Grey and white matter abnormalities in minimal hepatic encephalopathy: A study combining voxel-based morphometry and tract-based spatial statistics

Objectives: Low-grade cerebral oedema is considered to be pathognomonic of minimal hepatic encephalopathy (MHE) in cirrhotic patients. The purpose of this study was to investigate both the grey matter (GM) and white matter (WM) changes in a homogeneous cohort of patients with MHE by combining voxel-based morphometry (VBM) and tract-based spatial statistics (TBSS). Methods: Twenty-five MHE patients and 25 healthy controls participated in the study with three-dimensional T₁ and diffusion-tensor imaging. Group differences in regional GM volume were assessed using VBM analysis while differences in fractional anisotropy (FA), mean diffusivity (MD) of WM were compared using TBSS analysis. Results: VBM displayed extensively decreased GM volume in MHE, mainly located in the frontal and temporal cortices, paracentral lobule, caudate, putamen and amygdale, and increased GM volume in the thalamus. TBSS showed decreased FA in MHE patients in the corpus callosum, cingulum, internal/external capsule, corticospinal tract, superior longitudinal fasciculus and posterior corona radiata. Areas of increased MD in MHE patients were more extensive and included, in addition to all the areas of decreased FA, the anterior corona radiata, inferior fronto-occipital fasciculus, fornix and the middle cerebellar peduncle. Conclusion: The results suggest that cortical atrophy and low-grade brain oedema in WM co-exist in MHE. Key Points: • Minimal hepatic encephalopathy develops before major neuropathological destruction occurs. • Cortical atrophy and low-grade brain oedema of white matter co-exist in MHE. • Blood ammonia correlates with abnormal WM indices in MHE patients. • Imaging findings could assist decisions about therapy in patients with cirrhosis.