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Background: Occipitocervical junction instability can lead to serious neurological injury or death. Open surgical fixation is often necessary to provide definitive stabilization. However, long-term results are limited to small case series., Objective: To review the causes of occipitocervical instability, discuss the indications for surgical intervention, and evaluate long-term surgical outcomes after occipitocervical fixation., Methods: The charts of all patients undergoing posterior surgical fixation of the occipitocervical junction by the senior author were retrospectively reviewed. A total of 120 consecutive patients were identified for analysis. Patient demographic characteristics, occipitocervical junction pathology, surgical indications, and clinical and radiographic outcomes are reported., Results: The study population consisted of 64 male and 56 female patients with a mean age of 39.9 years (range, 7 months to 88 years). Trauma was the most common cause of instability, occurring in 56 patients (47%). Ninety patients (75%) were treated with screw/rod constructs; wiring was used in 30 patients (25%). The median number of fixated segments was 5 (O-C4). Structural bone grafts were implanted in all patients (100%). Preoperative neurological deficits were present in 83 patients (69%); 91% of those patients improved with surgery. Mean follow-up was 35.1 ± 27.4 months (range, 0-123 months). Two patients died, and 10 were lost to follow-up before the end of the 6-month follow-up period. Fusion was confirmed in 107 patients (89.1%). The overall complication rate was 10%, including 3 patients with vertebral artery injuries and 2 patients who required revision surgery., Conclusion: Occipitocervical fixation is a durable treatment option with acceptable morbidity for patients with occipitocervical instability., Abbreviations: AIS, American Spinal Injury Association Impairment ScaleCVJ, craniovertebral junctionmJOAS, modified Japanese Orthopaedic Association ScaleNLI, neurological level of injurySCI, spinal cord injury.

Background: On reviewing the database of patients with craniovertebral junction anomalies, the authors identified 70 patients with a bifid posterior arch of atlas., Objective: To speculate on the pathogenesis of spondyloschisis of both the anterior and posterior arches of atlas, particularly as it relates to atlantoaxial instability., Methods: Seventy patients with bifid anterior and posterior arches were identified by a retrospective review of the database from 2007 to 2013., Results: The ages of the patients ranged from 14 months to 50 years. The patients were divided into 3 groups. Group 1 (3 patients) had multiple additional spinal bony and neural abnormalities. Group 2 (34 patients) had mobile and partially (5) or completely (29) reducible atlantoaxial dislocation. Group 3 (33 patients) had atlantoaxial instability and related basilar invagination. The os odontoideum was identified in 21 patients, and C2-3 fusion was seen in 24 patients. Two of 3 patients in group 1 were treated conservatively and without any surgery. All patients in groups 2 and 3 were surgically treated. Surgery was done using lateral mass plate/rod and screw fixation techniques. The general observation during surgery included identification of discrete movements of both halves of the atlas, lateral positioning of the facets of atlas in relation to the facets of the axis and occipital condyle and closer approximation of the occipital bone, atlas, and axis resulting in "crumpling" of bone and neural elements., Conclusion: Understanding of the pathogenesis and mechanical alterations in cases with a bifid arch of atlas can assist in evaluating the clinical implications and in conduct of surgery.

Background: The continued evolution of instrumentation techniques for fusions at the craniovertebral junction has enabled surgical treatment of a wide range of developmental, neoplastic, traumatic, and degenerative conditions. There has been an increased recognition of the morbidity associated with the complications secondary to occipitocervical instrumentation., Objective: To present representative complications secondary to occipitocervical instrumentation in patients who presented to our institution and to emphasize underlying principles in diagnosis and management of craniovertebral disease conditions through illustrative examples of their presentation, management, and follow-up., Methods: Clinical records for patients referred to the senior author (A.H.M.) between 2005 and 2010 for evaluation and management of their symptoms arising as a consequence of surgical intervention by a different primary neurosurgeon were reviewed., Results: Eight patients were identified with representative complications secondary to occipitocervical instrumentation. These complications included incorrect surgical technique, persistent instability, hardware misplacement with potential for vascular injury, associated neural injury, and secondary complications of wound healing resulting from methyl methacrylate use. Surgical revision was required in 2 patients. The remaining patients improved with removal of the offending hardware and acrylic cement. All patients reported symptom resolution, and dynamic imaging studies on follow-up indicated stable alignment and bony fusion., Conclusion: These cases serve as illustrative examples of the spectrum of neural, vascular, biomechanical, and instrument-related complications associated with occipitocervical arthrodesis. Basic principles of occipitocervical instrumentation that enable safe and successful treatment of craniovertebral junction disease conditions have been highlighted. Potential complications and management strategies are discussed.

