Search

Background: Descriptions of intracranial extensions of vertebral venous plexuses are lacking., Objective: To identify vertebral venous plexuses at the craniocervical junction in cadavers and describe them., Methods: The authors dissected 15 ink-injected, formalin-fixed, adult cadaveric heads and measured cranial extensions of the spinal venous plexuses., Results: All specimens had vertebral venous plexuses at the craniocervical junction composed of multiple interwoven vessels concentrated anteriorly (anterior vertebral plexuses), posteriorly (posterior vertebral venous plexuses), and laterally (lateral vertebral venous plexuses). Veins making up the plexus tended to be largest for the anterior internal vertebral venous plexus. On 33%, a previously unnamed lateral internal vertebral venous plexus was identified that connected to the lateral marginal sinus. The anterior external vertebral venous plexus connected to the basilar venous plexus via transclival emissary veins in 13%; remaining veins connected either intracranially via small perforating branches through the anterior atlanto-occipital membrane (33%) or had no direct gross connections inside the cranium (53%). The anterior internal vertebral plexus, which traveled between layers of the posterior longitudinal ligament, connected to the anterior half of the marginal sinus in 33% and anterolateral parts of the marginal sinus in 20%. The posterior internal venous plexus connected to the posterior aspect of the marginal sinus on 80% and into the occipital sinus in 13.3%. The posterior external venous plexus connected to veins of the hypoglossal canal in 20% and into the posterior aspect of the marginal sinus in 13.3%., Conclusion: Knowledge of these connections is useful to neurosurgeons and interventional radiologists., (Copyright © 2017 by the Congress of Neurological Surgeons)

Traumatic injuries of the craniovertebral junction (CVJ) area are common and frequently the outcome of motor vehicle accidents, falls, and diving accidents. To define and characterize CVJ traumatic injuries, some international classifications are currently in use, and they are thought and focused on junction bone fracture. However, recent data point out a major important role of the CVJ ligaments and membranes in traumatic injuries with a secondary function of the osseous structures. Emphasizing the correct role of the ligaments and membranes is extremely important for determining appropriate medical or surgical planning for patients and also to design new CVJ injury classifications. We reviewed every recent major publication on the ligaments and membranes of the CVJ area. We divided the information into sections concerning anatomy, embryology, biomechanics, trauma, and CVJ bone fractures. A role of the ligaments and membranes in the traumatic injuries of the CVJ area has often been recognized; but only recently, with the increase in the knowledge of the anatomic and biomechanical junction area, supported by neuroradiological tools (magnetic resonance imaging) and a more detailed traumatic injuries assessment, has the role of the ligaments and membranes been highlighted. Ligaments and membranes have a pivotal role in each junctional ability and are the key to orienting any medical or surgical indications in this unique area of the spine.

Background: The extradural portion of the vertebral artery (VA-V3) has a unique anatomy at the craniovertebral junction. The exposure of V3 can be accompanied by profuse bleeding from the venous plexus in addition to the potential risk of inadvertent injury of the VA during surgery at the craniovertebral junction. The natural tissue planes represent a road map to the safe exposure of the VA in the suboccipital triangle., Objective: To describe the microsurgical anatomy of the tissue planes in the suboccipital region., Methods: The suboccipital region was bilaterally dissected in 6 fresh silicone-injected cadaver heads. An interfascial technique was used to expose the VA-V3 following a tissue plane between the deep suboccipital muscular fascia dorsally and posterior atlantooccipital membrane, the C1 periosteal membrane, and the membrane covering the VA and venous plexus ventrally. The craniovertebral junction was harvested from 2 heads and prepared for histological sections. The same technique was applied in 25 operative cases., Results: The anatomic dissections confirmed the existence of an interfascial plane that can be dissected in a blunt fashion to reach as far lateral as the transverse processes of C1 and C2. Application of the dissection technique did not require diathermy coagulation in the operating room. In 25 cases, there was no injury of the VA or bleeding from the venous plexus., Conclusion: Vertebral artery exposure in the suboccipital triangle (V3) can be achieved safely with minimal blood loss using a technique that follows the natural tissue plane between the deep suboccipital muscle fascia, the posterior atlantooccipital membrane, the membrane covering VA/venous plexus, and the periosteum of the C1 and C2 laminae.

