estimated level of radiculopathy. The two studies agreed in a majority (60%) of patients, with both normal in 11 and both abnormal in 17; however, only one study was abnormal in a significant minority (40%), suggesting that the two studies remain complementary diagnostic modalities. The agreement was higher in patients with abnormal findings on neurologic examination, underscoring the difficulty of confirming the diagnosis in mild radiculopathy.

Adult↗
PubMed1999

Reduction of motor artifact in antidromic ulnar sensory studies.

Motor artifact often interferes with recording of antidromic ulnar sensory responses from digit 5. In the belief that this artifact is due to a volume-conducted motor response, eight different recording electrode and finger positions were evaluated in 10 normal subjects in an attempt to reduce or eliminate it. Placement of the recording electrodes over the middle and distal phalanges of digit 5 while the fingers were extended and abducted reduced this artifact most effectively, with minimal decrease in amplitude of the sensory response. This finding has important implications for the routine performance of antidromic sensory conduction studies of the ulnar nerve.

Adult↗
PubMed1998

Effect of temperature on motor responses in organophosphate intoxication.

We studied the effect of temperature on median motor responses in a 41-year-old man with organophosphate intoxication. At 32 degrees C, a normal amplitude compound motor action potential (CMAP) and a smaller spontaneous repetitive discharge (SRMAP) were present. With warming to 39 degrees C, the CMAP amplitude decreased 20%, while the SRMAP amplitude decreased 33%. With cooling to 14 degrees C, the CMAP amplitude decreased 9%, while the SRMAP became unobtainable. Possible mechanisms for these findings are discussed.

Adult↗
PubMed1998

Fibrillations in lumbosacral paraspinal muscles of normal subjects.

Although paraspinal muscle fibrillations and positive sharp waves (PSWs) are used to help identify neuromuscular disorders, the frequency of these abnormalities in normal subjects is uncertain. We performed lumbosacral paraspinal electromyography in 65 normal subjects. Twenty-seven (42%) had fibrillations and/or PSWs, with the prevalence of these findings increasing with age (r = 0.830, P = 0.040). These data suggest isolated fibrillations and PSWs in lumbosacral paraspinal muscles, especially of older subjects, are nonspecific findings.

Adult↗
PubMed1998

High-temperature repetitive nerve stimulation in myasthenia gravis.

High temperature enhances the decrement on repetitive nerve stimulation (RNS) in patients with myasthenia gravis (MG). However, the limit of this phenomenon at high temperature is unknown. Three-hertz ulnar RNS was performed in 7 patients with MG at a skin temperature of 32 degrees C and then with the hand in a 44 degrees C water bath. At 32 degrees C, the mean decrement preactivation was 5% (range, 0-24%); after 1 min of exercise, the mean decrement reached a maximum of 11% (range, 1-34%) 2 min postactivation. At a hand temperature of 42 degrees C, the mean decrement preactivation was 17% (range, 0-65%); after exercise, the mean decrement reached a maximum of 29% (range, 5-74%) 1 min postactivation. In 3 subjects, RNS was normal at 32 degrees C, but a definite decrement developed with heating. These findings demonstrate that very high temperature can improve the sensitivity of ulnar RNS for postsynaptic neuromuscular transmission defects.

Action Potentials↗
PubMed1998

Three ulnar nerve conduction studies in patients with ulnar neuropathy at the elbow.

OBJECTIVE: Ulnar neuropathy at the elbow is often difficult to localize by standard electrophysiologic testing. This study compared three ulnar nerve conduction studies to determine which was more sensitive in localizing ulnar neuropathy at the elbow. METHODS: Motor studies to the first dorsal interosseous and the abductor digiti quinti and a mixed ulnar nerve sensory study across the elbow. RESULTS: Motor studies to the first dorsal interosseous and abductor digiti quinti were abnormal in 81% and 71% of patients, respectively. The ulnar mixed sensory study across the elbow was abnormal in 57%. In 38%, all three tests were abnormal. CONCLUSION: Motor studies were more sensitive than the ulnar mixed sensory study across the elbow in localizing ulnar neuropathy of the elbow.

Adult↗
PubMed1998

Forearm velocity in carpal tunnel syndrome: when is slow too slow? .

