The cochlear aqueduct (CA) connects between the perilymphatic space of the cochlea and the subarachnoid space in the posterior cranial fossa. The study aimed to examine 1) whether cavitation of the CA occurs on the subarachnoid side or the cochlear side and 2) the growth and/or degeneration of the CA and its concomitant vein. We examined paraffin-embedded histological sections from human fetuses: 15 midterm fetuses (crown-rump length or CRL, 39–115 mm) and 12 near-term fetuses (CRL, 225–328 mm). A linear mesenchymal condensation, i.e., a likely candidate of the CA anlage, was observed without the accompanying vein at 9–10 weeks. The vein appeared until 15 weeks, but it was sometimes distant from the CA. At 10–12 weeks, the subarachnoid space (or the epidural space) near the glossopharyngeal nerve rapidly protruded into the CA anlage and reached the scala tympani, in which cavitation was gradually on-going but without epithelial lining. However, CA cavitation did not to occur in the anlage. At the opening to the scala, the epithelial-like lining of the CA lost its meningeal structure. At near-term, the CA was often narrowed and obliterated. The CA develops from meningeal tissues when the cavitation of the scala begins. The latter cavitation seemed to reduce tissue stiffness leading, to meningeal protrusion. The so-called anlage of CA might be a phylogenetic remnant of the glossopharyngeal nerve branch. A course of cochlear veins appears to be determined by a rule different from the CA development.

中文翻译：

---

重新审视耳蜗导水管：利用人类胎儿进行的组织学研究

耳蜗导水管（CA）连接耳蜗的外淋巴间隙和后颅窝的蛛网膜下腔。该研究旨在检查 1) CA 空化是否发生在蛛网膜下腔侧或耳蜗侧，以及 2) CA 及其伴随静脉的生长和/或退化。我们检查了人类胎儿的石蜡包埋组织学切片：15 个中期胎儿（头臀长或 CRL，39-115 毫米）和 12 个近期胎儿（CRL，225-328 毫米）。 9-10 周时，在没有伴随静脉的情况下观察到线性间充质凝结，即可能是 CA 原基的候选者。静脉直到 15 周才出现，但有时距 CA 较远。 10-12周时，舌咽神经附近的蛛网膜下腔（或硬膜外腔）迅速突入CA原基并到达鼓阶，其中空化逐渐持续，但无上皮衬里。然而，原基中没有发生CA空化。在鳞阶开口处，CA 的上皮样内衬失去了脑膜结构。在近期，CA 经常被缩小和消除。当阶空化开始时，CA 从脑膜组织发展而来。后者的空化似乎降低了组织硬度，导致脑膜突出。所谓的CA原基可能是舌咽神经分支的系统发育残余。耳蜗静脉的走行似乎是由与 CA 发育不同的规则决定的。