Microsurgical anatomy for lateral approaches to the foramen magnum with special reference to transcondylar fossa (supracondylar transjugular tubercle) approach

Microsurgical anatomy for lateral approaches to the foramen magnum, especially for transcondylar fossa (supracondylar transjugular tubercle) approach, was studied using cadavers. The transcondylar fossa approach is an approach in which extradural removal of the posterior portion of the jugular tubercle through the condylar fossa is added to the far lateral approach. Some differences between this approach and the transcondylar approach are demonstrated. The atlanto-occipital joint and the jugular tubercle are obstacles for the lateral approaches. The condylar fossa forming the external occipital surface of the jugular tubercle is located supero-posterior to the occipital condyle. The fossa is limited laterally by the sigmoid sulcus and the jugular foramen. The posterior condylar canal communicating anteriorly with the distal end of the sigmoid sulcus, the jugular foramen, or the hypoglossal canal opens at the bottom of the fossa. The condyle is situated inferior to the posterior condylar and hypoglossal canals, and the jugular tubercle is located superior to them. In the transcondylar fossa approach the posterior part of the jugular tubercle is extradurally removed, but the condyle and the atlanto-occipital joint are untouched. On the other band, in the transcondylar approach the medial parts of the condyle and the lateral mass of Cl are removed. The latter approach offers better visualization of the inferior part of the foramen magnum. The essential difference of the two approaches is in the direction of looking and the extent of resection of the atlanto-occipital joint. Both approaches offer excellent view of the ventral dural space in the lower clivus and the foramen magnum, but the level of exposure differs somewhat between them. In the lateral approaches to the foramen magnum, the condylar fossa, the posterior condylar canal, and the posterior condylar emissary vein all play an important role as intraoperative anatomical landmarks.     

The supracondylar approach to the jugular tubercle and hypoglossal canal

Background Circumscribed lesions of the hypoglossal canal and of the jugular tubercle still remain a surgical challenge. So far, transpetrosal, transcondylar suboccipital, and extreme lateral approaches have been used to access this region. These surgical procedures bear a high risk for neurological deficits. Therefore, we introduce a new minimally invasive extradural approach to the hypoglossal canal that also allows access to the lateral aspects of the jugular tubercle.

Methods After a paramedian retromastoid skin incision, a basal suboccipital craniectomy lateral to the foramen magnum toward the jugular tubercle is performed. With this approach the occipital condyle and the lateral osseous circumference of the foramen magnum are preserved. Drilling extradurally, the dorsal parts of the jugular tubercle are removed. The exposure is extended downward to the posterior margins of the hypoglossal canal and laterally to the jugular bulb, enabling a minimally invasive exposure of the hypoglossal canal, the lateral aspects of the jugular tubercle, and medial aspects of the jugular bulb.

Results Using this supracondylar approach, surgical interventions were performed in three patients suffering from a hypoglossal neurinoma, a cholesterol granuloma extending into the jugular tubercle, and a cyst of the hypoglossal canal, respectively. No additional postoperative neurological deficits were seen.

Conclusions The supracondylar approach seems to be useful to gain access to benign lesions of the hypoglossal canal and of the jugular tubercle to decompress tumors or cysts. In contrast to previously reported techniques this approach has a low risk of morbidity. The surgical field, however, is restricted laterally by the jugular bulb, medially and basally by the residual occipital condyle and dorsally by the dura. Therefore, this approach is useful to remove small lesions or to perform extended biopsies. Radical removal of large tumors seems to be problematic using this approach.     

Posterior condylar canals and posterior condylar emissary veins—a microsurgical and CT anatomical study

