Prevalence of Alzheimer's disease.
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Aged↗
Biomedical subjects
I Prohovnik
Publications and source records attributed to I Prohovnik.
Regional cerebral blood flow in mood disorders. I. Comparison of major depressives and normal controls at rest.
We measured regional cerebral blood flow with the xenon 133 inhalation technique in 41 patients with major depressive disorder and 40 matched, normal controls during an eyes-closed, resting condition. The depressed group had a marked reduction in global cortical blood flow. To examine topographic abnormalities, traditional multivariate analyses were applied, as well as a new scaled subprofile model developed to identify abnormal functional neural networks in clinical samples. Both approaches indicated that the depressed sample had an abnormality in topographic distribution of blood flow, in addition to the global deficit. The scaled subprofile model identified the topographic abnormality as being due to flow reduction in the depressed patients in selective frontal, central, superior temporal, and anterior parietal regions. This pattern may reflect dysfunction in the parallel distributed cortical network involving frontal and temporoparietal polymodal association areas. The extent of this topographic abnormality, as revealed by the scaled subprofile model, was associated with both patient age and severity of depressive symptoms.
Adult↗
Intraoperative 133Xe cerebral blood flow measurements by intravenous versus intracarotid methods.
To document the comparability of cerebral blood flow (CBF) values determined by quantification of 133Xe washout after either intravenous or intracarotid administration, 12 patients undergoing elective carotid endarterectomy anesthetized with N2O/O2 and either isoflurane or halothane were studied. Scintillation counters were placed over the middle cerebral artery territory ipsilateral to the operated carotid artery. CBF was measured by the intravenous method during dissection of the carotid sheath and was calculated as the initial slope index from head washout curves collected for 11 min after injection of 10-20 mCi 133Xe in saline into a large vein. Immediately prior to carotid occlusion, CBF was determined by direct injection of 1 mCi 133Xe in saline into either the internal carotid artery or the common carotid artery with the external carotid artery occluded. For the intracarotid injections, the initial slope was calculated from the 1st min of washout. Data were analyzed by linear regression and analysis of variance. Values are expressed as mean +/- SD. The mean CBF for intravenous and intracarotid methods were both 29 +/- 10 ml.100 g-1.min-1. The correlation between CBF measured by intravenous and intracarotid methods was excellent and was described by the line y = x + 0.6, r = 0.92. We conclude that in the flow range studied, the intravenous technique may be applied to measure CBF in physiologically stable situations in which direct intracarotid injection is not feasible.
Anesthesia, Inhalation↗
The effect of arteriovenous malformation resection on cerebrovascular reactivity to carbon dioxide.
To investigate the cerebral hemodynamic changes associated with obliteration of arteriovenous malformations (AVMs), we studied 26 patients undergoing total microsurgical AVM resection during isoflurane and N2/O2 anesthesia. Detectors were placed 5 to 6 cm from the margin of the lesion and in a homologous contralateral position. Cerebral blood flow (CBF) was measured using the intravenous xenon-133 technique before and after AVM resection, during both hypocapnia and normocapnia at each stage. Intraoperative changes in CBF were related to a risk score system based on the patient's history and preoperative angiograms. Seven otherwise healthy patients undergoing spinal surgery were studied to control for anesthetic effects. Patient demographic and clinical data for the AVM group conformed to the expected strata of a large AVM population. The CBF increased after excision (22 +/- 1 ml/100 g/min before excision to 30 +/- 2 ml/100 g/min after excision; mean +/- SE, n = 25, P less than 0.002) without a hemispheric difference. CO2 reactivity increased slightly after excision (4.2 +/- 0.3% change/mm Hg before excision to 4.7 +/- 0.3% change/mm Hg after excision; n = 14, P less than 0.02). The baseline CBF and CO2 reactivity were not different from the control group. There was a weak correlation between the risk score and the percentage of change in the ipsilateral CBF, with a trend for the patients with the lowest risk to have the lowest CBF changes after resection. There was no relationship between CO2 reactivity and risk grade. None of the patients awoke from anesthesia with unexpected neurological deficits. The highest CBF increases were associated with postoperative brain swelling in one patient and fatal intracerebral hemorrhage in another. Both patients had normal CO2 reactivity before excision. One patient suffered postoperative intracerebral hemorrhage, attributable to technical problems, and had no increase in CBF. We conclude that, with an acute increase in the arteriovenous pressure gradient (and cerebral perfusion pressure) that results from shunt obliteration, there is an immediate global effect of AVM resection to increase CBF. Cerebrovascular reactivity to CO2 remains intact both before and after excision.
