Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Neurosurg Rev. 2013 Jan;36(1):39-43; discussion 43-4. doi: 10.1007/s10143-012-0400-7. Epub 2012 Jun 14.
The cochlear nerve is most commonly located on the caudoventral portion of the capsule of vestibular schwannomas and rarely on the dorsal portion. In such a condition, total removal of the tumor without cochlear nerve dysfunction is extremely difficult. The purpose of our study was to identify the frequency of this anatomical condition and the status of postoperative cochlear nerve function; we also discuss the preoperative radiological findings. The study involved 114 patients with unilateral vestibular schwannomas operated on via a retrosigmoid (lateral suboccipital) approach. Locations of the cochlear nerve on the tumor capsule were ventral, dorsal, caudal, and rostral. Ventral and dorsal locations were further subdivided into rostral, middle, and caudal third of the tumor capsule. The postoperative cochlear nerve function and preoperative magnetic resonance (MR) findings were reviewed retrospectively. In 56 patients that had useful preoperative hearing, useful hearing was retained in 50.0% (28 of 56) of patients after surgery. The cochlear nerve was located on the dorsal portion of the tumor capsule in four patients (3.5%), and useful hearing was preserved in only one of these patients (25%) in whom the tumor had been partially resected. This tumor-nerve anatomical relationship was identified in all tumors of <2 cm at preoperative MR cisternography. MR cisternography has the potential to identify the tumor-nerve anatomical relationship, especially in small-sized tumors that usually require therapeutic intervention that ensures hearing preservation. Hence, careful evaluation of the preoperative MR cisternography is important in deciding the therapeutic indications.
耳蜗神经通常位于前庭神经鞘瘤囊的尾侧腹侧部分，很少位于背侧。在这种情况下，要想在不损伤耳蜗神经功能的情况下完全切除肿瘤极其困难。我们的研究目的是确定这种解剖结构的发生率以及术后耳蜗神经功能状况，并讨论术前的放射学发现。本研究纳入了 114 例行乙状窦后（外侧枕下入路）入路手术的单侧前庭神经鞘瘤患者。耳蜗神经在肿瘤囊上的位置有腹侧、背侧、尾侧和头侧。腹侧和背侧位置进一步分为肿瘤囊的头侧、中间和尾侧三分之一。回顾性分析了术后耳蜗神经功能和术前磁共振（MR）检查结果。在术前有可利用听力的 56 例患者中，术后 50.0%（28/56）的患者保留了有用听力。4 例（3.5%）患者的耳蜗神经位于肿瘤囊的背侧，其中仅 1 例（25%）患者肿瘤部分切除后保留了有用听力，该患者肿瘤体积较小。术前磁共振池造影术可以识别这种肿瘤-神经的解剖关系，特别是在需要确保听力保留的治疗干预的小肿瘤中。因此，术前磁共振池造影术的仔细评估对于决定治疗指征非常重要。
