Is central nervous system processing altered in patients with heart failure?

AIMS: Breathlessness is a cardinal symptom of heart failure and the altered regulation of breathing is common. The contribution of abnormal central nervous system activity has not previously been investigated directly, although abnormal autonomic responses have been described. Our aim was to assess whether heart failure patients exhibit different patterns of regional brain activation after exercise stress. METHODS: We used positron emission tomography with H2(15)O, to measure changes in regional cerebral blood flow (rCBF) and absolute global cerebral blood flow (gCBF) in 6 male class II/III heart failure patients and 6 normal controls. Breathlessness (0-5 visual analogue scale) and respiratory parameters were measured at rest, after horizontal bicycle exercise and during isocapnic hyperventilation. CBF was measured in each condition in all subjects. RESULTS: Both groups were similarly breathless after exercise and the respiratory parameters were comparable. rCBF differences for the main comparison (exercise vs hyperventilation) were: activation of the right frontal medial gyrus (P < 0.001, Z = 4.90) and left precentral gyrus (P < 0.03, Z = 4.66) in controls but not in patients. Both groups had rCBF increases in the left anterior cingulate (P < 0.05, Z = 4.67) and right dorsal cingulate cortex (P < 0.05, Z = 4.66). The gCBF did not differ between exercise, isocapnic hyperventilation and rest in patients but, in controls, gCBF was greater after exercise compared to either isocapnic hyperventilation or rest. CONCLUSION: Heart failure patients had a distinct pattern of regional cortical activity with exercise-induced breathlessness but unvarying CBF values between conditions. These central neural differences in activity may contribute to some features of heart failure, such as variability in symptoms and autonomic dysregulation.     

Cerebral metabolism of ammonia and amino acids in patients with fulminant hepatic failure.

BACKGROUND & AIMS: High circulating levels of ammonia have been suggested to be involved in the development of cerebral edema and herniation in fulminant hepatic failure (FHF). The aim of this study was to measure cerebral metabolism of ammonia and amino acids, with special emphasis on glutamine metabolism. METHODS: The study consisted of patients with FHF (n = 16) or cirrhosis (n = 5), and healthy subjects (n = 8). Cerebral blood flow was measured by the 133Xe washout technique. Blood samples for determination of ammonia and amino acids were drawn simultaneously from the radial artery and the internal jugular bulb. RESULTS: A net cerebral ammonia uptake was only found in patients with FHF (1.62 +/- 0.79 micromol x 100 g(-1) x min(-1)). The cerebral glutamine efflux was higher in patients with FHF than in the healthy subjects and cirrhotics, -6.11 +/- 5.19 vs. -1.93 +/- 1.17 and -1.50 +/- 0.29 micromol x 100 g(-1) x min(-1), respectively (P < 0.05). Patients with FHF who subsequently died of cerebral herniation (n = 6) had higher arterial ammonia concentrations, higher cerebral ammonia uptake, and higher cerebral glutamine efflux than survivors. Intervention with short-term mechanical hyperventilation in FHF reduced the net cerebral glutamine efflux, despite an unchanged net cerebral ammonia uptake. CONCLUSIONS: Patients with FHF have an increased cerebral glutamine efflux, and short-term hyperventilation reduces this efflux. A high cerebral ammonia uptake and cerebral glutamine efflux in patients with FHF were associated with an increased risk of subsequent fatal intracranial hypertension.     

