Regional cerebral blood flow and cognitive deficits in chronic lyme disease

This study examined brain functioning in patients with Lyme encephalopathy. Eleven patients underwent neuropsychological tests and Xenon(133)-regional cerebral blood flow (rCBF) studies, using an external detector system. Each rCBF scan was age- and sex-matched to two archival, normal controls. While few differences were noted on gray-matter flow indices (ISI, fg), Lyme patients demonstrated significant flow reductions in white matter index (k(2)) (p=.004), particularly in the posterior temporal and parietal lobes bilaterally (p=.003). Flow reductions in white matter areas were significantly associated with deficits in memory (r=.66, p=.027) and visuospatial organization (r=.62, p=.041). Results suggest that Lyme encephalopathy may be a disease primarily affecting the cerebral white matter.     

晚发精神分裂症患者局部脑血流及认知功能的研究

目的　探讨晚发精神分裂症患者局部脑血流 (rCBF)及认知功能损害的特点。方法　对2 1例首次发病年龄≥ 5 0岁的精神分裂症患者进行脑单光子发射计算机体层摄影术 (SPECT)检查 ,并采用阳性和阴性症状量表 (PANSS)、简易精神状态量表 (MMSE)、中国修订韦克斯勒成人智力量表、韦克斯勒记忆量表 (WMS)及威斯康星卡片分类测验等进行评定 ,经利培酮 [(2 7± 0 8)mg/d ,2次 /d]治疗 8周后 ,其中 11例患者 (PANSS减分率大于 2 5 % )再次完成上述测定。 2 0名正常人完成SPECT、MMSE及WMS测定。结果　 (1)治疗前患者组左额叶、左顶叶、双侧颞下、双侧基底节及右丘脑 (P <0 0 1)的放射性计数比值 (RAR)低于对照组 (P <0 0 5 ) ,且左额叶RAR (0 85± 0 11)低于右额叶(0 86± 0 10 ;P =0 0 13) ;其MMSE评分 (2 3 33± 4 10 )低于对照组 [(2 8 35± 1 6 3)分 ,P <0 0 1];WMS总分及其大部分测验项目分亦均低于对照组 (P <0 0 1或 0 0 5 )。 (2 )治疗后患者组仅MMSE分[(2 4 73± 4 4 5 )分 ]、WMS的定向因子分 [(3 82± 1 0 8)分 ]和背数因子分 [(5 0 0± 3 4 9)分 ]高于治疗前[分别为 (2 2 4 5± 3 98)分、(3 18± 1 0 8)分和 (2 6 4± 3 88)分 ;P <0 0 5 ],而各脑区rCBF及其余认知功能的变化均无显     

Regional cerebral blood flow abnormalities in depressed patients with cognitive impairment.

Depression with cognitive impairment, so called depressive pseudodementia, is commonly mistaken for a neurodegenerative dementia. Using positron emission tomography (PET) derived measures of regional cerebral blood flow (rCBF) a cohort of 33 patients with major depression was studied. Ten patients displayed significant and reversible cognitive impairment. The patterns of rCBF of these patients were compared with a cohort of equally depressed non-cognitively impaired depressed patients. In the depressed cognitively impaired patients a profile of rCBF abnormalities was identified consisting of decreases in the left anterior medial prefrontal cortex and increases in the cerebellar vermis. These changes were additional to those seen in depression alone and are distinct from those described in neurodegenerative dementia. The cognitive impairment seen in a proportion of depressed patients would seem to be associated with dysfunction of neural systems distinct from those implicated in depression alone or the neurodegenerative dementias.     

Regional cerebral blood flow increases during wakeful rest following cognitive training

Positron tomography was used to investigate modulations of brain activity during the so-called resting state that may occur due to a concurrent cognitive training. Twelve subjects were repeatedly scanned during resting periods and while solving logical problems containing a bias causing them to make reasoning errors. At experiment mid-time, eight subjects were trained to inhibit the reasoning bias so that their performance in solving logical problems dramatically increased afterwards, while the other four subjects were trained to logical reasoning only which did not help improving their performance. In the subgroup of subjects who increased their performance after training, we found that during the post-training resting periods, as compared to pre-training resting periods, brain activity increases in areas not belonging to the classical resting network, namely the midbrain, thalamus, peristriate, inferior frontal, and ventromedial prefrontal cortices. Strikingly, in this subgroup of subjects, these same areas were found to be also more active during post-training successful execution of the logical task, as compared to pre-training erroneous execution of the task. Such findings were not observed in the subgroup of subjects who did not improve their performance after training to logic only. These results indicate that the brain default mode is a dynamic state during which context dependent local increases of cerebral blood flow may occur on a short-term, likely for the consolidation of newly acquired knowledge.     

