Organized Chronic Subdural Hematoma (OCSDH) Mimicking Meningioma.

Organized chronic subdural hematoma (OCSDH) is a relatively rare condition that forms over a longer period of time compared to chronic subdural hematoma and is sometimes difficult to diagnose with preoperative imaging. We resected an intracranial lesion in a 37-year-old Japanese man; the lesion had been increasing in size for >17 years. The preoperative diagnosis based on imaging findings was meningioma; however, pathological findings revealed OCSDH. Clinicians should be aware that OCSDH mimics other tumors and consider surgical strategies for this disease.