Department of Neurosurgery, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma, 371-8511, Japan.
Acta Neurochir (Wien). 2013 May;155(5):855-62. doi: 10.1007/s00701-013-1671-7. Epub 2013 Mar 15.
The root exit zone (RExZ) of the facial nerve has been considered to be the target in microvascular decompression (MVD) for hemifacial spasm. However, more proximal segments with oligodendrocyte-derived myelin, where the facial nerve root emerges at the pontomedullary sulcus and adheres to the brainstem surface (root emerging zone [REmZ]), may also be susceptible to neurovascular compression. This study evaluated the predictive value of magnetic resonance (MR) imaging in detecting and assessing the features of vascular compression, especially in the pontomedullary sulcus, and describes the technical considerations of MVD procedures for the more proximal segments of the facial nerve.
Twenty patients treated with MVD underwent three-dimensional constructive interference in steady-state MR imaging and three-dimensional time-of-flight MR angiography. Their fusion images were used to evaluate the anatomical neurovascular relationships and intraoperative findings were analyzed.
Most offending arteries at the REmZ and the RExZ of the facial nerve were correctly identified by fusion MR imaging. During surgery, neurovascular contacts were identified at one or more segments of the facial nerve in all patients. The REmZ of the facial nerve was affected in 55 % of the patients. The most common offending vessel at the REmZ was the posterior inferior cerebellar artery rather than the anterior inferior cerebellar artery. The key procedure to explore the deep-seated REmZ in the pontomedullary sulcus was full dissection of the lower cranial nerves to the brainstem origin.
Our definition more correctly describes the specific anatomical relationship of the facial nerve origin from the brainstem and the clinically relevant target for MVD surgery. Fusion MR imaging is very useful to identify neurovascular contacts at both the RExZ and the REmZ of the facial nerve.
面神经的神经根出口区（RExZ）一直被认为是微血管减压术（MVD）治疗面肌痉挛的目标。然而，面神经神经根从脑桥延髓沟穿出并附着于脑干表面的更靠近近端的节段（神经根穿出区 [REmZ]），也可能容易受到神经血管压迫。本研究评估了磁共振成像（MR）在检测和评估血管压迫特征方面的预测价值，特别是在脑桥延髓沟，同时还描述了面神经更靠近近端节段的 MVD 手术的技术考虑因素。
20 例行 MVD 治疗的患者接受了三维稳态干扰磁共振成像和三维时间飞跃磁共振血管造影检查。他们的融合图像用于评估解剖神经血管关系，同时分析术中发现。
融合 MR 成像可正确识别面神经 REmZ 和 RExZ 的大多数致压动脉。在手术中，所有患者均在面神经的一个或多个节段识别到神经血管接触。面神经的 REmZ 受累占 55%。REmZ 最常见的致压血管是小脑后下动脉而不是小脑前下动脉。在脑桥延髓沟深部探查 REmZ 的关键步骤是充分解剖颅神经至脑干起源处。
我们的定义更准确地描述了面神经从脑干发出的特定解剖关系以及 MVD 手术的临床相关目标。融合 MR 成像对于识别面神经 RExZ 和 REmZ 的神经血管接触非常有用。