OBJECTIVE: To correlate the frequency of superimposed processes (SPs) such as radiculopathies, polyneuropathies, and plexopathies with median motor forearm conduction velocity (MMFCV) in patients with carpal tunnel syndrome (CTS). DESIGN: All cases of diagnosed CTS were retrospectively analyzed for evidence of SPs. SETTING: Electrophysiology laboratory of a tertiary care center. PARTICIPANTS: One hundred fifty-five patients (44 men, 111 women), ages 19 to 94, who were referred for and met electrophysiologic criteria for CTS, both with and without MMFCV slowing. MAIN OUTCOME MEASURE: The frequency of SPs in patients with no, mild, moderate, and severe MMFCV slowing. RESULTS: A total of 192 arms from 155 patients were studied. Of 14 arms with mild slowing (MMFCV of 47.0 to 49.9 m/sec), 2 (14%) had an SP. Of 15 arms with moderate slowing (MMFCV of 43.0 to 46.9 m/sec), 7 [corrected] (46%) had an SP. Of 9 arms with severe slowing (MMFCV of < 43.0 m/sec), 4 (44%) had an SP. The frequency of SPs for both the moderate and severe groups was significantly higher than that in patients with a normal MMFCV (p < .01); of 154 arms with a normal MMFCV, only 9 (6%) had an SP. CONCLUSION: In cases of CTS, the finding of moderate to severe slowing of MMFCV (< 47.0 m/sec) should prompt a careful electrophysiologic investigation to exclude an SP.

Action Potentials↗
PubMed1997

An unusual axonal polyneuropathy induced by low-dose interferon alfa-2a.

OBJECTIVES: To describe a patient who developed an unusual polyneuropathy after treatment with interferon alfa-2a for hepatitis C and to discuss issues related to diagnosis and pathogenesis. DESIGN: Case report. SETTING: Tertiary care center. CASE: A 46-year-old man with chronic hepatitis C had acute onset of an axonal polyneuropathy with prominent small-fiber involvement shortly after completing a standard 6-month course of therapy with low-dose interferon alfa-2a. MAIN OUTCOME AND RESULTS: Further interferon treatment for hepatitis C was discontinued. CONCLUSION: Standard, low-dose interferon alfa-2a treatment can produce a persistent predominantly small-fiber polyneuropathy.

Axons↗
PubMed1997

Nerve, muscle, and neuromuscular junction electrophysiology at high temperature.

Although the effect of low temperature on the peripheral nervous system has been systematically studied, the effect of high temperature has not. We investigated the effect of elevating limb temperature from 32 degrees C to 42 degrees C by performing sequential motor studies, antidromic sensory studies, and 3-Hz repetitive stimulation in normal subjects. In addition, we recorded single motor units by using threshold stimulation. On average, motor amplitude and duration decreased by 27% and 19%, respectively, whereas sensory amplitude and duration decreased by 50% and 26%, respectively. Neuromuscular transmission remained normal at 42 degrees C. Single motor unit recordings revealed a reduction in amplitude of 26%, similar to the overall reduction in compound motor amplitude. These findings demonstrate that significant reductions in sensory and motor amplitudes can occur in normal nerves at high temperature; we hypothesize that these changes are secondary to alterations in nerve and muscle ion channel function.

Action Potentials↗
PubMed1997

Sural/radial amplitude ratio in the diagnosis of mild axonal polyneuropathy.

As proximal nerves are relatively spared in length-dependent, axonal polyneuropathy, we theorized that a sural/radial amplitude ratio (SRAR) might be a sensitive indicator of mild polyneuropathy. In this study, sural amplitudes and SRARs in patients with signs of mild axonal polyneuropathy were compared to those of normal, age-matched control subjects. Sural and radial sensory responses were measured in a standard fashion in all subjects. Thirty polyneuropathy patients had an average SRAR of 0.29 as compared to 0.71 for the 30 normal subjects. An SRAR of less than 0.40 was a strong predictor of axonal polyneuropathy, with 90% sensitivity and 90% specificity, as compared to an absolute sural amplitude of less than 6.0 microV, which had sensitivity of only 66%. Additionally, unlike the sural amplitude, the ratio did not vary significantly with age. We conclude that the SRAR is a sensitive, specific, age-independent electrodiagnostic test for mild axonal polyneuropathy.

Adult↗