Lateral suboccipital approach for vertebral and vertebrobasilar artery lesions

A modification of the unilateral suboccipital approach is elaborated and illustrated. This modification is useful for aneurysms of the vertebral artery, the vertebrobasilar junction, and the proximal basilar trunk, and for arteriovenous malformations of the inferolateral cerebellum. It entails extreme lateral removal of the rim of the foramen magnum toward the condylar fossa and posterolateral removal of the arch of the atlas toward the exposed vertebral artery. This extra bone removal allows an approach to the front of the brain stem from inferolaterally, after gentle upward and medial retraction of the tonsil, with minimal or no retraction of the medulla.     

经枕颈后外侧入路治疗寰枕区腹侧病变的安全性评估

目的 对经枕颈后外侧入路手术治疗寰枕区腹侧病变的不良事件作统计,评估该术式的安全性.方法 1999～2006年,对74例寰枕区以腹侧病变压迫为主的患者进行治疗,手术经枕颈后外侧入路,先行枕骨大孔扩大及寰椎后弓切除减压,再经枕颈区硬脊膜侧方显露齿突及C2椎体做相应压迫因素切除,达到脊髓前后方同时减压,并同期完成枕颈植骨...     

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.     

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.     

经枕颈后外侧入路行畸形齿突切除术

探索枕寰区畸形的外科治疗途径。方法在详细研究枕颈部解剖结构后,采用经枕颈后外侧入路先行枕骨大孔扩大及寰椎后弓切除减压,然后经枕颈区硬脊膜侧方显露齿突及Ｃ２椎体的后方,用高速磨钻切除畸形的齿突。作者于１９９７年１月－１９９８年１月和此术式治疗枕寰区畸形８例,其中５例合并寰枢椎脱位者行一期枕颈植骨融合。结果全组患者无手术死亡及术后感染。术后随访６－１８个月,发现８例患者躯体感觉接近正常,四肢肌张力明显     

Surgical possibilities in the third portion of the vertebral artery (above C2). Anatomical study and report of a case of anastomosis between subclavian artery and vertebral artery at C1-C2 level.

A reappraisal of surgical possibilities in the third portion of the vertebral artery (VA) above C2, has been done from an anatomical study on twenty autopsy specimens. A route passing between the internal jugular vein and the Sterno-cleido-mastoid muscle allows a simple approach to the transverse process of C1. After division of two muscles attached to this process, 1.5 cm of the VA can be exposed. For larger exposure of the artery, the foramen transversarium of C1 must be unroofed and the artery dissected in the guttering of the posterior arch of the atlas. This surgical route was used in a case of aneurysmal dysplasia at the C3 level. An anastomosis between the subclavian artery and VA at the C1-C2 level was performed with an autologous saphenous vein graft. The key points are the highest possible freeing of the XI nerve and the head position. Rotation and extension move the transverse process and the posterior arch of the atlas superficially and anteriorly.     

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.     

Far-lateral approach to intradural lesions of the foramen magnum without resection of the occipital condyle

OBJECT: The goal of this study was to determine whether drilling out the occipital condyle facilitates surgery via the far-lateral approach by comparing data from 10 clinical cases with that from studies of eight cadaver heads. METHODS: During the last 6 years at Louisiana State University Health Sciences Center-Shreveport, 10 patients underwent surgery via the far-lateral approach to the foramen magnum. Six of these patients harbored anterior foramen magnum meningiomas, one patient a dermoid cyst, two patients vertebral artery (VA) aneurysms, and an additional patient suffered from rheumatoid disease of the craniocervical junction. The surgical approach consisted of retromastoid craniectomy and C-1 laminectomy. The seven tumors and the pannus of rheumatoid disease were completely excised, and the two aneurysms were clipped without drilling the occipital condyle. In one patient a chronic subdural hematoma was found 3 months after surgery, but no patient displayed any complication associated with surgery. It is significant that in no patient was a cerebrospinal fluid leak present. All patients experienced improved neurological function postoperatively. To compare surgical visibility, eight cadaveric specimens (16 sides) were studied, including delineation of the VA and its segments around the craniocervical junction. Increase in visibility as a function of fractional removal of the occipital condyle was quantified by measuring the degrees of visibility gained by removing one third and one half of the occipital condyle. Removal of one third of the occipital condyle produced a mean increase of 15.9 degrees visibility, and removal of one half produced a mean increase of 19.9 degrees. CONCLUSIONS: On the basis of their findings the authors conclude that removal of the occipital condyle is not necessary for the safe and complete resection of anterior intradural foramen magnum tumors.     

