[Preoperative Simulation for Complication Control in Spinal Surgery]

The craniovertebral junction not only contains anatomically important structures such as the medulla oblongata, upper cervical spinal cord, and vertebral artery, but also controls the dynamic movements of flexion, extension, and rotation of the head and neck. Consequently, instability and spinal deformities can easily occur in the craniovertebral region, and appropriate treatment should be selected based on the specificity of the lesion. Basilar invagination often involves bone and vascular anomalies and fusion surgery is often required. Therefore, careful pre-operative simulations are necessary. The creation and use of three-dimensional bone models, including image navigation, are useful for surgical simulation.

Exploring the Pathogenesis of Atlanto-Occipital Instability in Chiari Malformation With Type II Basilar Invagination: A Systematic Morphological Study

BACKGROUND

Our previous study suggested that atlanto-occipital instability (AOI) is common in patients with type II basilar invagination (II-BI).

OBJECTIVE

To further understand the pathogenesis of AOI in Chiari malformations (CM) and CM + II-BI through systematic measurements of the bone structure surrounding the craniocervical junction.

METHODS

Computed tomography data from 185 adults (80 controls, 63 CM, and 42 CM + II-BI) were collected, and geometric models were established for parameter measurement. Canonical correlation analysis was used to evaluate the morphological and positional relationships of the atlanto-occipital joint (AOJ).

RESULTS

Among the 3 groups, the length and height of the condyle and superior portion of the lateral masses of the atlas (C1-LM) were smallest in CM + II-BI cases; the AOJ had the shallowest depth and the lowest curvature in the same group. AOJs were divided into 3 morphological types: type I, the typical ball-and-socket joint, mainly in the control group (100%); type II, the shallower joint, mainly in the CM group (92.9%); and type III, the abnormal flat-tilt joint, mainly in the CM + II-BI group (89.3%). Kinematic computed tomography revealed AOI in all III-AOJs (100%) and some II-AOJs (1.5%) but not in type I-AOJs (0%). Morphological parameters of the superior portion of C1-LM positively correlated with those of C0 and the clivus and significantly correlated with AOI.

CONCLUSION

Dysplasia of the condyle and superior portion of C1-LM exists in both CM and II-BI cases yet is more obvious in type II-BI. Unstable movement caused by AOJ deformation is another pathogenic factor in patients with CM + II-BI.

Atlanto-occipital Dissociation in the Setting of Relatively Normal Radiologic Findings

BACKGROUND

Craniocervical junction (CCJ) dislocations are often fatal. Atlanto-occipital dissociation can be challenging to diagnose, especially in patients who present with absent or subtle radiologic signs.

CASE DESCRIPTION

A neurologically intact 37-year-old patient presented to the hospital following a high-speed motor vehicle accident. Initial computed tomography scans showed normal CCJ anatomy, but magnetic resonance imaging (MRI) of the CCJ was performed to further evaluate perimesencephalic subarachnoid hemorrhage. MRI revealed partial disruption of the anterior atlantoaxial membrane and tectorial membrane as well as complete disruption of the posterior atlanto-occipital membrane, ligamentum flavum, and apical ligament, signifying atlanto-occipital dissociation. Halo spinal immobilization was performed in preparation for stabilization with posterior occipitocervical fusion; however, the CCJ distracted widely during surgery owing to the accident-related dislocation, signifying an unstable fracture. Posterolateral fusion was performed, and the distraction injury was corrected via posterior surgical instrumentation.

CONCLUSIONS

Normal occiput-C1 craniometric parameters in the setting of unexplained perimesencephalic subarachnoid hemorrhage does not eliminate the possibility of missed or delayed diagnosis of traumatic atlanto-occipital dissociation injuries. Cervical MRI without contrast should be considered in patients with vertebral artery dissection or perimesencephalic subarachnoid hemorrhage after a blunt injury with neck pain. When MRI shows evidence of disruption of ≥2 atlanto-occipital ligaments, surgical stabilization should be considered, as these are clinically very unstable injuries.

Biomechanical Rationale for the Development of Atlantoaxial Instability and Basilar Invagination in Patients with Occipitalization of the Atlas: A Finite Element Analysis

OBJECTIVE

Occipitalization of the atlas (OA) often is associated with atlantoaxial dislocation and basilar invagination. The purpose of this study is to determine the biomechanical difference between normal and OA conditions in the craniovertebral junction and to further explore the rationale for development of atlantoaxial dislocation and basilar invagination using the finite element model (FEM).

METHODS

A ligamentous, nonlinear, sliding-contact, 3-dimensional FEM of the occipitoatlantoaxial complex was generated. Validation of the model was accomplished by comparing kinematic predictions with experimental data. We defined the atlantooccipital joint as a tie contact to simulate the OA deformity. The range of motion and the value of the maximum Von Mises stress were compared between the intact and OA models.

RESULTS

We found all of the predicted data in the intact FEM fell within 1 standard deviation of the cadaver data for all 6 loadings. The OA simulation significantly reduced the overall range of motion of the occipitoatlantoaxial complex at all loadings. The maximum Von Mises stress was predicted to increase at the transverse ligament and the superior articular facet of the axis for all the flexion, extension, lateral bending, and axial rotation loadings.