Background: Atlas occipitalization and congenital C2-3 fusion often result in atlantoaxial dislocation (AAD) and superior odontoid migration that requires occipitocervical fixation. The widely used technique is posterior occiput-C2 fixation with pedicle screws. However, congenital C2-3 fusion cases tend to have thinner C2 pedicles that are inadequate for normal-sized pedicle screw fixation. With the presence of AAD, the strength of the fixation is further compromised as the C2 pedicle screws (C2PS) sustain considerable cephalic shearing force during the reduction procedure. Therefore, a novel technique has been developed to augment the C2 pedicle screw fixation with a strengthening cable., Objective: To introduce and assess this new technique., Methods: Seventy-six patients who underwent this procedure were reviewed. The position of the instrument and resultant fusion were examined retrospectively. In the biomechanical test, 6 fresh specimens were subjected to 2 types of fixation in the order of Oc-C2 screw-plate fixation followed by additional use of strengthening cable. Under 3 loading modes (extension-flexion, lateral bending, and axial rotation), the relative movement between the occiput and C2 was measured and compared in the form of range of motion., Results: The average follow-up time was 26 months. Solid fusion was achieved in 75 patients (98.7%) as assessed radiologically. The only patient who experienced hardware failure eventually obtained solid fusion between the occiput and C2 after revision. Biomechanically, there was significant difference between the occiput and C2 fixation and cable-strengthened fixation in range of motion for all modes., Conclusion: This technique is a promising option for the treatment of AAD with congenital C2-3 fusion and occipitalization. Biomechanically, this technique can reduce the occipital-axial motion significantly compared with occiput-C2 fixation.

Background and Importance: We report an extremely rare case with mirror-site spinal dural arteriovenous fistulas (DAVFs) at the craniocervical junction. Although multiple spinal DAVFs have been reported in the literature, complete mirror-site lesions with fistulas and feeding arteries in the symmetric position have not been previously described., Clinical Presentation: A 74-year-old man presented with walking disturbance, urinary incontinence, and constipation progressing over a 14-month period. T2-weighted magnetic resonance imaging showed a high-intensity area in the spinal cord at the level from C4 to C6 and multiple flow voids at the surface of the spinal cord. Three-dimensional computed tomographic angiography revealed bilateral DAVFs located in the mirror site of the craniocervical junction. Direct surgery with suboccipital craniectomy and C1 laminectomy revealed dilated tortuous red veins on the dorsal surface of the spinal cord. We found bilateral symmetric red veins around the dural penetration of the vertebral artery. Both red veins were successfully interrupted with the aneurysmal clips. Postoperative 3-dimensional computed tomographic angiography revealed a disappearance of the bilateral fistulas. Magnetic resonance images obtained 6 months after the surgery confirmed the disappearance of the intramedullary high-intensity area and flow voids. The symptoms before the operation improved after surgery, especially urinary incontinence and constipation, with slight walking disturbance., Conclusion: Because fistulas in the present case existed at the same spinal level, we found multiple fistulas on the first examination. This early notification resulted in a good outcome from the first operation. If patients with spinal DAVFs have rapidly progressing symptoms, one should suspect multiple fistulas.

Background: Anatomically and biomechanically, the atlantoaxial joint is unique compared with the remainder of the cervical spine., Objective: To assess the in vitro stability provided by 2 C2 screw sparing techniques in a destabilized model of the atlantoaxial joint and compare with the gold standard system., Methods: The 3-dimensional intervertebral motion of 7 human cadaveric cervical spine specimens was recorded stereophotogrammetrically while applying nonconstraining, nondestructive pure moments during flexion-extension, left and right axial rotation, and left and right lateral bending. Each specimen was tested in the intact state, followed by destabilization (odontoidectomy) and fixation as follows: (1) C1 and C3 lateral mass screws rods with sublaminar wiring of C2 (LC1-C3 + SW), (2) C1 and C3 lateral mass screws rods with a cross-link in the C1-2 interlaminar space (LC1-C3 + CL), (3) C1 and C3 lateral mass screw rods alone (negative control), and (4) C1 lateral mass and C2 pedicle screws rods augmented with C1-2 interspinous wire and graft (LC1-PC2, control group)., Results: Compared with the intact spine, each instrumented state significantly stabilized range of motion and lax zone at C1-2 (P < .001, 1-way repeated-measures analysis of variance). LC1-C3 + SW was equivalent to LC1-PC2 during flexion and lateral bending and superior to LC1-C3 + CL during lateral bending, while LC1-C3 + CL was equivalent to LC1-PC2 only during flexion. In all other comparisons, LC1-PC2 was superior to both techniques., Conclusion: From a biomechanical perspective, both C2 screw sparing techniques provided sufficient stability to be regarded as an alternative for C1-2 fixation. However, because normal motion across C2-3 is sacrificed, these constructs should be used in patients with unfavorable anatomy for standard fixations.

