Cytotoxic Lesions of the Corpus Callosum: A Single-Center Case Series of Eight Patients With an Emphasis on Infectious Etiologies.

Background and aim Cytotoxic lesions of the corpus callosum (CLOCCs) are transient lesions characterized by restricted diffusion on MRI and are associated with various infectious and noninfectious conditions. However, the clinical spectrum of infection-related CLOCCs, particularly those associated with bacterial infections, remains incompletely defined. This study aimed to describe the clinical, etiological, and neuroimaging characteristics of CLOCCs diagnosed at a single center, encompassing both infectious and noninfectious etiologies, with particular attention to infection-related cases. Methods We retrospectively reviewed patients diagnosed with CLOCCs at Jichi Medical University Saitama Medical Center between January 2016 and May 2025. Patients were identified by searching institutional radiology reports and electronic medical records for callosal lesions, followed by review of the corresponding records. Clinical characteristics, underlying etiologies, laboratory findings, MRI features, treatment, follow-up imaging, and clinical outcomes were extracted from medical records. Results Eight patients were identified (median age, 47.5 years; range, 12-70; five male and three female). Five patients had infection-related CLOCCs, including bacteremia, meningoencephalitis, and COVID-19-associated myocarditis. One patient had Fusobacterium nucleatum bacteremia, which, to the best of our knowledge, has not been well documented in association with CLOCCs. In all eight patients, the lesion was confined to the splenium of the corpus callosum. All patients showed hyperintensity on diffusion-weighted imaging, and six showed corresponding hypointensity on apparent diffusion coefficient maps. Follow-up MRI was available in seven patients (performed at a median of 17 days; range, 14-50 days); six showed complete resolution, whereas one showed near-complete resolution with faint residual fluid-attenuated inversion recovery hyperintensity. Seven patients improved clinically; one patient died during hospitalization from infection-related complications unrelated to the corpus callosum lesion, which had already resolved on follow-up MRI. Conclusions In this single-center case series, infection-related etiologies accounted for most of the cases. The association with F. nucleatum bacteremia, based on a single case, represents a possible rather than established addition to the bacterial infections reported in CLOCCs and should be regarded as hypothesis-generating. Early recognition of the characteristic MRI findings, evaluation for underlying infectious causes, and treatment directed at the underlying condition may support favorable clinical and radiological outcomes.