CONCLUSIONS

The OA could result in hypermobility of the atlantoaxial segment and cause overstress in the transverse ligament and the lateral atlantoaxial joints. These changes explain the pathogenesis of atlantoaxial dislocation and basilar invagination associated with OA. Follow-up should be scheduled regularly due to the nature of the dynamic development of atlantoaxial dislocation and basilar invagination.

Traumatic atlanto-occipital dislocation: do children and adolescents have better or worse outcomes than adults? A narrative review

BACKGROUND

Traumatic atlanto-occipital dislocation is an uncommon, severely unstable pathology, which can lead to detrimental or even fatal neurological impairment. Specifically, children have consistently been reported to be more susceptible to this type of injury because of their disproportionately larger head, ligament laxity, and injury mechanisms. However, to date, rates of missed injury and outcomes including neurologic recovery of pediatric and adult populations following this insult have not been comparatively evaluated.

METHODS

Standard search engines were used to investigate outcomes of traumatic atlanto-occipital dislocation in children and adolescents compared to adults.

CONCLUSIONS

Based on case reports and small series from the literature, it seems that children and adolescents tend to have a better likelihood of survival with the possibility of long-term neurological complications. Comparatively, adults who suffer traumatic atlanto-occipital dislocation either succumb to their injuries or survive with very little if any neurological complications.

Atlanto-occipital ligament calcification: a novel sign in nevoid basal cell carcinoma syndrome

BACKGROUND

The nevoid basal cell carcinoma syndrome (NBCCS), first described by Gorlin and Goltz in 1960, is a hereditary autosomal dominant disease with high penetrance and variable expressivity. Almost 70% of patients with NBCCS have some degree of craniofacial anomaly. Among these, the presence of ectopic calcification have been reported but Atlanto-occipital ligament calcification has never been described. Therefore this investigation was carried out to determine the prevalence of atlanto-occipital ligament calcification on lateral x-ray of NBCCS patients aiming to assess the effectiveness of this sign in NBCCS diagnosis.

PATIENTS AND METHODS

Lateral and frontal cephalometric radiographs of 18 patients (11 males and 7 females), aged 8-61 years, with the diagnosis of NBCCS were evaluated for the presence of intracranial calcifications (diaphragma sellae and falx cerebri) and or calcification of the atlanto-occipital ligament.

RESULTS

A total of 11 patients presented calcification of atlanto-occipital ligament to various degrees and in three cases this represented the only sign of ectopic calcification. When compared to the other two sites of ossification, atlanto-occipital ligament calcification had a similar prevalence.

CONCLUSION

The calcification of the atlanto-occipital ligament should be considered in addition to the other major criteria for NBCCS diagnosis.

Geometry of the articular facets of the lateral atlanto-axial joints in the case of occipitalization

This study investigates if atlanto-occipital fusion affects the size and geometrical configuration of the articular facets of the atlanto-axial joint. Morphometric analysis was performed on the male adult skull, the occipital bone of which is assimilated with the first cervical vertebrae (the atlas). The perimeter, Feret's diameter, surface area, and circularity of the inferior articular fa-cets were measured. However, we did not observe significant bilateral differences in size of the inferior articular facets of the assimilated atlas compared to normal first cervical vertebrae. Geometrical conformation of the articular facets of the atlas and axis was assessed using a coordinate measuring machine (PMM - 12106, Leitz). The results obtained from this machine indicated that the inferior articular facets of the assimilated atlas presented asymmetrical orientation compared to the normal anatomy of the atlas. Hence, in the case of occipitalization, the gap between the articulating facets of the atlas and the axis was measured to be greater than in the normal atlanto-axial joint. Computer assisted tomography was applied to visualise the anatomical relationship between the inferior articular facets of the assimilated atlas and the corresponding facets located on the axis. In this case, radiographic examination revealed that the bilaterally articulating facets (inferior and superior) showed disproportion in their adjustment within the lateral atlanto-axial joints. Thus, we concluded that the fusion of the atlas with the occipital bone altered the geometry of the inferior articular facets of the atlas and influenced the orientation of the superior articular facets of the axis.

[Skull-base plasmacytoma with craniocervical instability]

INTRODUCTION

Cranio-cervical instability is, in some cases, the main surgical concern in posterior skull base tumors. We report on a case in which a solitary plasmacytoma of the skull base presented with cranio-cervical instability. Vertebral artery was injured during surgery. The surgical anatomy is reviewed, with emphasis in vascular complications avoidance.

CASE REPORT

A 66 year-old woman was diagnosed of a cranial base solitary plasmacytoma and treated with radio and chemotherapy with complete remission. After receiving that treatment, she presented with tetraparesis and a cranio-cervical instability was diagnosed. She was operated on, under cranial traction, of posterior occipito-cervical instrumentation with C1 to C2 transarticular Magerl screws. The right vertebral artery was injured during surgery without additional neurological deficit. Two years after the operation she remains independent for daily activities.