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 and Importance: Posterior cervical stabilization for cervical fractures is common, and numerous techniques for fixation have been described. This case describes the novel usage of C1 laminar screws due to a persistent intersegmental artery and congenital fusion of C2-C3., Clinical Presentation: A 64-year-old woman presented with loss of consciousness after falling down a flight of stairs. Initial CT scan showed a type II odontoid fracture with significant malalignment, as well as an anomalous congenital fusion of C2-C3 and degenerative spondylolisthesis of C3 to C4. CT angiogram demonstrated bilateral persistent first intersegmental arteries coursing through the C1-C2 neural foramina., Intervention: The patient underwent C2 fracture reduction and posterior C1-C4 fusion. C1 posterior arch screws were placed due to the patient's anomalous vertebral artery location. The construct was anchored caudally by C2 pars interarticularis screws and C4 lateral mass screws. The patient experienced an excellent neurologic and radiographic outcome at 12.5 months., Conclusion: Posterior fixation for fractures of the cervical spine is common; however, the use of C1 posterior arch screws for fractures has not previously been described. The presence of a persistent intersegmental course of the vertebral artery, a rare but reported anomaly, should be regarded as a contraindication to placement of C1 lateral mass screws and necessitates careful consideration of the available surgical options.

Objective: This is a unique case report of a fractured atlantoaxial interspinous multistranded cable leading to intracranial hemorrhage and spinal cord injury., Clinical Presentation: A 61-year-old woman, with a history of rheumatoid arthritis and C1-C2 interspinous wiring with allograft for atlantoaxial instability, presented with neck pain and progressive decline in mental status. Prior to transfer to our institution from a referral hospital, imaging studies revealed progressive hydrocephalus with interval development of subarachnoid and fourth ventricular hemorrhage. Initial and repeat angiographic work-up was negative for vascular lesions. Magnetic resonance imaging revealed a subdural hematoma and signal changes at the cervicomedullary junction. Computed tomography of the cervical spine revealed a fractured interspinous cable, intradural penetration, and atlantoaxial instability., Intervention: After ventriculostomy, both the patient's mental status and quadriparesis improved to a C on the American Spinal Injury Association (ASIA) scale. During surgery, the fractured cable and subdural hematoma were removed revealing an area of spinal cord impalement. She underwent C1-C3 lateral mass fixation with iliac crest autograft for fusion and was discharged to rehabilitation after a ventriculoperitoneal shunt was placed. At her 6-month follow-up, she was independent and had improved to ASIA E. Computed tomography confirmed fusion., Conclusion: Spinal instrumentation eventually fails from pseudarthrosis and can cause neurological injury. In patients with atlantoaxial instability, direct C1-C2 screw fixation with posterior interspinous wiring using autograft offers the best chance for fusion. Cervical spine pathology can cause intracranial hemorrhage, and unconventional causes of injury must be considered when routine workup is negative.

Background: C1-C2 fusion has significantly advanced from predominantly wiring/cable modalities to more biomechanically stable screw-rod techniques. Minimally invasive surgical techniques represents the most recent modification of atlantoaxial fixation. The indications, rationale, and surgical technique of this novel procedure are described., Methods: Six patients requiring C1-C2 fusion (5 type II odontoid fractures and 1 os odontoideum) underwent minimally invasive C1-C2 fusion over a 2-year period. The cohort consisted of 5 men and 1 woman with a mean age of 51 years (age range, 39-64 y). All 6 patients underwent bilateral segmental atlantoaxial fixation using an expandable tubular retractor., Results: The mean follow-up time was 32 months (age range, 24-46 mo) There were no intraoperative complications, and the mean estimated blood loss was 100 mL. Solid fusion was achieved in all 6 patients, without pathological motion on dynamic studies. Postoperative computed tomographic images showed no hardware malposition in the scanned patients (4 of the 6 patients)., Conclusions: Placement of C1 and C2 instrumentation using minimally invasive techniques is technically feasible. Because the instrumentation and the means of obtaining arthrodesis do not differ substantively from the standard approach, we would not anticipate long-term results to be different from those of an open procedure, apart from the approach-related morbidity.

Background: Tumors at the craniovertebral junction are difficult to remove because of their location and complex anatomic relations. The lateral transcondylar approach is a versatile approach to this area and allows access to a variety of intra- and extradural tumors. The lateral transcondylar approach has been used for a series of chordomas in this location., Objective: The nuances of this operation and its effectiveness in this group of patients are presented., Methods: There were 29 chordomas (1991-2007) in this region treated by one of the authors (CS) that were retrospectively reviewed. The imaging studies and medical records were evaluated. The location and extent of the tumor were defined, and the postoperative images were studied to determine the degree of resection., Results: There were 11 male and 18 female patients; their age range was 7 to 67 years. Headache and neck pain were the predominant presenting symptoms, and hypoglossal nerve palsy was the most common cranial nerve palsy. Twelve patients had previous surgery and 9 had previous radiation. Anterior midline and lateral approaches were used independently or in combination to treat these patients. Dural invasion was found in 27 patients requiring resection of the dura. Surgery was performed in 1 stage in 19 patients, and the tumor resection in the remaining patients was done in 2 stages. The lateral transcondylar approach was used in 19 patients. The occipital condyle was involved in all these patients. Radical tumor resection was achieved in 17 patients. Patients who had complete removal of the occipital condyle required occipitocervical fusion (20 patients) in the immediate postoperative period., Conclusion: The lateral transcondylar approach is an effective approach to chordomas in this region. Most of the tumors were large and extended into multiple anatomic compartments. The approach allowed resection of all the involved tissues, intra- and extracranial, and afforded excellent neurovascular control.

