Resting-State Synchronisation in Hepatic Encephalopathy

• Published in: Klinische Neurophysiologie
• Main Authors: Butz, M, Gross, J, Timmermann, L, Montez, T, Pollok, B, Kramer, T, Kircheis, G, Häussinger, D, Schnitzler, A
• Format: Conference Proceeding
• Language: English
• Published: 08.04.2008
• ISSN: 1434-0275; 1439-4081
• DOI: 10.1055/s-2008-1072844

Objective: Hepatic encephalopathy (HE) is a complication occurring within patients suffering from cirrhosis of the liver. HE is characterised by a variety of cognitive and motor deficits. Previous studies demonstrated that motor symptoms like mini-asterixis at high grade HE arise from a pathologically slowed drive of the primary motor cortex towards the muscles and the thalamus. Furthermore, higher HE-grades lead to a gradual reduction in the critical flicker frequency (CFF), a measure for perception of oscillatory visual stimuli. Thus, CFF appears to be a sensitive and reliable diagnostic tool for classification of HE. Synchronization Likelihood (SL) is a novel measure that can be used to quantify the integration of many brain regions by comparing the activity of each sensor with all other sensors. In the present study we hypothesised that worsening of HE – determined by CFF – goes along with global alterations in the oscillatory processing in the human brain as expressed by SL. Materials and Methods: In 50 subjects, healthy controls and cirrhotic patients with no HE (HE 0; control patients), minimal HE (mHE) and manifest HE grade 1 and 2 (controls=10, HE0=10; mHE=10; HE1=10; HE2=10) spontaneous activity was recorded with a Neuromag™-122 wholehead MEG-system for 3 to 5min during a no-task eyes-closed condition. Additionally, individual CFF was assessed. Overall SL expressing the mean SL of all sensor combinations was calculated for an artifact-free period of 20 seconds for seven different frequency domains: 1–3Hz, 4–7Hz, 8–12Hz, 12–20Hz, 20–30Hz, 30–45Hz and 1–45Hz. Between group comparison was done by an univariate ANOVA and post-hoc-test paired comparison (Bonferroni) was calculated. Finally, we calculated regression between CFF and SL in all frequency ranges and between CFF and age. Results: We could show that compared to healthy controls SL is exclusively increased significantly in the 4–7Hz range ( theta ) in patients suffering from manifest HE grade 1 and 2. For HE0 and mHE patients a trend to a significant lower SL compared to HE2 patients could be observed. There were no significant difference in SL between controls, HE0 and mHE patients and between HE 1 and HE 2 patients. CFF and SL showed exclusively a significant regression in the theta range of 4–7Hz suggesting that with increasing CFF SL in the theta range decreases and vice versa. Conclusion: Our results reveal that worsening of HE is paralleled by global alterations in neural synchronisation. An increase of synchronisation in the theta range may imply a change to a coarser brain activity with ongoing deterioration and a gradually losing of differentiated brain function as observed in clinical routine. As these changes correlate with the lowering of CFF our data may imply that oscillatory processing of the human CNS seems to be closely related to the patho-physiology of HE.