The posterior condylar canals (PCCs) and posterior condylar emissary veins (PCEVs) are potential anatomical landmarks for surgical approaches through the lateral foramen magnum. We conducted computed tomography (CT) and microsurgical investigation of how PCCs and PCEVs can aid in planning and performing these approaches. We analyzed the microanatomy of PCCs and PCEVs using cadaveric specimens, dry skulls, and CT images. The recognition frequency and geometry of PCCs and PCEVs and their relationships with surrounding structures were evaluated. PCCs were identified in 36 of 50 sides in dry bones and 82 of 100 sides by CT. PCCs had a 3.5-mm mean diameter and a 6.8-mm mean canal length. We classified their courses into four types according to intracranial openings: the sigmoid sinus (SS) type, the jugular bulb (JB) type, the occipital sinus type, and the anterior condylar emissary vein type. In most cases, PCEV originated near the boundary between the SS and JB. PCCs and PCEVs can be useful anatomical landmarks to differentiate the transcondylar fossa approach from the transcondylar approach, thus preventing unnecessary injury of the atlantooccipital joint. They can also be used as landmarks when the jugular foramen (JF) and hypoglossal canal (HGC) are being exposed. The area anterior to the brain stem and the medial part of HGC can be accessed by removal of the lateral foramen magnum medial to PCC. JF and the lateral part of HGC can be accessed by removal of the skull base lateral to PCC without damaging the lateral rim of the foramen magnum.     

Surgical approach for hypoglossal schwannomas to prevent deformity of the atlanto-occipital joint

Background  Hypoglossal schwannomas are very rare tumors that often enlarge the hypoglossal canal and jugular foramen, and erode the bone bridge of the occipital condyle. We compared pre- and postoperative 3D bone CT images and discussed the ideal craniotomy to prevent fracture formation. Method  Seven patients with hypoglossal schwannomas underwent surgery in our department. Six cases were type B and 1 case was type C. All patients complained of hypoglossal nerve paresis and nuchal pain. Findings  We used the condylar fossa approach for four cases of type B, the lateral suboccipital approach with C1 laminectomy for two cases of type B and extradural transjugular approach for one case of type C. In all cases, the lateral rim of the foramen magnum or the posterior rim of the jugular foramen was not resected at the same time. The intracranial part of the tumor was removed in all type B cases. Radiotherapy was added for the residual tumor. No patient had deformity or fracture of the joint. Conclusions  Opening the hypoglossal canal and dural incision toward the hypoglossal canal are important for high radicality. However, preservation of the lateral rim of the foramen magnum must be noted to prevent consecutive deformity or fracture of the atlanto-occipital joint.     

A morphometric analysis of the foramen magnum region as it relates to the transcondylar approach

Summary Background. The transcondylar approach is being increasingly used to access lesions ventral to the brainstem and cervicomedullary junction. Understanding the bony anatomy of this region is important for this approach. The purpose of this study was to conduct a morphometric analysis of the hypoglossal canal (HC), occipital condyle (OC) and the foramen magnum (FM) as it pertains to the transcondylar approach.Methods. 50 dry skulls provided 100 hypoglossal canals, 100 occipital condyles and 50 foramina magna. Twenty one parameters were analyzed. They were: length of the HC, diameter of the intra- and extracranial ends of the HC, angle of the HC to the sagittal plane, distance of the HC from the posterior, anterior and inferior margins of the OC, antero-posterior and transverse diameter of the OC, presence of condylar foramen, distance of HC from the jugular foramen intra- and extracranially, distance of HC from basion, opisthion, carotid canal and jugular tubercle. The anteroposterior and transverse diameters of the FM were measured and a FM index was calculated by dividing the AP diameter of the FM by the transverse diameter. The angle of the long axis of the occipital condyles to the sagittal plane was measured. Protrusion of the occipital condyle into the foramen magnum was noted. Where applicable, the measurements were made separately for the right and left side.Findings. The average length of the hypoglossal canal in this study was 12.6 mms. The hypoglossal canal makes an angle of 49° to the sagittal plane. In 30% of the dry skulls studied, the HC was divided into two by a bony septum. The distance of the intracranial end of the HC from the posterior margin of the OC was 12.2 mms. The average anteroposterior length of the occipital condyle was 23.6 mms and the transverse diameter was 14.72 mms. The occipital condyle made an angle of 60° to the sagittal plane. In 20% of the skulls studied the occipital condyle protruded into the foramen magnum. The condylar foramen was absent on the right side in 4 skulls and on the left side in 16 skulls. The average anteroposterior length of the foramen magnum was 33.3 mms and the width was 27.9 mms. When the foramen magnum index was > 1.2, the foramen was found to be ovoid. Forty six percent of the skulls studied exhibited an ovoid foramen magnum.Conclusions. The occipital condyle is frequently being drilled to expose lesions ventral to the brainstem. From our study, it is evident that the occipital condyle can be safely drilled for a distance of 12 mms from the posterior margin before encountering the hypoglossal canal. In 20% of the skulls the occipital condyle protrudes significantly into the foramen magnum. Wide and sagittally inclined occipital condyles, medially protruberant occipital condyles along with a foramen magnum index of more than 1.2 will require much more extensive bony resection than otherwise. With the availability of recent imaging techniques, it is possible to anticipate the extent of bony resection required in an individual case by using the above mentioned morphometric features.     

