Department of Neurosurgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8574, Japan.
Acta Neurochir (Wien). 2011 Jun;153(6):1201-9. doi: 10.1007/s00701-011-0972-y. Epub 2011 Mar 3.
Intracranial schwannomas presenting with cyst formation following gamma knife radiosurgery (GKRS) were investigated to clarify their clinicopathological characteristics.
Between 1994 and 2006, 492 patients presenting with intracranial schwannomas 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.
These seven cases included five vestibular and two trigeminal schwannomas. 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. Neurological symptoms 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 cavernous angioma within the solid compartment of tumor. These two cases demonstrated enlargement of residual tumor 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 tumor cells. Extratumoral cysts enlarged despite effective control of the tumor itself, which may be caused by osmotic gradient induced by tumor degeneration following GKRS.
There were two types of cysts, intratumoral cyst and extratumoral arachnoid cyst, which developed following GKRS in intracranial schwannomas. Resection of the solid compartment as well as the cyst is required in schwannomas with expanding intratumoral cyst. Conversely, fenestration of the cyst alone might be effective in extratumoral arachnoid cysts.
研究伽玛刀放射外科（GKRS）后囊形成的颅内神经鞘瘤，以明确其临床病理特征。
1994 年至 2006 年间，492 例颅内神经鞘瘤患者接受 GKRS 治疗。其中，7 例出现新囊形成或原有囊扩大，行显微手术干预。回顾性分析这些患者的神经影像学表现和组织病理学特征。
这 7 例患者包括 5 例前庭神经鞘瘤和 2 例三叉神经鞘瘤。3 例患者的原有囊肿在 GKRS 后扩大，4 例患者新形成囊肿。GKRS 后 7-167 个月进行挽救性显微手术，3 例患者行次全切除，4 例患者行部分切除，囊肿开窗或不处理。所有 6 例有症状的患者神经症状均有改善。术前 MRI 显示两种特征性的囊肿类型。一种是瘤内型，MRI 上显示出血性改变。组织病理学分析显示实性肿瘤内有海绵状血管畸形。这两例患者在仅切除囊肿后，残留肿瘤增大并伴有新的囊肿形成。另一种是瘤外型囊肿，囊肿壁薄，无强化，结构类似于蛛网膜囊肿，囊内无肿瘤细胞。尽管肿瘤本身得到有效控制，但瘤外型囊肿仍会增大，这可能是 GKRS 后肿瘤变性导致的渗透压梯度引起的。
颅内神经鞘瘤 GKRS 后可形成两种类型的囊肿，即瘤内囊肿和瘤外型蛛网膜囊肿。对于瘤内囊肿扩大的神经鞘瘤，需要切除实性肿瘤和囊肿。相反，单纯囊肿开窗可能对瘤外型蛛网膜囊肿有效。