Adult↗
Nimodipine does not increase cerebral blood flow during hypocapnia in the rat.
Nimodipine is a calcium entry blocker that shows promise in the therapy for cerebral ischemia. This study was undertaken to examine the interaction of nimodipine with the use of hypocapnia to control cerebral blood volume by reduction in cerebral blood flow (CBF), as might be applicable to patients undergoing anesthesia for neurosurgical procedures. Male adult Sprague-Dawley rats were anesthetized with pentobarbital 50 mg/kg i.p. and were mechanically ventilated at either normocapnia (Paco2 35-40 mm Hg) or hypocapnia (Paco2 23-25 mm Hg). Animals were randomized into four experimental groups in a 2 x 2 factorial design, employing Paco2 level and drug group as between-group factors: vehicle plus normocapnia (group 1, n = 6), nimodipine plus normocapnia (group 2, n = 7), vehicle plus hypocapnia (group 3, n = 6), and nimodipine plus hypocapnia (group 4, n = 6). Nimodipine (1 mug/kg/min) or vehicle was administered i.v. for a period of 45 min. CBF was then measured using [C]iodoantipyrine autoradiography. Hypocapnia decreased global CBF (p <0.0001) and nimodipine increased CBF (p <0.05). Although nimodipine increased global CBF (p <0.05) during normocapnia (89 +/- 8 versus 61 +/- 4 ml/100 g/min), during hypocapnia there was no significant difference between nimodipine and vehicle (45 +/- 3 versus 40 +/- 2 ml/100 g/min). Hypocapnia decreased local CBF in all structures examined, whereas nimodipine increased local CBF in some, but not all structures. In this model, prior institution of hypocapnia prevented nimodipine-induced global CBF increases.
Journal Article↗
Three-minute blood flow index for assessment of cerebrovascular reserve.
Regional cerebral blood flow studies with xenon-133 are useful in the functional assessment of cerebrovascular diseases. Conventional models for cerebral blood flow calculation employ 11 minutes of data collection. However, in many circumstances it is not possible to maintain steady-state physiologic conditions for 11 minutes. We compared a monocompartmental model that requires only 3 minutes of data collection with the bicompartmental model that requires 11 minutes of data collection. The correlation between the absolute values for global cerebral blood flow (initial slope index, intravenous method) in 72 anesthetized patients was r = 0.88; for 54 awake patients inhaling xenon-133, the correlation was r = 0.77. Cerebral blood flow was determined with intravenous xenon-133 at baseline and during a CO2 challenge in 50 patients during cerebrovascular surgery under general anesthesia. Reactivity to a 10-mm Hg rise in PaCO2 was calculated in absolute terms and as a percentage change from baseline using both the 3-minute and the 11-minute models. The correlation of CO2 reactivity calculated with the two models was r = 0.9 for the absolute values and r = 0.8 for the relative change. Cerebral blood flow calculated with the two models correlated well in both awake and anesthetized patients. In addition, there was a good correlation between CO2 reactivity calculated with the two models. In situations in which physiologic conditions cannot be held stable for 11 minutes, the 3-minute initial slope index may be used to quantitatively assess cerebrovascular reserve with a CO2 challenge.
Adult↗
Perfusion insufficiency in limb-shaking transient ischemic attacks.
We describe a 63-year-old man with severe bilateral internal carotid artery disease who presented with repeated, brief attacks of left limb shaking precipitated by his standing up. Cerebral blood flow measured by xenon-133 inhalation showed reduced resting flows and a focal perfusion deficit in the right dorsofrontal and upper rolandic regions. Blood flow velocity and pulsatility index of the right middle cerebral artery measured by transcranial Doppler ultrasonography were also reduced. With hypercapnic challenge, both hemispheric tissue perfusion and blood flow velocity showed impaired reactivity. With induced hypotension, the focal perfusion deficit in the right dorsofrontal region was accentuated. Following right internal carotid endartectomy, resting cerebral blood flow and blood flow velocity improved, as did hypercapnic vasoreactivity. These reversible deficits in cerebral blood flow and vasoregulation, which were maximal in the dorsofrontal region, are consistent with low perfusion in the border zone territory or the distal fields and demonstrate that hemodynamic failure is the likely mechanism for limb-shaking transient ischemic attacks from severe carotid artery disease.
Biomechanical Phenomena↗
Dissociated effects of amphetamine on arousal and cortical blood flow in humans.
