Okamoto K, Furusawa T, Ishikawa K, Sasai K, Tokiguchi S
Center for Integrated Human Brain Science, Brain Research Institute, Niigata University, 1-757 Asahimachi-dori, Niigata 951-8585, Japan.
AJNR Am J Neuroradiol. 2006 Jun-Jul;27(6):1307-11.
The vestibular nucleus cannot be visualized on MR imaging, but some patients with vestibular schwannoma show a tiny area of hyperintensity in the dorsal brain stem on T2-weighted images. The aim of this study was to determine whether this tiny area is characteristic of vestibular schwannoma.
We retrospectively reviewed the postoperative MR images of 53 patients with cerebellopontine angle tumor. MR images were obtained with a 1.5T scanner. Spin-echo pre- and postcontrast 3-mm-thick T1-weighted axial images, 3-mm-thick fast spin-echo (FSE) T2-weighted axial images, and 0.8-mm-thick constructive interference in steady state (CISS) axial images were acquired. Surgical and histopathologic diagnosis was vestibular schwannoma (41/53 = 77%), meningioma (7/53 = 13%), epidermoid cyst (3/53 = 6%), glioma with exophytic growth (1/53 = 2%), and chordoma (1/53 = 2%).
A tiny area of hyperintensity was observed at the lateral angle of the fourth ventricle floor in 6 patients (3 men, 3 women; age range, 24-54 years; mean age, 43 years) with vestibular schwannoma larger than 2 cm in maximal diameter on both FSE T2-weighted and CISS images. Preoperative MR images with the same pulse sequences showed the same area of hyperintensity in all these patients.
Because the location of the area of hyperintensity is coincident with the vestibular nucleus, the hyperintensity may represent degeneration of the nucleus. This hyperintensity should not be confused with a postoperative lesion or a small infarction. If such hyperintensity is seen in a patient with a large cerebellopontine angle tumor, a diagnosis of vestibular schwannoma is suggested.
前庭神经核在磁共振成像（MR）上不可见，但一些前庭神经鞘瘤患者在T2加权图像上脑干背侧显示有一小片高信号区。本研究的目的是确定这一小片区域是否为前庭神经鞘瘤的特征表现。
我们回顾性分析了53例桥小脑角肿瘤患者的术后MR图像。MR图像由1.5T扫描仪获取。采集了自旋回波序列增强前后的3毫米厚T1加权轴位图像、3毫米厚快速自旋回波（FSE）T2加权轴位图像以及0.8毫米厚稳态构成干扰序列（CISS）轴位图像。手术及组织病理学诊断结果为前庭神经鞘瘤（41/53 = 77%）、脑膜瘤（7/53 = 13%）、表皮样囊肿（3/53 = 6%）、外生性生长的胶质瘤（1/53 = 2%）和弦瘤（1/53 = 2%）。
在6例（3男3女；年龄范围24 - 54岁；平均年龄43岁）最大直径大于2厘米的前庭神经鞘瘤患者中，在FSE T2加权图像和CISS图像上均观察到第四脑室底外侧角有一小片高信号区。术前相同脉冲序列的MR图像在所有这些患者中均显示相同的高信号区。
由于高信号区的位置与前庭神经核一致，该高信号可能代表神经核的退变。这种高信号不应与术后病变或小梗死混淆。如果在桥小脑角大肿瘤患者中看到这种高信号，则提示诊断为前庭神经鞘瘤。
