Higher rCBF Research Articles

Vascular risk factors, atherosclerosis, cerebral white matter lesions and cerebral perfusion in a population-based study.

We studied risk factors for cerebral vascular disease (blood pressure and hypertension, factor VIIc, factor VIIIc, fibrinogen), indicators of atherosclerosis (intima-media thickness and plaques in the carotid artery) and cerebral white matter lesions in relation to regional cerebral blood flow (rCBF) in 60 persons (aged 65-85 years) recruited from a population-based study. rCBF was assessed with single-photon emission tomography using technetium-99m d, l-hexamethylpropylene amine oxime (99mTc-HMPAO). Statistical analysis was performed with multiple linear regression with adjustment for age, sex and ventricle-to-brain ratio. A significant positive association was found between systolic and diastolic blood pressure and temporo-parietal rCBF. In analysis with quartiles of the distribution, we found a threshold effect for the relation of low diastolic blood pressure (</=60 mmHg) and low temporo-parietal rCBF. Levels of plasma fibrinogen were inversely related to parietal rCBF, with a threshold effect of high fibrinogen levels (>3.2 g/l) and low rCBF. Increased atherosclerosis was related to low rCBF in all cortical regions, but these associations were not significant. No consistent relation was observed between severity of cerebral white matter lesions and rCBF. Our results may have implications for blood pressure control in the elderly population.

A controlled positron emission tomography study of obsessive and neutral auditory stimulation in obsessive-compulsive disorder with checking rituals

Ten nondepressed patients with obsessive-compulsive disorder (OCD) who were characterized by predominant checking rituals were compared with 10 age- and sex-matched control subjects. Hemispheric and regional cerebral blood flow levels (rCBF) were measured with positron emission tomography (H 2 15O) across four conditions: rest, auditory stimulation with idiosyncratic normal or abnormal obsession, auditory stimulation with neutral verbal stimuli, and rest. Order of neutral and obsessive stimulation was randomized. Higher subjective responses to obsessive than to neutral stimulation were found in both groups; subjective response was higher in OCD patients when obsessive stimulation was presented first. A four-way analysis of variance (group × stimulation order × hemisphere × condition [neutral or obsessive stimulation]) was performed on stimulation minus rest normalized rCBF values. Control subjects had significantly higher rCBF in the thalamus and putamen. A trend toward higher rCBF in OCD patients was found in the superior temporal regions. When neutral stimulation was presented first, rCBF was significantly higher in the caudate region of control subjects. Obsessive stimulation was associated with higher rCBF than neutral stimulation in orbitofrontal regions in both groups of subjects. Under obsessive stimulation, superior temporal and orbitofrontal activities were correlated in OCD patients but not in control subjects. Our study suggests specific abnormalities of information processing in the basal ganglia and temporal structures of compulsive checkers.

L-Arginine ameliorates cerebral blood flow and metabolism and decreases infarct volume in rats with cerebral ischemia

Effects of l-arginine, 300 mg/kg, i.p., on the regional cerebral blood flow (rCBF), brain metabolism, and infarct volume were examined in spontaneously hypertensive rats subjected to occlusion of both left middle cerebral artery and left common carotid artery. Rats treated with l-arginine had higher rCBF, determined by hydrogen clearance method, in the ischemic core (7 ± 1 ml/100 g/min, mean ± S.E.M.) and penumbral regions (16 ± 2) than did rats treated with saline (5 ± 0 and 7 ± 1, respectively). Simultaneously, l-arginine attenuated metabolic derangement in the ischemic tissue at 60 min, i.e. well maintained adenosine triphosphate (ATP) in ischemic region (1.29 ± 0.07 mmol/kg in l-arginine group vs. 1.05 ± 0.06 in saline group), and also close to normal levels in ATP (2.61 ± 0.02 mmol/kg vs. 2.45 ± 0.05), glucose (2.29 ± 0.12 mmol/kg vs. 1.80 ± 0.17) and lactate (1.63 ± 0.10 mmol/kg vs. 2.24 ± 0.21) in periischemic region. In another experiment, the effects of l-arginine on rCBF in the subcortical regions and on infarct volume were evaluated. l-arginine, compared with saline, increased rCBF by 8 ml/100 g/min in the ischemic side and reduced infarct volume by 29% at 24 h of ischemia. These findings support that l-arginine may be potentially useful for the treatment of acute cerebral ischemia.