神经精神狼疮患者局部脑血流灌注显像的临床研究

目的 观察神经精神狼疮患者脑血流改变,探讨神经精神狼疮患者局部脑血流灌注(rCBF)显像的临床意义.方法 20例神经精神狼疮患者(NPSLE组)、20例无神经精神表现的狼疮患者(SLE组)和20名年龄相当的健康志愿者(健康组)行单光子发射计算机断层(SPECT)rCBF显像,并划取感兴趣区作半定量分析得半定量(HQ)值.比较各组SPECT rCBF显像结果,并对HQ结果进行分析.同时20例神经精神狼疮患者行CT/磁共振成像(MRI)显像并与rCBF显像进行对比.结果 NPSLE组患者rCBF显像均阳性100%,其中19例局部脑血流降低,1例局部脑血流增加;20例患者CT/MRI头部显像阳性4例(20%),同rCBF显像相比差异有统计学意义(P＜0.01).SLE组患者rCBF显像阳性1例(5%),表现为局部脑血流降低.20名健康志愿者rCBF显像未见异常.NPSLE组患者rCBF显像病灶主要分布在颞叶(36%)、额叶(18%).其颞叶、额叶HQ值与SLE对照组和健康对照组比较,差异有统计学意义(P＜0.01和P＜0.05). 结论 rCBF显像灵敏度高,对早期诊断和治疗神经精神狼疮有重要意义.神经精神狼疮患者rCBF显像多表现为局部脑血流降低,好发部位为大脑中动脉供血区,以颞叶、额叶多见.     

Cerebral diffusion tensor imaging and in vivo proton magnetic resonance spectroscopy in patients with fulminant hepatic failure

Background and Aim:  Cerebral edema is a major complication in patients with fulminant hepatic failure (FHF). The aim of this study was to evaluate the metabolite alterations and cerebral edema in patients with FHF using in vivo proton magnetic resonance spectroscopy (MRS) and diffusion tensor imaging, and to look for its reversibility in survivors.
Methods:  Ten FHF patients along with 10 controls were studied. Five of the 10 patients who recovered had a repeat imaging after three weeks. N-acetylaspartate, choline (Cho), glutamine (Gln), glutamine/glutamate (Glx), and myoinositol ratios were calculated with respect to creatine (Cr). Mean diffusivity (MD) and fractional anisotropy (FA) were calculated in different brain regions.
Results:  Patients exhibited significantly increased Gln/Cr and Glx/Cr, and reduced Cho/Cr ratios, compared to controls. In the follow-up study, all metabolite ratios were normalized except Glx/Cr. Significantly decreased Cho/Cr were observed in deceased patients compared to controls. In patients, significantly decreased MD and FA values were observed in most topographical locations of the brain compared to controls. MD and FA values showed insignificant increase in the follow-up study compared to their first study.
Conclusions:  We conclude that the Cho/Cr ratio appears to be an in vivo marker of prognosis in FHF. Decreased MD values suggest predominant cytotoxic edema may be present. Persistence of imaging and MRS abnormalities at three weeks' clinical recovery suggests that metabolic recovery may take longer than clinical recovery in FHF patients.     

Increased turnover of Gc-globulin in patients with hepatic encephalopathy

BACKGROUND: A low serum level (< 100 mg/L) of the actin-scavenger Gc-globulin is a prognostic marker of non-survival in fulminant hepatic failure (FHF). It is unknown whether decreased production or increased consumption (or both) is responsible for the low Gc-globulin levels. METHODS: Ten patients with FHF and four patients with acute or chronic liver disease (AOCLD) with hepatic encephalopathy (HE) grades II-IV were included. Eight patients with cirrhosis (chronic liver disease, CLD) without HE served as controls. Total, free, and actin-bound Gc-globulin were measured in samples from an artery, a central vein, and a hepatic vein. In 12 patients (9 FHF, 3 AOCLD), concentrations were measured before and after high volume plasmapheresis (HVP). RESULTS: Total Gc-globulin was reduced to 21%, 40%, and 43% of the normal level in the FHF, AOCLD, and CLD groups, respectively, whereas bound Gc-globulin was within normal range in all patients. The Gc:actin complex ratio was increased 3.8, 2.5, and 1.9-fold compared with normal levels. Total, free, and bound serum Gc-globulin levels did not differ among arterial, systemic venous, or hepatic venous blood. Total Gc-globulin rose to >100 mg/L in all patients after HVP, whereas bound Gc-globulin remained unchanged. The Gc-globulin production rate in FHF and AOCLD patients was increased to 4.1 +/- 1.3 mg/min compared to literature values of 0.6 mg/min in healthy individuals. The estimated half-life of total Gc-globulin was shorter in the patients compared to healthy individuals (127 +/- 56 min and 870 min, respectively). CONCLUSIONS: Gc-globulin levels were reduced in patients with FHF and AOCLD because a 7-fold increase of Gc-globulin production rate could not compensate for the accelerated clearance. Bound Gc-globulin was maintained within normal levels in all circumstances studied, indicating a possible regulatory role of this parameter in the clearance of actin.     

