【作者】 付万新；

【导师】 徐如祥；

【作者基本信息】 南方医科大学 ， 神经外科学， 2007， 博士

【摘要】 颈静脉孔(Jugular foramen，JF)位置深在，通行众多颅神经和血管。JF区疾患的治疗一直以来都是神经外科挑战之一。随着研究的不断深入，借助某些特定的颅底入路，诸如耳后经颞骨入路(postauricular transtemporal approach)、远外侧入路(far-lateral approach)等，JF区的肿瘤已可经外科手术去除，但危及其周围重要结构的风险犹存。迄今为止，对于JF区的解剖学研究已不乏文献报道，但仍存在一些需要进一步探讨的地方。毫无疑问，对JF区解剖学特征的充分把握是手术切除该区域肿瘤的基础。因此，本研究在标本上模拟不同亚型的远外侧入路，对JF区的显微外科解剖学特点进行了探讨，以此寻求JF区恰当的显露方法，并同时可避免该区域重要的血管神经不受损伤。第一部分：经枕下远外侧入路达骨性JF及其毗邻结构的显微外科解剖目的：通过经枕下远外侧入路的骨性JF及毗邻结构显微外科解剖学特征的观察，试图寻求在此入路中可行的JF定位标志及显露方法。方法：在10例成人颅骨干燥标本及10例成人寰椎标本上，借助手术显微镜对骨性JF及其毗邻结构，包括枕髁、舌下神经管、乳突、茎突、颈静脉结节、颈静脉突等的形态进行观察并测量相关的解剖学数据，尤其是对上述各毗邻结构与颈静脉孔内外口之间的距离。统计学软件对同一个标本的左右两侧的同一指标进行分析。结果：①颈静脉孔由颞骨岩部和枕骨髁部围成的不规则间隙，其前外侧边为颞骨岩部，后内侧边为枕骨，其长轴由后外至前内。骨性JF可分为前内侧较小的岩部和后外侧较大的乙状部两部分。两者之间借颞骨岩部和枕骨的颈静脉孔内突(intrajugular process，IJP)不完全分开。在所有标本上均可见到颞突，但枕突只出现在40％的样本中。1侧可见骨桥，占5％。骨性颈静脉孔的大小和形态差异较大，在大部分的样本中，右侧颈静脉孔大于左侧。颈静脉窝位于颈静脉孔内、外口之间，JF向颅外移行过程中静脉部膨大形成的骨性穹隆陷窝，容纳JB。颈静脉窝的深度在左侧13.75+2.30mm，右侧13.62+2.63mm，未见显著性差异。②JF前内侧有恒定存在的岩下窦沟，颈静脉孔后外侧接乙状窦(GSS)。16侧标本中，GSS的后壁有乳突孔，位于上下曲中点附近的后缘处者为80％(10侧)，位于上曲、枕乳缝前者5％(1侧)，位于下曲以下者为15％(5侧)。JF内侧有颈静脉结节，其厚度在左侧为7.55±1.57(4.67～10.26)mm，右侧为7.48±1.70(4.25～9.79)mm。JF前内侧部的前外上方、颞骨岩部后面内1／3处有内耳门。自颅底内面观察，内耳门、JF前内侧部、舌下神经管内口三者几乎在一条直线上。③枕髁位于JF外口的下内方，形态多为肾形，枕髁在其长轴的长度、最大宽度、枕骨大孔后缘中点距枕髁后缘之间的距离等方面，同一标本的左右两侧均未见显著性差异。髁窝和髁管位于JF的后内侧，髁管的出现率为90％。舌下神经管位于颈静脉孔的内下前方，其内口可被不同程度分隔，其中一侧被分隔者2例，两侧均被分隔者1例，分隔都位于内口处，没有延至外口。颈静脉结节位于JF的内侧，上面后部有一浅沟，其内走行有舌咽神经、迷走神经和副神经。颈动脉管在JF前方，内有颈内动脉通过，其与位于后外侧的的JF借助颈动脉嵴薄形骨板相隔。JF外侧为茎突、茎乳孔以及稍远处的乳突。寰椎位于JF的后方，其侧块上面有椎动脉沟。2侧的标本的椎动脉沟出现完全骨管化，另有6侧出现部分骨管化，其出现率分别为10％和30％。其余表现为浅沟。③除颈静脉孔外口的内缘与枕髁的最短距离以及茎乳孔与颈静脉孔外口之间的距离以外，其余的关于颈静脉孔内外口与毗邻结构之间的距离，在同一个体上的左右两侧差异不显著。上述两个指标的数据分别为6.39±1.32(4.27～8.17)mm(左)及5.70±1.46(3.29～7.30)mm(右)、6.21±1.43(4.05～8.93)(左)及4.81±1.23(3.61～7.15)(右)。结论：骨性JF与其毗邻结构之间存在着复杂的关系。星点、茎突根部、乳突尖以及SS在体表的投影有助于处理JF区病变时准确定位。切除或磨除枕骨颈静脉突、乳突、颈静脉结节、寰椎横突及枕髁均有助于JF的显露。颈静脉结节的切除存在损伤后组颅神经的潜在危险。第二部分：经枕下远外侧入路达JF区颅外软组织的显微外科解剖目的：观察JF区颅外部分软组织的显微外科解剖学的特征，从而为经枕下远外侧入路治疗颈静脉孔区肿瘤的切口的选择、骨窗的形成、椎动脉与颈静脉球的处理等提供形态学依据。方法：10例经福尔马林固定的成人头颅标本，动静脉分别灌注红色与蓝色乳胶。模拟经枕下远外侧入路的三种亚型，在手术显微镜下对JF区相关的颅外部分的肌肉、血管、神经等进行观察并获取相关数据。借此比较上述入路在显露颈静脉孔区及周围结构的优劣。标本解剖步骤如下：(1)头位：头颅Mayfield架固定，侧位，乳突处于最高位置。(2)切口：倒“U”形切口，切口起自颈后中线，约在枕外粗隆下方5 cm处，直行向上达枕外粗隆，然后沿上项线转向外方到达乳突根部后，于颈外侧沿胸锁乳突肌的后缘折向下大约5cm，略低于寰椎侧块在颈侧部的体表投影。(3)分离肌肉：逐层切开枕下区三层肌肉，暴露枕下三角，显露位于三角内的椎动脉及包绕其周围的椎动脉旁静脉丛、C1神经。(4)骨窗范围：以充分暴露JF区为目标，根据不同的远外侧入路的亚型，选择切除寰椎后弓和横突，磨除颈静脉结节、颈静脉突和枕髁。结果：①头侧直肌位于后组颅神经、交感干、颈内动静脉的前方，椎动脉及其周围静脉丛的后方。②椎动脉穿寰椎的横突孔，行于枕下三角，该动脉于椎动脉沟处被骨膜鞘所包绕，周围可见丰富的椎静脉丛。椎动脉第三段的垂直段的分支有肌支动脉、神经根动脉，本组发现神经根动脉出现恒定且发育较好(发现率为100％)，多起自颈2神经前支上方的椎动脉后内侧壁，而肌支动脉出现不恒定，且多纤细。在10个标本中，有9个标本的左右两侧的椎动脉直径较接近，另一个标本上，左右两侧的椎动脉严重不对称，右侧椎动脉细小。在1例标本的左侧，可见椎动脉沟完全骨管化。椎动脉穿寰枕筋膜内缘距正中线的距离：左侧为15.64±1.41(13.64～17.54)mm，右侧为15.68+1.55(13.29～17.58)mm。SCS内缘至正中线距离：左侧为12.73±2.17(9.85～16.63)mm，右侧为12.63±2.18(9.64～16.37)mm。颈静脉球及邻近的颈内静脉部分收纳颅内及颅外的静脉回流，包括乙状窦、岩下窦、椎静脉丛、舌下神经管静脉丛以及髁后导静脉等。髁后导静脉的个体差异较为显著，16侧(80％)注入乙状窦末端后缘，4侧(20％)注入颈静脉球后上壁。本组未见髁管缺如，2侧髁后导静脉直径小于2mm(10％)，17侧在2-5mm之间(85％)，1侧大于5mm(5％)。在10例标本中的7例中，颈静脉球的最高点高于内耳道下壁的水平。上述的7例中，右侧的为5例，左侧为2例。③舌咽神经、迷走神经和副神经共同行于颈静脉孔。离开颈静脉孔后，舌咽神经前行于颈内动脉外侧，至至茎突深面发出分支；迷走神经向下走行；副神经斜向外侧，行于颈内动脉与颈内静脉之间。舌下神经行于舌下神经管的下外侧，出颅后与迷走神经毗邻较为紧密。