Treatment of atlantoaxial dislocations among patients with cervical osseous or vascular abnormalities utilizing hybrid techniques.

OBJECTIVE Most cervical fixations for atlantoaxial dislocation (AAD) are bilateral and symmetric; however, in the setting of osseous and vascular deformity at the craniovertebral junction, asymmetrical and hybrid fixations are used as "salvage" techniques. Because of the rarity of these cases, hybrid cervical fixations for AAD have not been fully explored. The aim of this study was to evaluate the clinical feasibility and outcomes of posterior hybrid cervical fixations for AAD. METHODS Twenty-one AAD cases were retrospectively studied; 18 had cervical myelopathy with Japanese Orthopaedic Association (JOA) scores ranging from 9 to 16 (mean 13.5). Hybrid fixation techniques included unilateral pedicle screws, transarticular screws, C-2 laminar screws, cervical lateral mass screws, and spinous process screws. During the same period, 82 AAD cases, treated using symmetric traditional fixations, were analyzed as controls. RESULTS Atlantoaxial fixation was performed in 11 cases, while occiput-cervical fixation was used in 10 cases. All cases achieved solid osseous fusion. Anatomical reduction was achieved in 20 cases (95.2%). All 18 cases with myelopathy showed postoperative improvement, with JOA scores ranging from 13 to 17 (mean 15.5). Three cases (14.2%) experienced complications, including delayed wound healing, CSF leakage, and fixation loosening. Hybrid fixation techniques showed significantly greater estimated blood loss when compared with controls (208.1 ± 19.30 ml vs 139.63 ± 8.75 ml, p = 0.001). Operative duration (125.38 ± 6.29 min vs 119.41 ± 3.77 min, p = 0.464), complication rates (14.3% vs 4.9%, p = 0.148), and JOA improvement rates (61% ± 7% vs 49% ± 4%, p = 0.161) showed no significant differences. CONCLUSIONS For ADD with osseous or vascular deformity, posterior cervical reduction and stabilization can be achieved using hybrid techniques, resulting in comparable clinical results to symmetric traditional fixation.

Management Issues in a Case of Congenital Craniovertebral Junction Anomaly with Aberrant Retropharyngeal Midline Course of Bilateral Cervical Internal Carotid Arteries at C1-C2.

BACKGROUND: Aberrant medial retropharyngeal prevertebral course of the internal carotid arteries (ICAs) is extremely uncommon. In oropharyngeal surgeries, like transoral odontoidectomy (TOO), this unrecognized aberrant retropharyngeal course of ICAs can result in devastating complications secondary to inadvertent injury of ICAs. We describe this aberrant course of ICAs in a patient with a craniovertebral junction (CVJ) anomaly with a dysmorphic C1 lateral mass on one side and discuss in detail various management issues in this complex case. CASE DESCRIPTION: A 44-year-old patient presented with neck pain, paresthesia in all 4 limbs, and quadriparesis. Computed tomography (CT) of the CVJ revealed os odontoideum, basilar invagination, atlantoaxial dislocation (AAD), severe malalignment of the C1-C2 facets, and an unusually thin (dysmorphic) left C1 lateral mass. Computed tomographic angiography revealed an aberrant medial retropharyngeal course of the bilateral cervical ICAs with near midline location at the level of C1 and C2. Transoral odontoidectomy (TOO) was not considered safe in view of potential injury to medially located ICAs. Normal spinal alignment with reduction of BI and AAD was achieved by C1-C2 joint distraction with placement of a spacer only in the right C1-C2 joint space followed by occipitocervical fusion. The patient experienced complete recovery after surgery with improvement of power in all 4 limbs to 5/5. CONCLUSIONS: Identification of this rare aberrant prevertebral course of ICAs in a patient with a CVJ anomaly is critical because it precludes TOO as a treatment option. Correction of BI and AAD is possible even with a unilateral C1-C2 joint spacer when placement of a joint spacer on the other side is not technically feasible.

Anatomical Variations of the Vertebral Artery in the Upper Cervical Spine: Clinical Relevance for Procedures Targeting the C1/C2 and C2/C3 Joints.

