Encephalopathy assessment in children with extra-hepatic portal vein obstruction with MR, psychometry and critical flicker frequency

Background & Aims

Mild cognitive and psychomotor deficit has been reported in patients with extra-hepatic portal vein obstruction. This prospective study was done to ascertain the presence of minimal hepatic encephalopathy by neuropsychological testing and its correlation with diffusion tensor imaging derived metrics, T1 signal intensity, brain metabolites in ¹H magnetic resonance spectroscopy, blood ammonia and critical flicker frequency in patients with extra-hepatic portal vein obstruction.

Methods

Neuropsychological tests, critical flicker frequency, blood ammonia, diffusion tensor imaging, T1 signal intensity and ¹H magnetic resonance spectroscopy were determined in 22 extra-hepatic portal vein obstruction and 17 healthy children. Bonferroni multiple comparison post hoc analysis was done to compare controls with patient groups.

Results

Based on neuropsychological tests, 7/22 patients had minimal hepatic encephalopathy, and significantly increased Glx/Cr ratio, blood ammonia, mean diffusivity and globus pallidus T1 signal intensity with decreased critical flicker frequency in comparison to controls and in those without minimal hepatic encephalopathy. Cho/Cr, mI/Cr ratio and fractional anisotropy were unchanged in patient groups compared to controls. A significant inverse correlation of neuropsychological test with mean diffusivity, Glx/Cr ratio and blood ammonia and a positive correlation among mean diffusivity, blood ammonia and Glx/Cr ratio was seen.

Conclusions

Extra-hepatic portal vein obstruction is a true hyperammonia model with porto-systemic shunting and normal liver functions that results in minimal hepatic encephalopathy in one-third of these children. Hyperammonia results in generalized low grade cerebral edema and cognitive decline as evidenced by increased Glx/Cr ratio, mean diffusivity values and abnormal neuropsychological tests.

Abbreviations: EHPVO, extra-hepatic portal venous obstruction, PSS, porto-systemic shunts, HE, hepatic encephalopathy, MHE, minimal hepatic encephalopathy, MRI, magnetic resonance imaging, ¹H MRS, ¹H magnetic resonance spectroscopy, DTI, diffusion tensor imaging, T1SI, T1 signal intensity, Glx, glutamine/glutamate, Cr, creatinine, mI, myoinositol, Cho, choline, NPT, neuropsychological tests, GP, globus pallidus, CFF, critical flicker frequency, NAA, N-acetylaspartate, Glu, glutamate, CG, cingulate gyrus, FA, fractional anisotropy, MD, mean diffusivity

Keywords: ¹H Magnetic resonance spectroscopy, Diffusion tensor imaging, Minimal hepatic encephalopathy, Hyperammonemia, Neuropsychological tests, Extra-hepatic portal vein obstruction