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Biomedical subjects

R B Loewenson

Publications and source records attributed to R B Loewenson.

At least 19 recordsLinked to original sources
PubMed1992

Antiepileptics and the development of congenital anomalies.

We are conducting a prospective cohort study of epilepsy and pregnancy to determine the nature and extent of adverse pregnancy outcomes in infants of mothers with epilepsy (IME). Women with epilepsy were enrolled no later than the first trimester and were matched with controls; their infants were examined at 8 weeks by pediatricians blinded to maternal status. A number of variables were compared between case and control infants: birth weight, length, gestational age, head circumference, Apgar scores, feeding difficulties, neonatal irritability, and presence of major malformations and minor anomalies. The number of minor anomalies per infant was greater for IME than for controls (mean, 5.05 and 3.65, p less than 0.0001 per infant, respectively). Prominent occiput was the only anomaly seen significantly more often in IME than in controls (p less than 0.05).

Abnormalities, Drug-Induced↗
PubMed1991

Modulation of the stretch reflex during volitional sinusoidal tracking in Parkinson's disease.

Sinusoidal visually-guided wrist tracking, in normal and parkinsonian subjects, was perturbed by torque transients every 90 degrees throughout the movement. Long-latency stretch reflex and volitional EMG amplitude modulations were assessed as functions of the tracking phase. Reflex modulation during tracking, both in wrist flexor and extensor muscles, was found to differ significantly between parkinsonian and normal subjects. In the parkinsonian group, the abnormality consisted of an increased reflex activity during tracking phases in which the muscle was lengthening. At these phases the reflex generated torque is opposite in direction to the volitionally generated torque and the tracking movement. No differences in the unperturbed volitional EMG modulation were observed between groups for this error constrained tracking paradigm. Significant correlations were found between ratings of bradykinesia and the amount of abnormal reflex modulation in the wrist flexor. These data suggest that a component of bradykinesia results from a defective coordination of supraspinal reflex and volitional control systems.

Aged↗
PubMed1991

Quantitative I-123-IMP brain SPECT and neuropsychological testing in AIDS dementia.

We performed I-123-IMP SPECT brain imaging on seven mildly demented AIDS patients and seven normal subjects. In an attempt to detect and quantitate regions of decreased I-123-IMP uptake, pixel intensity histograms of normalized SPECT images at the basal ganglia level were analyzed for the fraction of pixels in the lowest quartile of the intensity range. This fraction (F) averaged 17.5% (S.D. = 4.6) in the AIDS group and 12.6% (S.D. = 5.1) in the normal group (p less than .05). Six of the AIDS patients underwent neuropsychological testing (NPT). NPT showed the patients to have a variety of mild abnormalities. Regression analysis of NPT scores versus F yielded a correlation coefficient of .80 (p less than .05). We conclude that analysis of I-123-IMP SPECT image pixel intensity distribution is potentially sensitive in detecting abnormalities associated with AIDS dementia and may correlate with the severity of dementia as measured by NPT.

AIDS Dementia Complex↗
PubMed1991

A pilot study of hyperbaric oxygen in the treatment of human stroke.

We administered hyperbaric oxygen or air in a double-blind prospective protocol to 39 patients with ischemic cerebral infarction. We interrupted the study when we noticed what appeared to be a trend favoring the air-treated patients, whose neurological deficits were less severe (mean +/- SEM score on graded neurological examination: air, 25.6 +/- 4.9; oxygen, 34.5 +/- 7.5) and whose infarcts were smaller (air, 29.0 +/- 12.2 cm3; oxygen, 49.2 +/- 11.7 cm3) at 4 months. The trend, we decided, was probably an artifact of the randomization process. Nevertheless, we chose not to resume the trial because the treatment was difficult to administer by schedule (for various reasons the treatment protocol was broken in 15 of the 39 patients), was poorly tolerated (eight of the 39 patients refused to continue treatments), and did not produce dramatic improvement.