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.

Background: Rheumatoid arthritis (RA) is the most common inflammatory disease involving the spine. It has a predilection for involving the craniocervical spine. Despite widespread involvement of the cervical spine with RA, few patients need surgery. The 3 major spinal manifestations of RA in the cervical spine are basilar invagination, atlantoaxial instability, and subaxial subluxations. Surgical management of RA involving the craniovertebral junction remains a challenge despite a decline in severe cases and an improvement in surgical techniques., Methods: We conducted an exhaustive review of English-language publications discussing RA involving the craniovertebral junction. We paid special attention to publications detailing modern surgical management of these conditions. In addition, we outline our own surgical experience with such patients., Results: We discuss alternative surgical methods for treating basilar invagination, atlantoaxial instability, and concurrent subaxial subluxations. We detail our surgical technique for transoral odontoidectomy, occipital cervical fusion, and atlantoaxial fusion. We detail the use of spinal surgical navigation in both of these procedures., Conclusion: Surgical management of RA remains a challenging field. There clearly has been a decrease in cases of mutilating RA involving the craniovertebral junction. Surgical techniques for managing these conditions have steadily improved.

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.

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.

Objective: This study reviews the relevant literature regarding the management of craniovertebral junction (CVJ) metastases. These rare tumors present significant diagnostic and treatment challenges., Methods: A PubMed search of cervical spine, cervical spine metastasis, craniovertebral junction, atlantoaxial spine, and metastasis radiation was conducted to define the epidemiology, imaging, and treatment protocols in the management of metastatic CVJ tumors., Results: CVJ tumors represent less than 1% of spinal metastases, and the literature is limited to small case series. CVJ tumors present with flexion, extension, and rotational pain, often associated with occipital neuralgia. Magnetic resonance imaging is the most sensitive imaging modality for the detection of spinal metastases, but plain x-rays, computed tomography, and [18F]2-fluoro-2-deoxy-D-glucose play a role in diagnosis and management. Conventional external beam radiation therapy or stereotactic radiosurgery effectively treat the majority of patients with normal spinal alignment or minimal fracture subluxations. Surgery should be considered in patients with fracture subluxations greater than 5 mm, or 3.5 mm subluxation with 11-degree angulation. The palliative goals for surgery favor posterior approaches only including laminectomy for decompression, without the need for anterior approaches with the associated morbidity. Occipitocervical instrumentation using screw-rod systems are effective for irreducible subluxations, but posterior strategies using C1-C2 or C1-C3 can be used for patients with reducible subluxations., Conclusion: Effective management of CVJ tumors using radiation and/or surgery results in significant pain and functional improvement in properly selected patients. Advanced surgical techniques and stereotactic radiation may improve outcomes with less morbidity.

Objective: We review our experience and technique for C1 lateral mass screw fixation. We compare the results of 3 different constructs incorporating C1 lateral mass screws: occipitocervical (OC) constructs, C1-C2 constructs, and C1 to mid/low cervical constructs., Methods: We performed a retrospective chart review of 42 consecutive patients who underwent C1 lateral mass fixation by 2 of the authors (PVM and DC). The patient population consisted of 24 men and 18 women with a mean age of 64 years. Twenty-two patients had C1-C2 constructs. Twelve patients had constructs that started at C1 and extended to the mid/low cervical spine (one extended to T1). Eight patients underwent OC fusions incorporating C1 screws (2 of which were OC-thoracic constructs). All constructs were combined either with a C2 pars screw (38 patients), C2 translaminar screw (1 patient), or C3 lateral mass screw (3 patients). No C2 pedicle screws were used. Fusion was assessed using flexion-extension x-rays in all patients and computed tomographic scans in selected cases. Clinical outcomes were assessed with preoperative and postoperative visual analog scale neck pain scores and Nurick grading. The nuances of the surgical technique are reviewed, and a surgical video is included., Results: Two patients (5%) were lost to follow-up. The mean follow-up for the remaining patients was 2 years. During the follow-up period, there were 4 deaths (none of which were related to the surgery). For patients with follow-up, the visual analog scale neck pain score improved a mean of 3 points after surgery (P < .001). For patients with myelopathy, the Nurick score improved by a mean of 1 grade after surgery (P < .001). The postoperative complication rate was 12%. The complication rate was 38% in OC constructs, 17% in C1 to mid/low cervical constructs, and 0% for C1-C2 construct cases. Patients with OC constructs had the statistically highest rate of complications (P < .001). Patients with C1 to mid/low cervical constructs had more complications than those with C1-C2 constructs (P < .001). Of the 42 cases, there were 3 pseudoarthroses (1 in an OC case, 1 in a C1 to midcervical construct, and 1 in a C1-C2 construct). OC constructs had the highest risk of pseudoarthrosis (13%) (P < .001)., Conclusion: Patients treated with C1 lateral mass fixation constructs have a high fusion rate, reduced neck pain, and improved neurologic function. Constructs using C1 lateral mass screws do not need to incorporate C2 pedicle screws. Constructs incorporating C1 lateral mass screws are effective when combined with C2 pars screws, C2 translaminar screws, and C3 lateral mass screws. Constructs using C1 screws are associated with a higher complication rate and a higher pseudoarthrosis rate if extended cranially to the occiput or if extended caudally below C2.