The effects of intravenous amphetamine infusion (0.3 mg/kg) on cerebral blood flow (CBF) and measures of autonomic and behavioral arousal were studied in 12 normal male volunteers in a placebo-controlled crossover design. Nonsignificant decreases were seen in CBF (measured by 133Xe inhalation), despite significant increases in autonomic and behavioral arousal. The apparent dissociation of CBF and arousal appears to be compatible with other human experiments suggesting that amphetamine decreases CBF and metabolism, as well as with neurobiological findings on the effects of catecholamines on resting cortical activity and mechanisms of increased attention. The results differ substantially, however, from findings of increased CBF and metabolism in animals. Although the larger doses used in animals most likely explain the discrepancy, technical limitations in human brain imaging cannot be excluded.
Affect↗
Gray-matter degeneration in presenile Alzheimer's disease.
Previous comparisons between presenile Alzheimer's disease (AD) and senile dementia of the Alzheimer type (SDAT) did not control for disease severity and duration. In the current study, 18 patients with each diagnosis were matched for disease duration, cognitive dysfunction, and behavioral symptoms (using the modified Mini-Mental Status [mMMS] examination and the Blessed Dementia Rating Scale [BDRS] ). Regional cerebral blood flow (rCBF) was quantified by the 133xenon inhalation technique, and several indices of tissue perfusion were examined. The two variables of primary interest were relative gray-matter relative weight (35% in presenile patients versus 39% in senile patients and healthy control subjects, p = 0.006), with neither perfusion nor disease severity differences between the two dementia samples. This loss of gray matter was significantly related to both severity and duration of disease in the patients with presenile AD, but not in patients with SDAT. These findings lend support ot previous suggestions of greater degenerative process in presenile AD and confirm the need to examine and control age of onset in future investigations of AD. Further, correlation analysis suggests greater proportion of common variance among clinical and physiological indices in presenile AD.
Age Factors↗
Regional cerebral blood flow during alcoholic blackout.
Regional cerebral blood flow was measured during alcoholic blackout in a 61-year-old man with a blood-alcohol level of 0.38%. The mean flow level was found to be elevated by about 30-60% compared to repeated studies during long-term abstinence. The regional pattern did not change greatly. Increases of mean regional cerebral blood flow have previously been reported during social drinking and in Wernicke-Korsakoff's syndrome. A common disturbance of subcortical activation systems is hypothesized.
Alcohol Amnestic Disorder↗
Cortical perfusion in Alzheimer's disease: beyond diagnosis.
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Aged↗
A comparison of the cerebral hemodynamic effects of sufentanil and isoflurane in humans undergoing carotid endarterectomy.
Prompted by reports of potentially deleterious cerebral vasodilation by the synthetic opioid sufentanil, the authors compared the effects of either isoflurane/N2O and sufentanil/N2O on cerebral blood flow (CBF), arteriovenous difference in oxygen content (AVDO2), and CBF reactivity to changes in PaCO2 during carotid endarterectomy. Cerebral blood flow was measured using the iv method of 133-Xe CBF determination and AVDO2 was measured using systemic arterial-jugular venous oxygen content differences. Patients, age 68 +/- 1 yr (mean +/- SE), received either isoflurane (n = 10), 0.75% in O2 and N2O, 1:1; or sufentanil (n = 10), 1.5-2 micrograms/kg bolus and then 0.2-0.3 micrograms.kg-1.h-1 infusion in addition to O2 and N2O, 2:3. Measurements were made immediately before carotid occlusion, and then at two levels of PaCO2 (approximately 32 and 42 mmHg) after insertion of a temporary in-dwelling bypass shunt. Prior to carotid occlusion, there was no significant difference in CBF (ml.100 g-1.min-1) between patients receiving isoflurane (22 +/- 3) or sufentanil (20 +/- 2). Similarly, there was no difference in AVDO2 (vol-%) between isoflurane (4.5 +/- 0.7) and sufentanil (5.4 +/- 0.8) groups. Using a two-way ANOVA design with anesthetic as the between-group factor and elevation of PaCO2 as the within-group repeated measure, there was a significant effect of hypercarbia to increase CBF (P less than 0.0001) and decrease AVDO2 (P less than 0.001). The product of AVDO2 and CBF, which reflects cerebral metabolic oxygen consumption, remained constant (P = 0.364).(ABSTRACT TRUNCATED AT 250 WORDS)
Aged↗
Correlation of intravenous vs. intracarotid cerebral blood flow (CBF) values.
