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

• Published in: The neuroradiology journal Vol. 37; no. 5; pp. 630 - 635
• Main Authors: Denk, CH, Kunzmann, J, Maieron, A, Wöhrer, A, Quinot, V, Oberndorfer, S
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01-10-2024
• Subjects: Acute Disease; Brain - diagnostic imaging; Brain - pathology; Humans; Hyperammonemia - diagnostic imaging; Hyperammonemia - etiology; Hyperammonemia - pathology; Magnetic Resonance Imaging - methods; Male; Middle Aged; Hyperammonemic encephalopathy; histopathological examination; MRI; hepatic encephalopathy
• ISSN: 1971-4009; 2385-1996
• DOI: 10.1177/19714009231212370

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.