Baló-Type Inflammatory Pseudotumoral Lesion Mimicking a Cerebral Metastasis: A Diagnostic Challenge

Baló's concentric sclerosis is a rare inflammatory demyelinating disorder characterized by concentric layers of demyelinated and relatively preserved myelin.Its clinical and radiological presentation may mimic an intracranial neoplasm, particularly when a solitary enhancing lesion is associated with diffusion restriction.We report the case of a 34-year-old woman who presented with acute right-sided motor symptoms involving the lower limb and fine movements of the right hand.Initial brain magnetic resonance imaging (MRI) revealed a solitary 15 mm left posterior frontal intra-axial lesion with T2/fluid-attenuated inversion recovery (FLAIR) hyperintensity, central T2 shine-through and peripheral diffusion restriction, intense contrast enhancement, and minimal surrounding edema.A metastatic lesion was initially considered the leading diagnosis.However, the patient experienced spontaneous clinical improvement without corticosteroid treatment.The lesion initially regressed in size and enhancement on serial MRI, with subsequent fluctuations in lesion size, while a new small left posterior subinsular lesion appeared during follow-up.Extensive oncological investigations, including thoracoabdominopelvic computed tomography, breast imaging, and dermatological examination, did not identify an underlying malignancy.Cerebrospinal fluid analysis demonstrated the presence of intrathecal oligoclonal bands.Subsequent MRI demonstrated a central vein within the initial left frontal lesion, providing an additional supportive, although nonspecific, feature of inflammatory demyelination.Retrospective MRI review also suggested a subtle, incompletely expressed concentric configuration, although the characteristic concentric-ring pattern was not clearly demonstrated.Although the clinical and radiological findings suggested an inflammatory demyelinating disorder within the multiple sclerosis spectrum, the diagnostic criteria for multiple sclerosis were not fulfilled because dissemination in space was not demonstrated.The final working diagnosis was a clinically isolated syndrome associated with a suspected Baló-type inflammatory pseudotumoral lesion, without histopathological confirmation.This case highlights the importance of serial imaging and multidisciplinary assessment when evaluating a solitary enhancing brain lesion in a young adult, particularly when spontaneous clinical and radiological improvement occurs.