Intradural jugular tuberclectomy in a case of inadequate extradural removal

BACKGROUND: The jugular tubercles are paired protuberances that arise from the inferolateral margins of the clivus and project posterosuperiorly over the hypoglossal canal. These bony structures sometimes obscure and hinder surgical manipulation of lesions situated in the lateral and premedullary cisterns during extended far lateral suboccipital approaches. The application of intradural jugular tuberclectomy is described to remove this bony eminence. METHODS: A case of ruptured dissecting aneurysm in the vertebral artery was treated through the transcondylar approach. Extradural removal of the posterior portion of the jugular tubercle was performed. The dura over the jugular tubercle was then removed, and the anterior part of the jugular tubercle was drilled away between the intradural hypoglossal canal foramen and jugular foramen under the lower cranial nerves. RESULTS: Great care was required during the intradural drilling procedure to prevent damage to the lower cranial nerves, brain stem, and jugular bulb. Intradural jugular tuberclectomy provided an adequate microscopic view of the midline anterior lower clival region. CONCLUSIONS: Intradural jugular tuberclectomy is a useful technique to remove the anterior part of this bony eminence after the transcondylar approach.     

Common surgical pitfalls in the skull

BACKGROUND: A detailed knowledge of the morphologic variations in the ossicles, foramina, and ridges of the skull vault and skull base is vital to performing safe radical surgery. METHODS: A surgical reminder of possible pitfalls was composed based on the incidences of most of the minor variations such as the supraorbital notch, frontal foramen, metopism, foramen caecum, parietal foramina, bony defects in the fossa occipitalis cerebellaris, Inca bone, foramen lacerum anterius, incomplete posterolateral wall of the foramen ovale, absence of the medial or posterior wall of the foramen spinosum, foramen innominatus, foramen meningoorbitale, bony dehiscence of the internal carotid canal, bony ridge or torus in the floor of the external auditory meatus, foramen of Huschke, precondylar tubercle, foramen hypoglossi, anterior condylar canal, hypoglossal bridging, divided articular surface of the occipital condyle, high jugular bulb, paramastoid process, atlanto-occipital assimilation, ossicle of Kerkring, delta or keyhole shaped bony defects in the anterior border of foramen magnum, foramen of Vesalius, posterior condylar canal, mastoid emissary foramen and occipital foramen in 200 skulls. CONCLUSION: Recognition of these structures and their possible variations will help in distinguishing normal from potentially abnormal structures during computed tomography and magnetic resonance imaging examinations, and in avoiding misinterpretations that lead to confusion during surgical interventions. Instrumentation near potential bone gaps may traumatize important neural or vascular structures.     

Transcondylar fossa approach to treat ventral foramen magnum meningioma--case report

A 41-year-old female presented with a meningioma of the craniocervical junction manifesting as tetraparesis and vesicourethral dysfunction. Neuroradiological examinations showed a homogeneous enhanced mass lesion extending from the foramen magnum to the upper aspect of the second vertebral body. The tumor was totally removed via the transcondylar fossa approach, which is one type of the lateral approach. She was discharged without neurological deficits. The transcondylar approach is often utilized for lesions that occupy the ventral portion around the foramen magnum. The transcondylar fossa approach, a variation of the transcondylar approach, is a refined technique which obtains a closely similar surgical working field. Use of the transcondylar fossa approach remains controversial when treating patients with little brain stem dislocation, a small condylar fossa, and a protruding occipital condyle, but the approach can easily be converted to the transcondylar approach. The transcondylar fossa approach could become a standard method to access the craniocervical junction.     

