Huang Sui-Qiao, Liang Bi-Ling, Yuan Jian-Peng, Zhong Jing-Lian
Department of Radiology, The Second Affiliated Hospital, Sun Yet-sen University, Guangzhou, Guangdong, 510120, P. R. China.
Ai Zheng. 2006 Sep;25(9):1178-82.
BACKGROUND & OBJECTIVE: Cranial nerve schwannomas originate frequently in posterior cranial fossae and have various and complex MRI performances, some of which are still not well known. This study was to explore MRI performances and features of schwannomas from cranial nerves in posterior cranial fossae.
The MRI performances of 75 cases of schwannoma from cranial nerves in posterior cranial fossae, including trigeminal (n=9), facial (n=1), acoustic (n=53), 9th-11th (n=9) and hypoglossal (n=3) schwannomas, confirmed by surgical and pathologic findings, were analyzed retrospectively.
Most of schwannomas in posterior cranial fossae were solid-cystic lesions when their sizes were larger than 1.5 cm in diameter. Small lesions (less than 1.5 cm in diameter) may be completely solid, which were closely related to cranial nerves. On T1WI, the solid part of tumor appeared iso- or slightly hypointense, while cystic part was hypointense. On T2WI, solid part appeared high or slightly high signal intensity, but cystic part appeared very high signal intensity. On contrast-enhanced T1WI, there was obvious enhancement in the solid part, but not in the cystic part. Some typical signs were very useful to infer tumor origin, such as, dumbbell-shaped trigeminal schwannoma extended across the middle and posterior cranial fossa, enlargement of internal auditory canal, widened jugular foramen and hypoglossal foramen caused by acoustic schwannoma, the 9th-11th shcwannoma, and hypoglossal schwannoma, respectively. The correct ratio for qualitative diagnosis of schwannoma was 92% using MRI, but the incorrect ratio for identifying the nerve of tumor origin was 8.7%.
MRI is a good method in qualitative diagnosis of schwannoma and identifying cranial nerves of tumor origin in posterior cranial fossae.
颅神经鞘瘤常起源于后颅窝，具有多样且复杂的MRI表现，其中一些表现仍未被充分了解。本研究旨在探讨后颅窝颅神经鞘瘤的MRI表现及特征。
回顾性分析75例经手术及病理证实的后颅窝颅神经鞘瘤的MRI表现，包括三叉神经鞘瘤（9例）、面神经鞘瘤（1例）、听神经鞘瘤（53例）、第9 - 11对颅神经鞘瘤（9例）和舌下神经鞘瘤（3例）。
后颅窝大多数直径大于1.5 cm的神经鞘瘤为实性 - 囊性病变。小病变（直径小于1.5 cm）可能完全为实性，且与颅神经关系密切。在T1WI上，肿瘤实性部分呈等信号或稍低信号，囊性部分呈低信号。在T2WI上，实性部分呈高信号或稍高信号，而囊性部分呈极高信号。在增强T1WI上，实性部分有明显强化，囊性部分无强化。一些典型征象对推断肿瘤起源非常有用，如哑铃形三叉神经鞘瘤跨越中后颅窝，听神经鞘瘤、第9 - 11对颅神经鞘瘤和舌下神经鞘瘤分别导致内耳道扩大、颈静脉孔增宽和舌下神经孔增宽。MRI对神经鞘瘤定性诊断的正确比例为92%，但在确定肿瘤起源神经方面的错误比例为8.7%。
MRI是后颅窝神经鞘瘤定性诊断及确定肿瘤起源颅神经的良好方法。
