J Korean Soc Radiol.  2015 Feb;72(2):131-135. 10.3348/jksr.2015.72.2.131.

Acute Hyperammonemic Encephalopathy with Features on Diffusion-Weighted Images: Report of Two Cases

• Kim JY
• Yu IK

• KMID: 2002810
• DOI: http://doi.org/10.3348/jksr.2015.72.2.131

Abstract

Acute hyperammonemic encephalopathy is a rare toxic encephalopathy caused by accumulated plasma ammonia. A few literatures are reported about MRI findings of acute hyperammonemic encephalopathy. It is different from the well-known chronic hepatic encephalopathy. The clinical symptom and MRI findings of acute hyperammonemic encephalopathy can be reversible with proper treatment. Acute hepatic encephalopathy involves the cingulate cortex, diffuse cerebral cortices, insula, bilateral thalami on diffusion-weighted imaging (DWI), and fluid-attenuated inversion-recovery. Acute hepatic encephalopathy might mimic hypoxic-ischemic encephalopathy because of their similar predominant involving sites. We experienced 2 cases of acute hyperammonemic encephalopathy consecutively. They showed restricted diffusion at the cingulate cortex, cerebral cortices, insula, and bilateral dorsomedial thalami on DWI. One patient underwent acute fulminant hepatitis A, the other patient with underlying chronic liver disease had acute liver failure due to hepatotoxicity of tuberculosis medication. In this report, we presented the characteristic features of DWI in acute hyperammonemic encephalopathy. In addition, we reviewed articles on MRI findings of acute hyperammonemic encephalopathy.

MeSH Terms

Ammonia
Cerebral Cortex
Diffusion
Gyrus Cinguli
Hepatic Encephalopathy
Hepatitis A
Humans
Hypoxia-Ischemia, Brain
Liver Diseases
Liver Failure, Acute
Magnetic Resonance Imaging
Neurotoxicity Syndromes
Plasma
Tuberculosis
Ammonia

Figure

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  Fig. 1 A 56-year-old male patient with underlying chronic liver disease and newly developed acute hyperammonemic encephalopathy due to tuberculosis medicine. Diffusion-weighted imaging (A, C) shows high signal intensities at both temporo-fronto-parieto-occipial cortices, insula (white solid arrows) (A), cingulate cortex (open arrows) (C) and dorsomedial thalami (dashed arrows) (A). It is confirmed to have reduced diffusion on apparent diffusion coefficient maps (B, D).

• 

  Fig. 2 A 47-year-old male patient with acute hyperammonemic encephalopathy due to acute hepatitis A. The diffusion-weighted imaging (A, C), apparent diffusion coefficient map (B, D) show diffusion restriction at insula (white solid arrows) (A), cingulate cortex (open arrows) (C), diffuse cerebral cortices, and bilateral dorsomedial thalami (dashed arrows) (A).

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