Cerebral Blood Flow Studies Research Articles

Motor-Related Intracortical Steal Phenomenon Detected by Multichannel Functional Near-Infrared Spectroscopy Imaging

Background: Patients with severe cerebral ischemia may lose autoregulation to increase cerebral blood flow following neural activity. Although the steal phenomenon under conventional cerebral blood flow study has been known as a high-risk factor for stroke, the cerebral oxygen hemodynamics in ischemic patients during functional activation has not been thoroughly investigated. In this study, we present rare cases with intracortical steal phenomenon during motor tasks detected by multichannel functional near-infrared spectroscopy before and after surgery. Methods: The relative concentration change of oxygenated, deoxygenated and total hemoglobin in and around the primary sensorimotor cortex during contralateral hand grasping was investigated in 11 patients with severe internal carotid artery stenosis. Results: In 3 patients, the concentration of total hemoglobin around the primary sensorimotor cortex significantly decreased in response to motor stimulation and returned to baseline soon after termination of the motor task. This phenomenon partially disappeared postoperatively in all patients who underwent surgery. The remaining 8 patients showed no signs of total hemoglobin decrease in and around the sensorimotor cortex. In 9 patients, lack of decrease in deoxygenated hemoglobin in the center of the primary motor cortex during the motor task was observed and 3 of them showed significant increase in deoxygenated hemoglobin. Conclusions: We have demonstrated that in some patients with severe ischemia, an abnormal motor-related steal phenomenon can be observed. This phenomenon can be modulated by surgical intervention and might imply the severity of ischemia.

CBF as a diagnostic tool in dementias: Revision required?

Dementia has several aetiologies. Common to them all is that they lead to dysfunction of cerebral neurons and thereby to clinical symptoms, and that they disturb cerebral blood flow and metabolism. The causes of dementia may be divided into three categories: degenerative, e.g., Alzheimer's disease (AD), vascular dementias, and dementia due to other causes, e.g., sequela of head trauma. It is well known that advanced dementia irrespective of cause is accompanied by marked changes in cerebral perfusion and metabolism. In most instances the changes in perfusion and metabolism seem to be coupled. More controversial are the questions: 1) To which extent can measurements of CBF be used in the early diagnosis of dementia? and 2) Can CBF measurements be used to distinguish between different types of dementia, especially between vascular dementia and AD? The neural damage in a dementing disease may lead to tissue atrophy as well as to reduction in flow and metabolism. Of major interest is whether an observed flow reduction reflects only tissue loss (less tissue and thus lower total flow in the voxel) or reflects a true reduction of flow in the remaining tissue. With the classical inert gas clearance techniques, Kety Schmidt's original method and Lassen and Ingvar's later method using intraarterial injection of tracer, the measurements yield a direct value of perfusion per gram tissue. Thus, these measurements would be independent of any tissue loss and directly reflect flow in remaining tissue. In contrast, with the more modern tomographic methods the measurements depend heavily on the amount of tracer taken up in the tissue. Thus, in any given voxel the uptake will be proportional to the fraction of tissue present, the so-called partial volume effect. In dementia with atrophy the partial volume correction becomes essential if the aim is to calculate true flow in the remaining tissue. Though the evidence is not conclusive, it seems as if there is a flow and metabolism reduction in addition to the partial volume loss. Vascular dementia typically refers to dementia of vascular origin apart from sequela of major stroke. It might either be caused by multiple small ischemic lesions, potentially with infarction, or to more widespread and diffuse hypoperfusion leading to threatening ischemia. In threatening cerebral ischemia the circulation is often sufficient or only marginally reduced but with daily fluctuation of blood pressure insufficient perfusion may occur if there is no autoregulatory reserve. Also, vasodilatory stimuli like moderate accumulation of carbon dioxide might result in an adverse effect leading to insufficient perfusion in the threatened areas. Such abnormalities would be expected to distinguish vascular dementia from AD. There are many reports of such threatening ischemia, but most studies have been in smaller selected patient groups with signs of insufficient perfusion. In conclusion studies of cerebral blood flow and metabolism in dementing diseases have given us valuable information about pathophysiology. But at present it remains unclear to which extent flow measurement can be used more broadly in the clinical evaluation of patients with memory disturbances and dementing diseases.

