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Karin Weissenborn

Publications and source records attributed to Karin Weissenborn.

16 recordsLinked to original sources
PubMed2006

Correlative assessment of cerebral blood flow obtained with perfusion CT and positron emission tomography in symptomatic stenotic carotid disease.

Twelve patients with ICA stenosis underwent dynamic perfusion computed tomography (CT) and positron emission tomography (PET) studies at rest and after acetazolamide challenge. Cerebral blood flow (CBF) maps on perfusion CT resulted from a deconvolution of parenchymal time-concentration curves by an arterial input function (AIF) in the anterior cerebral artery as well as in both anterior choroidal arteries. CBF was measured by [(15)O]H(2)O PET using multilinear least-squares minimization procedure based on the one-compartment model. In corresponding transaxial PET scans, CBF values were extracted using standardized ROIs. The baseline perfusion CT-CBF values were lower in perfusion CT than in PET (P>0.05). CBF values obtained by perfusion CT were significantly correlated with those measured by PET before (P<0.05) and after (P<0.01) acetazolamide challenge. Nevertheless, the cerebrovascular reserve capacity was overestimated (P=0.05) using perfusion CT measurements. The AIF selection relative to the side of carotid stenosis did not significantly affect calculated perfusion CT-CBF values. In conclusion, the perfusion CT-CBF measurements correlate significantly with the PET-CBF measurements in chronic carotid stenotic disease and contribute useful information to the evaluation of the altered cerebral hemodynamics.

Acetazolamide↗
PubMed2005

Attention, memory, and cognitive function in hepatic encephalopathy.

Deficits in attention and arousal play a major role in the clinical presentation of hepatic encephalopathy. Attention deficits are also the main components of minimal hepatic encephalopathy. The present paper summarizes some findings about attentional and memory dysfunction in hepatic encephalopathy, with reference to basic knowledge about normal attention and memory function and their cerebral representation.

Animals↗
PubMed2005

Neurological and neuropsychiatric syndromes associated with liver disease.

The clinical presentation of acute liver failure and hepatic encephalopathy (HE) in patients with cirrhosis differs significantly. The most serious neurological complication of acute liver failure is the development of devastating brain oedema. Therefore, intracranial pressure monitoring is urgently needed in these patients. Brain oedema is amplified by hypoglycemia, hypoxia and seizures, which are also frequent complications of acute liver failure. Therefore, these parameters must also be monitored. In contrast to acute liver failure in which cerebral dysfunction progresses rapidly, cognitive decline may be clinically undetectable for a long time in cirrhotic patients, until clinically overt symptoms such as psychomotor slowing, disorientation, confusion, extrapyramidal and cerebellar symptoms or a decrease in consciousness occur. Clinically, overt HE is preceded by minimal alterations of cerebral function that can only be detected by neuropsychological or neurophysiological measures, but which nevertheless interfere with the patient's daily living. Rapidly progressing spastic paraparesis (hepatic myelopathy) is a rare complication of cirrhosis. In contrast to HE, it does not respond to blood ammonia lowering therapies but must be considered as an indication for urgent liver transplantation. Cognitive dysfunction has recently been detected in hepatitis C virus (HCV)-infected patients with normal liver function. The patients presented with severe fatigue, cognitive dysfunction and mood disorders. Alterations in brain metabolites, as detected by magnetic resonance spectroscopy, indicated central nervous system alteration in these patients. In contrast to patients with HE, HCV-infected patients did not show motor symptoms or deficits in visual perception, but considerable deficits in attention and concentration ability.

Hepatic Encephalopathy↗
PubMed2004

Regional differences in cerebral blood flow and cerebral ammonia metabolism in patients with cirrhosis.

Clinical and histopathological findings hint at regional differences in the brain's sensitivity to metabolic changes in cirrhosis. The aim of the present study was to examine regional differences in cerebral ammonia metabolism in patients with cirrhosis and grade 0-to-I hepatic encephalopathy (HE). (13)N-ammonia, (15)O-water positron emission tomography (PET) and magnetic resonance imaging (MRI) were performed. Quantitative values of cerebral blood flow (CBF) and the initial cerebral ammonia uptake rate (K1) were derived for several regions of interest from images of the desired parameters after interactive coregistration with the patients' MRI-studies. CBF (mL/mL/min), K1 (mL/mL/min), and the ammonia extraction fraction (K1/CBF) showed marked regional variance with the highest levels in the thalamus, the lenticular nucleus, and the cerebellum. In conclusion, the regional differences in cerebral ammonia uptake correspond to the distribution of histopathological changes in the brain of patients with cirrhosis as well as clinical features of HE, characterized by signs of basal ganglia and cerebellar dysfunction with corresponding signs of functional impairment, especially of the frontal cortex and cingulate gyrus.