Objective: To review and compare the techniques of fixation of the axis vertebral segment. Also, to review the anatomy of the axis vertebrae, ligamentous attachments, and unique biomechanics of this segment., Methods: The use of wire, cable, screw, and plate fixation techniques are reviewed and discussed in the treatment of fractures of C1 and C2 along with utilization of the halo vest and cervical collar during the postoperative period., Results: All fixation methods were useful. However, the appropriate fixation technique is best determined by the local anatomy (eg, anomalous vertebral artery), posterior element fractures, or the necessity to remove the posterior elements for treatment of the underlying condition., Conclusion: New techniques for fixation and instrumentation for fixation of the axis are available. Advanced imaging allows for advanced aggressive instrumentation while avoiding injury to adjacent structures. Biomechanical studies have influenced the utility and popularity of each technique.

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: Transarticular screw (TAS) fixation is our preferred method for stable internal fixation of the atlantoaxial joint because of its excellent outcomes, versatility, and cost-effectiveness., Objective: In this article, we update our series of patients who have undergone TAS fixation, with attention to surgical technique, planning, complication avoidance, and anatomic suitability., Methods: We retrospectively reviewed 269 patients (150 women, 119 men; average age, 52.9 years; age range, 17-90 years) who underwent placement of at least 1 TAS. In total, 491 TASs were placed for stabilization necessitated by various pathologic conditions. The mean follow-up period was 15.7 months (range, 0-106 months)., Results: Fusion was achieved in 99% of 198 patients monitored until fusion or nonunion requiring revision, or for 2 years. Forty-five patients had a complication, for a rate of 16.7%. Five early patients had vertebral artery injuries, 1 of which was bilateral and fatal. No recent patients had vertebral artery injuries. Other complications did not result in neurologic morbidity. Review of all atlantoaxial fusions by the senior author (R.I.A.) revealed that the TAS fixation technique could be successfully applied in 86.7% of sides considered. The main reasons for inapplicability were anatomic (recognized on preoperative planning) in 77% and abandonment secondary to concern about possible vertebral artery injury on the first side attempted in 13.8%., Conclusion: The placement of TASs is safe and effective for stabilizing the atlantoaxial articulation. Refinements in technique, such as 3-dimensional stereotactic workstation for trajectory planning, have reduced the rate of serious complications. Clinical outcomes are excellent, with nearly 100% of patients achieving stable bony union.

Background: Chordomas are primarily malignant tumors encountered at either end of the neural axis; the craniovertebral junction and the sacrococcygeal junction. In this article, we discuss the surgical management of craniovertebral junction chordomas., Objective: In this paper, we discuss the surgical management of craniovertebral junction chordomas., Results: The following approaches are illustrated: transoral-transpalatopharyngeal approach, high anterior cervical retropharyngeal approach, endoscopic transoral approach, and endoscopic transnasal approach. No single operative approach can be used for all craniovertebral chordomas. Therefore, the location of the tumor dictates which approach or approaches should be used.

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: To evaluate surgical access to the craniocervical junction using 3 endoscopic approaches: endonasal, transoral, and transcervical., Methods: Nine cadaveric specimens were used. Image guidance was used in 1 specimen for each approach; fluoroscopy was used in every case. The Vitrea imaging station (Vital Images Inc., Minnetonka, MN) was used to evaluate the angles and distances to the target of the approach, centered on the tip of the odontoid. The entry site was defined as: 1) the endonasal approach (inferior midline of the nasal bone), 2) the transoral approach (the tip of the upper incisor), and 3) the transcervical approach (the skin at the C4-C5 level)., Results: Adequate lower clivus and craniocervical decompression was achieved using the endonasal and transoral approaches. Lower clivus decompression was not achieved with the transcervical approach. The average distance to the surgical target was as follows: endonasal (94 mm), transoral (102 mm), and transcervical (100 mm). The angle of attack was as follows: endonasal (28 degrees), transoral (30 degrees), and transcervical (15 degrees). The working area at the base of the field was as follows: endonasal (1305 mm2), transoral (1406 mm2), and transcervical (743 mm2)., Conclusion: The endonasal and transoral approaches allow wide exposure with large working angles to the craniocervical junction. The transcervical approach accesses the odontoid for resection from the body of C2 to the lip of the basion. The angles of attack in the transcervical approach when centered on the surgical target are limited, but this approach offers a clean, sterile operative field. Clinical investigation will be required to determine the optimal indications for each approach.

