Sylvan Lavy

Reduction in regional cerebral blood flow during normal aging in man.

Regional cerebral blood flow (rCBF) was measured by the 123Xenon inhalation method in a selected group of 44 normal non-hospitalized, normotensive subjects aged 19 to 79 years. rCBF was computed as the initial slope index value (ISI). Advancing age was associated with significant reductions in the mean brain and mean hemispheric ISI as well as in individual ISI levels measured from all areas in both hemispheres. Our findings suggest that decline of rCBF is not limited to normal elderly subjects but that it is a progressive phenomenon which begins at an earlier age.

Effect of chronic atrial fibrillation on regional cerebral blood flow.

The development of a non-invasive technique for simultaneous bihemispheric measurement of regional cerebral blood flow (rCBF) by inhalation of 123Xenon made available a safe method for evaluation of cerebral circulation under various cardiac conditions. Regional cerebral blood flow was measured by 133Xenon inhalation in 31 patients with chronic atrial fibrillation without symptoms of heart failure and free from neurological diseases. Their age ranged from 35 to 80 (mean 60.3 years). In 27 out of the 31 patients rCBF was found to be lower than for age-matched normal control subjects. A reduction in cerebral blood flow from 17.5% to 5.5% in various age groups was found. The highest reduction in mean rCBF (17.5%) was found in the younger age group (35–50 years). In the group of patients between 51–65 years, the reduction was 13.4% and in the patients above 65, only 5.5%. The reduction of rCBF observed in our patients apparently did not reach the level required to produce cerebral manifestations. However, it is plausible to assume that any superimposed rhythm or rate pathology and/or cerebral arteriosclerosis may further compromise the cerebral circulation. Although cerebral emboli are a frequent cause of cerebral manifestations in cardiac arrhythmia, a chronic reduction in cerebral perfusion consequent to rate or rhythm disturbances in patients with cerebral vascular diseases should be considered. Early recognition and therapy of chronic arrhythmia with reduced cerebral perfusion may prevent neurological complications at a later stage.

The Effect of Acute Stroke on Cardiac Functions as Observed in an Intensive Stroke Care Unit

Fifty-two stroke patients, 43 with cerebral ischemia and nine with cerebral hemorrhage, underwent continuous cardiac monitoring in an Intensive Stroke Care Unit shortly after the onset of the acute cerebrovascular accident. In the group of patients with no evidence of pre-existing heart disease, eight of 18 with cerebral ischemia and five of seven with hemorrhage developed ECG abnormalities. Additional ECG changes were noted in 21 of 25 patients with cerebral ischemia and two of two with hemorrhage who were known to have previous heart disease. Both disturbances in rhythm and conduction and “ischemic” ST-T alterations were detected and the frequency of the former exceeded that of the latter. The ECG alterations were transient in 32 patients and permanent in four. New electrocardiographical abnormalities in patients without evidence of heart disease prior to the stroke were associated with poorer prognosis. The pathogenetic mechanisms leading to the appearance of cardiac abnormalities in stroke patients are considered.

The Effect of Cerebral Infarction on the Regional Cerebral Blood Flow of the Contralateral Hemisphere

Regional cerebral blood flow (rCBF) measurements were performed over the contralateral hemisphere by the 133Xe intracarotid injection method in 20 patients with acute cerebral infarction in the territory of the internal carotid artery. The rCBF was found to be reduced, sometimes remarkably, in all of the patients. The mean reduction was 30% to 36% from the lowest normal value for the mean age of these patients. In the younger age group (40 to 59) the reduction was greater, 40% to 47% from the lowest normal value for this age. The rCBF depression was not related to cerebral dominance, previous hypertension or arterial Pco2 levels. It occurred in both patients who were fully alert and those with disturbances of consciousness, although it tended to be more diminished in the latter. It can be assumed that the flow reduction in the nonaffected hemisphere is part of a general phenomenon affecting the entire brain and caused by globally reduced cerebral metabolism.

Effect of insulin administered intracisternally on the glucose level of the blood and the cerebrospinal fluid in vagotomized dogs

Abstract Regular insulin injected into the cisterna magna of dogs caused a significant decrease in the glucose concentration in both cerebrospinal fluid (CSF) and blood. The decrease in CSF glucose was greater than in the blood. Injection of insulin in bilateral vagotomized dogs caused a significant drop of glucose in CSF, while only a slight decrease in glucose level was observed in the blood. Inactivated insulin injected intracisternally in bilateral vagotomized dogs caused no significant change in glucose concentration in blood and CSF. The results indicate that, although insulin does not pass the CSF blood-brain barrier, it increased the glucose utilization by the central nervous system and might stimulate the insulin secretion by the pancreas through the parasympathetic centers.

