As per electronic medical records, previously healthy our patient was referred to specialized neurology services from an outside institution for assessment of a tumefactive brain lesion. She reported 4 episodes of speech disturbances lasting seconds, happened few months apart, and right sided numbness lasting for around 20 minutes. No history of neurological disorder. No constitutional symptoms. Her physical exam was noncontributory. 

Though her symptoms were not recurrent, follow-up images demonstrated persistent fronto-parietal left hemispheric ill-defined lesions with additional lesions in the right occipital lobe, left caudate, external capsule, thalamus, and periventricular white matter of the temporal horn. A whole body PET/CT scan was performed (not shown) which excluded a lymphoproliferative disorder such as lymphoma or other systemic process: no distinct dominant FDG foci compared to normal brain parenchyma nor evidence of systemic lymphadenopathy to suggest aggressive lymphoma.

She underwent a stereotactic needle biopsy for tissue analysis.

Her histopathology exam revealed findings consistent with an acute leukocytoclastic CNS vasculitis with abundant eosinophils.

Findings of a vasculitis were also supported by an abnormal CSF analysis consistent of elevated CSF proteins (0.54 for a normal range of 0.15-0.45), increased IgG synthesis (IgG index 1.28 for a normal range of 0.34-0.66; IgG synthesis rate of 27.4 for normal value of < 4.0), and normal CSF glucose 3.2 (normal range 2.5-4.4).

MRV and MRA (not shown) showed no acute abnormality. Our patient did not undergo a cerebral angiogram prior to her biopsy.

Acknowledgments to Dr. Lam, S. for the radiological images and to Dr. Karamchandani, J. for contributing with the microscopic images.