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: Recent advances in microsurgical techniques facilitate surgical resection of brainstem lesions that were previously considered inoperable. In this article we present, for the first time, the tonsillouveal transaqueductal approach to access a progressively symptomatic cavernoma within the depth of the tegmentum of the mesencephalon., Methods: A 52-year-old woman presented with a history of slowly progressive right-sided hemiparesis and ataxia. On magnetic resonance imaging, a relatively large cavernoma involving the tegmentum of the mesencephalon was shown. The sylvian aqueduct was patent and there was no secondary ventriculomegaly. The patient underwent surgery via a suboccipital craniotomy and C1 laminectomy. The right tonsillouveal and medullotonsillar spaces were opened to the level of the choroidal point of the posteroinferior cerebellar artery. The tela choroidea was incised from the foramen of Magendie to the telovelar junction. Looking through the aqueduct and at a point 5 mm superior to its inferior inlet, there was a small cherry-like blister protruding into the aqueductal anterior surface. This was used as an entry point to access the cavernoma. The space around the cavernoma was gently dissected and the cavernoma was circumferentially coagulated to shrink it in a concentric manner toward its center., Results: The total removal of the lesion was achieved and the histopathological findings were consistent with a cavernoma. As a result of noncommunicating hydrocephalus, the patient needed a ventriculoperitoneal shunt. The 1-year postoperative neurological examination was consistent with preoperative findings., Conclusion: This report shows, for the first time, direct surgical removal of a cavernous hemangioma in the mesencephalic tegmentum via the aqueduct. This approach adds to contemporary microneurosurgery, respecting functional anatomy and minimizing neurological deficits.

Objective: To establish a scoring system and management algorithm for patients with diagnosed craniovertebral junction tuberculosis. The specific goals were: 1) to avoid new neurological deficits; 2) to avoid morbidity and compromise in the quality of life associated with prolonged, rigid, cumbersome external immobilization, such as with a sternal occipital mandibular immobilizer brace and halo traction; and 3) to prevent sudden death., Methods: All patients diagnosed with craniovertebral junction tuberculosis were studied prospectively over a 3-year period. The initial severity of the disease was evaluated with clinicoradiological grading, and patients were divided into 3 grades. Overall performance status was assessed with disability scoring. Patients with Grade 1 and 2 severity were managed conservatively. Grade 3 patients underwent transoral decompression and posterior fixation. The patients' neurological recovery was evaluated every 4 weeks with disability scoring, along with x-rays, for the initial 3 months and every 2 months thereafter., Results: Of 71 patients, there were 27 Grade 1, thirty-six Grade 2, and 8 Grade 3 patients. Children and young adults comprised 70% of the study population. All Grade 3 patients underwent early surgery. Five Grade 1 and 2 patients (8%) required delayed surgery for reducible atlantoaxial dissociation. The remaining 58 patients (82%) were effectively managed conservatively. The mean follow-up duration was 18.5 +/- 6.2 months. There was no mortality., Conclusion: Use of our proposed scoring system and management protocol allowed both speedy recovery and early mobilization. All patients had good clinicoradiological outcomes regardless of the grade.

Complex tumors OF the glomus jugulare present a surgical challenge because of their difficult location, extreme vascularity, and involvement with multiple cranial nerves. Modern microneurosurgical and cranial base techniques have enabled safe total removal of these complicated tumors. We describe a one-stage transjugular posterior infratemporal fossa approach for radical resection of glomus jugulare tumors located around the jugular foramen, the lower clivus, and the high cervical region from an anterolateral direction. This approach is a combination of transmastoid, suprajugular, transjugular, extreme lateral infrajugular transcondylar transtubercular, and high cervical approaches. Total exposure of the jugular foramen can be achieved, and multidirectional approaches can be performed, including infralabyrinthine/suprajugular, retrosigmoid/transcondylar/infrajugular, and transjugular exposures. Exposure of the vertical C7 segment of the infratemporal internal carotid artery and the lower clivus can be performed without permanent rerouting of the facial nerve. The details of this approach are described and illustrated in a stepwise fashion, and the microsurgical anatomy is reviewed.

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.

