Brain Edema in Chronic Hepatic Encephalopathy

Abstract

Brain edema is a common feature associated with hepatic encephalopathy (HE). In patients with acute HE, brain edema has been shown to play a crucial role in the associated neurological deterioration. In chronic HE, advanced magnetic resonance imaging (MRI) techniques have demonstrated that low-grade brain edema appears also to be an important pathological feature. This review explores the different methods used to measure brain edema ex vivo and in vivo in animal models and in humans with chronic HE. In addition, an in-depth description of the main studies performed to date is provided. The role of brain edema in the neurological alterations linked to HE and whether HE and brain edema are the manifestations of the same pathophysiological mechanism or two different cerebral manifestations of brain dysfunction in liver disease are still under debate. In vivo MRI/magnetic resonance spectroscopy studies have allowed insight into the development of brain edema in chronic HE. However, additional in vivo longitudinal and multiparametric/multimodal studies are required (in humans and animal models) to elucidate the relationship between liver function, brain metabolic changes, cellular changes, cell swelling, and neurological manifestations in chronic HE.

Keywords: 1H MRS, proton magnetic resonance spectroscopy; ADC, apparent diffusion coefficient; ALF, acute liver failure; AQP, aquaporins; BBB, blood-brain barrier; BDL, bile duct ligation; CNS, central nervous system; CSF, cerebrospinal fluid; Cr, creatine; DTI, diffusion tensor imaging; DWI, diffusion-weighted imaging; FLAIR, fluid-attenuated inversion recovery; GM, gray matter; Gln, glutamine; Glx, sum of glutamine and glutamate; HE, hepatic encephalopathy; Ins, inositol; LPS, lipopolysaccharide; Lac, lactate; MD, mean diffusivity; MRI, magnetic resonance imaging; MRS, magnetic resonance spectroscopy; MT, magnetization transfer; MTR, MT ratio; NMR, nuclear magnetic resonance; PCA, portocaval anastomosis; TE, echo time; WM, white matter; brain edema; chronic hepatic encephalopathy; in vivo magnetic resonance imaging; in vivo magnetic resonance spectroscopy; liver cirrhosis; mIns, myo-inositol; tCho, total choline; tCr, total creatine.