面神经由茎乳孔出颅，前行至腮腺。在腮腺内面神经干为一干者1侧(5％)，分为2干者19侧(95％)，未见3干者。结论：枕髁的切除对JF的暴露作用有限。切除颈静脉突、颈静脉结节、寰椎后弓及横突孔即可很好地显露JF区相关结构。颈静脉突可借头侧直肌辨认，并于枕骨大孔外缘磨除。颈静脉结节的切除应在骨膜外进行，同时应避免损伤后三组颅神经。寰椎横突、侧块以及后弓切除时，应切实保护椎动脉及静脉丛。术中逐层削磨骨质并保留一薄片骨质于静脉壁上，有利于颈静脉球的保护。第三部分：经枕下远外侧入路达JF区颅内软组织的显微外科解剖目的：探讨经枕下远外侧入路至颈静脉孔区的颅内软组织的显微解剖学特征，从而为借此入路切除颈静脉孔区肿瘤术中硬膜的切开以及颅内的操作提供形态学基础。方法：10例经福尔马林固定的成人头颅标本，动静脉分别灌注红色与蓝色乳胶。模拟经枕下远外侧入路的三种亚型。解剖操作在第二部分的基础上继续进行，其中，硬膜切开选择在椎动脉前方和后方进行，比较其优劣。在手术显微镜下对JF区相关的颅内部分的软组织，包括硬脑膜、颅内的血管神经等进行观察并获取相关数据。与第二部分结果结合，进一步比较上述入路在显露颈静脉孔区及周围结构的优劣。结果：①在颈静脉孔的内口，颈静脉孔借硬脑膜分为三个部分，前内侧的岩部，后外侧的乙状部，以及两者之间的神经部。硬膜深入神经部将其分为舌咽道和迷走道两个部分，前者内有舌咽神经穿过，后者内行有迷走神经和副神经。18侧(90％)其间被一恒定的硬膜隔分开，其宽度因人而异，约在0.7-5.2mm之间，2侧以骨桥被覆硬膜作为间隔，16侧以纤维桥相隔，2侧未分隔。②20侧椎动脉均走行于舌咽神经、迷走神经根和副神经颅根的前方，其与舌下神经的关系存在个体差异。15侧(75％)椎动脉穿经舌下神经根的腹侧达桥延沟；有4侧(20％)穿舌下神经根丝之间；还有1侧(5％)经舌下神经根丝的背侧。起自椎动脉的小脑下后动脉为18侧，占90％，多发自椎动脉穿硬膜点远侧9.45-26.57mm处。另有2侧的小脑下后动脉起自于基底动脉的起始，起始处直径是左侧1.65±0.70(0.53-2.64)mm，右侧1.59±0.59(0.63-2.26)mm。该动脉与舌咽神经、迷走神经和副神经之间的毗邻关系较为复杂，在不同的个体上存在差异。穿迷走神经根丝之间向后的12侧(60％)；穿副神经和迷走神经之间向后的4侧(20％)；勾绕副神经根下方向上的2侧(10％)；勾绕舌咽神经的上面行向下的2侧(10％)。本组20侧均出现AICA，出现率为100％，每侧1支。其中19侧(95％)起自基底动脉中、下1／3，1侧(5％)起自VA。在10例标本中的8例中，右侧乙状窦较同一个体的左侧为大。12侧中发现乳突导静脉，其出现率占60％。③舌咽神经在JF内走行在颈静脉内嵴和JB内侧之间，其头端根丝距舌咽神经根丝约2.0mm，手术时由此可分离两神经。副神经由颅根和脊髓根两部分组成，脑根干和脊髓根干中14侧(70％)两干合并，6侧(30％)被包在迷走神经鞘内，与迷走神经有蛛网膜间隔。舌下神经穿经蛛网膜和硬脑膜后进入分隔开的或完整的舌下神经管，本组标本中发现双舌下神经管左侧发生率为6／10，右侧发生率为2／10，两束神经在舌下神经管内或管外合成一千出颅。结论：在不磨除枕髁的情况下，可在椎动脉后内侧切开硬脑膜，此时，椎动脉无需移位，并可充分显露JF区相关的颅内结构，包括脑干腹侧面的结构以及枕骨大孔，并可提供较大的操作空间。应充分利用脑干外侧的血管神经间隙进行手术操作。全文小结：通过本研究，我们认为远外侧经寰椎横突-髁上-髁旁入路具有以下优点：1．同时暴露JF内外口，以微创的方式弥补了以往入路的不足，可以满足一期全切哑铃型神经鞘瘤的要求；2．倒“U”形切口的使用，便于沿肌间隙分离肌层及术后肌层严密对位缝合，脑脊液漏的机会小；3．有助于血管神经的保护；4．手术步骤得以简化；5．多数情况下无需切除枕髁和侧块，有助于维持颅颈交界的稳定。更多还原

【Abstract】 Jugular foramen, through which the numerous nerves and venous channels pass,is indeed the most complex of the foramina. Lesions originating from theneurovascular structures in the jugular foramen constitute one of the major challengesof skull base surgery. With the application of skull base approaches, such aspostauricular transtemporal approach, retrosigmoid approach and far-lateral approach,tumors in this area can be removed, surpassing the difficulties posed by deep locationand surrounding critical structures.Although the subject of many studies, the jugular foramen remains poorlyunderstand. Undoubtedly, knowledge of anatomy of jugular foramen is crucial inperforming tumor resections in this region. So, the microsurgical anatomy of thejugular foramen via mimics three extensions of far-lateral approach were carried outin this study, in order to select the optimal method to allow adequate exposure of thejugular foramen while preserving the blood vessels and cranial nerves in this region.PartⅠ.Microsurgical anatomy of osseous jugular foramen and its adjacentstructures via far-lateral suboccipital approachObjective: To investigate the microsurgical anatomy of the osseous jugularforamen (JF) and the adjacent structures via far-lateral approach, in order to explorethe feasible landmark and exposure method of jugular foramen.Methods: The morphology of the osseous jugular foramina and the