Effect of continuous positive airway pressure on regional cerebral blood flow during wakefulness in obstructive sleep apnea

Background

The alteration of regional cerebral blood flow (rCBF) during wakefulness after the treatment for obstructive sleep apnea syndrome (OSA) using continuous positive airway pressure (CPAP) has not been elucidated. The aim of this study was to investigate rCBF characteristics and the effects of nasal CPAP in OSA patients.

Methods

Fifteen severe OSA patients (apnea–hypopnea index, 62.7?±?22.4/h), when awake, underwent Technetium-99m ethyl cysteinate dimer single photon emission computed tomography before and after CPAP treatment, and the findings were compared to those of nine healthy controls matched for age and sex.

Results

Compared to controls, patients with OSA before CPAP treatment showed a significantly lower rCBF in the frontal lobe. After the treatment, no difference in rCBF was observed between the good CPAP compliance group and the controls. In the former group, there was a positive correlation between the 3 % oxygen desaturation index on diagnostic polysomnogram and the increase of rCBF after CPAP treatment in the frontal lobe.

Conclusions

When awake, patients with severe OSA were shown to have reversible decreases in rCBF, especially in the frontal lobe, and an appropriate CPAP treatment was thought to improve rCBF in this area. Our results support the importance of appropriate CPAP treatment for severe OSA patients.     

Cytotoxic Edema Is Responsible for Raised Intracranial Pressure in Fulminant Hepatic Failure: In Vivo Demonstration Using Diffusion-Weighted MRI in Human Subjects

It is not clear whether cerebral edema in fulminant hepatic failure is predominantly vasogenic or cytotoxic, though cytotoxic edema due to astrocyte swelling is more likely. Diffusion-weighted magnetic resonance imaging can differentiate vasogenic from cytotoxic edema. We performed diffusion-weighted imaging in patients with fulminant hepatic failure to clarify the issue by measuring apparent diffusion coefficient, which quantifies movement of water molecule across cell membrane. Seven patients with fulminant hepatic failure underwent conventional and diffusion-weighted magnetic resonance imaging. Apparent diffusion coefficient was measured in four cortical areas and 12 deep white and gray matter regions in both cerebral hemispheres. Thirteen healthy subjects served as controls. The apparent diffusion coefficient values in patients and controls were compared using Wilcoxon signed rank test. Two patients who survived underwent repeat imaging using same protocol. Patients with FHF had significantly lower apparent diffusion coefficient in all cortical and deep white and gray matter regions of interest compared to controls (p < 0.001), suggesting cytotoxic cell swelling. In two survivors with repeat imaging, one showed complete resolution while the changes persisted in the other, suggesting ischemic injury. Cerebral edema in fulminant hepatic failure is predominantly due to cytotoxic edema.     