Defining paramaters for an adaptative 3D Wiener filter in image restoration of SPECT cerebral blood flow studies: A novel approach

Multiple factors (attenuation, scattering, scanner response, etc) significantly degrade SPECT images. and multiple techniques have been proposed to correct for those and therefore yield more quantitatively exact SPECT studies, with the aim of improving clinical classification of patients as well as results from research using this technique. Application of a Wiener filter during reconstruction, which minimizes the mean square error between the original object and its estimate (the image), is a well-validated and relatively simple approach to this problem. Optimal use of this technique requires a priori information such as the point spread function (PSF) of the imaging system and the power spectrum ratio of the original object to image noise, but this information is not generally available. We have applied a new adaptation of this approach to cerebral blood flow studies obtained in SPECT with 99mTc labeled agents. Here, we start with a Gaussian function to model the PSF of the SPECT system, and a constant to replace the noise-to-signal power spectrum ratio 1. The PSF width and power-spectrum ratio are then iteratively optimized to improve image contrast between white and gray matter while keeping image mottle (or variance) within each region at a tolerable level (as defined in 2, 3). To track precisely the contrast and mottle, the white and gray matter regions are identified from an anatomical MRI of the same patient previously co-registered to the SPECT study 4. Simulation results with a realistic brain model (digital Hoffman phantom 5, with 3D Gaussian noise (at such count levels, Poisson noise would yield comparable results) and then blurred with a 3D Gaussian function to simulate an actual SPECT study) show marked contrast improvement while maintaining the mottle at an acceptable level: with object contrast between white and gray matter (as defined in 2) set at 0.427 and degraded to 0.074 post blurring, filtering increased contrast to 0.378, with the mottle (proportionally averaged for gray and white matter) actually decreasing (0.224 to 0.182). Tests conducted with actual clinical SPECT cases exhibit similar contrast improvement (0.045 to 0.104) with a limited (and still acceptable 2) mottle increase (0.198 to 0.276). We believe that this technique for defining the parameters of a 3D adaptive Wiener filter will be useful in clinical practice, where significant data degradation limits detection of anomalies with SPECT, because it automatically generates the best combination of those parameters, leading to significantly improved contrast quantification with little noise amplification.

Perfusion abnormality of the caudate nucleus in patients with paroxysmal kinesigenic choreoathetosis

Previous cerebral blood flow and glucose metabolism studies suggest that the basal ganglia or thalamus is involved in the pathogenesis of paroxysmal kinesigenic choreoathetosis (PKC). However, the underlying cerebral abnormalities in idiopathic PKC have not been elucidated. To localise cerebral perfusion abnormalities in PKC, we performed interictal brain perfusion 99mTc-ethylcysteinate dimer (ECD) single-photon emission computed tomography (SPECT) in PKC patients and in normal controls. Sixteen patients with idiopathic PKC and 18 age- and sex-matched normal controls were included. The patients were de novo diagnosed as having PKC, or had not taken medication for at least 3 months; none of them had structural abnormalities on MRI. Patients had a history of PKC attacks of a duration not exceeding 5 min and starting either on one side or on both sides of the body. These attacks were always induced by a sudden initiation of voluntary movement. PKC attacks were recorded in a hospital after being induced by neurology staff in 13 of the 16 patients. Interictal brain perfusion 99mTc-ECD SPECT was performed in all 16 patients and 18 normal controls. Differences between the cerebral perfusion in the PKC group and the normal control group were tested by statistical parametric mapping. Student's t test was used for inter-group comparisons. Compared with normal controls, patients with idiopathic PKC showed interictal hypoperfusion in the posterior regions of the bilateral caudate nuclei (false discovery rate-corrected P<0.001 with a small volume correction). This study showed that cerebral perfusion abnormality of bilateral caudate nuclei is present in idiopathic PKC.