Adult↗
PubMed1991

Cervical bruits: clinical correlates of stenosis.

To analyze the relationship among characteristics of buits, degree of underlying stenosis, and neurologic symptom complexes, the authors studied 157 patients with bruits undergoing digital subtraction angiography. Symptom status assignment (definite lateralizing, possible lateralizing, vertebrobasilar, diffuse, and asymptomatic) and cervical auscultation for location, duration, and other bruit characteristics were performed independently. Bruit occurrence was associated with stenosis of greater than or equal to 50% of the underlying vessel with the association being no stronger at higher levels of stenosis (greater than or equal to 80%). No relationship existed between the side of bruit and side of symptoms in those with lateralized symptoms. The authors found more severe degrees of carotid stenosis in two symptomatic groups (vertebrobasilar insufficiency [VBI] and definite lateralized) compared with asymptomatic patients. Those with VBI had more high-grade stenosis, whereas those with lateralized symptoms had more occlusions, which tended to be ipsilateral to the symptoms.

Aged↗
PubMed1990

Influence of pancreas transplantation on cardiorespiratory reflexes, nerve conduction, and mortality in diabetes mellitus.

Cardiorespiratory reflexes (CRR) were studied by measuring heart-rate variation during 6 breaths/min respiration and a Valsalva maneuver in 232 insulin-dependent diabetic subjects. Abnormalities were found in 175 patients. During a 7-yr follow-up, 41 (23.4%) patients with abnormal and 2 (3.5%) with normal CRR tests died. The mortality rates of diabetic patients with abnormal autonomic function tests were 17% at 2.5 yr, 33% at 5 yr, and 40% at 7 yr, significantly higher (P less than 0.002) than in patients with normal tests (rates of 4.6, 4.6, and 13.8% at the respective intervals). Nerve conduction studies (NCS) were indicative of somatic neuropathy in 148 of 205 patients. Mortality rates were higher in patients with abnormal NCS than in those with normal results (P less than 0.025). Among patients with abnormal autonomic function, patients with a functioning pancreas transplantation (PTx) had better survival rates than patients with a failed PTx (P less than 0.005) and, on long-term follow-up, better rates than patients without PTx. Similar results were found comparing the same group of patients who had abnormal NCS.

Adult↗
PubMed1985

Cerebral dysfunction after chronic hypoxia in children.

Although the long-term effects of acute anoxia have been studied, the effects of chronic hypoxia on the developing human brain have received little attention. We studied children with a cyanotic congenital heart defect to assess the impact of chronic hypoxia by eight measures: neurologic examination, visual evoked response, EEG, behavioral adjustment, cognitive, perceptual-motor, and attentional functioning, and school performance. On outcome evaluation, these children evidenced diverse neurophysiologic dysfunction. Chronic hypoxia was associated with impaired motor function, inability to sustain attention, and low academic achievement.

Brain Diseases↗
PubMed1984

Eye tracking dysfunction in Alzheimer-type dementia.

Performance on visual tracking tasks was measured in groups of Alzheimer-type dementia, pseudodementia of depression, and elderly normal controls. Smooth pursuit tracking errors were identified by counting the number of catch-up saccades required to compensate for failure of the smooth pursuit system. The group with Alzheimer-type dementia had significantly worse (p less than 0.0001) smooth pursuit tracking than either pseudodementia subjects or elderly normal controls. A strong correlation (r = 0.74, p less than 0.005) was found in Alzheimer patients between severity of visual tracking abnormality and severity of dementia.

Aged↗
PubMed1983

Variables affecting eye tracking performance.

The effect of age and gender on eye tracking performance was studied in normal healthy subjects. Two measures of tracking performance, phase corrected cross-correlation coefficients and number of catch-up saccades were determined. The cross-correlation measures revealed a differential effect with the elderly men demonstrating significantly better tracking performance than elderly women. An aging effect was found in women and an aging trend in men using the catch-up saccade measure. Other variables influencing tracking performance, in addition to age and sex, were target speed and type of measure. Recognition of this differential effect largely explains the existing controversy as to whether age or sex variables influence tracking performance.