Decrease of regional cerebral blood flow in liver cirrhosis

OBJECTIVE: Alterations of regional cerebral blood flow (rCBF) in subjects with liver cirrhosis have not been fully evaluated. We evaluated quantitative changes in rCBF using single photon emission computed tomography (SPECT). METHODS: Twenty-eight Japanese patients with liver cirrhosis were enrolled in this study. None of them exhibited advanced hepatic encephalopathy at the time of examination. The cause of liver cirrhosis was viral infection in 26 patients; the cause was unknown in two patients. Child-Pugh classification of the patients was as follows: Group A, 12 patients; Group B, 12 patients; and Group C, four patients. The control group consisted of 25 age-matched healthy subjects. Radionuclide angiography was performed by rapid injection of Tc-99m ethyl cysteinate dimer (ECD) (740 MBq) via the right cubital vein, and then SPECT brain images were taken. Using the Patlak graphical method, rCBF values (ml/100 g per min) were calculated in the frontal, parietal, temporal and occipital lobes and cerebellum on SPECT images. RESULTS: The rCBF values were lower in cirrhotic patients than in controls, i.e. by 15% in the frontal lobe, by 12% in the parietal lobe, by 10% in the temporal and occipital lobes, and by 7% in the cerebellum. They decreased concomitantly with the severity of liver disease. A significant negative correlation was noted between rCBF values and Child-Pugh score in the frontal (P<0.01), parietal (P<0.05) and occipital lobes (P<0.01). rCBF values of each region were not correlated with age or with results of neuropsychological test. The degree of association between rCBF values and results of laboratory examination was generally poor. CONCLUSION: Patients with liver cirrhosis without advanced encephalopathy showed widespread reduction in rCBF; this reduction was particularly evident in the frontal lobe. Tc-99m ECD SPECT may be useful for evaluating cerebral functional changes in patients with liver cirrhosis.     

Multi-dimensional MR spectroscopy: towards a better understanding of hepatic encephalopathy

Hepatic encephalopathy (HE) is normally diagnosed by neuropsychological (NP) tests. The goals of this study were to quantify cerebral metabolites, separate glutamate (Glu) from glutamine (Gln) in patients with minimal hepatic encephalopathy (MHE) as well as healthy subjects using the prior-knowledge fitting (ProFit) algorithm on data acquired by two-dimensional (2D) localized correlated spectroscopy (L-COSY) on two different MR scanners, and to correlate the metabolite changes with neuropsychological (NP) tests. We studied 14 MHE patients and 18 healthy controls using a GE 1.5?T Signa MR scanner. Another group of 16 MHE patients and 18 healthy controls were studied using a Siemens 1.5?T Avanto MR scanner. The following parameters were used for L-COSY: TR/TE?=?2?s/30?ms, 3?×?3?×?3?cm(3) voxel size, 96 Δt(1) increments with 8 averages per Δt(1). Using the ProFit algorithm, we were able to differentiate Gln from Glu on the GE 1.5?T data in the medial frontal white/gray matter. The ratios of myo-inositol (mI), Glu, total choline, scyllo-inositol (sI), phosphoethanolamine (PE), and total N-acetyl aspartate (NAA) showed statistically significant decline in HE patients compared to healthy controls, while the ratio of Gln was significantly increased. Similar trend was seen in the ProFit quantified Siemens 1.5?T data in the frontal and occipito-parietal white/gray regions. Among the NP domain scores, motor function, cognitive speed, executive function and the global scores showed significant differences. Excellent correlations between various NP domains and metabolite ratios were also observed. ProFit based cerebral metabolite quantitation enhances the understanding and basis of the current hypothesis of MHE.     

Functional hepatic flow in patients with liver cirrhosis

AIM: To evaluate hepatic reserve function by investigating the change of functional hepatic flow and total hepatic flow in cirrhotic patients with portal hypertension. METHODS: HPLC method was employed for the determination of concentration of D-sorbitol in human plasma and urine. The functional hepatic flow (FHF) and total hepatic flow (THF) were determined by means of modified hepatic clearance of D-sorbitol combined with duplex doppler color sonography in 20 patients with cirrhosis and 10 healthy volunteers. RESULTS: FHF, evaluated by means of the D-sorbitol clearance, was significantly reduced in patients with cirrhosis in comparison to controls (764.74+/-167.91 vs 1195.04+/-242.97 mL/min, P<0.01). While THF was significantly increased in patients with cirrhosis in comparison to controls (1605.23+/-279.99 vs 1256.12+/-198.34 mL/min, P<0.01). Portal blood flow and hepatic artery flow all were increased in cirrhosis compared to controls (P<0.05 and P<0.01). D-sorbitol total clearance was significantly reduced in cirrhosis compared to control (P<0.01), while D-sorbitol renal clearance was significantly increased in cirrhosis (P<0.05). In controls FHF was similar to THF (1195.05+/-242.97 vs 1256.12+/-198.34 mL/min, P=0.636), while FHF was significantly reduced compared with THF in cirrhosis (764.74+/-167.91 vs 1605.23+/-279.99 mL/min, P<0.01). CONCLUSION: Our method that combined modified hepatic clearance of D-sorbitol with duplex doppler color sonography is effective in the measurement of FHF and THF. FHF can be used to estimate hepatic reserve function.     

