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M Mandelkern

Publications and source records attributed to M Mandelkern.

144 records · Page 8Linked to original sources
PubMed1991

Localized brain metabolic response correlated with potentials evoked by words.

Evoked potentials (EPs) measure synaptic current flows that propagate from brain to scalp, Alternatively, positron emission tomography (PET) using fluoro-deoxyglucose (FDG) can measure the increased glucose metabolism supporting this synaptic activation. It is difficult to localize the brain activity-generating EPs from their scalp distribution, because activity originating in different regions tends to produce overlapping scalp topographies. In contrast, FDG-PET provides better spatial resolution for activity throughout the brain, but shows only the total metabolism integrated over a 30-min uptake period. We combined the temporal and psychological resolution of EPs with the spatial resolution of PET to help define when and where in the brain words are encoded for meaning.

Adult↗
PubMed1991

Memory dysfunction in epilepsy patients as a derangement of normal physiology.

Patients with CPS often display recent memory deficits. Typically, general intelligence, perceptual skills, language, remote memory, and primary memory are all normal. However, the ability to learn new combinations of cognitively complex material is deficient. This deficit may be specific for verbal material (e.g., as a difficulty with learning to recall a response word given an unrelated cue word), for nonverbal material (e.g., as a difficulty in drawing a complex figure from memory), or for both verbal and nonverbal material. Because these characteristics are typical of memory deficits after MTL damage, it is reasonable to suspect that these deficits in patients with epilepsy also reflect MTL damage. In many cases, MTL damage is apparent from neuroimaging studies, whereas seizure semiology suggests MTL onset. In these patients, the same pathology might be the cause of both the ictus and memory deficits. In other cases, memory impairment appears to be secondary to seizures. This suggestion is supported by cases where prolonged complex partial status resulted in a permanent global amnesia. Cases with shorter-lasting memory deficits were also presented. Neuropsychological testing revealed specific recent-memory deficits that cleared 2 weeks after a flurry of CPS and 24 hr after a single seizure. Depth recordings have demonstrated that MTL electrographic seizures can occur without subjective manifestations. When these are evoked by local electrical stimulation, a profound inability to learn new material may be observed during the afterdischarge. Similarly, artificially induced MTL spike-and-wave complexes interfere with the memory for simultaneously presented complex visual scenes. Recent evidence suggests that all of the above phenomena may reflect the engagement by epileptiform processes of the association-cortex (AC)-MTL circuits used in normal human memory. In recent memory tasks, cognitive evoked-potential components N4 and P3 are generated in the MTL and to a lesser degree in related AC regions. The N4/P3 are strongly modulated by familiarity in recent memory. This modulation is eliminated by anterior temporal lobectomy. The typical slow wave following spontaneous MTL interictal spikes has the same MTL voltage topography, and thus probably similar synaptic generators, as the cognitive P3 potential. Furthermore, MTL spike-and-wave complexes can be evoked in recent memory tasks at a fixed latency equal to that of the N4.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1990

Diagnosis of delayed cerebral radiation necrosis following proton beam therapy.

A 27-year-old man developed delayed cerebral radiation necrosis following proton beam therapy to an arteriovenous malformation. Neuroimaging with technetium 99m diethylenetriamine penta-acetic acid and positron emission tomographic scanning with fludeoxyglucose F 18 aided in his evaluation. Significant improvement of his neurologic deficits resulted from corticosteroid therapy. Clinical resolution was corroborated by serial computed tomographic scans demonstrating regression of the abnormality (a mass lesion). Various facets of radiation injury are discussed, including pathogenesis, risk factors, diagnosis, and therapy.

Adult↗
PubMed1989

Insight and interpretation of illness in recovery from psychosis.

The concept of insight as it applies to patients suffering from psychotic illness is reviewed. An exploratory study using structured interviews with patients recovering from psychotic illness indicated that the characteristics of insight fell into five main dimensions: (1) views about symptoms, (2) views about the existence of an illness, (3) speculations about etiology, (4) views about vulnerability to recurrence, and (5) opinions about the value of treatment. Some preliminary findings regarding the association of patterns of insight with diagnosis and chronicity of illness, and the implications of these findings for clinical work and for future research, are presented.

Adolescent↗
PubMed1986

Reversibility of cardiac wall-motion abnormalities predicted by positron tomography.

Positron emission tomography (PET) can be used with nitrogen-13-ammonia (13NH3) to estimate regional myocardial blood flow, and with fluorine-18-deoxyglucose (18FDG) to measure exogenous glucose uptake by the myocardium. We used PET to predict whether preoperative abnormalities in left ventricular wall motion in 17 patients who underwent coronary-artery bypass surgery were reversible. The abnormalities were quantified by radionuclide or contrast angiography or both, before and after grafting. PET images were obtained preoperatively. Abnormal wall motion in regions in which PET images showed preserved glucose uptake was predicted to be reversible, whereas abnormal motion in regions with depressed glucose uptake was predicted to be irreversible. According to these criteria, abnormal contraction in 35 of 41 segments was correctly predicted to be reversible (85 percent predictive accuracy), and abnormal contraction in 4 of 26 regions was correctly predicted to be irreversible (92 percent predictive accuracy). In contrast, electrocardiograms showing pathological Q waves in the region of asynergy predicted irreversibility in only 43 percent of regions. We conclude that PET imaging with 13NH3 to assess blood flow and 18FDG to assess the metabolic viability of the myocardium is an accurate method of predicting potential reversibility of wall-motion abnormalities after surgical revascularization.

