Georg Berding

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 arealso 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 knowledgeabout normal attention and memory function and their cerebral representation.

Evaluation of the incorporation of bone grafts used in maxillofacial surgery with [18F]fluoride ion and dynamic positron emission tomography

This study investigates the incorporation of bone grafts used in maxillofacial surgery by means of [18F]fluoride ion and positron emission tomography (PET). It considers patients who received pedicle grafts for mandibular reconstruction or onlay grafts for alveolar ridge augmentation. Dynamic PET images and arterialized venous blood samples were obtained within a 1-h period after i.v. injection of [18F-]fluoride. Assuming a three-compartment model and applying multilinear least squares fitting, bone blood flow (K1) and fluoride influx (Kmlf) were determined. Additionally Patlak plot analysis was used to calculate fluoride influx (Kpat). In cervical vertebral bodies as the reference region, mean values for flow ofK1 = 0.1162±0.0396 ml/min/ml and influx ofKmlf = 0.0508±0.0193 andKpat = 0.0385±0.0102 ml/min/ml were found. Essentially these figures are comparable with physiological values in animal and man reported in the literature. Early after surgery a significant increase in flow and influx compared to vertebral bodies was observed in the regions of osteosyntheses between grafts used for reconstruction and recipient bone (K1 = 0.2181,Kmlf = 0.1000 andKpat = 0.0666 ml/min/ml) and in onlay grafts (K1 = 0.2842,Kmlf = 0.1637 andKpat = 0.0827 ml/min/ml). At the same time pedicle grafts showed a significant increase in flow but not in influx (K1 = 0.2042,Kmlf = 0.0774 andKpat = 0.0529 ml/ min/ml). FurthermoreKpat was significantly lower in pedicle grafts than in onlay grafts. In follow-up studies a significant decrease in flow occurred in pedicle grafts and the regions of osteosyntheses. Moreover the latter showed a significant decrease inKmlf as well. It is concluded that [18F-] PET depicted increased blood flow and osteoblastic activity in onlay grafts and regions of osteosyntheses, indicating bone repair in the graft and adjacent host bone early after surgery. For the regions of osteosyntheses the decrease in both parameters corresponded to uncomplicated healing. The lack of increased influx, although flow was increased in pedicle grafts, most likely indicates that some necrosis occurred in these grafts despite patency of anastomoses. It may be concluded that [18F-] PET provides further insight into the biology of graft incorporation.

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.

Bone scintigraphy in the evaluation of bone grafts used for mandibular reconstruction

Bone scintigraphy was applied in the follow-up of 24 patients who received bone grafts for reconstruction of the mandible after partial resection. Semiquantitative assessment of the grafts was done with a six-grade scoring system, based on comparison of tracer uptake in the graft and in the calvarium (as an internal control). Sixty-nine bone scans were evaluated. Late planar imaging was carried out in all cases, and single-photon emission tomography (SPET) was performed additionally in 34 of these cases. Complications were observed in four grafts. They occurred less frequently in revascularized grafts than in non-revascularized grafts. Planar scintigrams performed within 14 days after reconstruction showed a significantly higher tracer uptake in grafts with an uncomplicated further course than in those which developed complications. Follow-up scintigrams after 1 and 3 months revealed a significant increase in tracer uptake in grafts with an uncomplicated course. This was not apparent in grafts which developed complications. The tracer uptake was estimated to be higher on the basis of the SPET scans as compared with the planar scintigrams. It is concluded that bone scintigraphy is of prognostic value in the evaluation of bone grafts used for mandibular reconstruction. SPET seems to be more sensitive than planar imaging for the assessment of graft viability.

Altered striatal dopamine D2 receptor density and dopamine transport in a patient with hepatic encephalopathy.

A patient suffering from liver cirrhosis presented with a bradykinetic-rigid syndrome suspected as Parkinsons disease. A detailed work-up of the case revealed hepatic encephalopathy as the cause of the neurological symptomatology. An alteration of striatal dopamine D2 receptor binding and dopamine re-uptake sites was demonstrated by123I-iodobenzamide (IBZM) and123I-ß-CIT single photon emission computed tomography (SPECT), respectively. It is suggested that the alteration of the dopamine re-uptake in cirrhotics may be the cause of an increased catabolism of dopamine in HE.

Imaging studies in hepatic encephalopathy

For decades, insights into the pathophysiology of hepatic encephalopathy (HE) had to be achieved using animal models, such as the portacaval shunted rat, or cell cultures. However, recent developments in brain imaging techniques, such as magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), single photon emission tomography (SPECT) and positron emission tomography (PET) provide new opportunities to study in vivo structural and metabolic changes, or even altered neurotransmission, in the brain of patients with HE.