Value of regional cerebral blood flow in the evaluation of chronic liver disease and subclinical hepatic encephalopathy

AIMS: Regional changes in cerebral blood flow in patients with chronic hepatitis, cirrhosis and subclinical hepatic encephalopathy were investigated in the present study using single photon emission computed tomography (SPECT). METHODS: Twenty patients with cirrhosis, 11 patients with chronic hepatitis, and nine healthy controls were included in the study. Cerebral SPECT were obtained for all patients. The percentages of cerebral blood flow of 14 regions to the cerebellar blood flow were determined. Only the patients with cirrhosis underwent psychometric evaluation: visual evoked potentials (VEP) measurements and electroencephalogram (EEG) recordings along with blood levels of albumin, bilirubin, and ammonia were measured and prothrombin time was determined in cirrhotic patients. These patients were classified according to the Child-Pugh classification. RESULTS: Among cirrhotic patients, six had abnormal results in VEP studies, 11 in psychometric tests and with six in EEG evaluation. Any abnormality in psychometric tests and/or VEP studies is taken as the main criterion; subclinical hepatic encephalopathy was detected in 12 of 20 patients. According to SPECT results in patients with subclinical encephalopathy, a statistically significant decrease in cerebral blood flow in right thalamus and nearly significant decrease in left thalamus were observed. Regional blood flow was significantly higher in the frontal lobes of patients with cirrhosis when compared with healthy controls. Similarly, cerebral blood flow in frontal and cingulate regions was significantly higher in patients with chronic hepatitis than in healthy controls. There was no relationship between cerebral blood flow and blood levels of ammonia or Child-Pugh score, in cirrhotic patients. CONCLUSION: Significant changes in cerebral blood flow may be present in chronic liver diseases and the authors suggest that the measurement of changes in cerebral blood flow might be useful in detecting subclinical hepatic encephalopathy.     

Regional cerebral blood flow patterns in extremely elderly patients with Alzheimer's disease

AIM: Clinical and pathologic features in Alzheimer's disease (AD) patients differ depending on the age of onset. The aim of our study was to compare the regional cerebral blood flow (rCBF) patterns of younger, elderly, and extremely elderly patients with AD with that of controls to characterize the rCBF patterns in extremely elderly patients with AD. METHODS: Single photon emission CT (SPECT) was performed in 113 patients with probable AD, including 34 younger (<70 years), 41 elderly (70-84 years), and 38 extremely elderly (>or=85 years) patients divided according to age at examination. The SPECT data were analyzed using three-dimensional stereotactic surface projection (3D-SSP). RESULTS: No significant differences regarding gender, duration of disease, education, and Mini-Mental State Examination score were found among the groups. As compared with controls, younger and elderly AD demonstrated significant reduction of rCBF in the temporo-parietal areas, posterior cingulate cortices and precunei, which is considered to be a characteristic rCBF pattern in AD. On the other hand, the extremely elderly AD group demonstrated significant reduction of rCBF in the frontal and medial temporal areas, in addition to the temporo-parietal areas, posterior cingulate cortices and precunei, but the reductions were milder than in those in younger and elderly AD groups. CONCLUSION: The extremely elderly patients with AD showed atypical rCBF patterns in AD compared to younger and elderly patients with AD. Our data suggest that pathological features in extremely elderly AD may be different from those in younger and elderly AD and that diseases different from AD, such as senile dementia of the neurofibrillary tangle type may be clinically diagnosed as extremely elderly AD.     