BACKGROUND AND OBJECTIVES: Accidental breach of the vertebral artery (VA) during the performance of cervical pain blocks can result in significant morbidity. Whereas anatomical variations have been described for the foraminal (V2) segment of the VA, those involving its V3 portion (between the C2 transverse process and dura) have not been investigated and may be of importance for procedures targeting the third occipital nerve or the lateral atlantoaxial joint. METHODS: Five hundred computed tomography angiograms of the neck performed in patients older than 50 years for the management of cerebrovascular accident or cervical trauma (between January 2010 and May 2016) were retrospectively and independently reviewed by 2 neuroradiologists. Courses of the VA in relation to the lateral aspect of the C2/C3 joint and the posterior surface of the C1/C2 joint were examined. For the latter, any medial encroachment of the VA (or one of its branches) was noted. The presence of a VA loop between C1 and C2 and its distance from the upper border of the superior articular process (SAP) of C3 were also recorded. If the VA loop coursed posteriorly, its position in relation to 6 fields found on the lateral aspects of the articular pillars of C2 and C3 was tabulated. RESULTS: At the C1/C2 level, the VA coursed medially over the lateral quarter of the dorsal joint surface in 1% of subjects (0.6% and 0.4% on the left and right sides, respectively; P = 0.998). A VA loop originating between C1 and C2 was found to travel posteroinferiorly over the anterolateral aspect of the inferior articular pillar of C2 in 55.5% of patients on the left and 41.9% on the right side (P < 0.001), as well as over the SAP of C3 in 0.4% of subjects. When present in the quadrant immediately cephalad to the C3 SAP, VA loops coursed within 2.0 ± 1.5 and 3.3 ± 2.5 mm on the left and right sides, respectively, of its superior aspect (P < 0.001). CONCLUSIONS: The VA commonly travels adjacent to areas targeted by third occipital nerve procedures and more rarely over the access point for lateral atlantoaxial joint injections. Modifications to existing techniques may reduce the risk of accidental VA breach.

Venous air embolus during prone cervical spine fusion: case report.

Venous air embolism (VAE) is a known neurosurgical complication classically and most frequently occurring in patients undergoing posterior cranial fossa or cervical spine surgery in a sitting or semi-sitting position. The authors present a case of VAE that occurred during posterior cervical spine surgery in a patient in the prone position, a rare intraoperative complication. The patient was a 65-year-old man who was undergoing a C1-2 fusion for a nonunion of a Type II dens fracture and developed a VAE. While VAE in the prone position is uncommon, it is a neurosurgical complication that may have significant clinical implications both intraoperatively and postoperatively. The aim of this review is 2-fold: 1) to improve the general knowledge of this complication among surgeons and anesthesiologists who may not otherwise suspect air embolism in patients positioned prone for posterior cervical spine operations, and 2) to formulate preventive measures as well as a plan for prompt diagnosis and treatment should this complication occur.

Civilian gunshot wounds to the atlantoaxial spine: a report of 10 cases treated using a multidisciplinary approach.

OBJECT: Gunshot wounds to the atlantoaxial spine are uncommon injuries and rarely require treatment, as a bullet traversing this segment often results in a fatal injury. Additionally, these injuries are typically biomechanically stable. The authors report a series of 10 patients with gunshot wounds involving the lateral mass and/or bodies of the atlantoaxial complex. Their care is discussed and conclusions are drawn from these cases to identify the optimal treatment for these injuries. METHODS: A retrospective review was conducted of patients presenting to the emergency rooms of 3 institutions with gunshot wounds involving the atlantoaxial spine. Mechanism of injury and neurological status were obtained, as was the extent of the osteoligamentous, vascular, and neurological injuries. Nonoperative and operative treatment, complications, and clinical and radiographic outcome were recorded. The data were then analyzed to determine the neurological and biomechanical prognosis of these injuries, the utility of the various diagnostic modalities in the acute management of the injuries, and the nature and effectiveness of the nonoperative and operative treatment modalities. RESULTS: Ten patients with gunshot wounds involving the lateral mass and/or bodies of the atlantoaxial complex were identified. All but 2 patients sustained a vertebral artery injury. Each patient was evaluated using cervical radiographs, CT scans, and vascular imaging, 8 in the form of digital subtraction angiography and 2 with high-resolution CT angiography. Uncomplicated patients were treated conservatively using cervical collar immobilization, local wound care, and antibiotics. One patient was treated using a halo for instability and 1 underwent posterior fusion following a posterolateral decompression for delayed myelopathy. One patient underwent transoral resection of a bullet fragment. One patient underwent embolization for a symptomatic arteriovenous fistula and a second patient underwent a neck exploration and a jugular vein ligation. None of the patients received anticoagulation therapy. The mean follow-up duration was 13 months. All but 2 patients regained their previous functional status and all ultimately attained a mechanically stable spine. CONCLUSIONS: These 10 patients represent a rare form of cervical spine penetrating injury. Unilateral gunshot wounds to the atlantoaxial complex are usually stable and the need for acute surgical intervention is rare. Unilateral vertebral artery injury is well tolerated and any information provided by angiography does not alter the acute management of the patient. Vascular complications from gunshot wounds can be managed effectively by endovascular techniques.