CONCLUSIONS

Transarticular screws at the C1 to C2 level of the cervical spine may provide rigid fixation in posterior cranio-cervical instrumentation for osteolytic lesions, but there is a risk of injury to the vertebral artery, specially when some variations in the surgical anatomy exist.

Craniovertebral junction lesions: our experience with the transoral surgical approach

The aim of this study is to review our experience with the transoral surgical management of anterior craniovertebral junction (CVJ) lesions with particular attention to the decision making and to the indication for a consecutive stabilization. During 10 years (1998-2007), 52 consecutive patients presenting exclusively fixed anterior compression at the cervicomedullary junction underwent transoral surgery. Mean age was 55.85 years (range 17-75 years). Encountered lesions were: malformation (32 cases), rheumatoid arthritis (11 cases), tumor (5 cases) or trauma (4 cases). A total of 79% of patients presented with chronic/recurrent headache (cranial and/or high-cervical pain), 73% with varying degrees of quadrip aresis, and 29% with lower cranial nerve deficits. All of the patients but two, with posterior stabilization performed elsewhere, underwent synchronous anterior decompression and posterior occipitocervical fixation. Adjuncts to the transoral approach (Le Fort I with or without splitting of the palate), tailored to the local anatomy and to the extension of the lesions, were performed in seven cases. Follow-up ranged between 4 and 96 months. Of 35 patients with severe preoperative neurological deficits, 33 improved. The remaining 15 patients who presented with mild symptoms, healed throughout the follow-up. Perioperative mortality occurred in two cases and surgical morbidity in eight cases (dural laceration, cerebrospinal fluid leak with meningitis, malocclusion, oral wound dehiscence and occipital wound infection). Delayed instability occurred in one patient because of cranial settling of C2 vertebral body. A successful surgery achieving a stable decompression at the CVJ is an expertise demanding procedure. It requires accurate preoperative evaluation and, appropriate choice of decompression technique and stabilization instruments. Enlarged transoral approaches (despite higher morbidity) are a supportive means in cases of severe basilar invagination, cranial extension of the lesion or limited jaw mobility.

Head-supporting sign during reclining: an indication of craniovertebral junction involvement

The craniovertebral (CV) junction can be involved in many diseases, e.g. rheumatoid arthritis, as well as destructive bone pathologies such as tumour and tuberculosis (craniovertebral Pott's disease). While some of these patients present acutely with neck pain and neurological deficits, in others the signs and symptoms may be more subtle. Two patients with CV junction involvement are described. One patient suffered from fracture of the anterior arch of atlas after being involved in a motor vehicle accident and the other had craniovertebral Pott's disease. A detailed history and clinical examination was carried out paying special attention to the situation when patients attempted to recline or while getting up from a reclining position. Patients were further investigated with imaging studies which focused on the CV junction. It was noted that patients with CV junction involvement frequently support their head while attempting to recline or when getting up from a reclining posture. This head supporting sign may be the sole neurological finding in some patients with involvement of the CV junction.

Occipitoatlantoaxial malformation in an adult goat

An occipitoatlantoaxial malformation was diagnosed in a 1-year-old Murciano-Granadina goat. At clinical examination, the head and cranial part of the neck were deviated to the right. Clinical signs of spinal cord or brain disease were not observed. At necropsy, morphological abnormalities were seen in the craniovertebral junction and cervical vertebrae, characterized by a firm attachment and incomplete articulation between the occipital bone and the atlas, and scoliosis in the cervical regions. The definitive diagnosis was bilateral asymmetrical occipitoatlantoaxial fusion with rotation of the atlas and atlantoaxial subluxation. To the authors' knowledge, this case report is the second occipitoatlantoaxial malformation described in a goat and the first description in an adult goat.

The mobile Condylus tertius occipitalis and fractures of the hypochordal clasp

The Condylus tertius is defined as a small bony hunch on the anterior surface of the clivus. Its presence means an enormous functional impairment of the upper head joint, looking at the 3-point-contact between the skull base and the upper cervical vertebrae. In 10 of the 2000 forensic examined bodies, analyses of neck vertebra + skull base revealed this feature. The origin of these findings is discussed, as stated in the literature of embryology, to be a suboccipital hypochordal plate. So in one of the cases the condylus was found at the hypochordal plate itself whereas the so-called socket was lying at the margin of the clivus. In three cases there was found a free body between the apex of the Dens and the Clivus forming a mobile Condylus tertius. In our opinion its position varies over the anterior arch of the atlas and the apex of the dens as a result of rotatory forces between the atlas and axis and physiological strain. Examples are given to elucidate this. There is a difference in the differentiation of the deposited material according to functional demand. A pressure bed (i.e. a Condylus tertius) is formed when a bony structure is deposited on the clivus. This functional prospect relativises the hypothesis of a purely constitutional genesis of the Condylus tertius. A fracture of the hypochordal clasp being joined with a bony connection to the anterior atlantic arch is described for the first time.

Concomitant fracture of bilateral occipital condyle and inferior clivus: what is the mechanism of injury?