adjacentstructures of 10 adult dry skulls and atlas were observed under 10×magnification, the relative data of osseous jugular foramina and the adjacent structures ,especially thedistances between the slected structures and intracranial or extracranial orifices ofjugular foramina were measured and analyzed with statistics software.Results:①The jugular foramen was located between the temporal bone and theoccipital bone with the long axis directly from posterolateral to anteromedial. Theanterolateral margin formed by the temporal bone and a posteromedial margin formedby the occipital bone. The jugular foramen was divided into the petrosal and sigmoidportion. The junction of the sigmoid and petrosal parts was bony prominence on theopposing surface of the temporal and occipital bones, called the intrajugular processes.The temporal processes were observed in all of spcimens , while the occipitalprocesses were occurred in 40% specimens. The bony bridge was only found in oneside, which occupied 5 percent. The jugular foramina were varied in size andshape,the right jugular formina were larger than left ones in major specimens. Thejugular fossa was located between the intracrinal orifice and extracranial orifice of thejugular foramen, the depth of the jugular fossa were 13.75±2.30mm at left side and13.62±2.63mm at right side with no significant difference.②The inferior petrosalsinus was anteromedial to the jugular foramen, and sigmoid sinus was locatedposterolateral to jugular foramen.The mastoid foramina were found in 16 of 20 sidesspceimens which possessed 80 percentage. The jugular tubercle located at thejunction of the basal and condylar part of the occipital bone and situated medial to themedial edge of the jugular foramen.The average thickness of the jugular tubercle was7.55 mm at left side and 7.48 mm at right side. No signifcant difference was found inthe thickness of the jugular tubercle. The internal ocoustic meatus was locatedanterolateral to the anteromedial part of jugular foramen. From the intracrinal view,the internal ocoustic meatus, the anteromedial part of jugular foramen and theintracrinal orifice of the hypoglossal canal were almost located on a beeline. ③The occipital condyle was located along the lateral margin of the anterior half ofthe foramen magnum in the area below and medial to the jugular foramen. Therewere no significant differencese were found in both sides of occipital condyle,including the length of long axis , maximum width and the distance between themidpoint of posterior edge of foramina magnum and posterior edge of occipitalcondyle. The condular fossa and canal were posteromedial to the jugular foramen.The occurrence of the condular canal was 18 sides, which occupied 90 percent.Thehypoglossal canals, which pass through the condylar parat of the occipital bone in theeara above the occipital condyles, were located medial to the jugular foramina. In 10specimen, the compartment in one side was found in 2 specimens, and thecompartment in two side was found in 1 specimen. The compartments were limited