Regional cerebral blood flow, diaschisis, and steal after stroke

Regional CBF was measured by 133Xe inhalation in unilateral cerebral infarction, carotid TIAs, and normal volunteers. Regional CBF values were bilaterally and symmetrically reduced in patients measured within 3 weeks after stroke. Later, rCBF values returned toward normal in the contralateral hemisphere of patients with infarction and in both hemispheres with carotid TIAs. In cases with carotid occlusive disease, flow reduction was seen in the contralateral posterior cerebral artery distribution, with hyperemia in ipsilateral occipital lobe caused by interhemispheric steal. Brainstem-cerebellar flow values were increased following acute cerebral infarction if patients were alert but reduced if consciousness was impaired.     

Disruptions of hemispheric blood flow and deep cerebral hematomas

Cerebral blood flow measurements with single photon emission tomography and 133Xe inhalation was performed in 18 patients with hematomas, 14 thalamo-capsular, 4 capsulo-lenticular. In thalamo-capsular cases and in standard conditions, ipsilateral hemispheric C.B.F. and contralateral cerebellar C.B.F. were decreased; a concomitant depression of frontal and temporal C.B.F. was often noted. A similar change was found in capsulo-lenticular cases, the frontal C.B.F. being however less depressed. An attenuation of interhemispheric asymmetry was often found after acetazolamide intravenous injection. A significant correlation was demonstrated between interhemispheric asymmetry index (AI) and frontal and temporal AI.     

Regional cerebral blood flow in depression

In the review article, the results of studies on regional cerebral blood flow (rCBF) in major depression are presented. Most studies have reported global and regional deficits in cerebral blood flow in major depression as compared to healthy controls. Longitudinal studies show that after recovery from depression an increase of CBF has been observed. The influence of different biological treatment methods on rCBF is also discussed. Findings regarding lateral asymmetries of cerebral function in patients with major depression are inconclusive but the deficit of rCBF is often more pronounced in the left hemisphere. The nature of regional brain flow abnormalities in depression is unclear. Structural changes of the brain and biochemical abnormalities are under consideration.     

Regional cerebral blood flow in neuropsychology

Measurements of regional cerebral blood flow (rCBF) provide information about the metabolic and functional level of the cortex. Different techniques for measurement of rCBF are described and their potentials and limitations are outlined. Typical results from measurements in normals during performance of mental tasks are shown and as well as clinical measurements in patients with organic dementia. Future improvements of the techniques regarding spatial as well as temporal resolution are outlined. It is concluded that measurements of rCBF are likely to be of great value in the future exploration of brain-behaviour relationships.     

Regional cerebral blood flow in depression

Regional cerebral blood flow (rCBF) was measured in patients with endogenous depression by the single photon emission computed tomography (SPECT) using N-isopropyl-p-[123I]iodoamphetamine (IMP). The subjects were 32 patients with endogenous depression and 20 normal controls. These 32 patients, who were divided into 10 unmedicated group and 22 medicated group, were reexamined when the depressed patients reverted to a euthymic state (remission). The value of rCBF was assessed by the corticocerebellar ratio (CCR), which was expressed as a ratio of activity per pixel in the cerebral regions of interests (ROIs) to the activity per pixel in the cerebellum. The depressive patients showed a decrease in rCBF all over the cerebral regions and, especially, the lower rCBF in the left than in the right hemisphere. These changes turned toward normal in a remitted state following treatments, though there was no significant difference in rCBF between the medicated and unmedicated patients. There was a significantly negative correlation between the severity of depressive symptoms and the mean rCBF in a total of patients with depression. These results suggest that psychiatric symptoms in the depressive patients might be related to the left hemispheric dysfunction.     

