Leptomeningeal form of Immunoglobulin G4-related hypertrophic meningitis with perivascular spread: a case report and review of the literature

Immunoglobulin G4 (IgG4)-related disease represents a spectrum of fibro-inflammatory disorders that affects various organ systems, including the central nervous system. Here we present the case of lgG4-related hypertrophic meningitis with exclusively leptomeningeal involvement and spread via perivascular spaces. A 58-year-old male patient presented with complex partial seizures. Initial computed tomography examination showed left frontal sulcal hyperdensity. Subsequent magnetic resonance examination revealed FLAIR hyperintensity in the central sulcus, with post-contrast enhancement in the form of dotted line. Physical examination, routine laboratory, and cerebrospinal fluid analyses were unremarkable. Meningeal biopsy confirmed IgG4-related meningitis. After corticosteroid treatment, a complete resolution of imaging findings was observed. Two months later, the patient presented with relapsing neurological symptoms and radiological findings in postcentral, precentral, and temporal sulci, resembling the form of dotted line contrast enhancement. In addition, linear intraparenchymal enhancement that followed perivascular spaces was seen in the left parietal lobe. After repeated steroid therapy, all lesions resolved completely. We reported the first case of isolated IgG4-related leptomeningeal involvement with a dotted line enhancement and perivascular intraparenchymal spread. Although IgG4-related meningitis represents a rare disease, both clinicians and radiologists should include this condition in the differential diagnosis of unclear leptomeningeal disease.