Open brain biopsy for nonneoplastic undiagnosed neurological conditions: diagnostic yield, clinical impact, and contemporary role

BACKGROUND: Open cranial biopsy is reserved for patients with progressive nonneoplastic neurological conditions of unknown etiology who have failed exhaustive noninvasive evaluation, raising questions regarding its diagnostic yield, clinical utility, and risk profile. AIMS: To characterize the diagnostic yield, treatment impact, and procedural risk of open cranial biopsy in a contemporary cohort of diagnostically refractory patients with nonneoplastic neurological conditions. METHODS: We performed a single-institution retrospective cohort study of patients undergoing open cranial biopsy for nonneoplastic undiagnosed neurological conditions (August 2016-July 2021). Primary outcomes were diagnostic yield, treatment alteration, and complication rate, reported with exact binomial 95% confidence intervals. RESULTS: Twenty-one patients (mean age, 54.3 years; 52% male) met the inclusion criteria. The definitive diagnostic yield was 23.8% (5/21; 95% CI 8.2%-47.2%); including suggestive findings, the informative yield was 52.4% (11/21; 95% CI 29.8%-74.3%). Treatment alteration occurred in 23.8% (5/21; 95% CI 8.2%-47.2%), including cases with nondiagnostic or suggestive results. The most common diagnoses were vasculitis and cerebral amyloid angiopathy. Three patients (14.3%; 95% CI 3.0%-36.3%) experienced fatal biopsy-attributable complications, all in patients with advanced comorbidity. No significant differences were observed between targeted and non-targeted approaches. CONCLUSIONS: Open cranial biopsy demonstrates limited definitive diagnostic yield but meaningful clinical impact in a subset of patients, highlighting a disconnect between histopathological diagnosis and therapeutic decision-making. Complication rates reflect patient severity rather than procedural risk. Careful multidisciplinary patient selection and preference for targeted biopsy when feasible are essential.