In vivo brain magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) in hepatic encephalopathy

Metabolic changes of anterior cingulate cortex in patients with hepatic cirrhosis: A magnetic resonance spectroscopy study

AIM

The anterior cingulate cortex (ACC) plays an important role in cognitive functions. The purpose of this study is to compare metabolite concentrations in the ACC of cirrhotic patients with normal controls, and to correlate metabolite changes with Child-Pugh class and with severity of hepatic encephalopathy (HE).

METHODS

Fifty-two cirrhotic patients and 30 healthy volunteers were included in this study. All subjects performed the number connection test type A (NCT-A) and digital symbol test (DST) before multiple resonance (MR) examinations. Single-voxel proton MR spectroscopy (MRS) data in the ACC were acquired on a 1.5-T scanner. The ratios of all metabolites to creatine and phosphocreatine (Cr) were obtained. Statistical analysis was performed to evaluate the difference between control and cirrhotic patients, with respect to metabolite ratios. The correlation between metabolite ratios and Child-Pugh scale, severity of HE, venous ammonia and neuropsychiatric test results was analyzed.

RESULTS

The ratios of choline (Cho)/Cr and myo-inositol (mIns)/Cr were significantly lower, and the ratio of glutamine- glutamate (Glx)/Cr was significantly higher in cirrhotic patients than those in controls (P < 0.001). mIns/Cr correlated negatively with Child-Pugh scale (r = -0.496, P < 0.001) and HE degree (r = -0.313, P < 0.05). Venous ammonia had a significant correlation with Cho/Cr (r = -0.329, P < 0.05) and mIns/Cr (r = -0.347, P < 0.05). No statistical correlation between metabolite ratios and neuropsychological tests was found for cirrhotic patients, but mIns/Cr did have a statistical correlation with NCT-A (r = -0.270, P < 0.05) and DST (r = 0.463, P < 0.001) when all subjects were included in the analysis.

CONCLUSION

Significant metabolite changes were seen in the ACC in cirrhotic patients. Of the metabolites examined, the mIns/Cr level in the ACC was most closely associated with the severity of HE and hepatic functional reserve reflected by Child-Pugh scale.

Role of Magnetic Resonance in Understanding the Pathogenesis of Hepatic Encephalopathy

A spectrum of neuropsychiatric abnormalities caused by portosystemic venous shunting occurs in hepatic encephalopathy (HE) patients with or without liver dysfunction. It is not completely clear how the astrocyte swelling leads to glial-neuronal dysfunction, and how the symptoms are manifested in HE. A major goal of this work is to review the current status of information available from the existing magnetic resonance (MR) modalities including MR imaging (MRI) and MR Spectroscopy (MRS) as well as other modalities in the understanding the pathogenesis of HE. First, we discuss briefly neuron-histopathology, neurotoxins, neuropsychological and neurophysiological tests. A short review on the progress with single-photon emission computed tomography (SPECT) and positron emission tomography (PET) is then presented. In the remaining part of the manuscript, the following topics pertinent to understanding the pathogenesis of HE are discussed: MRI, diffusion tensor imaging (DTI), one-dimensional MRS based single- and multi-voxel based spectroscopic imaging techniques and two-dimensional MRS.