Posterior C1-2 fusion using a polyaxial screw/rod system for os odontoideum with bilateral persistence of the first intersegmental artery.

The authors report the case of a patient with os odontoideum, myelopathy secondary to atlantoaxial instability, and bilaterally persistent first intersegmental artery at the craniovertebral junction. Instead of occipitocervical fusion, C1-2 posterior fusion was performed using a polyaxial screw/rod system. The information obtained from 3D CT angiography studies may highlight the potential risk of vertebral artery injury in advance and reduce the risk of an intraoperative vertebral artery injury. In addition, C-1 lateral mass screw placement may be a safe procedure for cases of atlantoaxial subluxation in which there are persistent C-1 intersegmental arteries.

Venous air embolism: an unusual complication of atlantoaxial arthrodesis: case report.

STUDY DESIGN: A unique case of a patient with intraoperative venous air embolism (VAE) during atlantoaxial arthrodesis has been discussed. OBJECTIVE: To describe an uncommon complication of atlantoaxial arthrodesis, VAE. SUMMARY OF BACKGROUND DATA: Although several techniques for atlantoaxial arthrodesis have proven effective, lateral mass or pedicle screw constructs have been shown to have superior strength with acceptable morbidity. Placement of lateral mass or pedicle screws into the C1 or C2 vertebrae requires consideration of relevant local anatomy, including vascular and nervous structures. We present a rare complication of surgery in this anatomic distribution, VAE. To the authors' knowledge, there has been no similar report described. METHODS: A previously healthy 38-year-old man was found to have os odontoideum with atlantoaxial instability; arthrodesis was thus planned, with C1 lateral mass and C2 pedicle screws. Intraoperatively, during dissection of the C1-C2 joint capsule, the patient experienced a precipitous drop in blood pressure, end-tidal CO2, and oxygen saturation. Shortly thereafter, the patient was noted to be asystolic. RESULT: With suspicion for air embolus, the surgical field was flooded with irrigant, the incision closed with haste, and the patient rolled to the supine position. Cardiopulmonary resuscitation was initiated with return of pulse within minutes. A transesophageal echocardiogram was performed approximately 15 minutes after the onset of suspected air embolus, revealing increased atrial pressures consistent with VAE. Following echocardiogram, the patient was returned to prone position for completion of arthrodesis. Remaining surgery and arousal were uneventful. CONCLUSION: This is the first report of intraoperative VAE occurring with atlantoaxial arthrodesis. Enlarged venous anastomoses present at the atlantoaxial junction should be taken into consideration during surgical dissection, and the potential danger of VAE with atlantoaxial arthrodesis should be understood. With aggressive intraoperative treatment, this patient suffered no long-term complications.

C1 lateral mass screw insertion with protection of C1-C2 venous sinus: technical note and review of the literature.

STUDY DESIGN: This is a technical note and review of the literature. OBJECTIVE: We propose to describe a revised surgical technique of C1 lateral mass screw insertion with protection of C1-C2 venous sinus surrounding the C2 nerve root. SUMMARY OF BACKGROUND DATA: During C1 lateral mass screw insertion and in posterior C1-C2 fixation, iatrogenic injury of C1-C2 venous sinus results in bleeding, which is troublesome. Appropriate management of the venous sinus in this region is critical to successful surgery in this complex anatomic region. METHODS: We reviewed 48 patients who underwent posterior C1-C2 fixation at our institution between September 2001 and October 2008. Twenty-four atlas screws were inserted by the originally described C1 lateral mass screw technique (group A), and 28 through a revised posterior arch and lateral mass screw technique (C1 transpedicular screw) (group B). The final group of 44 atlas screws was placed with our newly revised technique (group C). RESULTS: Bleeding of venous sinus was encountered in 3 group A, 2 group B, and 1 group C atlas screw insertions. The incidence rate was 12.50% (A), 7.14% (B), and 2.27% (C). Statistical comparison showed no significant difference between the groups. All the cases were followed for a mean period of 28.1 month. Four patients in group A complained of postoperative numbness in occipitocervical region. No patients in group B or group C voiced this complaint. A high fusion rate was found in all 3 groups with no signs of implant failure. CONCLUSION: Bleeding of C1-C2 venous sinus is vigorous and frustrating. The revised technique we describe provides theoretical and practical protection of venous sinus. In addition, the firm bony purchase of screws afforded by this technique contributes to achieving stabilization of the upper cervical spine and a high fusion rate.