Dynamic CT perfusion imaging in the study of perihematomal cerebral blood flow after intracerebral hemorrhage in rats

目的 探讨建立大鼠脑血肿周围脑组织血流变化的CT灌注成像方法,并对其可行性进行研究. 方法雄性大鼠70只,采用随机数字抽样法将其分为注血组和对照组.分别将40 μl新鲜自体血或生理盐水通过微量注射泵注入大鼠右侧尾状核制备脑出血模型.利用CT灌注成像对各组动物模型血肿周围脑组织血流变化进行观察,并与HE染色和红四氮唑(TTC)染色标本对照.通过计算机辅助CT脑灌注成像软件制作灌注CT参数图,并对血肿周围脑组织局部脑血流量(regional cerebral blood flow, rCBF)、局部脑血容量(regional cerebral blood volume, rCBV)和平均通过时间(mean transit time, MTT)进行相对值(病侧/健侧)测量. 结果注血组血肿周围脑组织存在不同程度低灌注梯度,血肿周围脑组织局部脑血流量(rCBF)呈波动性改变,在注血后1 h rCBF降至最低,随后逐渐回升、下降,分别于注血后6 h和24 h 2次回升至峰值.TTC染色血肿呈黑褐色,血肿周围未见白色梗死区.病理学检查显示在出血灶与正常脑组织间存在过渡带即血肿周围区,周围区内组织疏松,细胞不同程度水肿,星形细胞肿胀,神经细胞变性,出血灶周边可见毛细血管增生及炎细胞浸润.对照组CT灌注成像、TTC染色和病理学检查均未见明显异常. 结论大鼠脑血肿周围脑组织血流变化的CT灌注成像方法稳定可靠,能准确反映脑出血周围脑组织异常的血液动力学变化,是活体研究脑出血周围脑组织损伤较为理想的实验方法。

Clinical diagnosis of MM2-type sporadic Creutzfeldt-Jakob disease

No method for the clinical diagnosis of MM2-type sporadic Creutzfeldt-Jakob disease (sCJD) has been established except for pathologic examination. To identify a reliable marker for the clinical diagnosis of MM2-type sCJD. CSF, EEG, and neuroimaging studies were performed in eight patients with MM2-type sCJD confirmed by neuropathologic, genetic, and western blot analyses. The eight cases were pathologically classified into the cortical (n = 2), thalamic (n = 5), and combined (corticothalamic) (n = 1) forms. The cortical form was characterized by late-onset, slowly progressive dementia, cortical hyperintensity signals on diffusion-weighted imaging (DWI) of brain, and elevated levels of CSF 14-3-3 protein. The thalamic form showed various neurologic manifestations including dementia, ataxia, and pyramidal and extrapyramidal signs with onset at various ages and relatively long disease duration. Characteristic EEG and MRI abnormalities were almost absent. However, all four patients examined with cerebral blood flow (CBF) study using SPECT showed reduction of the CBF in the thalamus as well as the cerebral cortex. The combined form had features of both the cortical and the thalamic forms, showing cortical hyperintensity signals on DWI and hypometabolism of the thalamus on [18F]2-fluoro-2-deoxy-d-glucose PET. For the clinical diagnosis of MM2-type sporadic Creutzfeldt-Jakob disease, cortical hyperintensity signals on diffusion-weighted MRI are useful for the cortical form and thalamic hypoperfusion or hypometabolism on cerebral blood flow SPECT or [18F]2-fluoro-2-deoxy-d-glucose PET for the thalamic form.

