Hyperammonemic encephalopathy: time course of MRI diffusion changes.

A 55-year-old man with cirrhosis presented with hyperammonemic encephalopathy, subsequently fatal (plasma ammonia level 410 M/L). Three-Tesla MRI initially showed restricted diffusion (figure 1A) in the cerebral cortex, suggesting poor prognosis,1 thalami, and striatum. Apparent diffusion coefficient pseudonormalized 8 days after admission (figure 1B), comparable to the evolution of hypoxic encephalopathy.2 T2 hyperintensity of the gray matter progressively increased (figure 2A). High glutamate plus glutamine without lactate was detected on day 2 in the right thalamus, while N-acetylaspartate progressively declined (figure 2B). These imaging findings illustrate the time course of hyperammonemic encephalopathy.