Specific Imaging Findings

Classic brain MR imaging finding in patients with hepatic encephalopathy (HE) is bilateral symmetric globus pallidus hyperintensity on T1-weighted images. When more prominent, high T1 signal is also present in substantia nigra, subthalamic nucleus, tectum, and cerebellar denatate nucleus, with no corresponding findings on T2-weighted images or on CT. Additional MRI findings include diffuse white matter T2 hyperintensity involving predominantly the hemispheric corticospinal tract and focal bright T2 lesions in subcortical hemispheric white matter. MR spectroscopy obtained with short echo time shows depletion of myo-inositol. Myo/Cr ratios are decreased not only in cirrhotic patients with clinical or subclinical encephalopathy, but also in individuals without encephalopathy. Increased levels of glutamine/ glutamate have also been observed, particularly in severe cases. All these MR imaging findings – bright T1 lesions, white matter T2 hyperintensity, and MRS abnormalities – tend to improve and return to normal with restoration of liver function, such as following a successful liver transplantation. Characteristic MRI appearance of acute hyperammonemic encephalopathy appears to be bilateral symmetric cortical T2 hyperintensity involving the insula and cingulate gyrus, best seen on FLAIR and DWI.

Pertinent Clinical Information

HE includes a spectrum of neuropsychiatric abnormalities occurring in patients with liver dysfunction. Most cases are associated with cirrhosis and portal hypertension or portal-systemic shunts. It is a reversible metabolic encephalopathy, characterized by personality changes and shortened attention span, anxiety and depression, motor incoordination, and flapping tremor of the hands (asterixis). In severe cases, coma and death may occur.