Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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June 2, 2014
Hyperammonemic Encephalopathy
- Clinical Presentation: Lethargy, vomiting, irritability to seizures, coma, cerebral edema
- Causes: Acute hepatic dysfunction with secondary etiologies, including portosystemic shunt surgery, drugs (chemotherapy, sodium valproate), infection, hypothyroidism, multiple myeloma, or post-lung or bone marrow transplantation.
- Inborn errors of metabolism (eg, urea cycle disorders or organic acidemias) are the most common causes in the pediatric population.
- Key Diagnostic Features: Symmetric bilateral cortical injury with restricted diffusion and increased T2 and FLAIR signal, especially in the insular and cingulate cortices. Often appears with characteristic sparing of the perirolandic and medial occipital cortices as well as basal ganglia.
- It is postulated that more severe injury may involve the aforementioned spared regions in addition to the basal ganglia, thalami, subcortical white matter, and brainstem.
- Imaging findings and symptoms are potentially reversible with treatment, depending on severity and duration of hyperammonemia.
- DDx: Hypoxic ischemic encephalopathy, hypoglycemic encephalopathy, CJD, acute ictal episode
- Rx: Lactulose, or lactitol with addition of rifaximin if no improvement within 48 hours