Ammonia↗
PubMed1986

Regional perfusion, glucose metabolism, and wall motion in patients with chronic electrocardiographic Q wave infarctions: evidence for persistence of viable tissue in some infarct regions by positron emission tomography.

Positron-emission tomography with 13N-ammonia and 18F-2-deoxyglucose was used to assess regional perfusion and glucose utilization in 31 chronic electrocardiographic Q wave regions in 20 patients. With previously published criteria, regions of infarction were identified by a concordant reduction in regional perfusion and glucose utilization, and regions of ischemia were identified by preservation of glucose utilization in regions of diminished perfusion. Only 10 of the 31 regions (32%) exhibited myocardial infarction tomographically. In contrast, positron tomography revealed ischemia in six regions (20%) and was normal in 15 regions (48%). Even when Q wave regions were reassigned and consolidated to enhance the specificity of the electrocardiogram, uptake of 18F-2-deoxyglucose was noted in the majority (54%) of the regions. Neither electrocardiographic ST-T changes nor severity of associated wall motion abnormality reliably distinguished tomographically identified regions of ischemia from infarction. Thus positron tomography reveals evidence of persistent tissue metabolism in a high proportion of chronic electrocardiographic Q wave regions, and commonly used clinical tests do not reliably distinguish hypoperfused but viable regions from tomographically defined regions of myocardial infarction.

Adult↗
PubMed1981

Solution structural studies of chromatin fibers.

We report solution structural studies on 9--16-kilobase (kb) fragments of the 30-nm chromatin fiber isolated from calf thymus nuclei. Samples were stabilized by dimethylsuberimidate cross-linking in 100 mM salt concentration to ensure retention of a compact conformation. Electron microscopy, sedimentation diffusion, light scattering, and gel electrophoresis were used to characterize materials which were fractionated by size by utilizing sucrose gradient sedimentation. Measurements reported include the translational frictional coefficient as determined by quasielastic light scattering and the rotational frictional coefficient as deduced from transient electric dichroism. These frictional properties were combined to yield 33 +/- 3 nm for the diameter of the fiber and a length of 1.5 +/- 0.1 nm per nucleosome. Assuming a superhelix pitch of 11 nm, we calculate 7.5 +/- 0.5 nucleosomes per superhelical turn. The 30-nm fiber was found to reach saturation of electric field orientation at about 10--13 kV/cm and to lack a detectable permanent dipole moment, implying no polarity of the fiber. The limiting reduced dichroism rho was found to be +0.06, intermediate between the values expected if the nucleosomal disk diameters were parallel (rho expected = -3/8) or perpendicular (rho expected +3/4) to the fiber axis. This result implies an average angle of 51 degrees between the fiber axis and the local DNA (nucleosomal) superhelix axis and rules out many of the simple models which have been proposed for the detailed structure of the 30-nm fiber.

Animals↗
PubMed1981

Conversion of B DNA between solution and fiber conformations.

At low salt and high DNA concentration, rodlike DNA molecules form specific aggregates containing about seven parallel DNA molecules packed in a bundle. Bundle formation can be reversed by addition of small amounts of EDTA, and formation of the specific aggregates can be induced at higher salt concentration by addition of trivalent ions. In contrast to monomeric DNA, the aggregated species has the optical anisotropy expected for the B form as observed in fibers.

Animals↗
PubMedDate not supplied

Doxorubicin cardiotoxicity: response of left ventricular ejection fraction to exercise and incidence of regional wall motion abnormalities.

Gated radionuclide ventriculograms were performed to evaluate cardiac function in 53 patients who received doxorubicin treatment for various malignancies (mean dose: 449 +/- 128 mg/m2 BSA). In fourteen patients (Group I) function was evaluated before and after treatment; there was a significant decrease of resting left ventricular ejection fraction after therapy (p less than 0.001). Twenty-two patients (Group II) had serial studies during treatment which also showed a significant fall of resting left ventricular ejection fraction (p less than 0.001). Eighteen patients in Groups I and II had supine exercise studies. A normal exercise response was maintained in the majority of patients. Exercise testing added little to the diagnostic performance when compared to serial resting studies. We found regional wall motion abnormalities (mild apical hypokinesis) at rest by visual inspection in 33 of 36 Group I and Group II patients who had received doxorubicin. In the baseline or initial study, only 4 of these patients demonstrated WMA. In 18 Group I and II patients who were exercised, 3 had wall motion abnormalities during the initial study. All of these patients demonstrated wall motion abnormalities at rest after the second study, however only 7 of 18 demonstrated abnormalities during the exercise study. The results indicate that resting left ventricular ejection fraction declines after doxorubicin treatment. Exercise radionuclide angiography may not increase diagnostic accuracy for the detection of doxorubicin related cardiotoxicity. Regional wall motion abnormalities occur with a relatively high incidence following doxorubicin therapy, more readily detectable at rest. However, the exercise study can distinguish doxorubicin related wall motion abnormalities from those due to coronary artery disease.