Objective: Atlantal lateral mass screws provide an alternative to C1/C2 transarticular screws and, in some cases, can obviate the need for extending a fusion to the occiput. For these reasons, C1 lateral mass screws are becoming increasingly popular. However, the critical local anatomy and unfamiliarity with this new technique can make C1 screw placement more challenging., Methods: Morphometric analysis was performed on 74 cadaveric spines obtained from the Department of Anatomy at the Keck School of Medicine, University of Southern California. Critical measurements were determined for screw entry points, trajectories, and lengths for application of the technique described by Harms and Melcher., Results: The mean height and width for screw entry on the posterior surface of the lateral mass were 3.9 and 7.3 mm, respectively. The maximum medialized screw trajectory ranged from 25 to 45 degrees (mean, 33 degrees). The mean maximal screw length to obtain bicortical purchase was 22.5 mm, and the mean minimum screw depth was 14.4 mm. Screw depths varied on the basis of the entry point, trajectory, and vertebral morphology. The overhang of the posterior arch averaged 11.4 mm (range, 6.9-17 mm). All specimens could accommodate 3.5-mm lateral mass screws bilaterally with proper preparation of the entry site., Conclusion: Significant variations in the morphology of C1 exist. However, the large size of the atlantal lateral mass makes screw placement forgiving. Preoperative computed tomographic scans and intraoperative fluoroscopy are useful in guiding proper screw placement. Close attention should be paid to preparation of the screw entry site.

Objective: Compared with other lower cranial nerves, the glossopharyngeal nerve (GPhN) is well hidden within the jugular foramen, at the infratemporal fossa, and in the deep layers of the neck. This study aims to disclose the course of the GPhN and point out landmarks to aid in its exposure., Methods: The GPhN was studied in 10 cadaveric heads (20 sides) injected with colored latex for microsurgical dissection. The specimens were dissected under the surgical microscope., Results: The GPhN can be divided into three portions: cisternal, jugular foramen, and extracranial. The rootlets of the GPhN emerge from the postolivary sulcus and course ventral to the flocculus and choroid plexus of the lateral recess of the fourth ventricle. The nerve then enters the jugular foramen through the uppermost porus (pars nervosa) and is separated from the vagus and accessory nerves by a fibrous crest. The cochlear aqueduct opens to the roof of this porus. On four sides in the cadaver specimens (20%), the GPhN traversed a separate bony canal within the jugular foramen; no separate canal was found in the other cadavers. In all specimens, the Jacobson's (tympanic) nerve emerged from the inferior ganglion of the GPhN, and the Arnold's (auricular branch of the vagus) nerve also consisted of branches from the GPhN. The GPhN exits from the jugular foramen posteromedial to the styloid process and the styloid muscles. The last four cranial nerves and the internal jugular vein pass through a narrow space between the transverse process of the atlas (C1) and the styloid process. The styloid muscles are a pyramid shape, the tip of which is formed by the attachment of the styloid muscles to the styloid process. The GPhN crosses to the anterior side of the stylopharyngeus muscle at the junction of the stylopharyngeus, middle constrictor, and hyoglossal muscles, which are at the base of the pyramid. The middle constrictor muscle forms a wall between the GPhN and the hypoglossal nerve in this region. Then, the GPhN gives off a lingual branch and deepens to innervate the pharyngeal mucosa., Conclusion: Two landmarks help to identify the GPhN in the subarachnoid space: the choroid plexus of the lateral recess of the fourth ventricle and the dural entrance porus of the jugular foramen. The opening of the cochlear aqueduct, the mastoid canaliculus, and the inferior tympanic canaliculus are three landmarks of the GPhN within the jugular foramen. Finally, the base of the styloid process, the base of the styloid pyramid, and the transverse process of the atlas serve as three landmarks of the GPhN at the extracranial region in the infratemporal fossa.

Standards: There is insufficient evidence to support treatment standards., Guidelines: There is insufficient evidence to support treatment guidelines., Options: Treatment of atlas-axis combination fractures based primarily on the specific characteristics of the axis fracture is recommended. External immobilization of most C1--C2 combination fractures is recommended. C1--Type II odontoid combination fractures with an atlantodens interval of 5 mm or more and C1--hangman's combination fractures with C2--C3 angulation of 11 degrees or more should be considered for surgical stabilization and fusion. In some cases, the surgical technique must be modified as a result of loss of the integrity of the ring of the atlas.

Comprehensive anatomic and clinical analyses of 39 patients with injuries involving the transverse atlantal ligament or its osseous insertions were performed to assess the morphology of the injured ligaments and the patients' capacity to heal. Injuries of the upper cervical spine were screened with plain radiographs, thin-section computed tomography, and magnetic resonance imaging studies. The injuries were classified as disruptions of the substance of the ligament (Type I injuries, n = 16) or as fractures and avulsions involving the tubercle for insertion of the transverse ligament on the C1 lateral mass (Type II injuries, n = 23). These two types of injuries had distinctly different clinical characteristics that were useful for determining treatment. Type I injuries were incapable of healing satisfactorily without internal fixation; they should be treated with early surgery. Type II injuries, which rendered the transverse ligament physiologically incompetent even though the ligament substance was not torn, should be treated initially with a rigid cervical orthosis, because they had a 74% success rate nonoperatively. Surgery should be reserved for patients with Type II injuries that have nonunion with persistent instability after 3 to 4 months of immobilization. Type II injuries had a 26% rate of failure of immobilization; therefore, close monitoring is needed to detect patients who will require delayed operative intervention.

