Stereotactic radiosurgery for isolated intracranial immunoglobulin G4 disease: An illustrative case

Background: Isolated intracranial immunoglobulin G4 (IgG4) disease, a rare subset of IgG4-related disease, is characterized by the infiltration of IgG4-positive plasma cells along the meninges of the central nervous system. It results in a spectrum of clinical manifestations that can mimic other intracranial pathologies and is often misdiagnosed. When neurological deficits are present, effective and appropriate therapy is imperative. However, the application of stereotactic radiosurgery with Gamma-Knife (SRS-GK) in symptomatic isolated intracranial IgG4 disease remains underexplored. Case Description: A 72-year-old male presented with left cranial nerve (CN) VI palsy. Imaging revealed an enhancing soft-tissue mass within the left cavernous sinus extending along the left tentorial free edge, initially suggestive of a tentorial meningioma. The patient underwent SRS-GK. At the 3-month follow-up, complete resolution of CN VI palsy was observed alongside significant radiological improvement. Subsequently, the identification of a meningeal lesion along the frontal convexity necessitated further intervention, leading to the histological confirmation of isolated intracranial IgG4 disease. Conclusion: This case underscores the diagnostic challenges and therapeutic nuances associated with managing isolated symptomatic intracranial IgG4 disease, emphasizing the potential role of SRS-GK in achieving favorable clinical outcomes in this complex neuroinflammatory disorder.