Primary CNS vasculitis or primary angiitis of the CNS (PACNS) is a rare vascular inflammatory brain disease, often associated with variable neurological manifestations and a lengthy diagnostic evaluation. Secondary causes of CNS vasculitis and other inflammatory brain disorders must be excluded and a definite diagnosis relies on tissue biopsy. Some forms of PACNS can be rapidly progressive and life-threatening, further complicating the diagnostic and treatment process. 

Case report featuring clinical presentation, laboratory, pathology, and neuroimaging results, and discussion of diagnostic/treatment decision-making.

A 6-year-old previously healthy boy with intermittent headaches developed focal seizures and altered mentation. CSF had marked pleocytosis (WBC  139 cells/mm3) and elevated protein (299 mg/dL). MRI brain demonstrated multifocal areas of T2 hyperintense signal, restricted diffusion, and microhemorrhage involving the deep and superficial white matter of the right hemisphere. Despite maximal osmotic, sedative, and immune-directed therapies, he exhibited worsening cerebral edema and midline shift with persistently elevated intracranial pressures. He underwent decompressive hemicraniectomy and open brain biopsy showing perivascular lymphocytic cuffing and lymphocytes in the vessel walls, consistent with PACNS. He was treated with cyclophosphamide with gradual improvement in cerebral edema, and underwent cranioplasty four weeks after hemicraniectomy. His left hemiparesis improved significantly over one month in inpatient rehabilitation and he regained the ability to ambulate independently.

Our case demonstrates an unusual presentation of PACNS in a child given unilateral involvement and fulminant course.  Management of this child involved a multidisciplinary team of providers and complex diagnostic and therapeutic decision-making, ultimately resulting in a favorable outcome.