Cerebral water content mapping in cirrhosis patients with and without manifest HE.

Hepatic encephalopathy (HE) is a frequent and debilitating complication of cirrhosis and its pathogenesis is not definitively clarified. Recent hypotheses focus on the possible existence of low-grade cerebral edema due to accumulation of osmolytes secondary to hyperammonemia. In the present study we investigated increases in cerebral water content by a novel magnetic resonance impedance (MRI) technique in cirrhosis patients with and without clinically manifest HE. We used a 3 T MRI technique for quantitative cerebral water content mapping in nine cirrhosis patients with an episode of overt HE, ten cirrhosis patients who never suffered from HE, and ten healthy aged-matched controls. We tested for differences between groups by statistical non-parametric mapping (SnPM) for a voxel-based spatial evaluation. The patients with HE had significantly higher water content in white matter than the cirrhosis patients (0.6%), who in turn, had significantly higher content than the controls (1.7%). Although the global gray matter water content did not differ between the groups, the patients with HE had markedly higher thalamic water content than patients who never experienced HE (6.0% higher). We found increased white matter water content in cirrhosis patients, predominantly in those with manifest HE. This confirms the presence of increasing degrees of low-grade edema with exacerbation of pathology. The thalamic edema in manifest HE may lead to compromised basal ganglia-thalamo-cortical circuits, in accordance with the major clinical symptoms of HE. The identification of the thalamus as particularly inflicted in manifest HE is potentially relevant to the pathophysiology of HE.