Pharmacokinetics of sevoflurane uptake into the brain

Two recent studies have examined the pharmacokinetics of sevoflurane in adults. Lu et al.(Pharmacokinetics of sevoflurane uptake into the brain and body, Anaesthesia 2003; 58: 951-6) observed that jugular bulb sevoflurane concentration initially rose unexpectedly rapidly and then approached arterial concentrations unexpectedly slowly, suggesting that a blood-brain diffusion barrier exists. They also observed a large alveolar-arterial sevoflurane gradient, suggesting that an alveolar-arterial diffusion barrier exists. Nakamura et al. (Predicted sevoflurane partial pressure in the brain with an uptake and distribution model: Comparison with the measured value in internal jugular vein blood. Journal of Clinical Monitoring and Computing 1999; 15: 299-305) found no diffusion barriers. We used a computer model to analyse both data sets and show that the observations of Lu et al. can be explained by contamination of jugular samples with extracerebral blood. It is possible that the alveolar-arterial gradients observed by Lu et al. are due to discrepancies in conversions between blood concentrations and gas partial pressures. Our study suggests that there is no blood-brain diffusion barrier for sevoflurane and that the data of Lu et al. must be interpreted with caution.

Production of [ 17F]CH 3F ( [formula omitted]), an improved PET tracer for rCBF measurement

Production of 17F ( t 1 / 2 = 65 s ) in the form of [ 17F] F 2 has been achieved using both the 20Ne(p, α) 17F and 16O(d,n) 17F reactions with 11 MeV protons and 6 MeV deuterons, respectively. Yields have proven suitable for subsequent radiosynthesis of the blood flow tracer, [ 17F]CH 3F (>60 mCi in saline), currently in use for fast repetition human studies of regional cerebral blood flow with positron emission tomography. Thick target yields of 15 mCi/μA for protons and 44 mCi/μA for deuterons have been measured for [ 17F]F 2.

Cerebrovascular reactivity: rat studies in rheoencephalography

Here we describe a correlative study of cerebral blood flow (CBF) using global, local CBF and carotid flow measurements. The primary objective of this study was to establish a relationship between REG and CBF autoregulation. Rheoencephalography (REG), a rarely used method to measure CBF, is a potential tool of non-invasive continuous life sign monitoring and detection of early cerebrovascular alteration. However, the anatomical background of REG is not clearly understood. Two experimental studies were undertaken on anesthetized rats to define two CBF measurements: (1) CO2 inhalation, and, (2) clamping of common carotid arteries. Measurement of CBF was taken with REG, laser Doppler flowmetry (LDF) and carotid flow by Doppler ultrasound. Data were off-line processed. During CO2 inhalation, the increases in REG and LDF were significant (p = 0.0001), while carotid flow and systemic arterial pressure decreased. During carotid artery clamping, the decrease in REG and Doppler ultrasound was significant (p = 0.0001). REG showed cerebrovascular reactivity, indicating the relationship to arteriolar changes. Compared to LDF and carotid flow, only REG showed the classical CBF autoregulation.

P05.04: Timing of delivery in pregnancies with extremely preterm growth restricted fetuses

To evaluate the outcome of growth restricted fetuses delivered in very early pregnancy because of severely abnormal Doppler velocimetry. In a study during 1998–2002 we evaluated antenatal surveillance and outcome for 32 IUGR fetuses with abnormal blood flow examinations delivered between 24 + 0 and 29 + 6 gestational weeks at the Department of Obstetrics and Gynecology, University Hospital of Lund. The hospital is referral centre for the southern region of Sweden with a population of approximately 2.5 million. The decision to deliver on fetal indication was based on parental approval, knowledge of the rate of survival and of morbidity at the NICU at our hospital and of the deterioration of blood flow and in some cases with concomitant fetal heart rate changes. One hundred and fourteen gestational age matched newborns delivered for other reasons than blood flow changes were used as controls. All the fetuses in the study group showed severe blood flow changes in the umbilical artery with absent or reversed diastolic flow. They were initially followed with serial examinations when deteriorating blood flow. A combined evaluation of umbilical artery flow velocimetry with cerebral and central venous blood flow studies was done and FHR monitoring was done individually 2–4 times daily. There was an increased incidence of NEC in the IUGR group, but there was no increase in perinatal mortality or major cerebral morbidity compared with controls. All 32 IUGR newborns survived until discharge from the NICU. The survival at 1 year of age was 94%. The results from the study indicate that the integration of surveillance methods is beneficial for the sick extremely preterm fetuses. With our present knowledge optimal timing for delivery seems to be when severe umbilical artery Doppler blood flow changes coincides with deterioration of central venous fetal blood flow, especially in the ductus venosus.

