CNS Neoscytalidium dimidiatum: A Rare Cause of Fungal Brain Abscess.

Neoscytalidium dimidiatum is a dematiaceous fungus that primarily affects plants but can rarely act as an opportunistic pathogen in humans, particularly in immunocompromised patients. It typically causes superficial skin and nail infections in tropical regions; however, central nervous system (CNS) infections are extremely rare. The neurotropism of this fungus is not well understood, but hematogenous spread from cutaneous or pulmonary foci has been hypothesized. A 60-year-old male with chronic lymphocytic leukemia (CLL) treated with acalabrutinib, a second-generation Bruton's tyrosine kinase (BTK) inhibitor, presented with a 3-day history of personality changes, tension-type headache, and progressive right-sided weakness accompanied by dizziness. Physical examination revealed right hemiplegia and homonymous hemianopia. Brain MRI demonstrated a left parietal multiloculated ring-enhancing intra-axial lesion measuring 3.5 × 2 × 2.8 cm3, exerting mass effect on the ipsilateral lateral ventricle and causing rightward midline shift, with associated vasogenic edema and diffusion restriction. Given the immunocompromised state and atypical imaging findings, the patient underwent a left parietal stereotactic aspiration of the lesion. Histopathological examination using Grocott's methenamine silver (GMS) staining revealed numerous septate, branching hyphae within the brain parenchyma and vessel walls, confirming an angioinvasive fungal infection. Serum beta-D-glucan was markedly elevated at 238 pg/mL, while galactomannan was negative. Fungal culture confirmed Neoscytalidium dimidiatum, identified based on colony morphology, microscopic characteristics, arthroconidia formation, and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Dual antifungal therapy was initiated with intravenous liposomal amphotericin B and voriconazole, with subsequent dose escalation and route conversion. The patient was followed for ~12 months and survived with residual right-sided motor deficits. The present case underscores the importance of early diagnosis, prompt surgical management, and appropriate antifungal therapy in improving outcomes for patients with CNS Neoscytalidium dimidiatum infection, particularly in the context of hematological malignancy and BTK-inhibitor-associated immunosuppressive therapy.