Osseous and vascular anatomical variations within the C1-C2 complex: a radiographical study using computed tomography angiography.

BACKGROUND: One of the limiting factors of C1-C2 fixation is the location of the vertebral artery (VA). The authors sought to assess the potential variations in atlanto-axial VA anatomy using computed tomography angiography (CTA). METHODS: Detailed measurements were made on digital images of 106 patients undergoing CTA at our institution (54 males, 52 females; mean age 56, range 20-86). Distances, diameters and angles of osseous and vascular elements of the atlanto-axial complex were measured. RESULTS: Optimal C1 and C2 screw trajectories demonstrated wide variations among patients. The size of the VA groove or foramen was not predictive of exact arterial location or size. CONCLUSIONS: The size, location and path of the VA cannot be precisely predicted by the appearance of osseous structures such as the transverse foramina and/or the VA groove. CTA provides additional information regarding the atlanto-axial complex, and should be considered as a useful adjunct in the preoperative evaluation of select patients.

Dissecting aneurysm of the radiculomedullary artery originating from extracranial vertebral artery dissection in a patient with rheumatoid cervical spine disease: an unusual cause of subarachnoid hemorrhage. Case report.

The authors report the case of a 65-year-old woman with atlantoaxial subluxation caused by rheumatoid arthritis. The patient had been hospitalized because of an infection after a total-knee replacement, when she suddenly lost consciousness and became apneic after an episode of intractable neck pain. Cranial computed tomography scanning demonstrated subarachnoid hemorrhage (SAH), and angiography revealed a dissecting aneurysm of the radiculomedullary artery that had originated from an extracranial vertebral artery dissection at the level of the atlantoaxial joint. Although coil embolization for the parent artery, including the dissecting aneurysm, was performed successfully, the patient died of worsening infection. The authors believe that the SAH occurred because of a ruptured dissecting aneurysm in the intradural portion of the radiculomedullary artery.

Vertebral arteries and cervical rotation: modeling and magnetic resonance angiography studies.

OBJECTIVE: To determine whether lumen narrowing in vertebral arteries during atlanto-axial rotation is due to stretch or localized compression. DESIGN AND SETTING: Experiments with models were made in a private chiropractic clinic, whereas studies of cadaveric specimens were performed in an anatomy laboratory. Doppler ultrasound and magnetic resonance angiography (MRA) studies were carried out in the radiology department of a public hospital. PATIENTS: Eight patients had their vertebral arteries examined by use of a Doppler velocimeter and MRA. MAIN OUTCOME MEASURE: Stenosis of the vertebral arteries caused by stretch, localized compression, or kinking. RESULTS: All 16 vertebral arteries from the 8 patients displayed no changes in their lumen dimensions with full cervical rotation, although curves in each of the arteries did change. The model and cadaveric vertebral arteries demonstrated localized compression or kinking of the vessel wall with atlanto-axial rotation contralaterally but revealed no evidence of major contribution of stretching to stenosis. CONCLUSION: The lumen of vertebral arteries is usually unaffected by atlanto-axial rotation. In cases where there is stenosis, this is mainly due to localized compression or kinking. These findings are relevant to premanipulative screening of vertebral arteries with Doppler ultrasound scanning.

Anterior decompression of the atlantoaxial vertebral artery to treat bow hunter's stroke: technical case report.

OBJECTIVE AND IMPORTANCE: Bow hunter's stroke is a symptomatic vertebrobasilar insufficiency caused by stenosis or occlusion of the vertebral artery at the C1C2 level with head rotation. No case of anterior decompression of the vertebral artery for surgical treatment of bow hunter's stroke has been reported. CLINICAL PRESENTATION: A 47-year-old male patient presented with repeated episodes of unconsciousness caused by turning his head approximately 40 degrees to the right; he recovered consciousness within approximately 10 seconds after his head was returned to the neutral position. Angiography revealed an occluded right vertebral artery and temporary occlusion of the left vertebral artery, at the level of the C2 transverse foramen, when the patient's head was turned approximately 40 degrees to the right. INTERVENTION: Anterior decompression of the left vertebral artery at the transverse foramen of the axis was performed. Postoperative angiography demonstrated sufficient flow in the left vertebral artery even when the neck was rotated. CONCLUSION: The patient was discharged without neurological deficits. We demonstrate that simple surgical untethering of the vertebral artery at the transverse foramen of the axis is an effective method of treatment that avoids the limitation of head rotation. The advantage of this procedure is that it does not result in postoperative restriction of the patient's neck movements. The anterior approach, with decompression of the transverse foramen of the axis, in the present case provided adequate exposure of the vertebral artery and resulted in a satisfactory outcome.