With the routine use of multi-slice high resolution computed tomography, increasing number of occipital condyle fractures have been reported in the last decade. The authors report a very rare case of bilateral occipital condyle fracture complicated by the fracture of the inferior clivus and discuss the possible mechanisms of injury.

Screw fixation via diploic bone paralleling to occiput table: anatomical analysis of a new technique and report of 11 cases

Several types of posterior approaches have been adopted for occipitocervical fusion. Prior to this study, Foerater et al. in 1927 used a fibular strut graft in the site between the occiput and the lower cervical spine to achieve fusion. Since then, various techniques including wrings, Hartshill loop, AO reconstructive plate, and AXIS occipital plate were described and used widely. As far as we know, all these techniques involve the screw placement vertical to the diploic bone; however none has ever addressed the feasibility of screw placement in occiput parallelling to the diploic bone. In our study, 30 dry specimens of human occiputs were measured manually using vernier calipers and protractors. The intradiploic screw was first supposed to be inserted inferiorly to the superior nuchal line (SNL) prominence. The entry point located at the superior edge of the SNL prominence. Afterward, the measurements of extracranial occiput in SNL area on midline and bilateral 15 mm to the midline saggital-cutting planes of the occiput were conducted. The thickness of the occipital bone at the location of SNL prominence, the entry point, the exit point and the screw orientation were measured, respectively. Afterward, 11 patients with craniocervical malformation were treated surgically using this alternative and their X-ray radiographs and CT scans were evaluated postoperatively. The data showed that the occipital at the site of SNL prominence was the thickest. The thickest point was external occipital protuberance (EOP), which was up to 14 mm. The thickness decreased gradually from the site of SNL to the superior border of surgical decompressed area. The actual length of screw channel was about 26 mm. The mean thickness for safe screw insertion ranged from 5.73 to 14.14 mm. A total of 22 intraocciput screws parallel to diploic bone were placed precisely, without injury to the cerebral and inner occipital venous sinus. The results confirm that occiput is available for holding intraocciput screw paralleling to diploic bone.

Selection of a rigid internal fixation construct for stabilization at the craniovertebral junction in pediatric patients

OBJECT

Atlantoaxial and occipitocervical instability in children have traditionally been treated with posterior bone and wire fusion and external halo orthoses. Recently, successful outcomes have been achieved using rigid internal fixation, particularly C1-2 transarticular screws. The authors describe flow diagrams created to help clinicians determine which method of internal fixation to use in complex anatomical circumstances when bilateral transarticular screw placement is not possible.

METHODS

The records of children who underwent either atlantoaxial or occipitocervical fixation with rigid internal fixation over an 11-year period were retrospectively reviewed to define flow diagrams used to determine treatment protocols.

RESULTS

Among the 95 patients identified who underwent atlantoaxial or occipitocervical fixation, the craniocervical anatomy in 25 patients (six atlantoaxial and 19 occipitocervical fixations [26%]) required alternative methods of internal fixation. Types of screw fixation included loop or rod constructs anchored by combinations of C1-2 transarticular screws (15 constructs), C-1 lateral mass screws (11), C-2 pars screws (24), C-2 translaminar screws (one), and subaxial lateral mass screws (six). The mean age of the patients (15 boys and 10 girls) was 9.8 years (range 1.3-17 years). All 22 patients with greater than 3-month follow-up duration achieved solid bone fusion and maintained stable constructs on radiographic studies. Clinical improvement was seen in all patients who had preoperative symptoms.

CONCLUSIONS

Novel flow diagrams are suggested to help guide selection of rigid internal fixation constructs when performing pediatric C1-2 and occipitocervical stabilizations. Use of these flow diagrams has led to successful fusion in 25 pediatric patients with difficult anatomy requiring less common constructs.

Atlantoaxial subluxation–induced myelopathy in cleidocranial dysplasia

✓The authors describe the clinical course and treatment of a patient with cleidocranial dysplasia in whom spastic myelopathy developed due to atlantoaxial subluxation. This 27-year-old woman with cleidocranial dysplasia and a history of atlantoaxial subluxation presented with spastic myelopathy. Surgery was performed twice for cervical myelopathy and atlantoaxial subluxation, including laminectomy at the atlas and cervicooccipital fusion in which the Luque rod system was used, as well as C1–2 fusion via the transpharyngeal route. Solid bone fusion was achieved by 7 months postsurgery. Postoperative magnetic resonance imaging studies demonstrated that spinal cord compression was relieved, but atrophy persisted. At 2 years postsurgery there was no neurological disease progression, but spasticity persisted. The patient could walk with a cane. Cleidocranial dysplasia is an extremely rare cause of myelopathy in patients with atlantoaxial subluxation; the authors know of only two reports of this condition. When managing cleidocranial dysplasia, the practitioner should always be aware that atlantoaxial subluxation may be the cause of cervical myelopathy.

Craniocervical junction arachnoid cyst causing hydrocephalus: case report and review of the literature

OBJECTIVE

Arachnoid cysts (ACs) of the craniocervical junction are extremely rare entities. This report describes a craniocervical junction AC with unusual clinical course at an unusual anatomical location.