Relationship between brain structure and function in disorders of the schizophrenic spectrum: single positron emission computerized tomography, computerized tomography and psychopathology of first episodes.

Fifty newly diagnosed, briefly treated or drug-naive patients with schizophrenia or schizophreniform disorder were examined by psychopathology scales for positive (SAPS), negative (SANS) and overall psychotic symptoms (PSE and BPRS). CT-scan and regional cerebral blood flow (rCBF) measurement by 99mTc-HMPAO SPECT during rest and mental activation by Wisconsin Card Sorting Test was performed as well. Twenty-five age-matched normal healthy volunteers served as controls. Thought disorders and fundamental symptoms correlated positively with relatively high, though subnormal prefrontal (PFC) rCBF and high rCBF in temporal cortex; positive symptoms correlated positively with high rCBF in the striatum and temporal cortex during activation. Negative symptoms correlated with high prefrontal rCBF. The patients had sulcal enlargement and smaller brain volume compared with the healthy volunteers. There were no signs of ventricular enlargement. Neither total negative symptoms, thought disorder nor fundamental symptoms correlated with any CT measurements. Total positive symptoms correlated negatively with the size of the temporal horns. The relatively high rCBF in PFC and temporal cortex of cases with pronounced positive and negative symptoms and thought disorder may imply that an aberrant cortical network has to be active to express a malattuned clinical output. The striatal hyperfunction mainly in productive cases may be a secondary phenomenon and more pronounced in cases where no signs of subcortical atrophy has (yet?) ensued.

58 99mTc HMPAO BRAIN SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY (SPECT) AND PERINATAL ASPHYXIA

This study was designed to rate the clinical value of 99mTc HMPAO brain SPECT in perinatal asphyxia. 12 full-term babies were included. HMPAO SPECT were performed in neonates respectively at 1 and 10 hours after the asphyxial event and repeated 24 hours after. In the 10 remainders HMPAO SPECT were initiated within 1 to 4 days following the asphyxial event. TcPO2, TcPCO2, StaO2, pH values, mean arterial blood pressure, blood glucose levels, pulsed Doppler recordings of middle cerebral artery and ultrasound scans were available at the moment of the SPECT procedures. In acute phase of brain asphyxia (1.10 hours) (2 cases), HMPAO SPECT demonstrated reduction of regional cerebral blood flow (rCBF) in the cerebrum and cerebellum whereas brain stem and basal ganglia were perfused and CBF velocities were significantly reduced. In the subacute phase (24-96 hours), 6 neonates demonstrated high CBF velocities and high rCBF on BMPAO SPECT (two of them belonging to the first group) with total vaso-paralysis. In one case, high rCBF were noted in parasagittal areas. This infant domonstrated cerebral parasagittal lesions on magnetic resonance imaging; whereas the 4 remainders died. The 6 other neonates showed no abnormalities on rCBF neither on CBF velocities, and were neurologically nonual at 6 months of age. These results indicate that 99mTc HMPAO brain SPECT shows a potential clinical value in evaluating perinatal asphyxia. It documents reliably changes in rCBF and demonstrates two distinct features following cerebral asphyxia respectively hypo and hypercerebral perfusion associated with bad outcome.

High resolution regional cerebral blood flow measurements in psychiatric disorders

The present report describes the development of the first high resolution rCBF instrument, the Cortexplorer 256-HR, providing a spatial resolution for superficial cortical areas of about 1 cm. Examples will be given of how this improved resolution makes it possible to describe and interpret the flow pathology of individual patients. It also makes it possible to interpret rCBF changes induced by different mental tasks given to the patients during the recording

Quantification of regional cerebral blood flow with IMP-SPECT. Reproducibility and clinical relevance of flow values.

