title: Two cases of cystic enlargement of vestibular schwannoma as a late complication following gamma knife surgery.
abstract: Cyst formation is the most common long-term complication after gamma knife surgery (GKS) for cerebral arteriovenous malformations; however, this rarely occurs after GKS for vestibular schwannoma (VS). We describe two patients that developed aggressive, symptomatic large cysts at more than 4 and 12years after GKS for VS, although the tumor control for these patients had been acceptable at 3 and 11years, respectively. During the surgery, a reddish lesion, which was distinct from the surrounding tumor, was observed. The microscopic examination of the reddish lesion revealed dilated capillary vessels and hemorrhage, which was compatible with late radiation changes; these were usually seen in arteriovenous malformations following radiosurgery. The present patients indicated that cyst formation and enlargement may occur as a late complication following GKS even in extra-axial benign tumors such as VS.
authors.affiliation: Department of Neurosurgery, Yokohama Rosai Hospital, 3211 Kozukue-cho, Kouhoku-ku, Yokohama, Kanagawa 222-0036, Japan. Electronic address: shuto@yokohamah.johas.go.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Shuto
authors.affiliation: Department of Neurosurgery, Yokohama Rosai Hospital, 3211 Kozukue-cho, Kouhoku-ku, Yokohama, Kanagawa 222-0036, Japan.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Matsunaga
mesh_terms: D000328:Adult; D000368:Aged; D003560:Cysts / Q000150:complications* / Q000473:pathology; D005260:Female; D006801:Humans; D006984:Hypertrophy / Q000150:complications; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000150:complications* / Q000601:surgery*; D011183:Postoperative Complications / Q000473:pathology*; D016634:Radiosurgery / Q000009:adverse effects*
keywords: Arteriovenous malformations; Cyst; Gamma knife; Radiosurgery; Vestibular schwannoma