Objective: The indications and operative technique for a number of posterolateral approaches to the craniovertebral junction (CVJ) are reviewed., Methods: The literature addressing posterolateral approaches to the CVJ is reviewed, and illustrative cases are presented., Results: The far lateral approach and its variants, including the transcondylar, supracondylar, and paracondylar approaches, are an effective means of addressing intradural anterior and anterolateral CVJ lesions. These approaches provide exposure of the lower third of the clivus, the foramen magnum, and the upper cervical spine; do not cross contaminated regions; and enable a watertight dural closure to be performed. They are associated with minimal morbidity and usually do not significantly decrease the stability of the CVJ., Conclusion: All surgeons treating lesions of the CVJ should be familiar with the posterolateral approach and its modifications.

Objective: To describe the indications and techniques for occipitocervical (OC) fixation., Methods: The operative nuances of current OC fixation techniques are described. A surgical technique video is included., Results: Pertinent literature is reviewed regarding OC fixation techniques., Conclusion: OC fixation systems have evolved from wire and cable techniques to plates, rods, and screws. Screw-rod constructs are easy to implant and biomechanically more rigid than wire techniques.

An understanding of the regional anatomy and specific biomechanics of the craniovertebral junction is relevant to the specific diseases that affect the region as well as instrumentation of the occiput, atlas, and axis. This article reviews the bony, ligamentous, and vascular anatomy of the region, in relation to the posterior surgical approach to this anatomically unique segment of the cervical spine. Anatomic variations of the area are also discussed. Basic principles of instrumentation of the region are also reviewed. The kinematics of the region as they pertain to the anatomic discussion are reviewed and discussed.

Background: Defining the anatomic zones for the placement of occiput-C1 transarticular screws is essential for patient safety., Objective: The feasibility and accuracy of occiput-C1 transarticular screw placement were evaluated in this anatomical study of normal cadaveric specimens., Material and Methods: Sixteen measurements were determined for screw entry points, trajectories, and lengths for placement of transarticular screws, as applied in the technique described by Grob, on the craniovertebral junction segments (occiput-C2) of 16 fresh human cadaveric cervical spines and 41 computed tomographic reconstructions of the craniovertebral junction. Acceptable angles for screw positioning were measured on digital x-rays., Results: All 32 screws were placed accurately. As determined by dissection of the specimens, none of the screws penetrated the spinal canal. Screw insertion caused no fractures, and the integrity of the hypoglossal canal was maintained in all the disarticulated specimens., Conclusion: Viable transarticular occiput-C1 screw placement is possible, despite variability of the anatomy of the occipital condyle.

The craniovertebral junction is a complex region that incorporates the occiput-C1-C2 portions of the spine. It is a transition between the cranium and the mobile cervical spine that permits significant motion. The motions afforded and the anatomy are vastly different at the occiput-C1 and C1-C2 articulations. These differences make treating pathology in this region very difficult. Problems include bony fixation of the cranium and the cervical spine (specifically C1 and C2), which limits complex motions, and limited bony sites available for arthrodesis. A thorough knowledge of the normal anatomy and biomechanics is required for fixation of this region. Moreover, an understanding of pathologic motions and the biomechanics of fixation is needed for successful construct design and good patient outcome.

Background: Knowledge of the anatomy of ligaments that bind the craniocervical junction is important for treating patients with lesions of this region. Although the anatomy and function of these ligaments have been well described, those of the transverse occipital ligament (TOL) have remained enigmatic., Objective: To describe the anatomy and functions of the transverse occipital ligament., Methods: Via a posterior approach, 9 cadaveric specimens underwent dissection of the craniocervical junction with special attention to the presence and anatomy of the TOL., Results: The TOL was identified in 77.8% of the specimens. The ligament was found to be rectangular with fibers running horizontally between the lateral aspects of the foramen magnum. The attachment of each ligament near the occipital condyle was consistent, and each ligament was found superior to the transverse portion of the cruciform ligament and inserted just posterior to the lateral attachment sites of the alar ligaments. The average width, length, and thickness of the TOL was 0.34, 1.94, and 0.13 cm, respectively. The TOL in some specimens also had connections to the alar and transverse ligaments., Conclusion: The TOL was found in the majority of our specimens. The possible functions of this ligament when attached to the alar ligaments include providing additional support to these structures in stabilizing lateral bending, flexion, and axial rotation of the head. Knowledge of this ligament may aid in further understanding craniocervical stability and help in differentiating normal from pathology via imaging modalities.

