Widespread cortical lesions on diffusion-weighted imaging in acute portal systemic shunt encephalopathy caused by primary biliary cirrhosis

Histopathological examination of characteristic brain MRI findings in acute hyperammonemic encephalopathy: A case report and review of the literature

INTRODUCTION

Acute hyperammonemic encephalopathy is associated with distinct brain MRI findings, namely, hyperintensity in T2-weighted sequences as well as restricted diffusion in diffusion-weighted imaging with accentuation in the insular cortex and cingulate gyrus. The pathophysiology and the histopathological correlates of these characteristic MRI findings are largely unknown.

CASE REPORT

We present a 57-year-old male with a history of chronic alcohol abuse, liver cirrhosis and portal hypertension, and a clinical syndrome (variceal bleeding, depression of consciousness, seizures), elevated plasma ammonia levels, and characteristic brain MRI abnormalities suggestive of acute hyperammonemic encephalopathy. A postmortem histopathological examination revealed extensive hypoxic ischemic encephalopathy without evidence for metabolic encephalopathy. No episodes of prolonged cerebral hypoxemia were documented throughout the course of the disease. We conducted a review of the literature, which exhibited no reports of hyperammonemic encephalopathy in association with characteristic brain MRI findings and a consecutive histopathological examination.

CONCLUSION

This is the first report of a patient with acute hyperammonemic encephalopathy together with characteristic brain MRI findings and a histopathological correlation. Although characteristic MRI findings of acute hyperammonemic encephalopathy were present, a histopathological examination revealed only hypoxic pathology without signs of metabolic encephalopathy.

[Portal-systemic encephalopathy with bilateral thalamic and internal capsule lesions using diffusion-weighted MRI in a super-aged patient]

We describe the case of a 90-year-old woman who was hospitalized in July 2016 and subsequently experienced a sudden decline in consciousness level resulting in a state of deep coma. Involuntary movements were not observed, and bilateral Babinski signs were inconclusive. Diffusion-weighted MRI (DWI) of the brain showed bilateral hyperintensity in the thalamus and internal capsule, laboratory testing detected high levels of plasma ammonia, and an electroencephalogram showed delta waves and triphasic waves predominantly in the frontal lobe. Based on these results, treatment for hepatic encephalopathy was administered, which led to an improvement in consciousness level, a decrease in plasma ammonia levels, and a normalization in the DWI scan. Abdominal computed tomography scan showed no abnormality in the liver, but revealed an abnormal blood vessel leading from the ileocolic vein to the inferior vena cava; the patient was diagnosed with portal-systemic encephalopathy. In deep coma patients, acute encephalopathy with hyperammonemia is important for differential diagnosis when DWI shows high-density legions in the thalamus and internal capsule.