The midline suboccipital subtonsillar approach to the hypoglossal canal: surgical anatomy and clinical application

Summary Primary lesions of the hypoglossal canal, such as hypoglossal schwannomas, are rare. No consensus exists with regard to the surgical approach of choice for treatment of these lesions. Usually, lateral transcondylar approaches have been used. The authors describe the surgical anatomy of the midline subtonsillar approach to the hypoglossal canal. This approach includes a midline suboccipital craniotomy, dorsal opening of the foramen magnum and elevation of ipsilateral cerebellar tonsil to expose the hypoglossal nerve and its canal. The midline subtonsillar approach permits a straight primary intradural view to the hypoglossal canal. There is no necessity of condylar resections. The surgical anatomy of the subtonsillar approach is described and illustrated by an example of a case.     

Surgery on a saccular vertebral artery-posterior inferior cerebellar artery aneurysm via the transcondylar fossa (supracondylar transjugular tubercle) approach or the transcondylar approach: surgical results and indications for using two different lateral skull base approaches.

OBJECT: The authors report on the surgical results they achieved in caring for patients with vertebral artery-posterior inferior cerebellar artery (VA-PICA) saccular aneurysms that were treated via either the transcondylar fossa (supracondylar transjugular tubercle) approach or the transcondylar approach. In this report they clarify the characteristics of and differences between these two lateral skull base approaches. They also present the techniques they used in performing the transcondylar fossa approach, especially the maneuver used to remove the jugular tubercle extradurally without injuring the atlantooccipital joint. METHODS: Eight patients underwent surgery for VA-PICA saccular aneurysms (six ruptured and two unruptured ones) during which one of the two approaches was performed. Clinical data including neurological and radiological findings and reports of the operative procedures were analyzed. The Glasgow Outcome Scale was used to estimate the activities of daily living experienced by the patients. In all cases the aneurysm was successfully clipped and no permanent neurological deficits remained, except for one case of severe vasospasm. In seven of the eight patients, the transcondylar fossa approach provided a sufficient operative field for clipping the aneurysm without difficulty. In the remaining patient, in whom the aneurysm was located at the midline on the clivus at the level of the hypoglossal canal, the aneurysm could not be found by using the transcondylar fossa approach; thus, the route was changed to the transcondylar approach, and clipping was performed below the hypoglossal nerve rootlets. CONCLUSIONS: Both approaches offer excellent visualization and a wide working field, with ready access to the lesion. This remarkably reduces the risk of development of postoperative deficits. These approaches should be used properly; the transcondylar fossa approach is indicated for aneurysms located above the hypoglossal canal and the transcondylar approach is indicated for those located below it.     

枕骨大孔区肿瘤的显微外科治疗

目的 探索枕骨大孔区肿瘤的治疗方法以提高治疗效果。方法 通过显微外科手术治疗31例枕骨大孔区肿瘤,其中脑膜瘤13例,神经鞘瘤15例,脊索3例。根据肿瘤附着点、生长方式及手术入路将肿瘤分为2种类型：I型：肿瘤主要位于枕骨大孔前方,包括基底起源于枕骨大孔上方、前方和前侧方,共15例;Ⅱ型：肿瘤主要位于枕骨大孔后方,包括基底起源于枕骨大孔后方、后侧方和椎管内,共16例。采用3种手术入路切除肿瘤：枕颈后正中和侧方入路18例,远外侧或经髁入路10例,枕下乙状窦后入路3例。结果 肿瘤全部切除25例,次全切除5例,部分切除1例,无手术死亡。I型枕骨大孔区肿瘤全切除9例,次全切除5例,部分切除1例;Ⅱ型均全切除。结论 I型枕骨大孔区肿瘤,手术全切除肿瘤困难,远外侧经髁入路是切除I型枕骨大孔区肿瘤最有效的方法;Ⅱ型肿瘤容易全切除,预后良好。     

Dural arteriovenous fistula of the anterior condylar confluence and hypoglossal canal mimicking a jugular foramen tumor