Regional cerebral blood flow in the rat during prolonged seizure activity

In order to evaluate the possible contribution of regional insufficiency in blood flow to the development of epileptic brain damage, we have measured changes in total and regional cerebral blood flow (tCBF and rCBF) during the course of prolonged sustained seizures. We have used both a particle distribution method (radioactively labelled microspheres) and a diffusible tracer method (iodo [14C]antipyrine). Seizures were induced with bicuculline (1.2 mg/kg, i.v.) in rats with neuromuscular paralysis, mechanically ventilated with 70% N2O/30% O2, rCBF was determined in 13 brain regions after 10, 30, 60 and 120 min of seizure activity. Microsphere and iodo[14C]antipyrine methods gave identical control values for tCBF (0.88 +/- 0.02 vs 0.86 +/- 0.07 ml/g brain/min) and closely similar rCBF values. The increases in tCBF after 10 and 30 min seizure activity were less as measured with microspheres than with iodo [14C]antipyrine (2.42 +/- 0.29 vs. 4.99 +/- 0.94 and 1.79 +/- 0.18 vs 3.05 +/- 0.30 mg/g brain/min, respectively). With microspheres, rCBF values showed considerable interhemisphere variability, but did not do so with iodo [14C]antipyrine. The regional pattern of flow changed during seizures. Changes in neocortical rCBF tended to match changes in tCBF. Consistent decreases in rCBF relative to tCBF were seen in the pons-medulla and cerebellum at all seizures times. Relative increases in rCBF were seen at all seizure times in the thalamus, and at 10 and 30 min in colliculi and midbrain. In the hippocampus, rCBF was unchanged (relative to tCBF) at 10 and 30 min, but was increased at 60 and 120 min of seizure activity. Thus, regions developing epileptic brain damage in this model of status epilepticus (hippocampus, thalamus, neocortex) show increases in rCBF greater than those in regions not showing brain damage (cerebellum, brain stem).     

Regional cerebral blood flow effects of nicotine in overnight abstinent smokers.

BACKGROUND: Most people agree that dependence to tobacco is mediated by the effects of nicotine on the central nervous system, albeit the neural pathways involved are not clearly delineated. We investigated the effect of nasal nicotine spray on regional cerebral blood flow (rCBF) in a sample of habitual smokers, with H2 15O and positron emission tomography (PET). METHODS: Eighteen volunteer smokers were studied after 12 hours of smoking deprivation. Regional cerebral blood flow measures were obtained with PET and 50 mCi H2 15O in six consecutive scans. Nicotine spray and a placebo spray were administered in a single-blind design, preceded and followed by baseline studies. Images were coregistered and anatomically standardized. Square (9-mm side) regions of interest were placed in 10 preselected brain regions, bilaterally. The effects of the experimental condition and gender were tested with two-way repeated-measures analysis of variance in each of the regions studied. RESULTS: Nicotine reduced rCBF in the left anterior temporal cortex and in the right amygdala. Increases were noted in the right anterior thalamus. CONCLUSIONS: In habitual smokers after overnight abstinence, nicotine induced differing effects on regional blood flow relative to whole brain blood flow. Increases were observed in the thalamus, a region rich in nicotinic receptors, and reductions in limbic and paralimbic (amygdala, anterior temporal cortex) regions.     

Regional cerebral blood flow in Down's syndrome

Regional cerebral blood flow was measured in 14 patients with Down's syndrome, in 46 patients with Alzheimer's disease and senile dementia of the Alzheimer type, and in 114 age-matched controls, using the xenon 133 inhalation technique. Cerebral blood flow was reduced in 13 of 14 Down's patients by a mean of 16.8 +/- 2.5% from expected age-matched normal values. Degrees of regional cerebral blood flow reduction did not differ among the frontal, temporal, parietal, and occipital regions in both cerebral hemispheres. The regional cerebral blood flow decreases were similar in magnitude and pattern to those in Alzheimer patients. These findings constitute an additional similarity between the two disorders.     

Gaze related enhancement of hemispheric blood flow in a stroke patient.

OBJECTIVE: A patient with a right posterior cerebral artery territory infarction and a left superior quadrantanopia exhibited improvement on various visual tasks including Goldmann perimetry during extreme right gaze. The phenomenon was investigated by functional imaging of cerebral blood flow. METHODS: [(99m)Tc]HMPAO SPECT was carried out while the patient gazed to the right and to the left at an 8 Hz flash stimulus. RESULTS: When compared with left gaze, photic stimulation during right gaze was associated with an up to 39.8% increase in regional cerebral blood flow in the damaged right hemisphere, including Brodmann's areas 3-1-2, 7, 21, 22, 39, and 40. CONCLUSIONS: These gaze related alterations in function and synaptic activity suggest the engagement of a novel arousal-like mechanism that may account in part for comparable findings in patients with neglect and other disorders, and may have relevance to rehabilitation.