Adult↗
PubMed2004

Hepatitis C virus infection affects the brain-evidence from psychometric studies and magnetic resonance spectroscopy.

BACKGROUND/AIMS: Up to 50% of patients infected with the hepatitis C virus (HCV) complain of chronic fatigue and difficulties in concentration and memory. The aim of the present study was to seek evidence for the presence of central nervous system involvement in HCV infected patients with only mild liver disease. METHODS: Thirty HCV infected patients with normal liver function, 15 of whom were identified as having mild and 15 moderate to severe fatigue using the fatigue impact scale, underwent neurological and neuropsychological examination, electroencephalography (EEG) and cerebral proton magnetic resonance imaging (MRI) and spectroscopy (MRS). Fifteen healthy volunteers, matched for age and educational attainment, served as controls. RESULTS: In comparison to the healthy controls the patients with HCV infection showed evidence of cognitive impairment, primarily attention and higher executive functions, higher levels of anxiety and depression and impairment of quality of life. In addition they showed a significant decrease of the N-acetyl-aspartate/creatine ratio in the cerebral cortex on 1H MRS while the EEG was slowed in 25%. In general the deficits were more marked in the patients with moderate rather than mild fatigue. CONCLUSIONS: The data provide evidence of central nervous system involvement in patients with HCV infection.

Adult↗
PubMed2004

Functional imaging of the brain in patients with liver cirrhosis.

Brain imaging techniques have provided substantial insight into the pathophysiology of hepatic encephalopathy (HE). Magnetic resonance imaging gave hint to the fact that there is an increased deposition of manganese especially in the basal ganglia. Single photon emission computed tomography (SPECT) and positron emission tomography (PET) showed that the preference of the basal ganglia might be due to differences in regional cerebral blood flow and an additional redistribution of blood flow from the cortex to subcortical regions in cirrhotics. PET studies using ammonia as tracer showed that the cerebral metabolism of ammonia and the permeability of the blood brain barrier for ammonia is increased in cirrhotic patients compared to healthy controls. The regional ammonia supply is in accordance with the regional blood flow. In accordance with these findings fluorodesoxyglucose-PET-studies of the brain in cirrhotics showed characteristic alterations of glucose utilisation in the patients with a relative decrease of the glucose utilisation of the cingulate gyrus, the frontomedial, frontolateral, and parieto-occipital cortex, while the glucose utilisation of the basal ganglia, the hippocampus, and the cerebellum was relatively increased. These findings fit well with the clinical characteristics of early stages of HE such as deficits in attention, visuo-spatial orientation, visuo-constructive abilities, motor speed, and accuracy.

Ammonia↗
PubMed2003

Effect of sildenafil (Viagra) on cerebral blood flow velocity: a pilot study.

Sildenafil (Viagra) is a selective inhibitor of the cyclic guanosine monophosphate (cGMP) specific phosphodiesterase 5 (PDE5) used for the oral treatment of male erectile dysfunction due to vasodilation. However, assessment of direct effects of sildenafil on cerebral arteries is unknown. The aim of this present experiment is to measure the possible changes in blood flow velocity of the middle cerebral artery after the administration of sildenafil and a placebo. Blood-flow velocity changes of the middle cerebral artery were measured before and 1 to 2 h after the administration of the drug. Neither the intake of sildenafil nor the application of placebo resulted in any significant changes in blood flow velocity of the right middle cerebral artery. The next step for future experiments will be in vitro measurement of the diameters of the cerebral arteries under the influence of sildenafil and in vivo measurement of carbon dioxide and cerebral blood flow velocity during sexual stimulation after sildenafil intake instead of under resting conditions.

Adult↗
PubMed2003

Bradykinesia in minimal hepatic encephalopathy is due to disturbances in movement initiation.

BACKGROUND: One of the predominant symptoms of early stages of hepatic encephalopathy (HE) is bradykinesia. AIMS: To further analyze the pathophysiology of bradykinesia in HE. METHODS: A three-dimensional computer-assisted movement analysis was performed in 36 cirrhotics with grade 0-I HE compared to 18 controls selected with regard to sex and age and 16 patients with Parkinson's disease (PD). Four types of movement were studied: finger tapping, hand tapping, pronation/supination of the forearm and flexion/extension in the hip joint. RESULTS: The patients with PD presented with a decrease of the maximal movement velocity (VMAX) and a prolongation of the time needed to reach VMAX (VTIME). In patients with minimal or grade I HE, the VMAX of all movements was unchanged compared to controls while the VTIME was significantly prolonged. This was caused by a delay before the beginning of each new part of the diadochokinetic movement cycle. CONCLUSIONS: The data suggest an impairment of movement initiation as main cause of bradykinesia in early HE.