Interictal regional cerebral blood flow in patients with partial seizures

Interictal regional cerebral blood flow was determined in 11 adult patients with partial epilepsy and lateralized electroencephalographic abnormalities by means of the xenon 133 intracarotid injection method. A hemispheric area demonstrating significantly low regional cerebral blood flow values as compared with the hemispheric mean cerebral blood flow was observed in each of the patients. In 10 of the 11 patients the localized reduced regional cerebral blood flow levels deviated significantly from levels obtained from parallel regions and hemispheres of normal controls. In the majority of patients, the site of low regional cerebral blood flow closely correlated with the clinical type of partial seizures and/or the site of main electroencephalographic abnormality. On the basis of these data, we suggest that the epileptogenic focus responsible for the partial seizures may be localized within the hemispheric area demonstrating the abnormal regional cerebral blood flow reduction.

Hypertension and Diabetes as Risk Factors in Stroke Patients

The occurrence of hypertension and diabetes in stroke patients was evaluated in a retrospective epidemiological study in the Jerusalem district. During the years 1960 through 1967, 1,522 new stroke cases (834 males and 688 females) were diagnosed and included in the study. Cerebral ischemia was diagnosed in 509 patients (33%), 181 patients (12%) had an intracerebral or subarachnoid hemorrhage and 832 patients (55%) had a stroke of undetermined type. For the total stroke series, 42% had hypertension. Almost the same percentage was found for males (41%) and females (43%). There was almost no sex predominance in the hypertensive stroke cases in the different age groups and for the various types of stroke. The frequency of hypertension among the stroke cases was low in the 40 to 49 age group, higher in the 50 to 59 age group, maximal in the 60 to 69 age group, and declining in the above 70 age group. The percentage of hypertensives was about the same for the ischemic and the undetermined types of stroke and for the total stroke series in the different age groups. It was found to be slightly higher in the hemorrhage type. The prevalence of hypertension among the male stroke cases was compared with the prevalence of hypertension in the general male population aged 40 and above (9.6%). For the total stroke series, 20% had diabetes. The same percentage was found for males (19%) and females (20%). There was almost no sex predominance in the diabetic stroke cases in the different age groups and for the various types of stroke. There was no significant change in the distribution of diabetes in the various age groups and the different stroke types. The prevalence of diabetes among the male stroke cases was compared with its prevalence in the general male population aged 40 and above (5%). Our study shows that hypertension and diabetes play an important role as risk factors in the development of cerebral ischemia and hemorrhage alike.

Effect of insulin administered intracisternally in dogs on the glucose level of the blood and the cerebrospinal fluid

Abstract Regular insulin injected into the cisterna magna of dogs caused a significant decrease in the glucose level in both cerebrospinal fluid and blood. This drop was first noted during the initial 30 min of the experiments. The decrease in cerebrospinal fluid glucose was proportionately greater than in the blood. Insulin labeled with radioactive iodine-131 administered intracisternally produced the same depression in glucose level of the blood and cerebrospinal fluid, despite the fact that no radioactivity was detected in the blood, thyroid, and urine during the first 24 hours. This observation suggests the possibility that insulin acts by stimulation of the parasympathetic areas in the brain stem and in this way produces a drop in the cerebrospinal fluid and blood glucose levels. Considering that the final glucose level was lower in the CSF than in the blood it was further assumed that the utilization of glucose by the central nervous system is increased when insulin is administered directly into the cerebrospinal fluid.

Correlation between regional cerebral blood flow and brain atrophy in dementia. Combined study with 133Xenon inhalation and computerised tomography.

Measurement of the regional cerebral blood flow (rCBF) by the 133Xenon inhalation method and computerised tomography were performed in 25 patients with presenile and senile dementia. Reduction of rCBF and various degrees of ventricular enlargement and cortical sulcal widening were demonstrated in the majority of demented subjects. However, there was no correlation between rCBF values and the severity of ventricular dilatation or cortical atrophy. These findings suggest that loss of brain substance is not an important factor in the reduction of rCBF in dementia.

Correlation between regional cerebral blood flow and EEG frequency in the contralateral hemisphere in acute cerebral infarction.

The relationship between the rCBF and the electroencephalographic (EEG) frequency was investigated in the contralateral hemisphere of 22 patients with acute cerebral infarction. Reduced rCBF was observed in all patients studied. The degree of rCBF reduction was mild, moderate, or severe and ranged between 6 and 80% from the lowest age-matched normal values obtained in our laboratory. The frequency indices remained within normal limits (mean - 10.4 Hz) in 16 patients. Slower frequencies (mean - 6.3 Hz) were recorded in 6 patients. No correlation was found between the two parameters (P = 0.89). Both the EEG frequency and the rCBF are known to be closely related to the cerebral metabolic rate. The observed rCBF depression without concomitant changes in the EEG frequency raises the question of the role of globally-reduced cerebral metabolism as the cause of rCBF reduction in the noninfarcted hemisphere in stroke patients. Our findings constitute additional evidence that the contralateral hemisphere is involved in the haemodynamic changes occurring in acute cerebral infarction.