Age Factors↗
PubMed1983

Later competence and adaptation in infants who survive severe heart defects.

A model of risk potential for developmental outcome was created based on cardiac, medical, surgical, and family-stress factors in 31 children with transposition of the great arteries who had undergone reparative open heart surgery utilizing cardiopulmonary bypass during infancy. Impact of these potential risk factors was assessed by 4 current neurologic measures (neurologic anatomic abnormalities, functional impairment, electroencephalograph [EEG], and Pattern Visual Evoked Potential [PVEP]) and 4 psychologic measures (IQ, achievement, perceptual-motor function, and behavior). Results indicated that adverse developmental outcome was significantly associated with the following medical risk variables: failure of palliative surgery to alleviate hypoxia, prolonged hypoxia, growth failure, congestive heart failure, absence of ameliorating shunting heart defects, stroke, and CNS infection; and two psychosocial moderator variables: socioeconomic status and current life stress. Analysis of a "cumulative risk score" indicated significantly higher risk scores in children with abnormal EEGs, PVEPs, and neurologic examinations. The cumulative risk score highly correlated with composite neurologic outcome (r = .62), IQ (r = -.66), achievement (r = -.60), and perceptual-motor function (r = -.48). While overall outcome was favorable for children with TGA who experienced a single risk event, outcome was compromised if multiple risk factors occurred.

Achievement↗
PubMed1980

Predicting brain tumor histology: change of effective atomic number with contrast enhancement.

Thirty-eight enhancing intracranial neoplasms were evaluated with a dual kilovoltage technique to measure the change of effective atomic number (delta Z), and linear attenuation coefficients with the use of iodinated contrast material. The change of effective atomic number was found to separate intracranial neoplasms into three major groups: gliomas, meningiomas, and metastases. Other parameters, including linear attenuation coefficients and CT numbers, varied from less accurate to inaccurate. The change of effective atomic number with contrast enhancement not only predicted the appropriate histologic group of the neoplasm, but also aided in the differential diagnosis of neoplasms without a characteristic delta Z value.

Adult↗
PubMed1979

The design of clinical studies to assess therapeutic efficacy in multiple sclerosis.

Poorly designed trials of therapy for multiple sclerosis (MS) can waste time and money, and may lead either to false hopes or to the overlooking of a potentially effective treatment. A well-designed trial may well develop useful scientific information even if the putative therapy fails to show any therapeutic effect. The diagnosis, clinical course, and definitions of the stages of MS are discussed as they relate to trials of therapy. The goals of such trials include favorable modification of an exacerbation, favorable modification or prevention of future exacerbations, effective treatment of the progressive stage, and improvement of function in the stable-deficit stage. There should be an orderly progression from a small preliminary trial to a modest pilot trial and, when indicated, a full trial. All types of trials require careful organization and management, appropriate selection of patients, and properly planned and recorded observations. The treatment contrast--how the new treatment will be evaluated--provides the essential structure of the trial. The hypothesis being examined, the treatment contrast, and the observations being made in the designed clinical trial will govern the form of the analysis and the nature of the interpretations. Each goal requires that specific strategies and design considerations be applied to preliminary, pilot, and full trials.

Clinical Trials as Topic↗
PubMed1975

Essential tremor: treatment with propranolol.

A double-blind trial of propranolol, in a dosage of 120 mg a day, and placebo was conducted in 11 patients with essential tremor. An improvement in tremor was observed in all patients who received propranolol and was most pronounced in the upper extremities. The favorable clinical assessment was further confirmed by improvement in a grooved pegboard test and in the quality of handwriting as evaluated by two "blind" observers. No side effects were encountered. It is concluded that propranolol is at present the best available drug for the treatment of essential tremor.

Adult↗