METHODS

A 21-year-old man was admitted to our clinic after a craniospinal trauma. Examination was unremarkable. Computed tomography scans demonstrated mild to moderately enlarged third and the lateral ventricles, but the fourth ventricle was typically normal. Neuroimaging studies obtained after the onset of clinical symptoms revealed marked enlargement of the ventricular system and a new cyst formation at the C1-2 level which was absent before. He underwent suboccipital craniectomy and C1-2 laminectomies. The cyst was fenestrated into subarachnoid space.

RESULTS

He made a good recovery. The histopathological diagnosis was confirmed as AC.

CONCLUSION

Due to rarity of this clinical entity, we urge readers to keep in mind the possibility of the development of this kind of AC with unusual clinical course.

Bone morphogenetic protein for salvage fusion in an infant with Down syndrome and craniovertebral instability. Case report

The authors describe the use of bone morphogenetic protein (BMP) to promote bone fusion in an infant with craniovertebral instability after two attempts at arthrodesis had failed. To their knowledge, this is the first such report. Management of craniovertebral instability remains challenging in infants with Down syndrome. Surgical treatment may result in nonunion in this patient population. The authors report on a 4-month-old boy with Down syndrome who suffered a high cervical spinal cord injury secondary to craniovertebral instability. Two attempts to fuse and stabilize the craniovertebral junction resulted in nonunion. Finally, the use of BMP led to a stable fusion construct within 6 months without encroachment on the spinal canal. At 4 years of follow up, the patient has a solid fusion mass. The case suggests a role for the use of BMP to promote fusion in this patient population.

Management of cervicomedullary compression in patients with congenital and acquired osseous–ligamentous pathologies

We present our experience in the diagnosis, surgical management and long-term follow-up of congenital and acquired osseous-ligamentous abnormalities or pathologies of the craniovertebral junction. The purpose of this study was: (i) to determine the incidence and degree of cervicomedullary compression in pediatric and young adult patients with congenital and acquired abnormalities, and (ii) to correlate cervicomedullary compression with other imaging and clinical factors to determine to what extend cervicomedullary compression is successfully treated with a posterior decompressive procedure, transoral decompression, and medical management. Between January 1995 and December 2004, 26 cases were managed in our department. These patients had: rheumatoid arthritis (RA) (3); traumatic injury (2); congenital basilar impression (5, in 2 cases a posteriorly oriented or retroflexed odontoid); infection (10); craniovertebral junction Pott's disease (9); os odonteideum (3); condylus tertius (1); and tumor (2). Six of the patients (23.1%) had syringomyelia. Only three (11.3%) were in the pediatric age group. Symptoms and signs included headache (72%), ataxia (38%), lower cranial nerve dysfunction (54%), quadriparesis (44%), hyperreflexia (76%), Hoffman positivity (72%), achilles clonus (72%) nystagmus (33%) and dysphagia (22%). The mean follow-up time was 44 months (range 3-85). Twelve (46.2%) had undergone posterior fossa decompression; seven (26.6%) had ventral decompression. Seven of the patients (26.6%) had medical management. The major morbidity included pharyngeal wound sepsis leading to dehiscence (3.8%), valopharyngeal insufficiency (3.8%), cerebrospinal fluid leakage (3.8%), postoperative macroglossia (3.8%) and inadequate anterior decompression (3.8%). Transient neurological deterioration occurred in two patients (7.6%). Our management paradigm will result in some neurologic improvements and limit the progression of symptoms. Patients with these pathologies are likely to show a good neurologic outcome when treatment, whether with or without surgery, is administered early in the course of the disease.

[Traumatic atlanto-occipital dislocation as part of a complex cervical spine injury. Case report in a 12-year-old girl]

Traumatic atlanto-occipital dislocation (AOD) appears to be an unusual and almost universally fatal injury. Although AOD is the cause of death in about 10% of fatal cervical spine injuries an increasing number of reports document cases of survival following this injury. Improved pre-hospital and in-hospital emergency care according to ATLS guidelines that include early cervical spine stabilization, effective diagnosis because of improved imaging after trauma including whole body multislice CT followed by expeditious reposition and adequate immobilization are reasons for this phenomenon. We report the case of a 12-year-old girl surviving an AOD accompanied by a distraction injury C6/7 with unilateral fixed spinal luxation. After a primary attempt at closed reduction and external stabilization with a halo vest, the injury was treated by a navigated dorsal spondylodesis C0-C1 using the CerviFix rod system and open reposition of the remaining subluxation C6/7 with laminar hooks. The literature was reviewed for diagnostic possibilities, management and prognosis of AOD.