Does liver-disease aetiology have a role in cerebral blood-flow alterations in liver cirrhosis?

BACKGROUND: Studies using brain-imaging techniques have shown changes in regional blood flow (rCBF) in patients with liver cirrhosis. It remains unknown whether the aetiology of liver disease accounts for these changes. AIMS: To evaluate whether the aetiology of liver cirrhosis is associated with different patterns of rCBF. MATERIALS AND METHODS: A total of 50 patients with end-stage liver disease and no overt encephalopathy were studied. Thirteen age-matched subjects admitted to the neurology department for headache were used as controls. Exclusion criteria were focal brain lesions, severe brain atrophy and any abnormalities found on computed tomography scan suggesting other central nervous system diseases, alcohol intake or use of neuroactive drugs for at least 6 months. rCBF was assessed using single-positron-emission tomography (SPECT) with 99mTc-hexamethylpropylene amine oxime (99mTc-HM-PAO) as a tracer in all patients and controls. The Mann-Whitney U test was used for statistical analysis. RESULTS: The liver-disease aetiology was as follows: alcoholic (A) in 19 patients; viral (V) (hepatitis B virus, hepatitis D virus, hepatitis C virus) in 14 patients; alcoholic with concomitant viral (A + V) in five patients; and cholestatic (C) (primary biliary cirrhosis, primary sclerosing cholangitis) in 12 patients. SPECT showed significantly lower rCBF in cirrhotic patients than in controls for most cortical and subcortical regions and in alcoholic and viral patients than in cholestatic liver disease patients for some cortical regions. When patients were grouped according to previous alcohol abuse (including cases with a concomitant viral aetiology), rCBF was significantly lower in the frontal superior, medial and temporal inferior regions in the alcoholic group. CONCLUSIONS: Cerebral blood flow is significantly lower in patients with liver cirrhosis than in controls and, among cirrhotics, it is lower in alcoholic and viral cirrhosis than in cholestatic liver disease. In patients with previous alcohol abuse, cerebral blood flow was significantly more reduced in the frontal and temporal regions compared with patients without previous alcohol abuse.     

Visual and auditory evoked responses in acute severe hepatitis

Evoked responses have not been studied in patients with acute severe hepatitis (ASH) with or without hepatic encephalopathy. This prospective study was undertaken to find out diagnostic as well as prognostic value of visual evoked responses (VER), and brain stem auditory evoked responses (BAER) in patients with ASH with or without encephalopathy. Visual evoked responses and BAER were studied in 20 patients (14 males and six females) with ASH. The patients were diagnosed as having severe hepatitis if acute hepatitis was associated with raised serum bilirubin and serum transaminases, and if they had a prothrombin time index of < 50%. After a detailed neuropsychiatric examination of each patient, the study sample was divided into two groups of 10 patients: ASH without encephalopathy (ASH-WOE), and ASH with encephalopathy (fulminant hepatic failure, FHF). The median P100 latencies of FHF patients were significantly increased compared with controls and patients in the ASH-WOE group. Abnormal P100 latencies, exceeding 95th percentile values of the controls, were present in one patient in the ASH-WOE group and six patients in the FHF group. The median interpeak latencies I-III, III-V and I-V were significantly prolonged in the FHF group. Interpeak latencies III-V were also increased significantly in patients in the ASH-WOE group. While abnormal BAER were seen frequently in both groups, VER abnormalities were largely confined to patients in the FHF group. In the FHF group, six out of 10 patients survived and exhibited clinical improvement in the status of hepatic encephalopathy. Evoked responses were repeated after 2–3 weeks of recovery in these patients and VER abnormalities showed a tendency to normalize, thereby suggesting a prognostic implication. The incidence of abnormal VER in hepatic encephalopathy complicating ASH far exceeded that of abnormal BAER. Markedly prolonged P100 latencies in FHF patients indicate poor prognosis.     