Unilateral axis facet hypertrophy—a rare case of irreducible rotatory atlantoaxial dislocation and a review of the literature

Fixed atlantoaxial dislocations are difficult to treat and there is no consensus in the treatment protocol. Unilateral enlargement of the atlas–axis facet complex in fixed atlantoaxial dislocations is a very rare condition. These pathologies are usually quite unstable and surgical treatment is necessary in unreductable cases. A 52-year-old woman with a diagnosis of irreducible-fixed rotatory atlantoaxial dislocation presented with acute onset of dizziness, loss of balance, and tetraparesis. She was under 8 years of conservative follow-up. Review of radiology revealed unilateral C2 superior facet hypertrophy compressing the medulla and obstructing the vertebral artery. To treat this condition, we have used a posterior midline approach and removed the lateral portions of the posterior rim of the foramen magnum and the assimilated posterior arch of C1. The V3 segments of the vertebral arteries were exposed bilaterally. The atlantoaxial joint complex on the left was hypertrophied compressing V3. We have removed hypertrophied lateral mass of the atlas and the hypertrophic superior articular facet of C2 for decompression. Patency of both vertebral arteries were checked intraoperatively by Doppler and indocyanine green angiography. We have fixated craniocervical junction on the same session. Patient was neurologically intact and she had confirmed fusion on the surgical site after three years of follow-up. This is a rare case of unilateral hypertrophy of the C2 superior articular facet in a fixed atlantoaxial rotatory dislocation. Progressive compression of medulla and the left vertebral artery leaded to clinical worsening of neurology in this case after 8 years of follow-up. Surgical treatment was necessary for neurological decompression and to establish stability.     

Endoscopic Endonasal Approach to the Ventral Cranio-Cervical Junction: Anatomical Study

Summary. Summary.   Objective: In order to develop an endoscopic endonasal approach to the ventral cranio-cervical junction and odontoid process under the concept of a minimally invasive surgical strategy, a cadaver study was performed.   Methods: Sixteen artery-injected adult head specimens were used. Endonasal endoscopic approach was made through one- or two-nostril routes following the Jho's endonasal paraseptal technique. Rod-lens endoscopes, which were 2.7 or 4 mm in diameter, 18 cm in length with 0-, 30-, and 70-degree lenses, were used.   Results: Surgical landmarks leading to the craniocervical junction were the inferior margin of the middle turbinate, nasopharynx and Eustachian tube. The nasopharynx was readily identified following the inferior margin of the middle turbinate. The line drawn between the Eustachian tubes indicated the juncture between the clivus and atlas. With a midline mucosal incision, the ventral cranio-cervical junction was exposed. Odontoid resection was performed with removal of the anterior arch of the atlas. Clival resection can be performed as much rostral as required. Manoeuverability of the surgical instruments was better with a two-nostril technique than with a one-nostril. Although the entire midline clivus was accessible rostrally, C-2 was the caudal limit through this endonasal route. A suturing device needed to be developed for mucosal or dural closure for live operations.   Conclusion: This cadaver study demonstrates that an endoscopic endonasal approach to the ventral cranio-cervical junction and odontoid process can be a valid alternative to the conventional transoral approach.     

Surgery of the craniocervical junction in primary tumors of the spine

Tumors of the cranio-cervical junction can be surgically approached either anteriorly or posteriorly. The main anterior (transoral, transcervical or lateral) and posterior routes are described. Posterior approach is used for localization on the posterior arch and for anthrodesis. Anterior approach is proposed for extra-dural lesions of the anterior part of C1 and the foramen magnum.     

经枕颈后外侧入路齿状突切除治疗寰枢椎陈旧性脱位

目的　为解决难复性寰枢椎陈旧性脱位的外科治疗,探索手术入路措施。方法采用经枕颈后外侧入路切除齿状突并一期行枕颈融合治疗难复性寰枢椎陈旧性脱位5例。结果5 例手术经过顺利,术后神经症状均有明显改善,肌力均有一级以上恢复。无感染及死亡。结论　对难复性寰枢椎陈旧性脱位,尤其是压迫因素来自前方者,经枕颈后外侧入路切除齿状突和颈2 椎体后上份,能同时达到脊髓前、后方彻底减压及一期枕颈融合。此手术入路齿状突显露清楚,手术操作简便、安全。是一种较理想的手术方法。     

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.     