Bow hunter's stroke associated with an aberrant course of the vertebral artery--case report.

A 53-year-old male presented with repeated vertebrobasilar insufficiency on turning the head to the left. Angiography revealed severe stenosis of the dominant right vertebral artery at the atlantoaxial level in this position. Decompression surgery for the affected vertebral artery at the transverse foramen of the atlas was planned. However, surgery revealed an aberrant course of the artery, turning at the orifice of the transverse foramen of the atlas and perforating the dura at the occipitoatlantal level after passing through the bony canal of the atlas. Therefore, decompression was performed at the bony canal, which was the contributing site, and the symptoms improved. Bow hunter's stroke may be caused by atlantoaxial arterial anomalies, so accurate preoperative evaluation of the region is necessary to avoid anatomical confusion at surgery.

Critical neck position as an independent risk factor for posterior circulation stroke. A magnetic resonance angiographic analysis.

The purpose of this study was to compare the effects of critical neck angulation (rotation and hyperextension) on vertebral artery perfusion in symptomatic and control populations and to determine whether this represents a risk factor for ischemic stroke. In a cross-sectional study, 64 symptomatic individuals with well-documented brainstem ischemic events (average age, 70.9 yr) and 37 control subjects (average age, 66.3 yr) were evaluated using a dynamic magnetic resonance angiography technique designed to mimic activities of daily living. Abnormalities of perfusion at the atlantoaxial and atlantooccipital junction and distal vertebral artery were recorded and scored independently by two neuroradiologists. Volume flow analysis was also recorded at the basilar artery, and distal and proximal vertebral arteries. Symptomatic subjects displayed a consistent pattern (56.4%) of contralateral hypoperfusion at the atlantoaxial and atlantooccipital junction and distal segments (grades 3 and 4) (p < 0.001). Unsuspected hypoplasia was noted in 13% of the symptomatic subjects with a right-sided preponderance (88%), suggesting developmental susceptibility. Occlusion was noted in all subjects with contralateral neck rotation. Postpositional ischemia was present (68%) and correlated with female gender (p < 0.001), severity of stenosis (p < 0.001), vascular risk factors (p < 0.001), and microinfarction on magnetic resonance images (p < 0.05). Flow analysis showed low basilar artery perfusion (< 25 ml/min) in 63.6%, and unsuspected steal with neck motion in 4 subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

[Angiographic examination of the vertebral artery at the atlantoxial joint during head rotation].

Stenosis or occlusion of the vertebral artery at the atlantoaxial joint associated with head rotation is generally considered an uncommon cause of vertebrobasilar insufficiency. This rotational contralateral (to the face) vertebral artery occlusion is considered to be a "physiological phenomenon". The purpose of the present article is to investigate whether stenosis or occlusion of the vertebral artery at the atlantoaxial joint really occurs with head rotation. The authors performed vertebral angiography both in the neutral position and with contralateral rotation of the head (about 80 - 90 degrees) on 39 patients (44 vertebral arteries), who didn't have any disease of the cervical region or of the posterior cranial fossa. The authors discussed the angiographic findings concerning the vertebral artery at the atlantoxial joint during contralateral rotation of the head. In some cases a vertebral artery was stretched with head rotation. However occlusion or stenosis of the vertebral artery was never found to occur at the atlantoaxial joint level in any of the cases. This result indicates that rotational vertebral artery occlusion is not a "physiological phenomenon". There may be many other developmental and degenerative factors contributing to this rotational occlusion, such as atherosclerosis, kinking, and tortuosity of the vertebral artery, hyperosteosis, tightness of the paravertebral muscle, stenosis of transverse foramen and the depth of the vascular groove of the atlas.

[Atlanto-axial instability in injuries of the ligament system in children and adolescents]. / Atlantoaksial'naia nestabil'nost' pri povrezhdeniiakh sviazochnogo apparata u detei i podrostkov.

There has been carried out an experiment with 6 craniovertebral blocks with contrasting of the vertebral arteries and studying of the influence of different damages of ligamentous apparatus on blood flow in vertebral arteries. In all cases there has been discovered significant vertebrogenic influence. Experimental data have been corroborated with clinical material. There have been examined 31 patient with different damages of ligamentous apparatus of craniovertebral segment, with 21 of them has been detected significant vertebrogenic influence at ultrasound dopplerography of vertebral arteries.