RESIDENT & FELLOW SECTION Teaching NeuroImage: Unilateral Primary Angiitis of the CNS Samir Alkabie, MD, Madison T. Gray, MD, Jonathan C. Lau, MD, Lillian Barra, MD, Jennifer Mandzia, MD, Qi Zhang, MBBS, and Adrian Budhram, MD ® Neurology 2024;102:e208018. doi:10.1212/WNL.0000000000208018 Correspondence Dr. Budhram adrian.budhram@lhsc.on.ca Downloaded from https://www.neurology.org by 138.199.53.243 on 18 April 2024 Figure 1 Imaging Findings in Unilateral PACNS MORE ONLINE Prebiopsy brain MRI shows left hemispheric T2-FLAIR hyperintensity (A) with microhemorrhage (B, circle). Brain MRI 7 years prior also shows left hemispheric T2-FLAIR hyperintensity (C), reflecting long-standing disease. Patchy enhancement is seen (D, arrows). No diffusion restriction is seen (E), but a left cerebellar infarct is identified (F, arrow). FLAIR = fluid-attenuated inversion recovery; PACNS = primary angiitis of the CNS. For multiple-choice questions relevant to Teaching NeuroImages and Teaching Video NeuroImages, find @greenjournal on Twitter using the hashtag #NeurologyRF From the Departments of Clinical Neurological Sciences (S.A., J.C.L., J.M., Q.Z., A.B.) and Pathology and Laboratory Medicine (M.T.G., Q.Z., A.B.), Western University, London Health Sciences Centre; and Division of Rheumatology, Department of Medicine (L.B.), Western University, St. Joseph’s Health Care, London, Ontario, Canada. Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article. Copyright © 2023 American Academy of Neurology Copyright © 2023 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. 1 A 48-year-old woman was referred with an 18-year history of focal-onset seizures. She also reported years-long slowly progressive right-sided weakness that was corroborated on examination. Repeated brain MRIs over 15 years showed multifocal left hemispheric T2 fluid-attenuated inversion recovery-hyperintense lesions with patchy enhancement and microhemorrhages, no diffusion restriction, and a left cerebellar infarct (Figure 1, A–F). Only 2 nonspecific white matter lesions were seen contralaterally, indicating largely unihemispheric disease. Differential diagnosis included unilateral primary angiitis of the CNS (PACNS), Rasmussen encephalitis, and myelin oligodendrocyte glycoprotein antibody–associated disease.1 Serum and CSF testing for autoimmune, infectious, and malignant etiologies and whole-body fluorodeoxyglucose-PET, whole-exome genetic sequencing, and MR vessel-wall imaging were nondiagnostic. Brain biopsy revealed vasculitis (Figure 2, A–F), and the patient was diagnosed with unilateral PACNS. Treatment with mycophenolate mofetil has been initiated. Unilateral PACNS is a rare unihemispheric disease characterized by an indolent course and seizures, recognition of which is critical to accurate diagnosis.1,2 Contributions S. Alkabie: drafting/revision of the manuscript for content, including medical writing for content; major role in the acquisition of data; study concept or design; analysis or interpretation of data. M.T. Gray: drafting/revision of the manuscript for content, including medical writing for content; major role in the acquisition of data; study concept or design; analysis or interpretation of data. J.C. Lau: drafting/revision of the manuscript for content, including medical writing for content; major role in the acquisition of data; analysis or interpretation of data. L. Barra: drafting/revision of the Downloaded from https://www.neurology.org by 138.199.53.243 on 18 April 2024 Figure 2 Pathologic Findings in Unilateral PACNS Micrograph of a single white matter vessel (A) demonstrates intramural fibrinoid necrosis with perivascular haemorrhage and transmural inflammation mediated by CD4 (B) and CD8 (C) T-lymphocytes and CD68-positive histiocytes (D and inset A, arrow). Luxol fast blue/H&E (E) and neurofilament (F) staining show loss of myelinated axons and vascular thrombosis (E, arrow). Image magnifications: 10× (A–D) and 20× (E and F). PACNS = primary angiitis of the CNS. 2 Neurology | Volume 102, Number 1 | January 9, 2024 Neurology.org/N Copyright © 2023 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. manuscript for content, including medical writing for content; analysis or interpretation of data. J. Mandzia: drafting/revision of the manuscript for content, including medical writing for content; analysis or interpretation of data. Q. Zhang: drafting/ revision of the manuscript for content, including medical writing for content; major role in the acquisition of data; analysis or interpretation of data. A. Budhram: drafting/revision of the manuscript for content, including medical writing for content; major role in the acquisition of data; study concept or design; analysis or interpretation of data. Study Funding The authors report no targeted funding. Disclosure S. Alkabie, M. Gray, J. Lau, L. Barra, J. Mandzia, and Q. Zhang report no disclosures relevant to the manuscript; A. Budhram holds the London Health Sciences Centre and London Health Sciences Foundation Chair in Neural Antibody Testing for Neuro-Inflammatory Diseases, and receives support from the Opportunities Fund of the Academic Health Sciences Centre Alternative Funding Plan of the Academic Medical Organization of Southwestern Ontario (AMOSO). Publication History Received by Neurology July 26, 2023. Accepted in final form September 27, 2023. Submitted and externally peer reviewed. The handling editor was Resident & Fellow Section Editor Whitley Aamodt, MD, MPH. References 1. 2. AbdelRazek MA, Hillis JM, Guo Y, et al. Unilateral relapsing primary angiitis of the CNS: an entity suggesting differences in the immune response between the cerebral hemispheres. Neurol Neuroimmunol Neuroinflamm. 2021;8(2):e936. Santyr B, Pejhan S, Zhang Q, Budhram A. Unilateral primary angiitis of the central nervous system. Ann Neurol. 2021;90:999-1000. 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