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Biomedical subjects

M Ronthal

Publications and source records attributed to M Ronthal.

At least 19 recordsLinked to original sources
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↗
PubMed1993

Asymmetric catalepsy after right hemisphere stroke.

We describe the appearance of left hemineglect and striking cataleptic posturing, more prominent in left-sided extremities, in a patient without psychiatric illness. Neuroimaging demonstrated a large posterior right hemisphere infarct involving the parietal, occipital, and temporal lobes, the insula, and caudate. Additional movement abnormalities that comprise the full catatonia syndrome were absent, including stereotypy, mannerisms, ambitendency, automatic obedience, mutism, negativism, and echopraxia. Catatonia has been reported to be produced by lesions of diverse etiology affecting the frontal lobe, limbic system, diencephalon, or basal ganglia. In these cases, catalepsy has been manifest only rarely, and motor signs that are present are generally bilateral. This case demonstrates that asymmetric catalepsy can be produced by right hemisphere stroke, and provides partial support for earlier clinical literature relating catalepsy and the parietal lobe.

Aged↗
PubMed1992

Acute cerebral ischemia: evaluation with dynamic contrast-enhanced MR imaging and MR angiography.

Dynamic contrast-enhanced T2-weighted magnetic resonance (MR) imaging and MR angiography (MRA) were used to evaluate cerebral blood volume and the intracranial arterial system in 34 patients within 48 hours after the onset of cerebral ischemia. In 24 of the patients, an abnormality identified on T2-weighted images corresponded to the acute clinical deficit. Intracranial MRA demonstrated occlusions or severe stenoses of major vessels supplying the area of infarction in 16 of these patients, and decreased blood volume correlated well with MRA abnormalities. Infarcts less than 2 cm in diameter were not reliably shown with MRA or blood volume studies. Correlation between lesions seen with MRA and decreased blood volume in acute infarcts was good, and both techniques demonstrated lesions early in the clinical course. By providing information about hemodynamics not available with conventional T1- or T2-weighted images, MRA and dynamic MR imaging could prove helpful in describing the pathophysiologic characteristics of stroke and in guiding early therapeutic intervention.

Adult↗
PubMed1992

Fast magnetic resonance diffusion-weighted imaging of acute human stroke.

Rapid MRI of the molecular diffusion of water demonstrated cerebral infarcts in 32 patients. We studied these patients at various times following the onset of ischemic symptoms and found that diffusion-weighted imaging revealed the infarcts sooner than conventional T2-weighted spin-echo imaging did; four hyperacute infarcts were shown only by diffusion-weighted imaging. Acute infarcts had lower apparent diffusion coefficients (ADCs) than noninfarcted regions did. This relative difference in ADC reached a nadir in the first 24 hours and rose progressively thereafter. Chronic infarcts showed a relative increase in diffusion and were readily distinguishable from acute infarcts. The technique takes less than 2 minutes to apply using a standard 1.5-tesla scanner in the clinical setting. Diffusion-weighted imaging has the potential to play a role in improving the early anatomic diagnosis of stroke and therefore in the development and implementation of early stroke interventions.

Adult↗
PubMed1992

Reflex blink to visual threat.

The requisite visual modalities for the reflex blink to visual threat have not been thoroughly studied. We identified five patients with different focal cerebral lesions documented on computerized tomography scan who had abnormal blink-to-threat reflexes. One had a homonymous hemianopia secondary to posterior cerebral artery occlusion; another had a unilateral parietal neglect; and a third had a frontal neglect. They did not blink in response to visual stimuli contralateral to their lesion. A cortically blind patient and one with Balint's syndrome did not have a blink response. Observation of these and other similar patients and animals previously reported suggests that the blink-to-threat reflex is cortically mediated and requires intact primary visual cortex as well as higher order mechanisms for visual attention mediated in the inferior parietal lobule and frontal eye fields.

Adult↗
PubMed1990

Cerebral blood flow: assessment with dynamic contrast-enhanced T2*-weighted MR imaging at 1.5 T.

The authors assessed regional cerebral blood flow dynamics with magnetic resonance (MR) imaging enhanced with gadolinium diethylenetriaminepentaacetic acid (DTPA). After bolus administration of Gd-DTPA, rapid T2*-weighted gradient-echo images were acquired. Image acquisition time ranged from 2 to 3 seconds. The signal intensity (SI) of brain tissue and blood vessels markedly decreased during the first pass of contrast agent through the brain due to the local field inhomogeneity caused by the concentrated paramagnetic contrast agent. The method was used in 18 subjects with no cerebrovascular disease and 32 patients with stroke, vascular stenosis, arteriovenous malformation, and cerebral neoplasm. Comparison with intracranial angiography was performed in three patients and with single-photon emission computed tomography of blood flow in four. The change in T2* relaxation rate was approximately linearly related to the dose of contrast agent. The SI change increased as the echo time was lengthened. Regions in cerebral infarcts, metastases, and arteriovenous malformations showed different enhancement patterns than those of edema around a lesion and of normal brain tissue. Abnormal circulation times in patients with vascular stenoses were demonstrated. The method provides information about cerebral blood flow dynamics not available from conventional MR imaging and MR angiography.

