Intraventricular black fungal hyphal masses caused by Cladophialophora bantiana: illustrative case.

backgroundCNS fungal infections are rare, life-threatening conditions primarily affecting immunocompromised hosts. While they typically present as brain abscesses, intraventricular proliferation of fungal hyphae is exceedingly rare, and its neuroendoscopic findings have seldom been reported. OBSERVATIONS: A man in his 80s with a history of malignancies presented with a 1-month history of headache. Brain MRI showed contrast-enhancing lesions along the genu of corpus callosum and lateral ventricles, as well as a nonenhancing lesion protruding into the ventricles. Although these findings were atypical, an endoscopic biopsy was performed because the lesions showed a tendency to enlarge, raising suspicion of a malignant tumor. Neuroendoscopic examination revealed a black-pigmented intraventricular fungal mass, which was partially resected. Shotgun metagenomic analysis identified the pathogen as Cladophialophora bantiana. LESSONS: C. bantiana exhibits marked neurotropism and is known to cause CNS fungal infections even in immunocompetent individuals. Although intraventricular extension of phaeohyphomycosis is extremely rare and preoperative differential diagnosis remains challenging, a nonenhancing lesion protruding into the ventricles was considered to reflect the presence of fungal hyphae in this case. https://thejns.org/doi/10.3171/CASE26730.