Case-Control Studies↗
PubMed2003

Memory function in early hepatic encephalopathy.

BACKGROUND: Early hepatic encephalopathy (HE) is characterized by deficits in motor performance, visual perception, visuo-constructive abilities and attention. Whether defective memory is a feature of early HE is controversial. AIMS: To analyze memory function in patients with early HE. METHODS: Memory tests were applied to cirrhotic patients with grade 0 HE, minimal HE and grade I HE (n=45) and controls (n=52). The battery included short and long term memory tests requiring free recall or recognition. Minimal HE was diagnosed by assessing the psychometric hepatic encephalopathy score using the PSE-Syndrom-Test and by carrying out a neurological examination. Group differences of the test results were analyzed using analysis of covariance. RESULTS: HE 0 patients achieved test results similar to the controls in all but two tests. Patients with early HE (minimal and grade I HE) scored lower than the controls in all tests applied. A detailed analysis of test performance showed that the patients' deficits were in attention and visual perception, rather than memory. CONCLUSIONS: Patients with early HE score lower than controls in memory tasks predominantly because of deficits in attention and visual perception.

Adolescent↗
PubMed2003

Liver transplantation improves hepatic myelopathy: evidence by three cases.

BACKGROUND & AIMS: Hepatic myelopathy is a rare complication of chronic liver disease, causing progressive spastic paraparesis. Today, no therapy of this disorder has been established. Commonly used therapeutic strategies for hepatic encephalopathy aiming at the reduction of plasma ammonia levels such as protein restriction, oral neomycin, lactulose, or ornithine aspartate fail to improve the symptoms of hepatic myelopathy. The aim of this study was to find out whether orthotopic liver transplantation (OLT) may improve hepatic myelopathy. METHODS: Follow-up examinations of 3 patients with severe hepatic myelopathy before and after OLT. RESULTS: In all 3 patients, the neurologic status improved significantly after liver transplantation. The grade of improvement was related to the time interval between onset of the first symptoms of hepatic myelopathy and liver transplantation. CONCLUSIONS: Early recognition of hepatic myelopathy is important because timely liver transplantation as an established therapy for end-stage liver disease offers the chance of complete recovery from hepatic paraparesis.

Adult↗
PubMed2002

Decrease of middle cerebral artery blood flow velocity after low-frequency repetitive transcranial magnetic stimulation of the dorsolateral prefrontal cortex.

OBJECTIVES: Repetitive transcranial magnetic stimulation (rTMS) has been tried therapeutically in a variety of neuropsychiatric disorders. Both, inhibition and activation of cortical areas may be achieved using different stimulation parameters. Using low-frequency rTMS (0.9 Hz), inhibition of cortical areas can be observed. METHODS: In the present study, 38 right-handed, healthy, normotensive subjects (aged 21-50 years, mean 30.2 years, SD=4.9; 17 women) were enrolled. Twenty-five participants received active rTMS (5 min of 0.9 Hz rTMS, stimulus intensity 90% of motor threshold) of the right dorsolateral prefrontal cortex. Sham stimulation (n=13 subjects) occurred in the same manner as active rTMS, except that the angle of the coil was at 45 degrees off the skull. Simultaneously, ipsilateral and contralateral maximal middle cerebral artery (MCA) flow velocity (and pulsatility index, PI) was monitored using transcranial Doppler sonography. RESULTS: In the group with active rTMS, maximal MCA flow velocity decreased from a baseline (before rTMS) of 101.6 cm/s (SD=26.0) to a mean of 92.6 cm/s (SD=23.7) immediately after rTMS, T=5.06, P<0.001. This equals a mean decrease of 9.0 cm/s (SD=8.3) or approximately 8.9% of baseline flow. Five and 10 min after rTMS, there was a return to baseline. PI significantly decreased 10 min after rTMS (mean difference -0.05, SD=0.05, T=2.29, P<0.05). In the contralateral MCA, maximal flow velocity tended to increase 10 min after rTMS (mean difference +7.4 cm/s, SD=17.5; T=-2.03, P=0.054). With sham rTMS, no significant changes occurred. CONCLUSIONS: The results from our study support the hypothesis that low-frequency rTMS may influence cerebral blood flow (CBF) over short periods of time, inducing a temporary decrease of maximal CBF in the ipsilateral MCA followed by an increase in the contralateral MCA.

Adult↗
PubMed2002

Correlations between cerebral glucose metabolism and neuropsychological test performance in nonalcoholic cirrhotics.