Intraoperative monitoring of a patient with craniovertebral junction meningioma

Intraoperative monitoring is considered as a useful tool to prevent neurological damage during different neurosurgical procedures. Somatosensory evoked potentials (SEP) allow simultaneous assessment of several cortical and sub cortical centers. In this case presentation, we report intraoperative monitoring of an elderly patient with craniovertebral junction meningioma. Tibial SEP responses were elicited by stimulation of the tibial nerve; the recordings were visually analyzed for the presence of the main peaks P40-N50, peak to peak amplitudes, peak latencies and compared to baseline recordings throughout the procedure. During decompression from the medial aspect of the medulla SEP responses were lost for a brief period of time. Surgeons achieved total tumor removal and the patient left the operating room without any neurological deficit.

Occipitalization of the atlas in children. Morphologic classification, associations, and clinical relevance

BACKGROUND

Occipitalization is defined as a congenital fusion of the atlas to the base of the occiput. We are not aware of any previous studies addressing the morphologic patterns of occipitalization or the implications of occipitalization in children. We present data on what we believe is the largest reported series of children with occipitalization studied with computed tomography and/or magnetic resonance imaging, and we provide a description of their clinical characteristics.

METHODS

We retrospectively reviewed all cases of occipitalization in children included in our spine database. Patient charts and imaging studies were reviewed. A new morphologic classification of occipitalization was developed from the two-dimensional sagittal and coronal reformatted computed tomographic reconstructions and/or magnetic resonance images. The classification includes four patterns according to the anatomic site of occipitalization (Zones 1, 2, and 3 and a combination of those zones), and it was applied to this group of patients. Imaging studies were also reviewed for evidence of cervical instability and for other anomalies of the craniovertebral junction.

RESULTS

Thirty patients with occipitalization were identified. There were twenty-four boys and six girls with a mean age of 6.5 years. The morphologic categorization was Zone 1 (a fused anterior arch) in six patients, Zone 2 (fused lateral masses) in five, Zone 3 (a fused posterior arch) in four, and a combination of fused zones in fifteen. Seventeen patients (57%) had atlantoaxial instability, and eight of them had an associated C2-C3 fusion. Eleven patients (37%) had spinal canal encroachment, and five of them had clinical findings of myelopathy. The highest prevalence of spinal canal encroachment (63%) was noted in patients with occipitalization in Zone 2.

CONCLUSIONS

Occipitalization is associated with abnormalities that lead to narrowing of the space available for the spinal cord or brainstem. The risk of atlantoaxial instability developing is particularly high when there is an associated congenital C2-C3 fusion. Two-dimensional sagittal and coronal reformatted computed tomographic reconstructions and/or magnetic resonance images can help to establish the diagnosis and permit categorization of occipitalization in three zones, each of which may have a different prognostic implication.

Successful treatment of atlantooccipital luxation in an alpaca (Lama pacos)

A 7-mo-old male alpaca (Lama pacos) presented with an abnormal lowered posture of the head and neck and reluctance to walk. Cervical radiographs demonstrated atlantooccipital luxation. Successful manual closed reduction was achieved while the animal was anesthetized, resulting in complete return to normal gait and posture.

Basilar impression in osteogenesis imperfecta: can it be treated with halo traction and posterior fusion?

Basilar impression (BI) and hydrocephalus complicating osteogenesis imperfecta (OI) is usually treated by anterior transoral decompression and posterior fixation. Nevertheless, it may be questioned if posterior fusion following axial halo traction is adequate in patients with symptomatic BI complicating OI. We report on a case with progressive symptomatic hydrocephalus and BI complicating OI that was successfully treated by halo traction followed by posterior occipitocervical fusion. However, after a symptom free interval of 2 years the patient suffered from recurrence of symptomatic hydrocephalus needing additional ventriculoperitoneal (VP) shunt placement. In conclusion, posterior fusion without additional VP shunt placement may not be effective in the long term for ameliorating symptoms and signs and halting progressive hydrocephalus in BI complicating OI.

Posterior correction and fusion for severe cervical kyphosis in a patient with myotonic dystrophy: a case report

STUDY DESIGN

A case report.

OBJECTIVE

To report the first myotonic dystrophy case in which cervical kyphosis had been surgically corrected.

SUMMARY OF BACKGROUND DATA

Myotonic dystrophy is an autosomal dominant disease that shows myotonia, progressive muscle atrophy, and other various symptoms. Instability of the neck is expected to cause disorders of the cervical spine; however, there are no detailed reports on deformity of cervical spine associated with this disease.

METHODS

A 43-year-old man with cervical kyphosis due to myotonic dystrophy had undergone an occiput-T2 fusion with autogenous iliac bone using spinal instrumentation.

RESULTS

The activity of daily life of the patient had improved markedly, and the good results continued to be preserved for 5 years. There were not any major perioperative complications.

CONCLUSIONS

Surgical correction of cervical spine is not necessarily a contraindication for myotonic dystrophy.

Morphometric and qualitative analysis of congenital occipitocervical instability in children: implications for patients with Down syndrome

OBJECT

Congenital occipitocervical (OC) instability is uncommon in healthy children but can occur in many children with Down syndrome. A simple morphometric method of evaluating the OC joint in children with OC instability is presented, supported by a qualitative image analysis based on computed tomography (CT).