Objective: To develop a safe and accurate method of image-guided placement of instrumentation in the upper cervical spine and occiput in which the reference arc is fixed to the headholder., Methods: The authors describe a technique for placing screws at the occipital, C1, and C2 levels using 3-dimensional image guidance in which the reference arc is fixed to the headholder. Technical details are discussed as well as modifications to the technique to maximize navigation accuracy and decrease the need for re-registration. One of 2 paired systems, the BrainLAB Vector Vision system (BrainLAB Inc., Westchester, IL) used in conjunction with the Arcadis Orbic Isocentric C-arm (Siemens Medical Solutions, Erlangen, Germany) or the Stealth Treon system (Medtronic, Littleton, MA) paired with the O-arm (Medtronic), was used for image guidance in this study. A total of 18 patients had 82 screws placed at the occipital, C1, or C2 level using this technique. An independent radiologist interpreted postoperative computed tomographic scans of these patients and graded the screws for bony breach., Results: No complications resulted from the use of image guidance or from the placement of instrumentation. Postoperative computed tomography revealed 1 screw with a minimal breach of the outer lamina of C2. Another screw was replaced intraoperatively secondary to a minimal bony breach. No other bony breach occurred., Conclusions: This technique allows safe and accurate placement of instrumentation in the posterior occipitocervical junction using 3-dimensional image guidance in which the reference arc is attached to the headholder.

A number of anterior approaches to the craniocervical junction have been described to allow exposure to the midline and lateral aspects of both the cranial base and upper cervical spine. The transoral-transpharyngeal approach, a technique that is well known to many spine surgeons, provides surgical access to the anterior clivus, C1, and C2. Transoral approaches provide the fundamental anatomy and technique upon which the more complex jaw-splitting approaches are based. This article discusses fundamental concepts regarding anatomy, perioperative considerations, and technical aspects critical to this important approach to the craniocervical junction. The transoral-transpharyngeal approach remains the "gold standard" for anterior approaches to the cervical spine. Endoscopic endonasal and endoscopic transcervical approaches are promising alternatives that may become more mainstream as experience with these approaches increases.

Background: The transoral approach provides the most direct exposure to extradural lesions of the ventral craniovertebral junction. Lesions that extend beyond the exposure provided by the standard transoral approach require an extended transoral modification. The exposure can be expanded in the sagittal and axial planes by adding mandibulotomy, mandibuloglossotomy, palatotomy, and transmaxillary approaches to the standard transoral approach. Extended transoral approaches increase the surgical complexity and the risk of cosmetic and functional complications. Until recently, selection of an extended approach has been arbitrary and dependent on the surgeon's familiarity with the surgical approach., Objective: We review the literature of extended transoral approaches and analyze the different modifications in terms of the technical aspects, added exposure, and complications., Methods: Classic approaches and recently published morphometric studies that objectively document the gain in exposure provided by several modifications were analyzed and tabulated to outline the limits of exposure and risk of complications associated with the various modifications., Results: Transmaxillary approaches expand the exposure to include the sphenoid sinus and upper lateral clivus. To expand the exposure more inferiorly to C4-C5, mandibulotomy or mandibuloglossotomy can be applied. Mandibuloglossotomy increases the rostral exposure as well to the upper third of the clivus. Palatotomy increases rostral exposure without requiring a facial incision or perioperative tracheostomy, but is associated with a significant risk of velopharyngeal insufficiency., Conclusion: Surgical decisions can be based on comprehensive preoperative evaluation of anatomy, pathology, and radiographic studies to maximize exposure while minimizing complications.