Many cirrhotics have abnormal neuropsychological test scores. To define the anatomical-physiological basis for encephalopathy in nonalcoholic cirrhotics, we performed resting-state fluorodeoxyglucose positron emission tomographic scans and administered a neuropsychological test battery to 18 patients and 10 controls. Statistical parametric mapping correlated changes in regional glucose metabolism with performance on the individual tests and a composite battery score. In patients without overt encephalopathy, poor performance correlated with reductions in metabolism in the anterior cingulate. In all patients, poor performance on the battery was positively correlated (p < 0.001) with glucose metabolism in bifrontal and biparietal regions of the cerebral cortex and negatively correlated with metabolism in hippocampal, lingual, and fusiform gyri and the posterior putamen. Similar patterns of abnormal metabolism were found when comparing the patients to 10 controls. Metabolic abnormalities in the anterior attention system and association cortices mediating executive and integrative function form the pathophysiological basis for mild hepatic encephalopathy.

Aged↗
PubMed2002

Hepatic encephalopathy--definition, nomenclature, diagnosis, and quantification: final report of the working party at the 11th World Congresses of Gastroenterology, Vienna, 1998.

Research on hepatic encephalopathy is hampered by the imprecise definition of this disabling complication of liver disease. Under this light, the Organisation Mondiale de Gastroentérologie commissioned a Working Party to reach a consensus in this area and to present it at the 11th World Congress of Gastroenterology in Vienna (1998). The Working Party continued its work thereafter and now present their final report. In summary, the Working Party has suggested a modification of current nomenclature for clinical diagnosis of hepatic encephalopathy; proposed guidelines for the performance of future clinical trials in hepatic encephalopathy; and felt the need for a large study to redefine neuropsychiatric abnormalities in liver disease, which would allow the diagnosis of minimal (subclinical) encephalopathy to be made on firm statistical grounds. In the interim, it proposes the use of a psychometric hepatic encephalopathy score, based on the result of 5 neuropsychologic tests. Finally, the need for a careful evaluation of the newer neuroimaging modalities for the diagnosis of hepatic encephalopathy was stressed.

Clinical Trials as Topic↗
PubMed2002

Upper sympathetic trunk lesion after video-assisted fracture stabilization of the thoracic spine: a case report.

This case report draws attention to the upper sympathetic trunk lesion as a complication of video-assisted thoracic spine surgery. A 39-year-old man developed an upper sympathetic trunk lesion after right-sided thoracoscopic fracture stabilization of T5 and T6. Dizziness and reduced perspiration persisted at the most recent follow-up 8 months after surgery. This rare complication can be overlooked and remain undiagnosed. Diagnosis is based on clinical symptoms and neurologic examination. There are no treatment options. Symptoms can be bothersome for the patient and may persist. In the upper thoracic spine, the course of the sympathetic trunk lies in close proximity of the vertebral bodies; thus, care must be taken to avoid it when resecting the posterior parts of the vertebral body.

Adult↗
PubMedDate not supplied

Comparison of perfusion computed tomography with diffusion-weighted magnetic resonance imaging in hyperacute ischemic stroke.

OBJECTIVE: In this study, perfusion CT and diffusion-weighted magnetic resonance imaging (DWI) were compared as means of assessing the ischemic brain in hyperacute stroke. METHODS: Twenty patients with ischemic stroke underwent perfusion computed tomography (CT) and magnetic resonance imaging (MRI) studies <3 hours after stroke onset. Cerebral blood flow thresholds were used to delineate the ischemic lesion, penumbra, and infarct. Correlations between the volume of the hypoperfused areas, the abnormality volume in admission DWI and follow-up CT/MRI studies, and the clinical National Institutes of Health Stroke Scale (NIHSS) scores were performed. RESULTS: The volume of the ischemic (core and penumbra) lesion on admission perfusion CT was correlated with the volume of admission DWI abnormalities (r=0.89, P=0.001). The infarcted core tissue volume (on admission CT) correlated more strongly (r=0.77, P=0.0001) than the admission DWI abnormality volume (r=0.69, P=0.002) with the follow-up infarct volume on fluid-attenuated inversion recovery images. A correlation was demonstrated between infarct volume in perfusion CT and follow-up DWI abnormality volume (r=0.89, r=0.77, P=0.002). Significant correlations were found between ischemic and infarct region volumes in perfusion CT and NIHSS admission and follow-up scores (P < or = 0.01). CONCLUSIONS: Both imaging modalities provide a sufficient assessment of the hyperacute brain infarct, with significant correlation between them and the clinical condition at admission. Perfusion CT allows differentiation of the penumbra and infarct core region with significant predictive value of follow-up infarct volume and clinical outcome.

Adult↗