METHODS

Thin-cut CT scans of the OC joint were obtained in eight patients with Down syndrome and one patient with congenital OC instability. These patients' CT scans were compared with those of 15 healthy age-matched control individuals. Morphometric analysis was performed by measuring the depth and length of the superior articular surface (SAS) of C-1, and these values were normalized for a comparison between groups. Qualitative data were acquired using a surface-rendering technique for a visual comparison of the C-1 SAS. Morphometric analysis demonstrated an absence of the concave C-1 SAS anatomy in patients with congenital OC instability compared with age-matched control individuals (0.083 compared with 0.202, p < 0.001). Three-dimensional (3D) image analysis of the C-l SAS supported this finding.

CONCLUSIONS

Congenital differences in the shape of the OC joint are highly associated with atraumatic OC instability in children with Down syndrome. High-resolution CT imaging combined with 3D rendering techniques and surface mapping provides support for this assessment. It appears that abnormal OC joint shape is a contributing factor to congenital OC instability, especially in patients with Down syndrome.

Traumatic retroclival epidural hematoma - a pediatric entity?

BACKGROUND

Traumatic retroclival epidural hematoma is very rare and only a few cases are described in literature. All previous cases occurred in the pediatric population and were classically seen in pedestrians or cyclists hit by speeding motor vehicles. It is probable that horizontal articulation between the cranium and the atlas and ligamentous laxity at the craniocervical junction in this age group predispose them to ligamentous injury at the craniospinal junction and formation of retroclival hematoma. MRI or three-dimensional reconstructed CT is considered essential for diagnosing this condition. Conservative treatment is an option if neurological deficits are mild and brainstem compression is not significant. Bony fixation is, however, required if there is suspicion of instability.

CASE REPORT

The authors describe the case of an 8-year-old girl who developed traumatic retroclival epidural hematoma after a motor vehicle accident and who was managed conservatively with good recovery.

CONCLUSION

This case and the review of literature suggest that retroclival epidural hematoma is a pediatric entity usually associated with ligamental injury at the craniocervical junction.

The median atlanto-occipital joint in advanced age

STUDY DESIGN

Exploration of the craniocervical junction in cadavers of elderly individuals.

OBJECTIVE

Histologic evaluation of osseous contact zones observed between the basiocciput and anterior arch of the atlas.

SUMMARY OF BACKGROUND DATA

Previous findings of possible osseous contact zones at the anterior rim of the foramen magnum and anterior arch of the atlas suggested the existence of real joints.

METHODS

A total of 100 cadaver specimens were investigated using magnetic resonance imaging, computerized tomography, and median saw-cut and histologic sections.

RESULTS

Of the specimens, 42% showed osteoarthritis-related osteophytes (primarily directed cranially) of the articular surfaces of the median atlantoaxial joint. In 5 cases, a large osteophyte of the anterior arch of the atlas touched the basiocciput. In 3 cases, a third occipital condyle touched the anterior arch of the atlas and/or tip of the dens. These osseous contact zones were histologically verified as real joints (the median atlanto-occipital or occipito-odontoid joints).

CONCLUSIONS

Of the 8 median atlanto-occipital joints found in this study, 3 were third occipital-condyle based, and 5 osteoarthritis-based. The former were congenital in character, while the latter were acquired.

Tuberculosis of the Craniovertebral Junction: Is Surgery Necessary?

OBJECTIVE:

Tuberculosis of the craniovertebral junction is an uncommon entity and its optimal management remains controversial. In this study, we present the evolution of management protocol of this disease in our institute in the past 3 decades.

METHODS:

A total of 51 patients with craniovertebral junction tuberculosis presenting as atlantoaxial dislocation from 1978 through 2004 were reviewed. The disease was rated from Stage I to Stage III, depending on the radiological findings. All patients received antitubercular treatment for 18 months. In the initial period of this study (1978–1986), all patients (n = 10) underwent surgery, usually a posterior fusion. In the second period (1987–1998), patients with less severe disease (Stages I and II, n = 14) were managed with external rigid immobilization, whereas patients with severe disease (Stage III, n = 11) underwent either a transoral decompression with or without posterior fusion or posterior fusion alone. More recently (1999–2004), all patients (n = 16) in all stages (Stages I–III) have been managed without surgery by a rigid external immobilization.

RESULTS:

Except for two patients who died (one because of miliary tuberculosis, the other because of acute hydrocephalus), clinical recovery occurred in all. Follow-up imaging demonstrated radiological healing as well, with regrowth of the destroyed bone.

CONCLUSION:

The mainstay of management of tuberculosis of the craniovertebral junction is prolonged antitubercular treatment with a rigid external immobilization. Surgery is not necessary, even in patients with advanced stages of disease. Complete clinical and radiological healing occurs in all patients with conservative treatment.

Traumatic atlanto-occipital dislocation with atlantoaxial subluxation

STUDY DESIGN

This is a case report of a patient who survived traumatic atlanto-occipital dislocation with atlantoaxial subluxation.

OBJECTIVE

To describe the useful points of 3-dimensional computerized tomography (CT) and magnetic resonance imaging (MRI) for an evaluation of atlanto-occipital dislocation.

