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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↗
PubMed1982

Seizure recurrence after a first unprovoked seizure.

We studied 244 patients (of all ages) who presented with a first unprovoked seizure and were followed for a median of 22 months in order to ascertain the risk of subsequent seizures. The cumulative risks of recurrence were 16 per cent at 12 months, 21 per cent at 24 months, and 27 per cent at 36 months after the initial seizure. The risk of recurrence in patients with a history of prior neurologic insult was 34 per cent; all recurrences in this group were observed within the first 20 months. Only 17 per cent of patients without such a history (classified as idiopathic) had a recurrence by 20 months; recurrence in this group was 26 per cent by 36 months. Patients with no recurrence for 36 months did not have a recurrence after that time. Among idiopathic cases the risk of recurrence was increased in patients with generalized spike-wave electroencephalograms (50 per cent at 18 months) and in those who had a sibling with seizures (35 per cent at four months). Age at first seizure, sex, seizure type, onset with status epilepticus, or abnormality on neurologic examination did not affect the risk of recurrence.

Adult↗
PubMed1982

Medical complications of cardiopulmonary arrest.

The clinical courses of 63 survivors of cardiopulmonary arrest were reviewed to determine the incidence and temporal occurrence of noncardiac complications and their relationships to mortality. Complications were grouped as occurring within 48 hours or less, within 48 to 96 hours, or more than 96 hours after cardiopulmonary arrest. Pneumonia, electrolyte level disturbances, and gastrointestinal tract hemorrhage each occurred in more than 28 (45%) of the 63 patients. Resuscitation-related injuries, seizures, and liver function test abnormalities each occurred in at least 18 (28%) of the 63 patients. Pneumonia and liver function test abnormalities were each significantly correlated with increased mortality. Septicemia, acute renal failure, and adult respiratory distress syndrome each occurred in three (5%) to four (7%) of the 63 patients and were always associated with mortality.

Acute Kidney Injury↗
PubMed1980

Neurologic prognosis after cardiopulmonary arrest: II. Level of consciousness.

Sixty-three patients with isolated global anoxic-ischemic injury were prospectively evaluated after cardiopulmonary arrest (CPA); 25 (40%) survived, 16 to an excellent recovery, 8 to a good recovery, and 1 with severe deficits. Forty-six percent of the patients achieved full alertness, and only patients who did so survived. Seventy-five percent of patients arousable or initially alert (level of consciousness [LOC] greater than or equal to 4) survived, all but two with excellent outcomes. Twenty-eight percent of patients initially in deep coma (LOC less than or equal to 3) survived, all with excellent or good outcomes. Ninety percent of patients who became fully alert did so within 72 hours. The likelihood of alerting is correlated with the LOC at given intervals after CPA. Reliable predictions of survival and outcome can often be based upon LOC alone within 2 days after CPA.

Aged↗
PubMed1980

Neurologic prognosis after cardiopulmonary arrest: III. Seizure activity.

Nineteen (30%) of 63 adult survivors of cardiopulmonary arrest had seizures after admission to the hospital. Eleven of 19 had more than one type of seizure. Myoclonic seizures began within 12 hours of the arrest in eight patients, and after 3 or more days in four patients. Only two (17%) patients with myoclonic seizures survived. Partial seizures usually began within 12 hours of the arrest and were controllable with anticonvulsants; 4 of 12 patients survived. Two of four patients with generalized tonic-clonic seizures survived; one of four with "shivering" lived. Overall, patients with seizures had a survival rate of 32% (6 of 19), compared with 43% for patients without seizures. None of the survivors had recurrent seizures within 6 months after hospital admission.

Adult↗
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↗