Hyperammonemia is a well-known cause of encephalopathy, the rarity of focal neurologic manifestations may delay timely diagnosis. We describe three cancer patients hospitalized for various reasons who developed severe hyperammonemic encephalopathy.

Case 1

A 20-year-old woman with leukemia admitted for cellulitis developed super-refractory status epilepticus requiring ICU admission on hospital day eight. Initial head CT was unremarkable. Laboratory data were notable for hyperammonemia (276µmol/L) which increased to 348µmol/L after 24h, after which she was started on lactulose followed by rifaximin with little efficacy. After four days in ICU, she stopped breathing spontaneously. Head CT demonstrated tonsillar herniation, neurologic exam was consistent with brain death and care was withdrawn.

Case 2

A 41-year-old woman with metastatic colorectal cancer underwent resection of liver metastases and post-operatively went into shock associated with encephalopathy and rhythmic right head turning. Ammonia was 136µmol/L. Two days later, she required intubation.  Lactulose was trialed but discontinued due to high colostomy output and worsening hemodynamic status. Head CT six days after surgery showed diffuse cerebral edema with tonsillar herniation. Neurologic exam was consistent with brain death, and care was withdrawn.  

Case 3

A 19-year-old woman was admitted with fulminant liver failure due to leukemic involvement and required intubation on the second hospital day. Ammonia was 125µmol/L. MRI brain demonstrated restricted diffusion in bilateral basal ganglia, thalami, and corpus callosum. After four plasma exchanges she began following commands; ammonia was 53µmol/L.  She was eventually discharged home. A follow-up MRI two weeks later was normal.

Our experience highlights that hyperammonemia should always be considered as a potential cause of acutely progressive encephalopathy attended by focal neurologic signs, and if confirmed should be aggressively treated to forestall decline.