Development of intratumoral cyst or extratumoral XXXX in @entity932 following gamma knife radiosurgery.

@entity808 @entity1 @entity932 @entity41 @entity5 @entity16 @entity145 @entity2477
PURPOSE: Intracranial @entity808 presenting with cyst formation following gamma knife radiosurgery (GKRS) were investigated to clarify their clinicopathological characteristics. METHODS: Between 1994 and 2006, 492 @entity1 presenting with @entity932 underwent GKRS. Among them, seven cases demonstrated either new formation of cysts or enlargement of preexisting cysts, which were treated with microsurgical intervention. These cases were retrospectively reviewed with regard to neuroradiological findings and histopathology. RESULTS: These seven cases included five vestibular and two trigeminal @entity808 . Preexisting cysts were enlarged following GKRS in three cases, while they were newly formed in four cases. Salvage microsurgery was carried out at 7-167  months after the GKRS, and subtotal resection was achieved in three, partial resection with or without cyst fenestration in four. @entity16 were improved in all six symptomatic cases. Preoperative MRI demonstrated two characteristic types of cyst. One was the intratumoral type, indicating hemorrhagic change on the MRI. Histopathological analysis demonstrated a @entity2477 within the solid compartment of @entity5 . These two cases demonstrated @entity41 with new cyst formation after resection of only the cyst. The other type was extratumoral cyst, which had a structure with a thin cyst wall without contrast enhancement, and the cyst was composed of arachnoid cells without @entity5 cells. Extratumoral cysts enlarged despite effective control of the @entity5 itself, which may be caused by osmotic gradient induced by @entity5 following GKRS. CONCLUSIONS: There were two types of cysts, intratumoral cyst and extratumoral @entity145 , which developed following GKRS in @entity932 . Resection of the solid compartment as well as the cyst is required in @entity808 with expanding intratumoral cyst. Conversely, fenestration of the cyst alone might be effective in extratumoral @entity145 .