Increased Turnover of Gc-Globulin in Patients with Hepatic Encephalopathy

Background: A low serum level (_&lt;100 mg/L) of the actin-scavenger Gc-globulin is a prognostic marker of non-survival in fulminant hepatic failure (FHF). It is unknown whether decreased production or increased consumption (or both) is responsible for the low Gc-globulin levels. Methods: Ten patients with FHF and four patients with acute or chronic liver disease (AOCLD) with hepatic encephalopathy (HE) grades II-IV were included. Eight patients with cirrhosis (chronic liver disease, CLD) without HE served as controls. Total, free, and actin-bound Gc-globulin were measured in samples from an artery, a central vein, and a hepatic vein. In 12 patients (9 FHF, 3 AOCLD), concentrations were measured before and after high volume plasmapheresis (HVP). Results     

Prediction of progression in patients with mild cognitive impairment using IMP-SPECT

To examine the difference in functional brain imaging between mild cognitive impairment (MCI) and normal aging, we measured rCBF on functional brain imaging using 123I-IMP single photon emission computed tomography (IMP-SPECT) in 19 MCI patients who progressed to develop AD on follow-up and 23 probable Alzheimer's disease (AD) patients as well as 15 age-matched normal subjects. Baseline MMSE score was 25.3 (SD 1.2) in the MCI group and 17.5 (SD 3.3) in the AD group. The regions of interest (ROI) in the posterior cingulate gyrus, frontal, temporal and parietal cortices were drawn on the image of IMP-SPECT with reference to an individual MRI image. The rCBF ratio was calculated using ROI value in the cerebellum as a reference. Voxel-based analysis was also preformed using statistical parametric mapping (SPM). The rCBF ratio in the posterior cingulate gyrus was significantly reduced in the MCI group (mean 0.956, SD 0.080) and the AD group (mean 0.833, SD 0.118) compared to that in the normal group (mean 1.083, SD 0.084). In the frontal, temporal and parietal cortices, the rCBF ratio was significantly reduced only in the AD group compared to the normal group. At a fixed specificity of 80%, the diagnostic sensitivity in the discrimination between MCI patients and normal subjects was 80.5% when using rCBF ratio in posterior cingulate gyrus. In the SPM analysis, significant reduction of the rCBF in MCI group was observed only in the posterior cingulate gyrus, compared with normal subject group. Our results suggest that MCI patients presenting with a posterior cingulate hypoperfusion are at higher risk for transition from MCI to clinically recognizable AD.     

Effect of single oral administration of nilvadipine on cerebral blood flow in chronic cerebral infarction.

The effect of nilvadipine, a newly developed calcium antagonist, on regional cerebral blood flow (rCBF) was investigated in 7 patients with chronic cerebral infarction. rCBF was measured by the 133Xenon inhalation method. Patients were given a single dose of 4 mg of nilvadipine after the first measurement of rCBF, and the second measurement was done one hour after the administration. All patients had hemiparesis and 2 of them had mild to moderate mental deterioration, but all patients could walk to the outpatient clinic by themselves. Results: (1) rCBF of the affected side significantly increased by 22.7% after single oral administration of nilvadipine (p < 0.05). The increase of rCBF was significantly marked in frontal regions of the affected hemispheres. (2) No significant changes in blood pressure or end tidal partial pressure of carbon dioxide were observed during the examination. These results indicate that nilvadipine has a potent selective vasodilatory action on the cerebral arteries in patients with cerebral infarction.     

Quantitative T1 mapping of hepatic encephalopathy using magnetic resonance imaging

