腦膜血管外皮細胞瘤是中樞神經系統內罕見的腫瘤之一，其發生機率小於一百分比。此腫瘤的特性是發展慢，但復發率高，且易於神經系軸內甚至遠處轉移。本案例因多次的腫瘤復發，故接受了兩次完整劑量之放射治療，間隔時間為五年，累積於腦部重疊的局部區域大於一百格雷。於第二次放射治療七個月後，病患發生進展式的神經症狀及顱內壓升高，經再次的外科手術後發現原因為腦細胞壞死，病理並且証實無任何腫瘤細胞。經手術後病患症狀減輕，至今仍存活。自第一次發現顱內腫瘤至今病患已存活了十四年。重複腦部放射治療，預期可能發生腦細胞壞死，但經文獻回顧後，吾人的結論為並非所有的病例經重複放射治療後一定發展成不可逆的神經症狀，若考慮可能延長病患的生命時，重複腦部的放射治療是有意義的。

Meningeal hemangiopericytoma is a rare tumor in central nervous system (CNS), consisting of less than one percent in incidence. It has distinctive characteristics of being slow in tumor progression and high in tumor recurrence. Unlike other CNS tumor, there exists also risk of neuroaxis and distant metastasis. Due to repeated recurrence, the presented case had received two full courses of irradiation to tumor bed with an interval of five years. The cumulative dose in the overlapped region of brain is greater than 100Gy, overt brain necrosis developed with progressive neurologic symptoms at seven months after second radiotherapy. After surgical decompression and removal of necrotic mass, the patient is still alive at present with improved neurologic symptoms. As a matter of fact, this patient has been alive for over 14 years since the first time that she found out about her brain tumor. After review of papers, we conclude that radiation induced brain necrosis may be expected in reirradiation, but not every case reirradiated results in brain necrosis with clinically severe neurologic deficit or mortality. If there is survival benefit and/or symptomatic improvement, reirradiation in the CNS may be considered in selected case.