• Naoto Kuroda, Chikanori Inenaga, Yoshifumi Arai, Yoshiro Otsuki, and Tokutaro Tanaka.
• Department of Neurosurgery, Seirei Hamamatsu General Hospital, Hamamatsu, Shizuoka, Japan. Electronic address: h20ms-kuroda@jikei.ac.jp.
• World Neurosurg. 2019 Dec 1; 132: 69-74.

BackgroundImmunoglobulin (Ig)G4-related disease (IgG4-RD) was defined only recently and can be found in many organs. As intracranial lesions, hypophysitis and pachymeningitis are well known, whereas intracranial pseudotumor is unusual. This case involved multiple intracranial pseudotumors without extracranial lesions, mimicking multiple meningioma.Case DescriptionA 72-year-old woman was referred to our hospital with an incidental mass lesion at the craniocervical junction on magnetic resonance imaging (MRI). MRI showed diffuse enhanced extra-axial nodules around the medulla and middle cranial fossa. Surgery was performed for the gradually enlarging tumor. Intraoperative findings showed hard nodules around the vertebral artery. We performed subtotal resection. Neuropathological findings showed diffuse lymphoplasmacytic infiltration with lymphoid follicles. Immunohistochemical studies for IgG4 and IgG showed the histological criteria for IgG4-RD were met. Given the high IgG4 serum level, we diagnosed IgG4-RD. Steroid was administered initially but was then tapered, and nodules have since remained small.ConclusionsThis case demonstrates IgG4-RD mimicking meningioma with multiple masses but without extracranial lesions. This case and previous descriptions suggest the possibility of pseudotumor due to IgG4-RD in the presence of multiple extra-axial lesions at the dura and supplying artery, hard nodules with thickening of the artery, and frozen section findings of lymphoplasmacytes surrounded by rich collagen fibers. In such cases, the pseudotumor due to IgG4-RD should be resected, and total resection might not be warranted.Copyright © 2019 Elsevier Inc. All rights reserved.

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