上颈段椎管内哑铃型神经鞘瘤的外科治疗

目的：探讨枕大孔区至颈2椎管内哑铃型神经鞘瘤的手术与稳定性重建方法及技巧。方法：2002年1月～2007年1月收治的19例患者，枕大孔到颈1水平5例，颈1到颈2水平14例。后正中入路，显露枕骨大孔至颈3水平，肿瘤位于枕大孔至颈1水平者，先切除枕骨大孔，依据情况切除寰椎后弓。肿瘤位于颈1、2水平者切除颈2椎板。从背外侧显露肿瘤的全貌，先自肿瘤移行部将肿瘤横断，切除椎管内肿瘤，然后切除椎管外肿瘤。肿瘤若与神经根粘连紧密可切除宿主神经根。然后依据情况重建其稳定功能。结果：19例完全切除，所有患者术后第3天颈围领保护下下床活动。恢复良好13例，改善4例，无明显改善1例，恶化1例，无手术死亡。随访1～6年，MRI检查未见肿瘤复发。所有患者术后6个月均获得骨性融合，稳定性良好。结论：上颈段哑铃型椎管内神经鞘瘤手术难度火，术中尽可能的减少骨性结构的破坏。稳定性的重建非常必要。     

枕颈部畸形合并颈脊髓空洞症的外科治疗

报告８例枕颈部畸形合并颈脊髓空洞症（Ｃｈｉａｒｉ畸形Ａ型）并经手术治疗。根据临床表现和影像学（ＭＲＩ）征象，应用枕骨大孔扩大，寰椎后弓切除减压，枕颈自体髂骨植骨融合及脊髓空洞蛛网膜下腔分流术。术后症状和体征明显改善７例，无变化１例。本文对有临床症状的Ｃｈｉａｒｉ畸形的发病和治疗进行了讨论．     

Anterior video-assisted approach to the craniovertebral junction: transnasal or transoral? A cadaver study

Background

Endoscopy represents both an alternative and useful complement to the standard microsurgical approach to the anterior craniovertebral junction (CVJ). Nevertheless, few studies provide an experimental comparison between transnasal and transoral endoscopic control on CVJ. We compared the surgical exposition angle and the working channel volume of both the transnasal and transoral approaches in the cadaver.

Methods

Eleven fresh non-perfused cadavers were studied. Transnasal and transoral linear and angled exposure of the CVJ were evaluated by means of X-ray and CT scan both in sagittal and lateral planes.

Results

The transoral endoscopic surgical exposition was wider compared with the transnasal in anterior and lateral projections:(1)in the sagittal plane, both in vertical exposition (transnasal inferior to transoral from 5.89 % to 76.48 %, average 35.89 %) and in vertical surgical angle (from 22 % to 77.42 %, average 56.53 %); (2)in the coronal plane, both in coronal exposition (transnasal inferior to transoral from 50.77 % to 83.88 %, average 70.34 %) and in coronal surgical angle (from 65.58 % to 86.71 %, average 76.70 %). The sagittal surgical domain was found to spanning from the inferior third of the clivus to C3 with the transoral and from the middle third of the clivus to the nasopalatal line (NPL) with the transnasal approach. The overlapping surgical domain area was found to be the inferior third of the clivus.

Conclusions

The endoscope assisted transoral approach allows a better surgical control of the CVJ. It provides a better CVJ exposure, in sagittal and transverse planes, providing a larger working channel and an easier manoeuvrability. The transnasal approach is limited in caudal direction down to the NPL, otherwise the transoral approach is limited in the rostral direction with a maximum to the foramen magnum in normal specimen. In every individual case, pros and cons of the appropriate approach have to be taken into account as well as the choice of a combined transnasal and transoral approaches strategy.     