Posterior wiring techniques are the most commonly used methods of achieving C1-C2 arthrodesis. Recently, transarticular screw fixation and interlaminar clamping have been advocated to achieve more secure fixation. A retrospective review of patients undergoing C1-C2 fusion for nonneoplastic disease was undertaken at the University of Toronto Hospital, with the aim of determining the long-term outcome of the selected procedures. Thirty-two patients underwent 36 procedures from 1986 to 1992, with a mean follow-up of 4.7 +/- 2.2 years (range, 2.0-8.0 yr). The most common disease processes were odontoid fracture (18 patients), transverse atlantal ligament injury (5 patients), os odontoideum (5 patients), and rheumatoid C1-C2 instability (3 patients). Thirty-one Gallie fusions, one Brooks-Jenkins fusion, two transarticular screw fusions, and two Halifax clamp applications were performed. Six (19%) of Gallie/Brooks-Jenkins fusions failed. These occurred with os odontoideum (three patients), Type II odontoid fracture (two patients), and transverse atlantal ligament injury (one patient). All transarticular screw and Halifax clamp procedures resulted in successful fusions. Two procedures (6%) resulted in new neurological deficit; both of these patients underwent posterior wiring for os odontoideum. This study suggests that Type II odontoid fractures may be successfully managed by a posterior wiring technique alone. Rheumatoid C1-C2 instability may be managed by posterior wiring supplemented with halo immobilization. Transarticular screw fixation has several potential advantages as a technique for C1-C2 arthrodesis and, in particular, may be appropriate for os odontoideum that had a high failure rate (75%) with conventional posterior wiring, even when this was supplemented with halo bracing.

Posterior atlantoaxial fusion is a common procedure performed for instability at C1-C2. This operation requires intact posterior elements of both the atlas and the axis. When this is not the case, the incorporation of the occiput and the lower spinal segments is usually required for adequate posterior fusion, but such a procedure limits the mobility of the upper cervical spine. A technique for the reconstruction of the posterior arch of the atlas with calvarial bone is described in this report. This technique allowed the successful fusion of the C1 and C2 vertebrae in a patient with traumatic atlantoaxial subluxation who also had a congenital absence of the posterior arch of the atlas.

For the past 20 years, the transoral approach to the upper cervical spine has been utilized for odontoid fractures, the removal of an abnormal odontoid process, decompression of basilar impression, and biopsy or resection of nasopharyngeal or metastatic tumors. The effectiveness and safety of this procedure is well documented. Use of the surgical microscope adds to the efficiency and safety of the procedure. We are reporting a case of fusion of the odontoid base to the anterior arch of the atlas. To our knowledge, this entity has not been described previously. The spinal cord was protected by an initial posterior fusion of C-1, C-2, followed in 10 days by a tracheostomy and the transoral removal of the anterior C-1 arch and the abnormal dens. Because the medical history did not reveal a source of trauma, it is supposed that the patient had malunion of the odontoid process to C-2, with subsequent migration and fusion of the dens to the C-1 arch.

Anatomically, the vertebral artery courses through six foramina transversaria of the cervical vertebrae, passing through the groove on the surface of the arch of the atlas and then penetrating the dura mater. Because of this anatomical course, the vertebral arteries are often affected by head motion. Stenotic change of the vertebral artery can occur at the atlantoaxial level in head rotation. Such a special type of stroke was named "bow hunter's stroke" by Sorensen. We report three cases of bow hunter's stroke and discuss the angiographic examinations. As surgical treatment, we performed partial transversectomy of the atlas vertebra, with favorable results. The usefulness of this surgical procedure is discussed.

The os odontoideum is a congenital anomaly of the 2nd cervical vertebra. It is an ossicle that is separated from the body of the axis by a variable transverse gap. This weakens atlantoaxial stability. When ligamentous support also fails, subluxation ensues. Compressive myelopathy and vertebral artery obliteration may occur. Eight cases, all in children, were studied prospectively. The neurological manifestations and surgical indications and treatment are discussed.

Hyperekplexia in an 8-year-old boy with myelodysplasia was greatly improved by surgical decompression of the cervicomedullary region. The possible implications for treatment and for understanding the cause of this syndrome are discussed.

Fractures of the 1st cervical vertebra (C1) represent 7% of all acute cervical spine fractures. Isolated atlas fractures are most commonly bilateral or multiple fractures through the ring of C1. Frequently (44% of cases), the atlas will be fractured in combination with the axis. Treatment of isolated C1 fractures should be governed by the rules of Spence. The treatment of combination C1-C2 fractures is dictated by the type and severity of the C2 fracture. Experience with 57 cases of acute atlas fractures is reviewed. Nonoperative external immobilization was used in 53 patients (with 1 failure), and early surgical wiring and fusion were performed in 4 patients. The long term outcome from an atlas fracture is good (median follow-up, 40 months).