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Journal Article↗
Organic affective disorder and vascular dysregulation in systemic lupus erythematosus.
A case is reported in which an exacerbation of systemic lupus erythematosus presented as an organic depressive disorder with psychotic features. Brain imaging using regional cerebral blood flow techniques demonstrated vascular dysregulation in the left frontal lobe of this patient. The implications for understanding the pathogenesis of psychiatric disorders in lupus are discussed.
Adolescent↗
Cerebral hyperemia, stroke, and transfusion in sickle cell disease.
To investigate cerebral hemodynamics in sickle cell disease (SCD), we used the 133Xenon inhalation technique of quantifying cerebral blood flow (CBF) in 67 patients. Clinical examinations and cerebral magnetic resonance imaging also were performed in all patients. Compared with age-matched healthy controls, CBF was elevated by 68% in patients, and inversely related to hematocrit. An experimental index of cerebral blood volume, pr4, was also elevated in the patients in a similar manner. Cerebral blood volume was positively correlated to CBF in SCD patients but not in controls. History of stroke and current neurologic symptoms were associated with lower flow and higher cerebral blood volume. Transfusion therapy reduced the hyperemia, the reduction being greater than expected by hematocrit elevation alone. These findings document a vasodilatory hyperemia in SCD. This dilatation may be a risk factor for ischemic distal-field infarctions, as visualized by MRI, due to a limitation of cerebrovascular reserve capacity.
Adolescent↗
Neurologic complications of sickle cell disease.
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Anemia, Sickle Cell↗
Cerebral blood flow and metabolism in patients undergoing anesthesia for carotid endarterectomy. A comparison of isoflurane, halothane, and fentanyl.
The effects of isoflurane, halothane, and fentanyl on cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) during anesthesia prior to carotid endarterectomy were compared using the intravenous method of 133-Xenon CBF determination. Patients, mean (+/- SE) age 68 +/- 2, received either isoflurane (N = 16), 0.75% in O2 and N2O, 50:50; halothane (N = 11), 0.5% in O2 and N2O, 50:50; or fentanyl (N = 10), 5-6 micrograms/kg bolus and then 1-2 micrograms.kg-1.h-1 infusion in addition to O2 and N2O, 40:60. Measurements were made immediately before carotid occlusion. Mean (+/- SE) CBF (ml.100 g-1.min-1) was 23.9 +/- 2.1 for isoflurane, 33.8 +/- 4.8 for halothane, and 19.3 +/- 2.4 for fentanyl. CMRO2 (ml.100 g-1.min-1) was available from 22 patients and was 1.51 +/- 0.28 for isoflurane (N = 7), 1.45 +/- 0.24 for halothane (N = 6), and 1.49 +/- 0.21 for fentanyl (N = 9). Although CBF was greater during halothane than during isoflurane or fentanyl anesthesia (p less than 0.05), there were no demonstrable differences in CMRO2 among the 3 agents. We conclude that choice of anesthetic agent for cerebrovascular surgery with comparable anesthetic regimens should not be made on the basis of "metabolic suppression." During relatively light levels of anesthesia, vasoactive properties of anesthetics are more important than cerebral metabolic depression with respect to effects on the cerebral circulation.
Aged↗
Brain infarction in sickle cell anemia: magnetic resonance imaging correlates.
Brain infarction is a well-known but poorly understood complication of sickle cell disease. Seventy-three sickle cell disease patients underwent neurological examinations and high-field, heavily T2-weighted axial cranial magnetic resonance image (MRI) scanning. Eighteen of the 73 had a history of stroke, defined as an acute, focal neurological sign lasting longer than 1 hour; in the event of a convulsive onset, an MRI abnormality as a correlate was necessary. Sixteen of the 18 stroke patients demonstrated focal MRI abnormalities consistent with arterial borderzone infarctions. Fifty-five of the 73 patients had no history of stroke. Six of the 55 (11%) had focal MRI abnormalities suggesting previous subclinical stroke. Five of these lesions were in borderzone regions. The distinguishing feature in 21 of the 22 patients with MRI abnormalities was the predilection for lesions in the high cortical convexity, in the general regions of arterial borderzones between the major cerebral arteries and adjacent deep white matter. The pattern of MRI lesions suggests two pathogenetic mechanisms: (1) proximal large-vessel disease with inadequate cerebral perfusion (distal field insufficiency syndrome) and (2) distal small-vessel disease (sludging syndrome).
Adolescent↗