Symptomatic Cerebellar Cyst Formation after Foramen Magnum Meningioma Removal: A Case Report

Background  Symptomatic cerebellar cyst formation after surgery is rare and the mechanism remains unknown. We describe a cerebellar cyst that gradually expanded, becoming symptomatic, after the removal of a foramen magnum meningioma and discuss the mechanism of cyst formation. Case Description  A 76-year-old woman with a tumor at the foramen magnum was treated by posterior fossa craniotomy and C1 hemilaminectomy. The patient suddenly developed cerebellar symptoms and consciousness disturbance approximately 1 week into an otherwise good postoperative course. Imaging showed a subcutaneous pseudomeningocele in the occipital region and cerebellar cyst formation. After resolution by fenestration of the cerebellar cyst and duraplasty, the patient's symptoms gradually improved. No tumor or cerebellar cyst recurrence has been detected in over 5 years since the surgery. Conclusion  Postoperative pseudomeningocele appeared crucial for cerebellar cyst formation. Postoperative development of symptomatic cerebellar cysts is rare but should be recognized as a serious, sometimes life-threatening, postoperative complication of posterior fossa surgery.