Reversible dementia associated with communicating hydrocephalus secondary to spinal hypertrophic pachymeningitis in ANCA-associated vasculitis

Microscopic polyangiitis (MPA) is a subtype of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), a small-vessel vasculitis that can cause organ-threatening complications. Hypertrophic pachymeningitis is a rare, central nervous system manifestation of AAV rarely involving the spine. We herein report a patient with myeloperoxidase (MPO)-ANCA-positive MPA presenting with progressive cognitive decline and gait disturbance associated with communicating hydrocephalus secondary to spinal hypertrophic pachymeningitis. The patient responded well to high-dose prednisolone and rituximab and showed significant clinical and radiological improvement without surgery. The present case not only demonstrated that spinal hypertrophic pachymeningitis in AAV can cause reversible dementia associated with communicating hydrocephalus but also highlighted the potential of timely immunosuppressive therapy to induce remission.