Adolescent↗
PubMed1989

Chronic confusional state.

An acute confusional state after infarction in the distribution of the right middle cerebral artery has been described. Patient recovery usually is excellent. Some patients, however, do not improve, resulting in a chronic confusional state.

Aged↗
PubMed1987

Cerebral infarction: shortcomings of angiography in the evaluation of intracranial cerebrovascular disease in 25 cases.

We studied the utility and limitations of conventional cerebral angiography in 25 patients with cerebral infarction unassociated with extracranial cerebrovascular disease during a 7-year period. In only one-third of cases was the angiogram diagnostic, and in a single case it altered the pre-angiogram diagnosis by revealing a previously unsuspected embolus. Among the cases clinically diagnosed as cerebral emboli, the 2 confirmatory angiograms were performed early (within 48 hours), and demonstrated medium-large or large vessel filling defects. Two-thirds of the negative angiograms in the embolic clinical category were delayed, but there was no statistically relevant predilection for specific vessel size involvement. The category, primary cerebral vasculopathy, comprised the largest group, 10 in all, and one-half had angiographic confirmation despite time delays. Angiographic recognition was dependent on a characteristic picture of vascular involvement, and not on timing or vessel size predilection. Mitral valve prolapse figured prominently in the clinical cases of vasculopathy of uncertain etiology, which contained a total of 4 cases. The 3 cases with nondiagnostic angiograms were all delayed and demonstrated nonspecific radiographic changes. Clinically, these cases demonstrated signs or symptoms of autoimmune dysfunction, raising the specter of primary cerebral vasculopathy as a cause of cerebral infarction, in contrast to recurrent cerebral emboli.

Adult↗
PubMed1983

Gait disorders among elderly patients. A survey study of 50 patients.

A series of 50 patients (mean age, 79.5 years) were examined for undiagnosed gait disorders. A single causal diagnosis was made in 56% (28) of the patients. Myelopathy from cervical spine disease was a common cause in 16% (eight patients). Eighteen percent (nine patients) had multiple sensory disorders. Sixteen percent (eight patients) had an idiopathic senile gait disorder, as defined by failure to establish other causes. Twenty-four percent (12 patients) had disorders for which effective primary therapy was available. As a group, patients with gait disorders had ventricular enlargement by computed tomography, when compared with age-matched controls.

Aged↗
PubMed1983

Subacute sclerosing panencephalitis: an immune complex disease?

Vascular osmiophilic deposits of entangled tubular profiles were demonstrated by electronmicroscopy in the cerebral tissue of a patient with subacute sclerosing panencephalitis. Measles viral antigen, IgG, IgM, and C3 were found in the same distribution, indicating that the deposits represent immune complexes. To our knowledge, this is the first demonstration of immune complexes in the vessels of the central nervous system.

Adult↗
PubMed1983

Psychiatric symptomatology in an outpatient neurology clinic.

The self-report Symptom Checklist-90 (SCL-90) was used to screen 105 consecutive first-visit patients in an outpatient neurology clinic. Neurologists diagnosed a primary psychiatric disorder in 35 patients (33%) and a secondary psychiatric disorder in 5. The SCL-90 uncovered previously unidentified emotional distress in 14 patients, for an overall incidence of psychiatric symptoms of 51%. Pain was the most common chief complaint (N = 49), and pain patients accounted for 86% of the primary psychiatric diagnoses. Tricyclic antidepressants were the most often prescribed medications; 81% of these prescriptions were given to pain patients, usually in low doses. Depression was the most common diagnosis (N = 15). Despite the high incidence of psychiatric symptoms, only 3 patients received a psychiatric referral. Neurologists and consulting psychiatrists should maintain a high index of suspicion for psychiatric symptoms when examining patients complaining of pain and, after assessing the presence and severity of depression, prescribe tricyclics judiciously.

Adolescent↗
PubMed1980

Visual field defects produced by basilar artery ectasia.

The authors report two cases of visual field defects which are postulated to be due to the distal end of an elongated basilar artery compressing the visual pathways in the posterior suprasellar region. The mechanism of production of these defects is discussed, relating the abnormal position of the distal end of the basilar artery to a normally situated or only slightly post-fixed optic chiasm and optic tract and to a markedly post-fixed optic chiasm.

Basilar Artery↗