Solitary thalamic abscess without meningitis from Coccidioides immitis: illustrative case.

backgroundDespite decreased mortality over the past several decades, the prognosis of brain abscesses remains dependent on intracranial location and causative organism. Deep-seated brain abscesses carry a risk of intraventricular rupture, an event with reported mortality near 80%. Coccidioidomycosis from the fungus Coccidioides immitis, endemic to the American Southwest, is growing in incidence but uncommonly produces deep brain abscesses, making management unclear.The authors report the diagnosis and management of a solitary thalamic Coccidioides abscess without meningitis. OBSERVATIONS: A 59-year-old female presented with 1 week of gait instability, left facial weakness, dysarthria, and intermittent headache, but no meningismus. Cranial imaging was consistent with abscess or, less likely, a neoplasm, and a stereotactic brain biopsy was pursued. Despite negative fungal cultures and lack of serum antibody detection, findings of pathognomonic spherules in pathology tissue with confirmatory polymerase chain reaction testing helped diagnose coccidioidomycosis. The patient's symptoms resolved 3 weeks postoperatively with a dexamethasone taper and, due to relapse risk, planned lifelong fluconazole therapy. The patient self-discontinued fluconazole at 11 months postoperatively but remained disease free at 1 year. LESSONS: C. immitis can present as solitary brain abscesses despite negative fungal cultures. Postoperative dexamethasone and long-term fluconazole can clear the pathogen and suppress recurrence. https://thejns.org/doi/10.3171/CASE25381.