MDMA-evoked changes in [11C]raclopride and [11C]NMSP binding in living pig brain.

Positron emission tomography (PET) studies with radiolabeled dopamine D2-like receptor ligands reveal d-amphetamine-evoked increases in the competition from endogenous dopamine. However, the corresponding effects of methylenedioxymethamphetamine (MDMA, "Ecstasy"), which releases catecholamines and also serotonin, are unknown. Using PET, we measured the binding potentials (pBs) of the benzamide [11C]raclopride and the butyrophenone N-[11C]methylspiperone ([11C]NMSP) in brain of living pigs first in a baseline condition and at 45 and 165 min after infusion of (+/-)-MDMA-HCl (1 mg/kg, i.v.). Concomitant studies of cerebral blood flow did not reveal significant perfusion changes in the cerebellum reference region or in striatum, supporting the present use of reference tissue methods for the mapping of MDMA-evoked pB changes. Relative to the baseline pB of [11C]raclopride for dopamine D(2/3) receptors in striatum (pB = 1.5-2.2), MDMA-treatment reduced pB by 35% in the first posttreatment scan and by 22% in the second posttreatment scan, comparable to changes typically evoked by d-amphetamine at a similar dose. In most previous studies, the in vivo binding of butyrophenones has been nearly insensitive to d-amphetamine-evoked dopamine release. However, we found the baseline pB of [11C]NMSP for dopamine D2-like receptors in striatum (pB = 4-5) was decreased by 30% in the first post-MDMA scan and by 50% in the second post-MDMA scan, irrespective of assumptions about the extent of equilibrium binding attained during the 90-min-long PET recordings. Distinct properties of MDMA such as simultaneous release of dopamine and serotonin in brain may account for the present finding of progressive decline in the availability of [11C]NMSP binding sites in striatum.

Distraction produces an increase in pain‐evoked anterior cingulate activity

AbstractThis study examined the effects of distraction on pain‐evoked activity in the anterior cingulate cortex (ACC). Twenty‐eight healthy adults were given painful electrical stimulation of the sural nerve during an attend condition, where they rated the subjective magnitude of each electrical stimulus, and during a distraction condition, where they performed an arithmetic distraction task. The magnitude of the pain‐evoked ACC activity was estimated from the dipole source localization analysis of the somatosensory evoked potential. Subjective pain ratings were smaller and pain‐evoked ACC activity was larger during the distraction condition than during the attend condition. Recent regional cerebral blood flow studies have also reported a distraction‐related increase in pain‐evoked ACC activity. Our results confirm these reports, and verify that the distraction effect specifically involves pain‐evoked ACC activity. The cognitive demands of the distraction task present the possibility that the pain‐evoked ACC activity might be involved, at least in part, in response competition and/or orienting attention toward painful stimuli.

