Proposed mechanism for cyst formation and enlargement following Gamma Knife Surgery for arteriovenous malformations

Abstract

Object The authors retrospectively studied the mechanism of cyst formation and enlargement after Gamma Knife surgery (GKS) for arteriovenous malformations (AVMs). Methods Eighteen patients in whom cyst formation developed following GKS for AVM were retrospectively identified among 775 patients who underwent GKS for AVM at Yokohama Rosai Hospital. The study group was composed of 12 male and 6 female patients ranging in age from 17 to 47 years. Results Chronic encapsulated expanding hematoma was associated with the cyst in 5 patients. The AVM nidus volume at the time of GKS ranged from 1.9 to 36 cm3, and the prescription radiation dose was 18–25 Gy. Complete obliteration of the AVM nidus was obtained in 13 patients and partial obliteration in 5 patients. Cyst formation was detected between 2.6 and 15 years after GKS. Craniotomy was performed in 10 patients, including 2 patients in whom the incompletely obliterated nidus was removed at the same time, and an Ommaya reservoir was placed in 2 patients. Spontaneous regression of the cyst was observed in 1 patient. Serial MR imaging was performed in the other patients because the size of the cyst was stable or the lesion was asymptomatic. Histological examination of the cyst wall revealed linear hemosiderin deposits with gliosis. The nodular lesion, which was enhanced on MR images, contained granulation tissue with chronic hemorrhage from newly developed capillary vessels. Conclusions Cysts developing after GKS for AVM enlarge mainly due to repeated minor hemorrhages from a reddish nodular angiomatous lesion that develops within an adjacent brain area. Thus, the optimal treatment is wide opening of the cyst with removal of the associated angiomatous lesion by craniotomy.

Cerebral cyst formation following stereotactic ablative irradiation for non-nasopharyngeal head and neck malignancies: imaging findings and relevant dosimetric parameters

“…Pathological examinations revealed no viable tumour tissue and otherwise similar findings to the reported cases of CCF: 9,11 pseudocyst, non-epithelium-lined cyst, surrounded by congestive brain tissue associated with subacute and chronic haemorrhage, hyalinization of vessels, gliosis and perivascular lymphocyte infiltration, 9,11 whereas no hypervascular/angiomatous lesion attributable to repetitive haemorrhage was identified. 9 These patients recovered well after surgery. All patients retained no evidence of viable disease in and near the irradiated site and were alive with generally favourable performance status at the last follow-up visit ( Table 1).…”

“…The number of reports on CCF cases from various types of primary pathology have been increasing, whilst the aetiopathogenesis of CCF remains to be elucidated. 9,10 Repetitive haemorrhage from an abnormal angiomatous lesion located within or underlying the cyst wall was suggested as a plausible mechanism for cyst enlargement in AVM cases. 9 The CCF in the present cases appeared more than 2-7 years after SRT, and are plausibly derived from a part or the entirety of pre-existing parenchymal injury rather than degenerative change of the necrotic tumour.…”

“…[1][2][3] Brain radiation necrosis is one of the important untoward sequelae after radiotherapy, including SRT for HNM, especially nasopharyngeal carcinoma (NPC), with imaging findings being characterized by central loss of enhancement surrounded by feathery or reticular enhancement associated with perilesional oedema. [4][5][6][7] Cerebral cyst formation (CCF) is an unusual subset of radiation-induced brain injury and is usually encountered in cases harbouring intracranial disorders embedded in the parenchyma, such as arteriovenous malformation (AVM) 8,9 or brain metastases, 10,11 and rarely extra-axial tumours, such as meningioma 12 and neuroma, 13 treated with stereotactic radiosurgery (SRS). CCF might also occur as a rare consequence of brain injury following definitive radiotherapy for NPC.…”

Late complications of radiosurgery for cerebral arteriovenous malformations: report of 5 cases of chronic encapsulated intracerebral hematomas and review of the literature.

“…weighted images there existed usually nodular or multinodular enhancement (Table 1). CEIHs were associated with cyst in 62,1% of cases pointing to a possible common pathophysiologic mechanism 3 . The latency time from radiosurgery to CEIHs diagnosis was 7,7 years sd 3,7 years.…”

Radiation-associated Tumors in the Central Nervous System and the Head and Neck: What Radiologists Should Know

“…Another imaging finding is cyst formation. 70 Cerebral cyst formation is usually reported as a complication after stereotactic radiosurgery for arteriovenous malformation. Recently, cyst formation in the brain was reported after stereotactic RT for a head and neck tumor (Fig 10).…”