inthe intracrinal orifice of hypoglossal canal. On the extracranial side, the styloid andmastoid processes were laterally to JF. The jugular process of the occipital bone wasposterior to JF. The tympanomastoid notch was laterally to the stylomastoid foramen.The styloid process ,mostoid process and the stylomastoid foramen were locatedlateral to the outer orifice of the jugular foramen, with the styloid process beinglocated slightly anteromedial to the stylomastoid foramen. The grooves of vertebralartery of two in 20 sides were tubelized completely and other 6 sides were tubelizedpartially .The appearance percentages were 10% and 30% respectively.③Beside ofthe minimum distance between the internal margin of extracranial orifice of jugularforamina and occipital condyle, which were 6.39 mm at left and 5.70 mm at right side,and the distance between the stylomastoid foramina and the extracranial orifices ofjugular foramina ,which were 6.2hnm at left and 4.81ram at right side, the othermorphological data about relationship of adjacent structures with intracranial orextracranial orifices of jugular foramina were invariable without significantdifference in both side of same specimen. Conclusions: The complex relationship exists between the osseous jugularforamen and it’s adjacent structures. The root of styloid process, mostoid process andthe surface project of SS can be used as landmark to identify jugular foramen.Thegrinding of jugular process of the occipital bone, mastoid process, jugular tubercleand transverse process of atlas, drilling of condyle are beneficial to exposure thejugular foramen. The removal of the jugular tubercle should be performed accuratelyto avoid the defect of the crainial nervesPartⅡMicrosurgical anatomy of extracranial soft tissues in jugularforamen region via far-lateral suboccipital approachObjective: To study the extracranial soft tissue in jugular foramen and providean anatomic basis for selection of incision, formation of bone window, and treatmentof vertebral artery and jugular bulb in performing tumor resection via far-lateralsuboccipital approach.Methods: 10 adult cadaveric head specimens fixed in formalin were used todissect via mimics three extensions of far-lateral suboccipital approach. Theprocedures were described as follow : The skin was incised in a inverse U shape, andthe muscles of the suboccipital region were dissected from superficial to deep toexpose the vertebral artery, venous plexus and C2 nerve. To expose the JF areasufficently, the anterior arch of the atlas, transverse process of the atlas, the jugulartubercle and the jugular process were removed in part or in whole. The occiptialcondyle was maitained .During this operation, the soft tissues of extracarnial part injugular foramen, including muscles, blood vessels and nerves were observed under10×magnification. The relative data were obtained. And then, the advantage anddisadvantage of the the three extensions of far-lateral suboccipital approach to exposure the jugular foramen region and surronding structures were analyzed.