Widespread subdural metastasis from breast cancer progressing rapidly with cerebral herniation: A case report.

We herein present the case of a 49-year-old female patient presenting with nausea and headache. The patient's medical history included breast cancer with bone and lymph node metastasis. Computed tomography (CT) examination revealed a high-density lesion in the right subdural space, suggesting hematoma. During surgery planned for subdural hematoma drainage, an en plaque subdural yellowish-white tumor was identified, without hematoma. Histopathological examination revealed metastatic breast cancer. The patient was administered predonisolone and her neurological symptoms gradually recovered. However, 12 days after the first operation, the clinical course was complicated by vomiting and rapid loss of consciousness. Emergency CT revealed that the subdural tumor had enlarged and decompression was performed as life-saving surgery. However, the patient's condition progressively deteriorated and she finally succumbed to the disease 2 months after the second operation. The aim of this study was to present the case of a patient with a large en plaque subdural tumor mimicking subdural hematoma and causing rapid loss of consciousness and cerebral herniation.