Lyme neuroborreliosis: An unusual case with extensive (peri)vasculitis of the middle cerebral artery

Lyme disease is a tick‐borne infection caused by Borrelia burgdorferi sensu latu. Neuroborreliosis is reported in approximately 10% of patients with Lyme disease. We report a patient with central nervous system (CNS) large vessel vasculitis, ischemic stroke, and tumefactive contrast‐enhancing brain lesions, an unusual complication of neuroborreliosis. A 56‐year‐old man presented with headache and disorientation for 1 month. Magnetic resonance imaging revealed basal meningitis with rapidly progressing frontotemporoinsular edema and (peri)vasculitis. Transcranial ultrasound confirmed stenosed medial cerebral arteries. [18F]GE‐180 microglia positron emission tomography (PET) showed frontotemporoinsular signal more pronounced on the right. [18F]FET amino acid PET demonstrated low tracer uptake, suggesting an inflammatory process. Cerebrospinal fluid (CSF) showed lymphomonocytosis (243/μl), intrathecal anti‐Borrelia IgM (CSF/serum index = 15.65, normal