異常之動脈系統－極稀罕的左枕基底動脈系統之一例報告

A Very Rare Case of the Anomalous Left Occipital-Basilar Arterial System

蕭廷鑫(Tin-Hsin Hsiao)

《The Kaohsiung Journal of Medical Sciences》 2卷5期 (1986/05) Pp. 348-352

https://doi.org/10.6452/KJMS.198605.0348

摘要

作者在1984年本學院的解剖學實驗中，發現了一中年男獻體的頭部存有一左枕基底動脈系統，此一變異為以前文獻所未曾報導過的，其實際的情形如下記錄：左頸外動脈只有5分支，少了第6支耳動脈，由枕動脈分出1支來補償。左枕基底動脈：異常粗大的左枕動脈發出後往左耳下後行，在胸鎖乳突肌的下面分出一耳枝到乳突區，此並未依照正常的行徑在上頭斜肌的外緣往上行到後頭皮區，而是由肌肉的下緣進入左枕下三角區，在此處動脈呈球狀肉含有血塊，其後走在寰椎後弓的淺溝上，此時左椎動脈由寰椎的左橫突孔穿出後往內轉折注入左枕動脈，往後穿過硬脊膜和蜘蛛膜進入蜘蛛膜下腔，在枕骨斜台的左下角漸漸斜走到正中央，在橋腦的下緣接受右椎動脈的注入而合成基底動脈。基底動脈留有5個無法確定的動脈分支孔。

並列摘要

The present report describes a rare case of the left occipital-basilar arterial system as a substitute for the normal vertebral-basilar arterial system, which was encountered in a Chinese male cadaver for dissection at the gross anatomy laboratory of Kaohsiung Medical College in 1984. The results of the observation is described in the following report:
I. The left external carotid artery ranupwards for a distance about 29mm from the origin and gave a branch of the left occipital artery. The left occipital artery ran backward under the posterior belly of the digastric muscle and the stylophoideus muscle, then passed deep to the sternocleidomastoideus, splenius capitis, and longissimus capitis, also gave a branch of auricular artery to the mastoid region. Furthermore, this artery entered anomalously into the suboccipital triangle at the lower margin of the obliquus capitis superior. At this region this artery expanded into a globular structure (Maximal D.: 7.0mm)within which blood clots were found. After then it ran between the groove on the posterior arch of the atlas and the freemargin of the posterior atlanto-occipital membrane, in this part the left vertebral artery which ran inward from the left trasverse foramen of the atlas joined this artery; furthermore, this artery penetrated the dura mater spinalis and arachnoid membrane, entered the subarachnoid space of the cranium through the foramen magnum, and ran between the medulla and the occipital clavius. At the lower margin of the pons the right vertebral artery(D:1.8mm) joined this occipital artery to form the basilar artery(D:4.7mm). However, the willis’ artery circle of this case (Fig.2) was normally distributed, except for the superior cerebellar artery which was arisen abnormally from the posterior cerebral artery.
II. The right and left vertebral arteries (O.D.: 20.mm)
They arose normally from the upper wall of the right and left subclavian arteries, Both diameters are smaller than normal ones. They ran a normal course from the origin through the six transverse foramens of C6-C1 cervical vertebrae. The left one ran inward from the transverse foramen of the atlas, and joined the anomalous left occipital artery, which lay on the groove of the posterior arch of the atlas. The right one ran normal course, turned inward on the vertebral artery groove, then penetrated the dura mater spinalis and arachnoid membrane, entered the skull through the foramen magnum, and ran along the right side of the occipital clavius in a short distance, then joined the left occipital artery (D.: 5.5mm) to form the basilar artery at the lower border of the pons.
III. The embryological interpretation
The embryological process of the formation of the present arterial anomaly can be interpreted as follows: 1) This anomalous left occipital artery was formed by the remains of the connections of the first aortic arch with the left dorsal aorta, It then ran continuously by the remainder of the first cervical intersegmental artery which connected with the left vertebral artery. The diameter of this anomalous artery expanded wider than that of the normal right occipital artery, while the diameter of the right and left vertebral arteries compensated being narrower than that of the normal vertebral artery 2) The right and left vertebral arteries were formed normally by the connection of the intersegmental artery with the longitudinal channels from the first to the seventh intersegmental arteries.
VI. The others
The right occipital artery was of normal origin and course. Both right and left subclavian arteries branched into the descending scapular artery which passing through the upper and middle trunk of the brachial plexus, This artery branching on each side is a rare development in addition to the transverse cervical artery and suprascapular artery.

並列關鍵字

left occipital artery ； basilar artery ； vertebral artery