Brain Gray Matter Alterations in Hepatic Encephalopathy: A Voxel-Based Meta-Analysis of Whole-Brain Studies

Gray matter alterations and neurotransmitter system associations in hepatitis B virus-related cirrhosis: insights into neuropathogenesis and therapeutic targets

INTRODUCTION

The associations between gray matter (GM) change and neurotransmitter systems in hepatitis B virus-related cirrhosis (HBV-RC) are still poorly understood.

METHODS

We recruited 60 HBV-RC patients and 60 healthy controls (HCs). Difference of GM volume between HBV-RC and HC groups was evaluated at global and voxel levels. The potential relationship between GM morphology and prognostic models of liver function was evaluated at voxel level in HBV-RC patients. The spatial correspondence between regional GM alteration and the distribution of multiple neurotransmitter systems in HBV-RC compared to healthy controls was assessed by the JuSpace toolbox covering various neurotransmitter maps.

RESULTS

Total GM volume in HBV-RC group was smaller than in HC group (p < 0.05), and the pattern of GM volume alterations showed significantly increased volume in bilateral thalamus and ventral diencephalon and decreased volume in bilateral basal ganglia and cerebellum (p < 0.05, FWE corrected). In HBV-RC group, the volume of left superior frontal gyrus medial segment and right middle frontal gyrus was positively correlated with serum albumin level and negatively correlated with ALBI score, and serum bilirubin level was negatively correlated with right hippocampus and caudate (p < 0.05, FWE corrected). GM alterations in HBV-RC patients relative to HCs were significantly associated with the intrinsic distribution of various neurotransmitter pathways, including GABAergic, cholinergic, serotonergic, and dopaminergic (p < 0.05).

CONCLUSION

The pattern of GM alteration correlated with liver function and specific neurotransmitter deficits in HBV-RC patients. These findings provide new insight into the complex neuropathogenesis of HBV-RC and the possible therapeutic targets based on neurotransmitter modulation.

Identifying Minimal Hepatic Encephalopathy: A New Perspective from Magnetic Resonance Imaging

Type C hepatic encephalopathy (HE) is a condition characterized by brain dysfunction caused by liver insufficiency and/or portal-systemic blood shunting, which manifests as a broad spectrum of neurological or psychiatric abnormalities, ranging from minimal HE (MHE), detectable only by neuropsychological or neurophysiological assessment, to coma. Though MHE is the subclinical phase of HE, it is highly prevalent in cirrhotic patients and strongly associated with poor quality of life, high risk of overt HE, and mortality. It is, therefore, critical to identify MHE at the earliest and timely intervene, thereby minimizing the subsequent complications and costs. However, proper and sensitive diagnosis of MHE is hampered by its unnoticeable symptoms and the absence of standard diagnostic criteria. A variety of neuropsychological or neurophysiological tests have been performed to diagnose MHE. However, these tests are nonspecific and susceptible to multiple factors (eg, aging, education), thereby limiting their application in clinical practice. Thus, developing an objective, effective, and noninvasive method is imperative to help detect MHE. Magnetic resonance imaging (MRI), a noninvasive technique which can produce many objective biomarkers by different imaging sequences (eg, Magnetic resonance spectroscopy, DWI, rs-MRI, and arterial spin labeling), has recently shown the ability to screen MHE from NHE (non-HE) patients accurately. As advanced MRI techniques continue to emerge, more minor changes in the brain could be captured, providing new means for early diagnosis and quantitative assessment of MHE. In addition, the advancement of artificial intelligence in medical imaging also presents the potential to mine more effective diagnostic biomarkers and further improves the predictive efficiency of MHE. Taken together, advanced MRI techniques may provide a new perspective for us to identify MHE in the future. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY: Stage 2.

Altered Spontaneous Brain Activity in Cirrhotic Patients with Minimal Hepatic Encephalopathy: A Meta-Analysis of Resting-State Functional Imaging

(1) Background: Minimal hepatic encephalopathy (MHE) is an important complication of decompensated cirrhosis. Previous studies have demonstrated spontaneous brain activity alterations in cirrhotic patients with MHE. However, the reported results are inconsistent, which has limited our understanding of the potential neural mechanisms. Thus, we conducted a quantitative meta-analysis of resting-state functional imaging studies to identify the regional activity alterations consistently involved in MHE. (2) Methods: We searched six databases to include resting-state functional imaging studies and compared spontaneous brain activity patterns between MHE patients and healthy controls (HCs), and between cirrhotic patients without minimal hepatic encephalopathy (NMHE) and HCs. Then, a separate whole-brain voxel-wise meta-analysis between MHE or NMHE patients and HCs was conducted using seed-based d mapping with permutation of subject images. We further conducted the conjunction analysis to assess the distinct regional activity alterations between MHE and NMHE patients as compared to HCs. (3) Results: Thirteen studies with twenty datasets were included in this meta-analysis. Compared with HCs, MHE patients showed decreased spontaneous brain activity in the left superior frontal gyrus, left median cingulate/paracingulate gyri, and right precuneus. Compared with NMHE patients, MHE patients indicated decreased spontaneous brain activity in the left superior frontal gyrus, left median cingulate/paracingulate gyri, and right precuneus. (4) Conclusions: MHE is associated with spontaneous brain activity alterations involving the left superior frontal gyrus and median cingulate/paracingulate gyri, which may implicate primarily in spatial working memory and emotional disorders. These findings may contribute to a better understanding of the potential neural mechanisms, and guide further research.