Changes are shown in the spin-lattice (T1) relaxation time caused by the putative deposition of manganese in various brain regions of hepatic encephalopathy (HE) patients using a novel and fast magnetic resonance imaging (MRI) method for quantitative relaxation time mapping. A new method, T1 mapping with partial inversion recovery (TAPIR), was used to obtain a series of T1-weighted images to produce T1 maps. Imaging of 15 control subjects and 11 patients was performed on a 1.5T MRI scanner. The measurement time per patient with this technique, including adjustments, was approximately 5 minutes. Regions of interest in the globus pallidus, the caudate nucleus, the posterior and anterior limbs of the internal capsule, the putamen, the frontal and occipital white matter, the white matter of the corona radiata, the occipital visual and frontal cortices, and the thalamus were interactively defined in the left hemisphere and analyzed with respect to their T1 values. T1 changes in the brains of HE patients can be determined quantitatively with TAPIR in short, clinically relevant measurement times. Significant correlations between the change in T1 and HE severity have been shown in the globus pallidus, the caudate nucleus, and the posterior limb of the internal capsule. No significant correlation of T1 with grade of HE was found in the putamen, frontal white matter, white matter of the corona radiata, white matter in the occipital lobe, the anterior limb of the internal capsule, visual cortex, thalamus, or frontal cortex. In conclusion, these measurements show that T1 mapping is feasible in short, clinically relevant acquisition times.     

Resting cerebral blood flow alteration in severe obstructive sleep apnoea: an arterial spin labelling perfusion fMRI study

Study objectives

The aim of this study is to investigate changes in regional cerebral blood flow (rCBF) in awake people with untreated severe obstructive sleep apnoea (OSAs) compared with good sleepers (GSs).

Design

Arterial spin labelling perfusion imaging was used to quantify cerebral perfusion based on resting-state functional magnetic resonance imaging (MRI).

Setting

Lying supine in a 3.0-T magnetic resonance imaging scanner in the night was done.

Participants

Included in this study were 30 subjects with OSA (males; mean age 38.4 years, range 25–55) and 30 controls (males; mean age: 38.3 years, range 26–52) matched for age and years of education.

Results

Compared with GSs, participants with severe OSA had reduced rCBF in the left cerebellum posterior lobe, left temporal lobe, right medial frontal gyrus, and bilateral parahippocampal gyrus and increased rCBF in the bilateral superior frontal gyrus. The lower mean CBF in the right parahippocampal gyrus exhibited a significant positive correlation with arousal index (r = 0.365, P = 0.047). The increased mean CBF in the left superior frontal gyrus exhibited a significant positive correlation with the longest apnoea time (r = 0.422, P = 0.020), and the increased mean CBF in the right superior frontal gyrus exhibited a significant positive correlation with the longest apnoea time (r = 0.447, P = 0.013).

Conclusions

Our results show that the altered rCBF pattern in the left cerebellum posterior lobe, left temporal lobe, left medial frontal gyrus, bilateral parahippocampal gyrus and superior frontal gyrus in patients have with severe OSA. The arterial spin labelling perfusion imaging method is a useful non-invasive imaging tool for detection of early changes in the regional cerebral blood flow in patients with OSA.

     

Decreased protein C activation in patients with fulminant hepatic failure

OBJECTIVE: Abnormalities of the blood coagulation system have an influence on outcome in patients with fulminant hepatic failure (FHF). The protein C (PC) pathway is one of the main modulators of the blood coagulation system. The role of the PC pathway in FHF is not clear. In the present study, we evaluated endothelial cell injury and the grade of activated protein C (APC) generation in FHF patients. MATERIAL AND METHODS: The effect of APC on the expression of tumor necrosis factor (TNF)-alpha and monocyte chemoattractant protein (MCP)-1 from LI90 stellate cells was also evaluated. This study comprised 5 patients with FHF, 6 with acute hepatitis (AH), 12 with chronic hepatitis (CH) and 20 healthy subjects. RESULTS: The plasma concentrations of thrombin-antithrombin complex and thrombomodulin were significantly increased in FHF patients compared with those in AH patients and healthy subjects. The circulating levels of activated protein C-protein C inhibitor (APC-PCI) complex and the APC-PCI/PC ratio were significantly decreased in patients with FHF compared to healthy controls. APC significantly inhibited in vitro the expression of TNFalpha and MCP-1 from LI90 stellate cells. CONCLUSIONS: This study demonstrated enhanced endothelial cell injury in association with decreased PC activation and hypercoagulability in FHF.