③④Results:①The rectus capitis lateralis muscle was located anteriorly to posteriorgroup of cranial nerves , sympathetic trunk, internal carotid artery and vein, andanteriorly to vertebral artery and surrounding venous plexus.②The vertebral arteryrun through the transverse foramen of atlas and encased in the suboccipital triangleand covered posteriorly behind the lateral mass of atlas in the vertebral groove andsurrounded by a periosteal sheath enclosing the perivertebral venous plexus. Thearteries of the nerve roots were origined invariably from the posteromedial wall ofverical part of the third segment of vertebral artery, whereas, the muscular brancheswere variable. In 9 samples, the right and left vertebral arteries were in similardiameter. And, anther one specimen showed a severe asymmetry in diameter of rightand left vertebral artery, with a fine right vertebral artery. Tubelization of vertebralgroove were only found in left side of one specimen. The average distance betweenthe site where the vertebral artery enter atlantooccipital fascia and the median linewere 15.64mm at left and 15.68mm at right side. The jugular bulb and adjacent partof the internal jugular vein receive drainage from both intracranial and extracranialsources, which include the sigmoid and inferior petrosal sinuses, the vertebral venousplexus, the venous plexus of the hypoglossal canal, the posterior condylar emissaryvein. Individual differences were observed in the posterior condylar emissary vein. 16posterior condylar emissary veins poured into posterior margin of the end of sigmoidsinus, 4 poured into the posterosuperior wall of jugular bulb. The diameter of twoposterior condylar emissary veins were less than 2mm, which possessed 10 percent.The diameter ranged from 2 to 5mm were found in 17 veins (85%) and more than5ram in 1 side(5%).In 7 of 10 specimens, the peak of the jugular bulb was higher thanthe level of inferior wall of the internal acoustic meatus with 5 at right and 2 at left.③The glossopharyngeal, vagus and accessory nerves passed through the jugular foramina together and apart in extracranial side . After exited from the jugularforamen, the glossopharyngeal nerve turned forward, crossing the lateral surface ofthe internal carotid artery deep to the styloid process;the vagus nerve run downward;the accessory nerve descended obliquely laterally between the internal cartoid arteryand internal jugular vein and then backward across the lateral surface of the vein toreach its muscles. The hypoglossal nerve exited the inferolateral part of thehypoglossal canal and passed adjacent to the vagus nerve, descended between theinternal carotid artery and the internal jugular vein to the level of the transverseprocess of the atlas.Conclusions: Removal of the occipital condyle has a limited help to expose thejugular foramen. In most cases,with drilling the jugular process, jugular tubercle andremoving arch of posterior atlas and transverse foramen of atlas without disturbingthe condyle, the approach through transverse process of atlas combined