Abstract 169: A Case of Vile Vindictive Primary CNS Vasculitis
Authors: Baumann E. G. , Shaffer S. , Kendall T. , Diaz G. 
Published: January 2025

Primary Angiitis of the Central Nervous System (PACNS) is a rare cause of inflammation of the small and medium vessels of the brain, leptomeninges and spinal cord. It often masquerades as other pathologies, presenting diagnostic challenges. We present a case of PACNS, demonstrate these diagnostic challenges, and appreciate prognosis with and without treatment.

A 29‐year‐old male with no medical history presented with headaches, vertigo, dysarthria, and gait ataxia. Brain computed tomography (CT) demonstrated a hemorrhagic cerebellar lesion with mass effect, and brain magnetic resonance imaging (MRI) revealed numerous hemosiderin foci. Magnetic resonance angiogram (MRA) and cerebral angiography were non‐diagnostic. Workup for vasculitis, infectious, and inflammatory markers were unremarkable. Lumbar puncture was deferred because of the cerebellar bleed with mass effect. He improved with high‐dose steroids and was transitioned to an oral steroid taper. A few months later symptoms recurred, and a brain MRI revealed increased burden of small vessel infarcts and cerebellar hematoma resolution. Spinal fluid showed pleocytosis and elevated protein, but otherwise normal glucose with negative infectious and neoplastic workup. Repeat diagnostic angiography was negative for pathological vascular findings. A brain biopsy resulted in angiocentric lymphohistiocytic infiltrates, rare giant cells, non‐necrotizing granulomas, and perivascular inflammation, confirming PACNS. He was acutely treated and bridged to cyclophosphamide. After five years of controlled PACNS, self‐discontinuation of cyclophosphamide precipitated aphasia and right sided weakness consistent with a new left intracerebral hemorrhage. He was treated for active PACNS, discharged on a steroid bridge to mycophenolate, and eventually transitioned to rituximab. He is presently with near resolution of all deficits.

PACNS occurs in 2.4 cases per 1 million person‐years, disproportionately affecting males, and remains of unclear etiology.MRA and CTA may be valuable with medium vessel activity but are inadequate with distal small vessel involvement. Digital subtraction angiogram (DSA) sensitivity for PACNS varies and may also miss small vessel involvement. In this case, multiple advanced vessel imaging and cerebral angiograms showed no evidence of vasculitis. Spinal fluid studies may non‐specifically show mild pleocytosis or elevated protein, as occurred in this case. The utility of this finding in PACNS requires the exclusion of infectious and neoplastic mimics, which was ruled out in this patient.The definitive diagnosis of PACNS is made by brain biopsy, which can also be falsely negative, given the segmental nature of disease activity. In one systematic review, a brain biopsy was diagnostic in 71% of cases.Acutely, PACNS treatment involves high‐dose intravenous steroids and data is lacking regarding long‐term treatment. Anecdotally glucocorticoids or combination glucocorticoids and cyclophosphamide have shown benefit. Rituximab has been used as either a primary treatment or as second‐line in cyclophosphamide failure. This case highlights diagnostic challenges in PACNS and emphasizes the necessity of high clinical suspicion, given the non‐specific symptomatology, mimicking conditions, and imperfections in current diagnostic modalities. Further research is needed to improve diagnostic and treatment approaches since prognosis appears to be favorable with treatment. Without consistent treatment, as demonstrated in this case, PACNS can have a vile and vindictive course.