Study of regional cerebral blood flow around hematoma in acute intracerebral hemorrhage by xenon-CT

To study the change of regional cerebral blood flow (rCBF) around hematoma in acute intracerebral hemorrhage. Xenon-CT was performed on 5 patients of basal ganglia hemorrhage with the hematoma volume less than 30 ml, 3 males and 2 females, aged 56.8 +/- 5.6. within 36 hours of the onset and 13 days after to measure the rCBF was measured by 27 pixel rings respectively in the core of hematoma, edema region around the hematoma and compared with rCBF in the uninvolved hemisphere. (1) all the 5 patients had a history of hypertension, the mean intracerebral hemorrhage volume was 13 ml +/- 7 ml (6.4 approximately 23.7 ml). The first examination was conducted 23 h +/- 6 h (19 approximately 34 h) after the onset and the second examination was conducted 13.0 d +/- 0.7 d (12 approximately 14 d) after the onset. (2) Within 36 hours of the onset, the mean rCBF in the core of hematoma was 15 ml.100 g(-1).min(-1) +/- 8 ml.100 g(-1).min(-1), and the mean rCBF in edema region around the hematoma was 30 ml.100 g(-1).min(-1) +/- 8 ml.100 g(-1).min(-1). Thirteen days after the onset the mean rCBF in the core of hematoma was 9 ml.100 g(-1).min(-1) +/- 4 ml.100 g(-1).min(-1), significantly reduced in comparison with that measured in the first examination (P = 0.014), and the mean rCBF in the edema region around the hematoma was 23 ml.100 g(-1).min(-1) +/- 13 ml.100 g(-1).min(-1), reduced in comparison with those measured in the first examination too, however, not significantly (P = 0.055). The rCBF reduction was more significant in the edema region adjacent to the hematoma (P = 0.004), but not in the distant edema region. During the first examination the rCBF in the edema region around the hematoma was lower than the enantiomorph rCBF by 20.9%. Thirteen days after, the rCBF in the edema region around the hematoma was lower than the enantiomorph rCBF by 46.3%, significantly greater than the reduction during the first examination (P = 0.324). There was no difference between the values of enantiomorph rCBF during the first and second examinations (P = 0.038). There exists reduced perihematoma rCBF after intracerebral hemorrhage by xenon-CT examination, this phenomenon lasts 14 days and have the tendency of further reduced.

内頚動脈閉塞症における側副血行路としての眼動脈血流―血行力学的脳虚血との関係―

We attempted to evaluate the function of ophthalmic artery (OA) flow as the collateral pathway in cases of internal carotid artery occlusion (ICAO). Methods. We examined 18 patients having symptomatic ICAO who underwent OA color Doppler flow imaging (CDFI) and quantitative SPECT regional cerebral blood flow (rCBF)study. Results. (1) The OA CDFI findings were reversed OA flow in 10 patients and antegrade flow in 8. (2) The mean resting rCBF was 25.2ml/100 g/min in the patients with reversed OA flow, and 26.7 ml/100 g/min in the patients with antegrade OA flow. The mean cerebral blood flow reserve capacity with acetazolamide was 8.68% in the former and 28.3% in the latter. This difference was statistically significant (p<0.05). (3) In eight patients with severe hemodynamic compromise with a cerebral blood flow reserve capacity of less than 10% and a resting rCBF of less than 80%, the reversed OA flow was visualized significantly frequently (p<0.05). Conclusion. In ICAO patients, OA CDFI findings are well correlated with the hemodynamic stage and development of other collateral pathways. Reversed OA flow indicates severe intracranial hemodynamic compromise.

Resting regional cerebral perfusion in recent posttraumatic stress disorder

Background Brain imaging research in posttraumatic stress disorder has been largely performed on patients with chronic disease, often heavily medicated, with current or past alcohol and substance abuse. Additionally, virtually only activation brain imaging paradigms have been done in posttraumatic stress disorder, whereas in other mental disorders both resting and activation studies have been performed. Methods Twenty-eight (11 posttraumatic stress disorder) trauma survivors underwent resting state hexamethylpropyleneamineoxime single photon emission computed tomography and magnetic resonance imaging 6 months after trauma. Eleven nontraumatized subjects served as healthy controls. Results Regional cerebral blood flow in the cerebellum was higher in posttraumatic stress disorder than in both control groups. Regional cerebral blood flow in right precentral, superior temporal, and fusiform gyri in posttraumatic stress disorder was higher than in healthy controls. Cerebellar and extrastriate regional cerebral blood flow were positively correlated with continuous measures of depression and posttraumatic stress disorder. Cortisol level in posttraumatic stress disorder was negatively correlated with medial temporal lobe perfusion. Anterior cingulate perfusion and cortisol level were positively correlated in posttraumatic stress disorder and negatively correlated in trauma survivors without posttraumatic stress disorder. Conclusions Recent posttraumatic stress disorder is accompanied by elevated regional cerebral blood flow, particularly in the cerebellum. This warrants attention because the cerebellum is often used as a reference region in regional cerebral blood flow studies. The inverse correlation between plasma cortisol and medial temporal lobe perfusion may herald hippocampal damage.

