Biomedical subjects
Publications and source records attributed to Kathrin Giewekemeyer.
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.
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.
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.