Spontaneous Development of Encapsulated Subdural Hematoma in the Posterior Cranial Fossa after Cardiac Surgery: A Case Report.

We report a case of an encapsulated subdural hematoma in the posterior cranial fossa, showing spontaneous development and rapid increase in size after cardiac surgery. An 86-year-old woman underwent aortic valve replacement for aortic valve stenosis, followed by anticoagulant therapy with heparin. Three days after the cardiac surgery, she complained of headache. Computed tomography revealed development of a subdural hematoma in the posterior cranial fossa. The hematoma rapidly increased in size within 7 days. Eleven days after cardiac surgery, she underwent removal of the subdural hematoma by craniotomy. Intraoperatively, the subdural hematoma was covered by a thick granulomatous capsule, with histopathological findings similar to those of a chronic subdural hematoma. She was discharged 2 weeks after the craniotomy without any neurological deficits. Encapsulated subdural hematoma in the posterior cranial fossa is rare and its etiology is unknown. In this case, postoperative anticoagulant therapy can promote the rapid growth of thick hematoma capsule. It is possible that previously reported cases of "posterior fossa chronic subdural hematoma" contain similar lesions to that in our patient.