Clinical Summary

This 4 year old girl was brought to hospital in status epilepticus (lasting ~ 45 minutes), with the history of a prodromal febrile illness. During the prodromal illness, bloodwork and blood cultures performed elsewhere had been unremarkable, and she was prescribed amoxicillin. Her medical history was also notable for B cell non-Hodgkin lymphoma, diagnosed 6 months prior. She had completed chemotherapy approximately 3 months earlier, with no evidence of residual disease at that time.

 She was emergently managed and admitted to the PICU. CT imaging of the brain was normal. She was able to be extubated the following day, but within 48 hours showed significant neurologic deterioration with further seizure activity and a progressively worsening encephalopathy, with confusion, decreased level of consciousness, minimal words, and reduced right-sided movements. Initial pan-cultures and serology were negative. Initial CSF analysis was clear/colourless with 6 total nucleated cells (normal 0-5 10*6/L); and a normal glucose and total protein. CSF cytology was negative for malignancy.

 Initial MR imaging performed the day after admission showed focal areas of T2/T2 FLAIR hyperintensity and edema, with restricted diffusion in the cortex of the bilateral parieto-occipital and posterior temporal lobes. Repeat MRI showed evolving findings (see Images).

 A stereotactic biopsy of the left parietal region was performed.

Discussion points

1. What are the major histopathological findings?

2. What is the differential diagnosis?

3. What ancillary studies are recommended?