The anterior condylar confluence (ACC) is located on the external orifice of the canal of the hypoglossal nerve and provides multiple connections with the dural venous sinuses of the posterior fossa, internal jugular vein, and the vertebral venous plexus. Dural arteriovenous fistulas (DAVFs) of the ACC and hypoglossal canal (anterior condylar vein) are extremely rare. The authors present a case involving an ACC DAVF and hypoglossal canal that mimicked a hypervascular jugular bulb tumor. This 53-year-old man presented with right hypoglossal nerve palsy. A right pulsatile tinnitus had resolved several months previously. Magnetic resonance imaging demonstrated an enhancing right-sided jugular foramen lesion involving the hypoglossal canal. Cerebral angiography revealed a hypervascular lesion at the jugular bulb, with early venous drainage into the extracranial vertebral venous plexus. This was thought to represent either a glomus jugulare tumor or a DAVF. The patient underwent preoperative transarterial embolization followed by surgical exploration via a far-lateral transcondylar approach. At surgery, a DAVF was identified draining into the ACC and hypoglossal canal. The fistula was surgically obliterated, and this was confirmed on postoperative angiography. The patient's hypoglossal nerve palsy resolved. Dural arteriovenous fistulas of the ACC and hypoglossal canal are rare lesions that can present with isolated hypoglossal nerve palsies. They should be included in the differential diagnosis of hypervascular jugular bulb lesions. The authors review the anatomy of the ACC and discuss the literature on DAVFs involving the hypoglossal canal.     

The dorsolateral, suboccipital, transcondylar approach to the lower clivus and anterior portion of the craniocervical junction.

The authors review their experience with a dorsolateral approach to the anterior rim of the foramen magnum and adjacent region. The operative technique includes exposure of the vertebral artery at C1, partial resection of the occipital condyle and lateral atlantal mass, and extradural drilling of the jugular tubercle. This approach has been applied in six patients who harbored intradural space-occupying lesions located ventral to the lower brain stem. Excision of the neoplasm was virtually total in all but one patient, in whom biopsy was the primary goal of the intervention. No morbidity and no mortality were associated with this approach. The main advantage of the dorsolateral, suboccipital, transcondylar route is the direct view it offers to the anterior rim of the foramen magnum without requiring brain stem retraction.     

The extreme lateral transcondylar approach to aneurysms of the vertebrobasilar junction, the vertebral artery, and the posterior inferior cerebellar artery

The unilateral suboccipital craniotomy is the commonly performed approach to aneurysms of the vertebrobasilar junction, the vertebral artery, and the posterior inferior cerebellar artery (PICA). Many of these aneurysms are placed anterior or anterolateral to the brain stem, necessitating brain stem retraction for adequate exposure. Small dorsolateral enlargement of the foramen magnum, partial resection of the occipital condyle, and removal of the jugular tubercle allow access to the neurovascular structures ventral to the medulla without retraction of the neuroaxis. This extreme lateral transcondylar approach was performed in 20 patients with aneurysms of the vertebrobasilar junction, the vertebral artery, and the PICA; intraoperatively, two suspected aneurysms proved to be vascular malformations. Occlusion of the aneurysm and vascular malformation was successfully performed in 16 patients, resection of the vascular malformation was achieved in 1 patient, and the vertebral artery was clipped in 3 patients with fusiform aneurysms without complications related to the extreme lateral transcondylar approach. Unobstructed exposure of the aneurysm, parent artery, and neural structures without retraction of the sensitive lower brain stem are the major advantages of the extreme lateral transcondylar approach.     

