Nontraumatic acute subdural hematoma is rare, and no associations with the COVID-19 vaccine have been reported. This report presents the case of a 77-year-old woman who developed a nontraumatic acute subdural hematoma eight days after vaccination with the BNT162b2 COVID-19 vaccine. The patient regularly took 50 mg/day of clopidogrel and was diagnosed with severe acute subdural hematoma and brain herniation at admission. Although the BNT162b2 vaccine has not been determined as a risk factor, intracranial hemorrhage after its administration has been reported in Japan. Nontraumatic acute subdural hematoma may be included as an extremely rare adverse event of the BNT162b2 vaccine, but more data may be needed to confirm this.

Background: Movement disorders are rare in brain tumors. We describe a 45-year-old woman with hemichorea, a concomitant contralateral sphenoid ridge meningioma. Case Description: The meningioma enlarged as her hemichorea worsened, and after meningioma resection, the hemichorea gradually subsided. N-isopropyl-p-[123I]-iodoamphetamine single-photon emission computed tomography performed preoperatively showed decreased regional cerebral blood flow (CBF) to the basal ganglia circuit ipsilateral to the tumor and, when repeated postoperatively, confirmed improved regional CBF. Conclusion: We propose that the enlarging sphenoid ridge meningioma had a remote effect on regional CBF and the thalamocortical motor center and that complex changes in the basal ganglia output may have caused the hemichorea.