Computed tomography in developmental anomalies of craniocervical junction

We reviewed 27 patients with developmental anomalies in craniovertebral junction, and special attention was paid to computed tomography (CT) findings in congenital atlantoaxial dislocation (AAD), basilar invagination and Chiari malformations. In ADD, CT clearly demonstrated the relationships of the atlas to the axis in axial plane. Four major types were distinguished; anteroposterior (6 cases), transverse (0 case), anteroposterior-transverse (4 cases) and rotatory (5 cases) dislocations. It was feasible by CT to analyse the pathomechanics in each individual with AAD. Soft tissue wad was shown on the posterior aspect of the odontoid in 7 out of 15 patients with AAD. Those two features, pathomechanics of AAD and intraspinal soft tissue wad, were felt to be important for patient's symptomatology. Basilar invagination presented in no patient as a single deformity and was always associated with other bony and neural abnormalities in 14 patients. Basilar invagination might be suggested of its existence in such a case as CT showing; (1) the odontoid at or above the level of the foramen magnum, (2) distinctive margin of the foramen magnum above the bottom of the posterior fossa, and (3) the posterior arch of the atlas at the same level as foramen magnum. Nevertheless, it is essential to confirm occipital hypoplasia by using either reformatting CT images in coronal and sagittal plane or conventional tomography; whereas high resolutional CT machine provides new dimension for demonstration of bony details. In Chiari malformations, plain CT scanned by high resolutional machine often makes it possible to delineate caudal migration of the cerebellar tonsils, so that it may be a choice of examination as a screening of the anomaly. In addition, metrizamide CT clearly demonstrated caudal migration both of cerebellar tonsils and medulla oblongata. Therefore, CT apparently exceeds other diagnostic modalities in evaluating this anomaly.     

Endoscope-assisted microsurgical transoral approach to the anterior craniovertebral junction compressive pathologies

At the present time, an update to the classical microsurgical transoral decompression is strongly provided by the most recent literature dealing with the introduction of the endoscopy in spine surgery. In this paper, we present our experience on the endoscope-assisted microsurgical transoral approach to anterior craniovertebral junction (CVJ) compressive pathology. We analysed seven patients (3 paediatrics and 4 adults ranging from 6 to 78 years) operated on for CVJ decompressive procedures using an open access, microsurgical technique, neuronavigation and endoscopy. All techniques mentioned were simultaneously employed. Among the endoscopic routes described in the literature, we have preferred the transoral using 30° endoscopes. In all the cases endoscopy allowed a radical decompression compared to the microsurgical technique alone, as confirmed intraoperatively with contrast medium fluoroscopy. In conclusion, endoscopy represents a useful complement to the standard microsurgical approach to the anterior CVJ; it provides information for a better decompression with no need for soft palate splitting, hard palate resection, or extended maxillotomy. Moreover, intraoperative fluoroscopy helps to recognize residual compression. Virtually, in normal anatomic conditions, no surgical limitations exist for endoscopically assisted transoral approach, compared with the pure endonasal and transcervical endoscopic approaches. In our opinion, the endoscope deserves a role as “support” to the standard transoral microsurgical approach since 30° angulated endoscopy significantly increases the surgical area exposed at the level of the anterior CVJ.     

Comparison of the far lateral and extreme lateral variants of the atlanto-occipital transarticular approach to anterior extradural lesions of the craniovertebral junction

OBJECTIVE: Managing lesions situated in the anterior aspect of the craniovertebral junction (CVJ) remains a challenging neurosurgical problem. The purposes of this study were to examine the microsurgical anatomy of the anterior extradural aspect of the CVJ and the differences in the exposure obtained by the far lateral and extreme lateral atlanto-occipital transarticular approaches. The far lateral approach, as originally described, is a lateral suboccipital approach directed behind the sternocleidomastoid muscle and the vertebral artery and just medial to the occipital and atlantal condyles and the atlanto-occipital joint. The extreme lateral approach, as originally described, is a direct lateral approach deep to the anterior part of the sternocleidomastoid muscle and behind the internal jugular vein along the front of the vertebral artery. Both approaches permit drilling of the condyles at the atlanto-occipital joint but provide a different exposure because of the differences in the direction of the approach. METHODS: Fifteen adult cadaveric specimens were studied using a magnification of x3 to x40 after perfusion of the arteries and veins with colored silicone. The microsurgical anatomy of the extradural aspects of the CVJ and the two atlanto-occipital transarticular approaches were examined in stepwise dissections. RESULTS: The far lateral atlanto-occipital transarticular approach provides excellent exposure of the extradural lesions located in the ipsilateral anterior and anterolateral aspects of the extradural region of the CVJ. The extreme lateral atlanto-occipital transarticular approach provides excellent exposure, not only on the side of the exposure, but also extending across the midline to the medial aspect of the contralateral atlanto-occipital joint and the lower clivus. CONCLUSION: The far lateral and extreme lateral variants of the atlanto-occipital transarticular approach provide an alternative to the transoral approach to the anterior extradural structures at the CVJ. Compared with the transoral approach, both approaches provide a shorter operative route, avoid the contaminated nasopharynx, reduce the incidence of cerebrospinal fluid leak, and are not limited laterally by the atlanto-occipital joint.