Quantitative description of the far-lateral transcondylar transtubercular approach to the foramen magnum and clivus

OBJECT: The purpose of this study was to evaluate the far-lateral transcondylar transtubercular approach (complete FLA) based on quantitative measurements of the exposure of the foramen magnum and petroclival area obtained after each successive step of this approach. METHODS: The complete FLA was reproduced in eight specially prepared cadaveric heads (a total of 15 sides). The approach was divided into six steps: 1) C-1 hemilaminectomy and suboccipital craniectomy with unroofing of the sigmoid sinus (basic FLA); 2) partial resection of the occipital condyle (up to the hypoglossal canal); 3) removal of the jugular tuberculum; 4) mastoidectomy (limited to the labyrinth and the fallopian canal) and retraction of the sigmoid sinus; 5) resection of the lateral mass of C-1 with mobilization of the vertebral artery; and 6) resection of the remaining portion of the occipital condyle. After each successive step, a standard set of measurements was obtained using a frameless stereotactic device. The measurements were used to estimate two parameters: the size of the exposed petroclival area and the size of a spatial cone directed toward the anterior rim of the foramen magnum, which depicts the amount of surgical freedom available for manipulation of instruments. The initial basic FLA provided exposure of only 21 +/- 6% of the petroclival area that was exposed with the full, six-step maximally aggressive (complete) FLA. Likewise, only 18 +/- 9% of the final surgical freedom was obtained after the basic FLA was performed. Each subsequent step of the approach increased both petroclival exposure and surgical freedom. The most dramatic increase in petroclival exposure was noted after removal of the jugular tuberculum (71 +/- 12% of final exposure), whereas the least improvement in exposure occurred after the final step, which consisted of total condyle resection. CONCLUSIONS: The complete FLA provides wide and sufficient exposure of the foramen magnum and lower to middle clivus. The complete FLA consists of several steps, each of which contributes to increasing petroclival exposure and surgical freedom. However, the FLA may be limited to the less aggressive steps, while still achieving significant exposure and surgical freedom. The choice of complete or basic FLA thus depends on the underlying pathological condition and the degree of exposure required for effective surgical treatment.     

Surgical Treatment of Glossopharyngeal Neuralgia as Vascular Compression Syndrome via Transcondylar Fossa (Supracondylar Transjugular Tubercle) Approach

Summary  Objective. These are the first reported cases in whom the transcondylar fossa approach was applied for the treatment of glossopharyngeal neuralgia (GPN) as a vascular compression syndrome.  Cases Presentation. All three cases presented with severe paroxysmal pharyngeal pain which could not be controlled by medical treatment. The patients all underwent microvascular decompression surgery (MVD) via transcondylar fossa approach. The posterior inferior cerebellar artery or the anterior inferior cerebellar artery was clearly verified to be compressing the glossopharyngeal nerve and then was safely and completely moved and fixed to the dura mater by the sling retraction technique to effect decompression. No patient has since experienced any further pain or permanent neurological deficit after surgery.  Technical Advantage. The transcondylar fossa approach is one of the lateral approaches which is different from the transcondylar approach. In this approach, the posterior part of the jugular tubercle is extradurally removed without injuring the atlanto-occipital joint. The entire course of the cisternal portion of the glossopharyngeal nerve can be sufficiently seen with gentle retraction of the cerebellar hemisphere, when using this approach.  Conclusion. This approach makes the MVD for GPN both effective and safe.     

The Extreme Lateral Transcondylar Approach to Aneurysms of the Vertebrobasilar Junction, the Vertebral Artery, and the Posterior Inferior Cerebellar Artery

The unilateral suboccipital craniotomy is the commonly performed approach to aneurysms of the vertebrobasilar junction, the vertebral artery, and the posterior inferior cerebellar artery (PICA). Many of these aneurysms are placed anterior or anterolateral to the brain stem, necessitating brain stem retraction for adequate exposure. Small dorsolateral enlargement of the foramen magnum, partial resection of the occipital condyle, and removal of the jugular tubercle allow access to the neurovascular structures ventral to the medulla without retraction of the neuroaxis. This extreme lateral transcondylar approach was performed in 20 patients with aneurysms of the vertebrobasilar junction, the vertebral artery, and the PICA; intraoperatively, two suspected aneurysms proved to be vascular malformations. Occlusion of the aneurysm and vascular malformation was successfully performed in 16 patients, resection of the vascular malformation was achieved in 1 patient, and the vertebral artery was clipped in 3 patients with fusiform aneurysms without complications related to the extreme lateral transcondylar approach. Unobstructed exposure of the aneurysm, parent artery, and neural structures without retraction of the sensitive lower brain stem are the major advantages of the extreme lateral transcondylar approach.     

