Cerebral microbleeds after whole brain radiation therapy in medulloblastoma patients

BACKGROUND: Radiation therapy is part of the standard treatment for medulloblastoma patients. The pattern and incidence of neurovascular toxicities, such as cerebral microbleeds (CMBs) following whole brain radiation therapy (WBRT) is poorly characterized in long-term survivors. The aim of this study is to determine the temporal and spatial pattern of CMBs after WBRT in medulloblastoma patients. METHODS: We retrospectively identified medulloblastoma patients treated with WBRT at the Massachusetts General Hospital between 1999 and 2014. Longitudinal magnetic resonance imaging data was reviewed, and the incidence, prevalence and spatial pattern of CMBs were characterized over time. RESULTS: We identified 27 patients previously treated with WBRT for medulloblastoma and who had complete longitudinal imaging datasets available for review, including GRE, T1 and T2 imaging sequences. CMBs were found in >65% (18/27) of patients when followed for a median time of at least 4 years. Incidence of CMBs was increasing with each year from time of WBRT, and was more likely in patients treated at age of <20 years (100% incidence). CMBs were mostly found in lobar distribution and predominately in occipital and temporal lobes. Antithrombotic use and hypertension were associated with a significantly higher incidence of CMBs (p=0.041). CONCLUSIONS: Our data demonstrate a surprisingly high prevalence of CMBs following WBRT, increasing with each year from time of WBRT. Strikingly, the spatial distribution of CMBs was similar to a pattern seen in patients with cerebral amyloid angiopathy. Use of antithrombotic therapy appears to accelerate the rate of CMBs and may represent an independent risk factor for long-term neurovascular injury.