Tanriover Necmettin, Rhoton Albert L
Department of Neurological Surgery, University of Florida, Gainesville, Florida 32610-0265, USA.
Neurosurgery. 2005 Aug;57(2):314-9; discussion 314-9. doi: 10.1227/01.neu.0000166677.70797.5e.
The purpose of this study is to call attention to an anomaly in which a segment of the anteroinferior cerebellar artery (AICA) is embedded in the dura or bone surrounding the subarcuate fossa, a small depression in the bone posterior to the internal acoustic meatus (IAM), through which the subarcuate artery enters the bone. This anomaly places the artery at risk in removing the posterior wall of the IAM.
An anomalous AICA having a segment that was embedded in the dura covering on the bone surrounding the subarcuate fossa was found during a microsurgical dissection course. The senior author (ALR) has observed this anomaly in four patients during surgery for acoustic neuromas and in three specimens in microsurgery dissection courses. To define the microsurgical anatomy of the anomalous artery further, the latex-injected specimen was dissected in a stepwise manner using x3 to x40 magnification.
The anomalous AICA described in this report bifurcated into a rostral trunk and a caudal trunk near the facial-vestibulocochlear nerve complex. The caudal trunk formed a sharp lateral loop that was embedded in the dura covering the subarcuate fossa. The involved trunk continued to supply the suboccipital area normally supplied by the posteroinferior cerebellar artery, which was hypoplastic. The dura surrounding the anomalous loop was opened, and the adjacent bone was removed to free the anomalous loop from the subarcuate fossa so that the artery could be displaced medially to remove the posterior wall of the IAM. Although it has been reported that the AICA may occasionally be adherent to the dura over the subarcuate fossa, this study is the first to demonstrate an AICA that is embedded in the dura and bone of the subarcuate fossa.
Mobilizing the AICA loop that is embedded in the subarcuate fossa posterior to the IAM places the involved AICA at significant risk in exposing the contents of the IAM.
本研究旨在引起人们对一种异常情况的关注，即小脑前下动脉（AICA）的一段嵌入到弓下窝周围的硬脑膜或骨质中，弓下窝是内耳道（IAM）后方骨质中的一个小凹陷，弓下动脉通过该凹陷进入骨质。这种异常情况使该动脉在切除IAM后壁时面临风险。
在一次显微手术解剖过程中发现了一条异常的AICA，其一段嵌入到覆盖弓下窝周围骨质的硬脑膜中。资深作者（ALR）在听神经瘤手术过程中观察到4例患者存在这种异常情况，在显微手术解剖课程的3个标本中也观察到了。为了进一步明确异常动脉的显微手术解剖结构，使用3倍至40倍放大倍数对注入乳胶的标本进行了逐步解剖。
本报告中描述的异常AICA在面听神经复合体附近分为一个头侧干和一个尾侧干。尾侧干形成一个尖锐的外侧袢，嵌入到覆盖弓下窝的硬脑膜中。受累的干继续正常供应通常由小脑后下动脉供应的枕下区域，而小脑后下动脉发育不良。打开异常袢周围的硬脑膜，去除相邻骨质，将异常袢从弓下窝中游离出来，以便将动脉向内侧移位以切除IAM后壁。尽管有报道称AICA偶尔可能附着于弓下窝上方的硬脑膜，但本研究首次证明了一条AICA嵌入到弓下窝的硬脑膜和骨质中。
在暴露IAM内容物时，移动嵌入到IAM后方弓下窝中的AICA袢会使受累的AICA面临重大风险。