Objective: The transoral approach is the most direct and commonly used method to access the ventral craniocervical junction. Recently, an endonasal, endoscopic approach to the craniovertebral junction was proposed. We reasoned that the coupling of the endoscope with the direct transoral approach and image guidance could result in a minimally invasive, simple approach to the ventral craniovertebral junction. We investigated the potential usefulness of such an approach in a cadaver model., Methods: A direct transoral approach to the craniovertebral junction was performed using computed tomography-based image guidance in 9 fresh adult head specimens. Endoscopic odontoidectomy was performed in 5 specimens. In the remaining 4 specimens, the surgical working area and surgical freedom associated with an endoscopic and a microscopic approach to the ventral craniovertebral junction were evaluated and compared. In these 4 specimens, we also measured and compared the exposure of the clivus provided by the endoscope and by the operating microscope without splitting the soft palate., Results: With variously angled endoscopic assistance and image guidance, it was possible to tailor the excision of the anterior arch of the atlas and to precisely identify the odontoid process and its related ligaments intraoperatively, resulting in a complete and controlled odontoidectomy. The surgical area exposed over the posterior pharyngeal wall was significantly improved using the endoscope (606.5 +/- 127.4 mm3) compared with the operating microscope (425.7 +/- 100.8 mm3), without any compromise of surgical freedom (P < 0.05). The extent of the clivus exposed with the endoscope (9.5 +/- 0.7 mm) without splitting the soft palate was significantly improved compared with that associated with microscopic approach (2.0 +/- 0.4 mm) (P < 0.05)., Conclusion: With the aid of the endoscope and image guidance, it is possible to approach the ventral craniovertebral junction transorally with minimal tissue dissection, no palatal splitting, and no compromise of surgical freedom. In addition, the use of an angled-lens endoscope can significantly improve the exposure of the clivus without splitting the soft palate. An endoscope-assisted transoral approach is a direct and powerful tool for the treatment of surgical pathology at the craniovertebral junction.

Objective: Instability of the craniocervical junction can cause neurological sequelae or pain. Stability of this region depends on extensive ligamentous support structures, most of which are well studied by magnetic resonance imaging (MRI) scanning. Although the contribution of the accessory atlantoaxial ligament to rotational stability has been described, this ligament has not been identified by imaging. Therefore, we investigated the imaging characteristics of this ligament and its relationship to the ligamentous complex of the craniocervical junction using the high resolution offered by 3-T MRI scans., Methods: Ten healthy volunteers underwent MRI scanning at 3-T to determine the normal anatomy of this ligament., Results: The atlantoaxial (C1-C2) segment of the ligament was identified in all 10 subjects bilaterally and symmetrically. Its mean dimensions were 2.8 x 1.8 mm. In four out of 10 subjects, the occipitoatlantal (C0-C1) segment was observed. At this level, the mean dimensions of the ligament were 1.6 x 1.2 mm on the right and 1.8 x 1.4 mm on the left. Its size varied between the right and left sides., Conclusion: The accessory atlantoaxial ligament can be visualized using high-resolution MRI scans at 3-T. The ligament was most consistent and robust at C1-C2. The ligament may, therefore, contribute to rotational stability at this level. Future studies will determine the biomechanical importance of this ligament, especially in the setting of trauma.

Objective: Aneurysms of the vertebral artery are rare, comprising less than 5% of all aneurysms. They can present with subarachnoid hemorrhage, medullary compression, and cranial neuropathies. In consideration of their surrounding regional anatomy, they present a formidable surgical challenge to the neurosurgeon using traditional techniques. Recent advances in endoscopic transnasal surgery have provided an additional approach for the treatment of these difficult lesions., Clinical Presentation: We present a case of a large vertebral artery aneurysm causing mass effect on the medulla. Initial treatment consisted of endovascular trapping of the aneurysm; however, because of concerns that the remaining aneurysm and intraluminal thrombus was causing mass effect and continued brainstem compression, a decompressive procedure was required., Intervention: After the endovascular trapping, the patient underwent a completely endoscopic transnasal surgical clipping and aneurysmorrhaphy. After exposure of the aneurysm, distal and proximal clips were applied transnasal, and the aneurysmorrhaphy completed using suction and ultrasonic aspiration., Conclusion: In consideration of their surrounding regional anatomy, aneurysms of the vertebral artery present a formidable surgical challenge to the neurosurgeon. Although endovascular techniques have proven to be extremely valuable for the treatment of these lesions, they are limited when patients have significant mass effect with brainstem compression or cranial neuropathy. Advances in endoscopic transnasal surgery have provided an additional approach for the treatment of these difficult lesions. This case report represents, to our knowledge, the first literature report of a transnasal endoscopic aneurysm clipping and thrombectomy.