Symptomatic Remote Cyst after BCNU Wafer Implantation for Malignant Glioma

A 43-year-old man was operated on for right frontal oligoastrocytoma. 14 years after the surgery, magnetic resonance imaging and positron emission tomography revealed a new lesion near the surgical cavity. He underwent gross total resection of the lesion and implantation of bis-chloroethylnitrosourea (BCNU) wafers after intraoperative pathological diagnosis of recurrent high-grade glioma. A few days after the operation, the level of consciousness gradually worsened and left hemiparesis developed. A computed tomography scan revealed a cyst remote to the surgical cavity which did not exist 3 days prior. We performed anterior cyst wall fenestration and removed all wafers. The characteristic pathological finding at the wafer implantation site was severe inflammation within and around small vessels. This inflammatory reaction was not seen on the surface of the brain parenchyma. After surgery and rehabilitation, the patient's Karnofsky Performance Status stabilized to a pre-incident score of 90 and he returned to work. The exact pathophysiological mechanism of the cyst was not clear, but check-valve and/or osmotic gradient mechanisms related to BCNU wafer implantation could have contributed to this phenomenon. As remote cyst development happened a week after surgery, surgeons should be aware of such a rare condition when implanting wafers as consciousness impairment and hemiparesis may occur. Close radiological follow-up is therefore necessary.