Adolescent↗
PubMedDate not supplied

Multidisciplinary analysis of patients with extratemporal complex partial seizures. I. Intertest agreement.

In 15 patients we hypothesized the origin of epilepsies to be 'extratemporal' based on videotaped seizures and surface EEG. Neuropsychological tests and neuroimaging (CAT, MRI, and PET scans) were then compared to the hypothesized ictal sites. Neuropsychological tests were abnormal in 86.6% and FDG-PET scans were abnormal in 73%. The neuropsychological tests and PET localized or lateralized areas of dysfunction to the same sites as electroclinical characteristics did in 85% of patients (P less than 0.01, Fisher exact test). No statistically significant correlation between lesion sites on CT and MRI and the ictal origin was observed due to the high proportion of normal or non-specific scans. These observations should be verified in a larger series of extratemporal seizures.

Adolescent↗
PubMedDate not supplied

Cortical metabolic activation in humans during a visual memory task.

A delayed match-to-sample (DMS) task of abstract, visual memory was performed during the uptake period of 18F-fluorodeoxyglucose. The increase in glucose uptake of cortical and subcortical regions ("activation") during the DMS task was compared with that during a control, immediate match-to-sample task using positron emission tomography. Both discriminant analysis and paired t tests supported the observation that the dorsolateral prefrontal area underwent the greatest activation, while a factor analysis revealed the functional correlation matrices of the tasks. Activations in the ventral premotor cortex and supramarginal and angular gyri were highly correlated with the change in the dorsolateral prefrontal cortex. The basal forebrain/ventral pole region showed a smaller but independently significant change. The findings support the role of the dorsal prefrontal region in the nonspatial working memory of humans.

Adult↗
PubMedDate not supplied

Cerebral activation in patients with irritable bowel syndrome and control subjects during rectosigmoid stimulation.

OBJECTIVE: Patients with irritable bowel syndrome (IBS) show evidence of altered perceptual responses to visceral stimuli, consistent with altered processing of visceral afferent information by the brain. In the current study, brain responses to anticipated and delivered rectal balloon distension were assessed. METHODS: Changes in regional cerebral blood flow were measured using H2(15)O-water positron emission tomography in 12 nonconstipated IBS patients and 12 healthy control subjects. Regional cerebral blood flow responses to moderate rectal distension (45 mm Hg) and anticipated but undelivered distension were assessed before and after a series of repetitive noxious (60-mm Hg) sigmoid distensions. RESULTS: Brain regions activated by actual and simulated distensions were similar in both groups. Compared with control subjects, patients with IBS showed lateralized activation of right prefrontal cortex; reduced activation of perigenual cortex, temporal lobe, and brain stem; but enhanced activation of rostral anterior cingulate and posterior cingulate cortices. CONCLUSIONS: IBS patients show altered brain responses to rectal stimuli, regardless of whether these stimuli are actually delivered or simply anticipated. These alterations are consistent with reported alterations in autonomic and perceptual responses and may be related to altered central noradrenergic modulation.

Adult↗
PubMedDate not supplied

Neuroimaging in patients with seizures of probable frontal lobe origin.

Twenty-two patients whose electroclinical ictal characteristics suggested frontal lobe seizure foci were studied. Computed tomography (CT) scans showed abnormalities in only 32% of patients whereas magnetic resonance imaging was informative in 45%. 18FDG-Positron emission tomography (PET) scanning revealed decreased metabolism in 64% of the group. The areas of hypometabolism were focal, regional, or hemispheric. Focal frontal hypometabolism was significantly correlated with the electroclinical (semiologic) ictal localization. Therefore, FDG-PET scanning is a sensitive and specific technique for investigating patients with seizures of probable frontal lobe origins.

Deoxyglucose↗
PubMedDate not supplied

Neuroimaging in temporal lobe epilepsy: test sensitivity and relationships to pathology and postoperative outcome.

We studied patients with documented temporal lobe seizures to evaluate the predictive value of computed tomography (CT), magnetic resonance imaging (MRI), and F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) for surgical therapy and the relationships between these tests and the pathologic diagnoses. CT detected abnormalities in 32.5%, with an accuracy of 19% when accuracy was defined as congruence with electrophysiologic studies. MRI detected abnormalities in 81%, with an accuracy of 67%. FDG-PET detected abnormalities in 85%, with an accuracy of 82%. Pathologic change was detected in 79% of the excised temporal neocortex, 65% of amygdalae, and 93% of hippocampi. After follow-up periods of 20-71 months (mean 41 months), 67% of patients were free of seizures and 94% had at least a 90% reduction in seizure frequency. There was no relationship between the type of abnormality on MRI or the type of pathology and postoperative outcome. Better outcomes were associated with focal or regional ictal onsets as recorded by surface EEG. Worse outcomes were associated with hypometabolism that extended outside the temporal lobe. Pathologic change in the temporal neocortex was associated with extension of hypometabolism outside the temporal lobe.

Adult↗