Three-dimensional CT angiography for the surgical management of the vertebral artery-posterior inferior cerebellar artery aneurysms

Summary Background. Surgery of vertebral artery-posterior inferior cerebellar artery (VA-PICA) aneurysms is not easy because there is a close anatomical relationship between aneurysms and the surrounding neurovascular structures, and bony structures in the lateral foramen magnum. The preoperative evaluation for a circumstantial comprehension of anatomical relationships is very important for the surgical treatment of the VA-PICA aneurysms. Our experience in using three-dimensional CT angiography (3D-CTA) for the surgical management of VA-PICA aneurysms is herein reported.Methods and findings. We successfully performed neck clipping in 5 cases of VA-PICA aneurysm using 3D-CTA. On 3D reconstructed images, we could see the characteristics of the aneurysms such as their relationships to the jugular tubercle and hypoglossal canal, the projecting direction of the dome, and the configuration of the neck in each case. 3D-CTA also provided a clear surgical view as well as the relationships of the aneurysms to the VA and origin of the PICA. Based on such information, we selected the most appropriate surgical approach among the transcondylar fossa approach, the transcondylar approach, or the far lateral approach with a C1 laminectomy.Conclusions. Since 3D-CTA demonstrates the surgical anatomy of VA-PICA aneurysms in detail, it is very useful for helping surgeons to select the optimal approach.     

Persistent primitive hypoglossal artery associated with proximal posterior inferior cerebellar artery aneurysm

BACKGROUND: A persistent primitive hypoglossal artery (PPHA) is a rare anomaly. The association of PPHA with intracranial aneurysms of the artery has also been rarely reported. We surgically treated a case of PPHA associated with a ruptured saccular aneurysm at the proximal posterior inferior cerebellar artery (PICA). CASE DESCRIPTION: The patient was admitted because of subarachnoid hemorrhaging. Angiography and three-dimensional computed tomography (CT) angiography (3D-CTA) demonstrated a left PPHA entering the posterior fossa through the left large hypoglossal canal. The left vertebral artery was absent. A saccular aneurysm was found at the junction of the PPHA and the proximal PICA. 3D-CTA showed not only the aneurysm itself but also the anatomical relationship between the aneurysm and the surrounding structures. Therefore, 3D-CTA was very useful in planning the surgery. The neck of the aneurysm was clipped through a far lateral approach associated with a C1 laminectomy, because this case had a large posterior condylar emissary vein and the aneurysm was located just posteroinferior to the hypoglossal canal. CONCLUSIONS: A case of PPHA associated with an aneurysm at the proximal PICA is reported. This case not only had a large hypoglossal canal but also had a huge posterior condylar emissary vein in the large posterior condylar canal. Anomalous structures associated with PPHA are also discussed. Finally, 3D-CTA proved to be very useful in planning the optimal surgical modality around the lateral portion of the foramen magnum.     

联合上颈段经颈静脉孔区入路的显微解剖学研究

目的 研究颈静脉孔区(JF)入路的显微解剖,利用该入路一期切除颅内外沟通型复杂病变.方法 成人尸头标本15例(30侧),在手术显微镜下进行联合上颈段经JF区入路的解剖操作,测量相关数据.结果 对C1～C4上颈段解剖,切除C1横突,游离椎动脉C1～C2段及水平段;充分切除颈静脉结节、颈静脉突及部分枕骨髁;迷路后切除乳突,显露半规管,轮廓化面神经垂直段,全程暴露乙状窦,打开颈静脉孔;扩大了JF区的显露并测得相关参数,如乳突尖间距枕髁外缘中点为(29.65±3.24)mm;枕髁后缘距舌下神经管内口为(10.10±0.81)mm;颈静脉球距面神经垂直段间距左为(6.8±0.35)mm,右为(4.6±0.33)mm.结论 此入路从多个方向对JF区充分暴露,使面神经、耳蜗、椎动脉、后组脑神经等结构得到保护,术中结合相关解剖参数可很好的完成一期全切JF区颅内外沟通型及延伸到上颈位的病变,提高治愈率、减少并发症、降低死亡率.