Single-photon emission computed tomography with N-isopropyl[123I]-p-iodoamphetamine (IMP-SPECT) was performed in 14 normal volunteers (seven men and seven women aged 25.1 +/- 5.3 years) and 29 patients with cerebrovascular disease (18 men and 11 women aged 54.1 +/- 13.7 years). The fluid microsphere model was used to estimate cerebral blood flow (CBF). Normal subjects were scanned twice, 1 week apart, to determine the reproducibility of the CBF estimates. Hemispheric blood flow (hCBF) was calculated as the mean of regional cerebral blood flow (rCBF) values in 16 gray matter regions per hemisphere. In normal subjects mean hCBF was 68 ml/100 g/min. The highest rCBF was found in the occipital cortex, followed by the frontal, temporal, and parietal cortexes. CBF values were reproducible (p less than 0.001 except the right thalamic region, where p less than 0.01). Intraindividual variation ranged between 0.3% and 15%. Women exhibited significantly higher (16%, p less than 0.02) CBF than men. Patients were subdivided into groups with reversible (n = 19) and persistent (n = 10) symptoms. Significant hCBF differences between the affected and the contralateral hemispheres were recorded only in the group with reversible symptoms (p less than 0.005), whereas the group with persistent symptoms showed a significant bilateral decrease of hCBF compared with normal subjects and patients with reversible symptoms. Focal CBF was significantly lower in patients with completed stroke than in patients with transient symptoms (p less than 0.001). Our results indicate that IMP-SPECT can be used for the routine estimation of CBF in normal and pathologic states.

Patterns of regional cerebral blood flow in patients with occlusive or stenotic lesions of both the internal carotid and vertebrobasilar arteries.

For the study of cerebral hemodynamics in patients with multiple occlusive or stenotic lesions of the internal carotid artery (lCA) and vertebral/basilar artery (V A/BA), six male patients (mean aged 62.5 years) were examined by regional cerebral blood flow(rCBF; Fg: intravenous bolus injection of Xe 133). The highest rCBF(73.3 ± l6.l(SD)m2/100g/min) was observed in two patients with stenosis of the VA and biiaterallCAs and the lowest rCBF(47.l ± 5.9), in patients with severe stenosis of the BA including unilateral occlusion or stenosis of the VA and ICA. Intermediate rCBF (56.1 ± 10.0) was found in patients with occlusion of the VA and occlusion or stenosis of the bilateral ICAs. Among them lesions without VA-occlusion and BA-stenosis were important in keep­ ing rCBF high.

Cerebral blood flow in systemic lupus erythematosus with and without central nervous system involvement.

Regional cerebral blood flow (rCBF) was studied by the intravenous 133Xe method in 38 patients with systemic lupus erythematosus (SLE); 21 patients had neuropsychiatric manifestations (N+) and 17 did not (N-). Twelve of the N+ patients had had neuropsychiatric episodes less than one year before measurement of CBF ("recent" N+), while seven patients in this group had had episodes over a year before measurement ("old" N+). The results were compared with those obtained from a group of 27 age-matched normal healthy subjects. It was found that, in most of the N+ and N- patients, rCBF was evenly distributed bilaterally, but there was a "patchwork" of high/normal and low flow areas. This disturbance of rCBF distribution was significantly greater in "recent" N+ patients than in "old" N- patients, but was not a function of the potential evolution of systemic lupus erythematosus. It was also found that there was a reduction in the physiological high frontal rCBF in the "old" N+ patients. No correlation could be found between rCBF, the topography of the neuropsychological lesions, other neurological investigations or the glucocorticoid dosage and treatment schedules.

133Xe-DSPECT: Normalwerte von zerebraler Ruhedurchblutung und Reservekapazität

Using the 133Xe-DSPECT technique, quantitative measurements of regional cerebral blood flow (rCBF) were performed before and after provocation with acetazolamide (Diamox) i. v. in 32 patients without evidence of brain disease (normals). In 6 cases, additional studies were carried out to establish the time of maximal rCBF increase which was found to be approximately 15 min p. i. 1 g of Diamox increases the rCBF from 58 ±8 at rest to 73±5 ml/100 g/min. A Diamox dose of 2 g (9 cases) causes no further rCBF increase. After plotting the rCBF before provocation (rCBFR) and the Diamox-induced rCBF increase (reserve capacity, Δ rCBF) the regression line was Δ rCBF = −0,6 x rCBFR +50 (correlation coefficient: r = −0,77). In normals with relatively low rCBF values at rest, Diamox increases the reserve capacity much more than in normals with high rCBF values before provocation. It can be expected that this concept of measuring rCBF at rest and the reserve capacity will increase the sensitivity of distinguishing patients with reversible cerebrovascular disease (even bilateral) from normals.