Mapping of brain function after MPTP-induced neurotoxicity in a primate Parkinson's disease model

Neurophysiological studies of the brain in normal and Parkinson's disease (PD) patients have indicated intricate connections for basal ganglia-induced control of signaling into the motor cortex. To investigate if similar mechanisms are controlling function in the primate brain (Macaca fascicularis) after MPTP-induced neurotoxicity, we conducted PET studies of cerebral blood flow, oxygen and glucose metabolism, dopamine transporter, and D2 receptor function. Our observations after MPTP-induced dopamine terminal degeneration of the caudate and putamen revealed increased blood flow (15%) in the globus pallidus (GP), while blood flow was moderately decreased (15–25%) in the caudate, putamen, and thalamus and 40 % in the primary motor cortex (PMC). Oxygen extraction fraction was moderately increased (10–20%) in other brain areas but the thalamus, where no change was observable. Oxygen metabolism was increased in the GP and SMA (supplementary motor area including premotor cortex, Fig. 3) by a range of 20–40% and decreased in the putamen and caudate and in the PMC. Glucose metabolism was decreased in the caudate, putamen, thalamus, and PMC (range 35–50%) and enhanced in the GP by 15%. No change was observed in the SMA. In the parkinsonian primate, [11C]CFT (2β-carbomethoxy-3β-(4-fluorophenyltropane) dopamine transporter binding was significantly decreased in the putamen and caudate (range 60–65%). [11C]Raclopride binding of dopamine D2 receptors did not show any significant changes. These experimental results obtained in primate studies of striato-thalamo-cortico circuitry show a similar trend as hypothetized in Parkinson's disease-type degeneration.

A Tc-99m HMPAO SPECT study of regional cerebral blood flow in drug-free schizophrenic patients with deficit and non-deficit syndrome

Twenty-nine patients with DSM-IV diagnoses of schizophrenia were categorized into deficit syndrome ( n=14) and non-deficit syndrome ( n=15) subgroups on the basis of the Schedule for the Deficit Syndrome. The patients, who had all been free of antipsychotic medication for at least 3 weeks, and 17 sex- and age-matched normal controls were studied with single-photon emission computed tomography with Tc-99m HMPAO. Age at onset, Brief Psychiatric Rating Scale (BPRS) total scores, BPRS positive symptom subscores and duration of illness were similar between the two schizophrenic subgroups. As expected, the deficit patients had more negative symptoms than the non-deficit patients. There were no statistically significant correlations between clinical parameters and regional cerebral blood flow (rCBF) values. The deficit syndrome subgroup showed diminished rCBF in the frontal regions bilaterally, right parietal regions and right superior temporal region compared with the control groups. Deficit patients showed significantly lower rCBF perfusion ratios in the right superior and inferior frontal cortex than did the non-deficit patients. No differences were detected between the controls and the non-deficit schizophrenic patients in terms of rCBF perfusion indices. The results of the present study confirm previous reports of different patterns of rCBF in deficit vs. non-deficit schizophrenic subgroups.

Regional cerebral blood flow in patients with primary hyperparathyroidism before and after successful parathyroidectomy.