withsupracondylar and paracondylar approach provides wide and sufficient exposure ofthe structures in the jugular foramen region. The jugular process can be located basedon its relationship with the rectus capitis lateralis muscle and shoul be removed viaposterior margin of the foramen magnum. The extradural removal of the jugulartubercle should be performed with caution because of the risk of injuring theglossopharyngeal, vagus, and accessory nerves. The vertebral artery and venousplexus should be protect while the atlas was removed.PartⅢMicrosurgical anatomy of intracranial soft tissues in jugular foramenregion via far-lateral suboccipital approachObjective: To explore the morphological characteristics of the intracranial softtissue in jugular foramen region, and provide an anatomic basis for incision of dura,intracranial operation in performing tumor resection via far-lateral suboccipital approach.Methods: 10 adult cadaveric head specimens fixed in formalin were used todissect via mimics three extensions of far-lateral suboccipital approach. The softtissues of intracarnial part in jugular foramen, including dura architecture and divisionof the jugular foramina, intracranial blood vessels and nerves were observed under10×magnification. The relative data were obtained. And then, the advantage anddisadvantage of the the three extensions of far-lateral suboccipital approach toexposure the jugular foramen region and surronding structures were analyzed.Results:①At the intracranial orifice, the jugular foramen was divided into threecompartments by dura mater. The petrosal compartment situated anteromedially, thesigmoid compartment situated posterolaterlly , and neural compartment situatedbetween the petrosal and sigmoid parts at the site of the intrajugular process of thetemporal and occipital bones, the intrajugular septum, and the glossopharyngeal,vagus and accessory nerves. The dura mater over the neural part of the foramen hadtwo characteristic perforation, a glossopharyngeal neatus, through which theglossopharyngeal nerve passed, and a vagal meatus, through which the vagus andaccessory nerves passed. 18 sides (90%) were separated by dura mater with differentwidth ranging from 0.7 to 5.2mm. The septum were formed by bony bridge covereddura mater in 2 sides and fibous tissue in 16 sides. No septum was found in 2 sides.,.②The intracranial segment of vertebral artery were run anteriorly to theglossopharyngeal, vagus and accessory nerves, and varied in the relationship with thehypoglossal nerve. 15(75%) vertebral arteries passed ventrally to theglossopharyngeal nerve roots; 4 (20%)vertebral arteries acossed through theglossopharyngeal nerve roots; one vertebral artery run dorsally to this nerve.Theposterior inferior cerebellar artery origined from the vertebral artery was found in 18sides with 90% occurance percentage, the origins of the posterior inferior cerebellar arteries were laterally to the site where the vertebral passed through the dura materwith a distance ranging from 9.45 to 26.57mm Another 2 posterior inferiorcerebellar