Determination of regional cerebral blood flow in patients with cerebral infarction. Use of fluoromethane labeled with fluorine 18 and positron emission tomography.

Regional cerebral blood flow (rCBF) was determined using the tissue kinetic of fluoromethane labeled with fluorine 18 and positron emission tomography (PET) in 13 normal subjects and 21 patients with cerebrovascular diseases. The mean brain rCBF was 42.9 +/- 4.3 mL/100 g/min during the resting state. The highest rCBF (60 +/- 8 mL/100 g/min) was noted in the mesial occipital region corresponding to cortical area 17. All 17 cases of cerebral ischemic infarcts had depressed rCBF in the hemisphere ipsilateral to the infarct. Every area of decreased density shown in the conventional computed tomograms (CT) was detected on the PET as an area of decreased rCBF (mean rCBF of infarcted area, 14.3 +/- 6 mL/100 g/min). The PET images showed a wider area of depressed rCBF than the region of the anatomic infarct. Five types of remote effects were noted in areas without structural damage: (1) decreased flow in the thalamus and caudate ipsilateral to the infarct; (2) decreased flow in the hemisphere contralateral to the cerebral infarct; (3) decreased flow in the cerebellar hemisphere contralateral to the cerebral infarct; (4) decreased flow in the visual cortex distal to the optic radiation lesion; and (5) decreased flow in the frontal cortex ipsilateral to the infarct. The effects in the contralateral hemisphere and the cerebellum were present only in the acute postictal phase. In four cases of transient ischemic attacks, rCBF was normal. It is concluded that this technique of measuring rCBF is a reliable method of identifying cerebral ischemia and that the determination of the extent of impaired rCBF provides a more accurate assessment of the region of brain dysfunction than CTs.

Cerebral blood flow after carotid occlusion and extracranial-intracranial bypass.

Eleven patients with occlusion of one internal carotid artery showed marked reduction of regional cerebral blood flow (rCBF) through the hemisphere on the affected side with high rCBF on the opposite side. Six of the patients had no surgery, during follow-up of 2 to 5 years. rCBF increased on both sides leaving a persisting asymmetry of rCBF. Five patients had extracranial-intracranial bypass; rCBF increased on the affected side but not on the opposite side. Asymmetry of rCBF between the hemispheres remained but was much less than in the non-operated group.

Effect of two levels of induced hypocapnia on cerebral autoregulation in the acute phase of head injury coma.

In eight unconscious and artificially ventilated patients with severe head injury, cerebral autoregulation (CA) was tested during angiotensin infusion, before and after a reduction of Paco2. Intracranial pressure (ICP) and systemic arterial pressure (SAP) were continuously recorded. Regional cerebral blood flow (rCBF) was measured by the intracarotid Xe133 washout technique as initial slope index, stochastic and compartmental analysis. In contradistinction to previous human studies, we found a preserved CA during moderate hypocapnia (mean Paco2 34.2 mmHg) while the CA after a further decrease in Paco2 (mean value 23.1 mmHg) was lost. The apparently preserved CA may be a "false phenomenon" due to a regional increase in ICP. After a decrease in Paco2, an association between high CO2 reactivity and rCBF increase during angiotensin was disclosed, while a decreased or unchanged rCBF was observed in regions with inverse steal or abolished CO2 reactivity. The study indicates that the interpretation of CA is facilitated by performing the test during two levels of Paco2, but the presence of impaired autoregulation in the acute phase of head injury indicates that deliberate increase in SAP may be dangerous, as it may provoke an increase of regional ICP and brain oedema.