Single-photon emission computed tomography (SPECT) is used to study cerebral blood flow and cerebral metabolism in various neuropsychiatric disorders. Reduced regional cerebral blood flow has been demonstrated in patients with depression and chronic fatigue, symptoms that are common in primary hyperparathyroidism. The aim of this study was to reveal possible changes in regional cerebral blood flow in patients with primary hyperparathyroidism before and after operative treatment. This was a prospective study of regional cerebral blood flow in 16 consecutive women of median age 72 (range 50-82) years using SPECT with (99m)Tc-labelled hexamethylpropylenamine-oxime. The measurements were performed before and 2, 4 and 12 months after parathyroidectomy. The Montgomery and Asberg depression rating scale (MADRS) depression score was used as a parallel clinical test. Reduced (pathological) regional cerebral blood flow was seen before operation in 14 patients, 13 with a solitary adenoma and one with double adenoma. After surgery, this improved to normal values in 13, but was further reduced in one. In two patients with preoperative normal regional cerebral blood flow, both of whom were asymptomatic and had diffuse hyperplasia, a slight reduction was demonstrated. Eight patients had a pathological preoperative MADRS score, which normalized in seven after surgical treatment. The finding of reduced regional cerebral blood flow in patients with primary hyperparathyroidism followed by significant improvement after operation might influence the case for surgical treatment.

Imaging methods for evaluating brain function in man

Imaging of brain function and neurotransmission is an important bridge between basic and clinical research. Regional cerebral energy metabolism and blood flow are normally coupled to regional cerebral function. Positron tomography (PET) studies of cerebral glucose metabolism and blood flow, single photon tomography (SPECT) and MRI studies of cerebral perfusion, have been used to image cerebral development and aging in man. The sensitivity, temporal resolution, spatial resolution and lack of radiation have led to the widespread utilization of blood oxygen level dependent (BOLD) and MRI perfusion techniques. PET and SPECT methods for studying cerebral neurotransmission include studies of dopaminergic, serotonergic, cholinergic, opiate and GABAergic neurotransmission in man. Studies of cerebral neurotransmission in man have helped to delineate the mechanisms of action of antipsychotic and antidepressant drugs, the diagnosis and progression of Parkinson’s disease, and to evaluate neuroprotective drugs. The strengths, limitations, and application of these modalities are reviewed. The application of these methods to cerebral development and aging are briefly discussed.

Positron Emission Tomographic Cerebral Perfusion Disturbances and Transcranial Doppler Findings among Patients with Neurological Deterioration after Subarachnoid Hemorrhage

Abstract OBJECTIVE After aneurysmal subarachnoid hemorrhage, approximately 30% of patients experience delayed neurological deficits, related in part to arterial vasospasm and dysautoregulation. Transcranial Doppler (TCD) ultrasonography is commonly used to noninvasively detect arterial vasospasm. We studied cerebral perfusion patterns and associated TCD indices for 25 patients who developed clinical signs of delayed neurological deficits. METHODS Patients were treated in a neurosurgical intensive care unit and were studied if they exhibited delayed focal or global neurological deterioration. Positron emission tomographic cerebral blood flow (CBF) studies and TCD studies measuring the mean flow velocity (FV) of the middle cerebral artery and the middle cerebral artery FV/internal carotid artery FV ratio (with the internal carotid artery FV being measured extracranially at the cranial base) were performed. Glasgow Outcome Scale scores were assessed at 6 months. RESULTS A markedly heterogeneous pattern of CBF distribution was observed, with hyperemia, normal CBF values, and reduced flow being observed among patients with delayed neurological deficits. TCD indices were not indicative of the cerebral perfusion findings. The mean CBF value was slightly lower for patients who did not survive (32.3 ml/100 g/min), compared with those who did survive (36.0 ml/100 g/min, P= 0.05). CONCLUSION Among patients who developed delayed neurological deficits after aneurysmal subarachnoid hemorrhage, a wide range of cerebral perfusion disturbances was observed, calling into question the traditional concept of large-vessel vasospasm. Commonly used TCD indices do not reflect cerebral perfusion values.