arteries were origined from the initial point of the basilar artery withavarage diameter 1.65mm at left and 1.59mm at right. Complex relationship of theposterior inferior cerebellar artery with glossopharyngeal, vagus and accessorynerves were observed.12 posterior inferior cerebellar arteries were passed through the vagus rootlets; 4posterior inferior cerebellar arteries run between the accessory nerve and vagus nerve,which occupied 20 percent. The posterior inferior cerebellar artery rolled inferiorly tothe accessory nerve and to upward were found in 2 specimens. Anther one was rolledsuperiorly to the vagus nerve and to downward. The anterior inferior cerebellararteries were found in all specimens. 19 of 20 specimens, the anterior inferiorcerbellar arteries were origined from the basilar arteries . One anterior inferiorcerebelllar artery was derived from the vertebral artery. Sigmoid sinus was larger onright side in 8 spceimens. The mastoidal emissary veins were found in 12 sides,which possessed 60 percent.③The glogssopharyngeal nerve coursed through thejugular foramen along the medial side of the intrajugular ridge.The vagus nervecoursed anterior and inferior as it acossed below the midportion of the intrajugularprocess of the temporal bone. In the area immediately below the dura at the level ofthe intrajugular processes, there were no fibrous bands between the glossopharyngealnerve and the vagal ganglion. The accessory nerve was composed of the cranial andspinal portions. In this study, 70% of the carinal and spinal portions were united. 6accessory nerves were banded in vagal sheath and separated with vagus nerves byarachnoid septum. The hypoglossal nerves entered the hypoglossal canal after runthrough the archnoid mater and dura mater.Conclusions: The opening of the dura mater can be performed posteriorly to the vertebral artery without rerouting, and can provide sufficient exposure and operationspace of the vetral structures of brain stem down to the C2 cervical nerve, theforamen magnum region. It is essential to maste the microanatomic characteristic tosurgeon for treating the tumors in jugular foramen area.SUMMARY TO THIS STUDYThe advantages of the approach descrided in previous study ,which was combinatedwith the approach through transverse process of atlas , supracondylar andparacondylar approach, could be summized briefully as follow:1. The integrality of the atlantooccipital joint was maintained, because the occipitalcondyle was not removed.2. The better exposure of the intracranial orifice of jugular foramen could beprovided by removal of the jugular tubercle. Furthermore, the posterior wall ofjugular foramen can be exposed sufficently by removing the jugular process.3. The usage of the inverse U shape cision is helpful to separate the muscles.4. This appoach is helpful to protect the blood vessels and nerves.5. The procedure of operation is simplified.6. Based on this approach, the tumor in the jugular foramen region with intracranialand/or extracranial extension could be removed completely at one stage.更多还原