Abstract
A 66-year-old man presented to our emergency department with acute consciousness disorder, headache, and fever. Initial laboratory data indicated a high level of inflammatory reaction. Enhanced magnetic resonance imaging revealed a thickening of the right cranial dura mater on T1-weighted images. We presumed the patient was diagnosed as having myeloperoxidase antineutrophil cytoplasmic antibody (MPO-ANCA)-related hypertrophic pachymeningitis (HP). Acute impaired consciousness without focal signs is an unusual presentation of HP. This treatable disease should be considered as a differential diagnosis when a patient presents with drowsiness and headache.