SUMMARY OF BACKGROUND DATA

Atlanto-occipital dislocation is a severe ligamentous injury that usually results in either a fatal outcome or severe neurologic deficit. To our knowledge, no patient who has survived atlanto-occipital dislocation with atlantoaxial subluxation has yet been reported.

METHODS

Three-dimensional CT was performed to confirm the diagnosis of atlanto-occipital dislocation and precisely evaluate the magnitude of displacement. MRI clearly showed a disruption of the ligamentous structures, which play a role as the primary stabilizers of the cranium on the cervical spine.

RESULTS

As soon as the patient's general condition improved, the posterior spinal fusion with internal fixation was performed to maintain the stability of cervical spine. A significant degree of motor function was regained within 2 years after injury.

CONCLUSIONS

In this case, the diagnosis was accurately confirmed, and the cervical spine was evaluated in detail using both 3-dimensional CT and MRI as a reliable examination for atlanto-occipital dislocation.

Endoscope-assisted microsurgical resection of an intraneural ganglion cyst of the hypoglossal nerve

✓ An unusual case of an intraneural ganglion cyst of the hypoglossal nerve is presented. Only one case of this rare clinical entity has been reported previously. A 51-year-old woman presented with a 6-month history of left-sided hypoglossal nerve palsy. Magnetic resonance imaging revealed a cystic lesion related to the hypoglossal canal. There was no enhancement of the lesion after administration of Gd. A high-resolution computerized tomography scan of the skull base demonstrated an enlargement of the hypoglossal canal.

To access the lesion, a far-lateral endoscope-assisted microsurgical approach was used. An intraneural ganglion lesion invading the hypoglossal nerve was found and resected. A histopathological examination confirmed that the lesion was an intraneural ganglion cyst. The occurrence of an intraneural ganglion cyst at the hypoglossal nerve is very rare. This case exemplifies an atypical location of a synovial cyst with cranial nerve involvement.

Anatomical data on the craniocervical junction and their correlation with degenerative changes in 30 cadaveric specimens

>Object. The goal of this project was to measure vertebral dimensions at the craniocervical junction and to investigate degenerative changes in this region and their correlations with the anatomical data. These studies will assist in an understanding of biomechanical conditions in this region, which are clinically relevant in cases of cervicogenic headaches and vertigo.

Methods. The authors examined 30 cadaveric specimens obtained from patients ranging in age from 24 to 88 years at death. Measurements of angles of the vertebrae were conducted using an imprint method. Microsections of osseous endplates and articular cartilage were graded according to their degrees of degeneration by using the Petersson classification (0, no sign of degeneration; I, superficial degeneration with several fragmentations; II, deeper degeneration with cartilaginous disintegration and penetrating ulceration; or III, complete cartilaginous degeneration with the appearance of subchondral bone in > 50% of the articular surface).

The authors found Grade I changes in 100% of the occiput specimens. In the superior articular cartilage of C-1 no changes (Grade 0) were found in two specimens, whereas 6% of the specimens exhibited Grade II changes and 89% exhibited Grade I changes. In the inferior articular cartilage of C-1, 57% of the specimens displayed Grade I changes, 14% Grade II, and 20% Grade III changes. In the superior articular cartilage of C-2, 62.5% of the specimens displayed Grade I changes and 25% Grade II changes. At the occiput—C1 level the authors found a higher frequency of degeneration at the upper left articular surface of the atlas (Quadrants 1 and 3), and at the C1–2 level they found a higher frequency of degeneration at the upper left and upper right articular surfaces of the axis (Quadrants 2 and 3, respectively). Using the McNemar test, the authors investigated the frequency of affection of single quadrants in a left—right side comparison (lateral reversal). Significant differences were identified for Quadrant 2 of the upper left articular surface of C-2 and Quadrant 3 of the upper right articular surface of C-2. These results correlate with the analysis of single articular surfaces of the axis, but contradict the results for the atlas, in which no significant difference in the left—right side comparison was found.

Conclusions. Severe degeneration in the atlantooccipital joints appears to be a rare condition, with no Grade II or III degeneration found in the occipital condyles and 6% Grade I, 89% Grade II, but no Grade III changes in the superior articular cartilage of the atlas. Degeneration of the inferior articular cartilage of C-1 and the superior articular cartilage of C-2 indicates that the atlantoaxial joint faces more intense mechanical exposure, which is increased at the upper joint surfaces.

Accessory joints between basiocciput and atlas/axis in the median plane

To explore the many osseous irregularities that are found in the area between the basiocciput, the anterior arch of the atlas and the tip of the dens axis we studied 99 cadaver specimens using magnetic resonance tomography (MRT), computed tomography (CT), median saw-cut sections, and histological sections. Additionally, "dry" specimens of the skull (n = 110), atlas (n = 56), and axis (n = 33) were investigated. In the median plane, the dry and cadaver specimens exhibited osteoarthritis-related osseous outgrowths and osteophytes of the articular surfaces of the median atlanto-axial joint (n = 63), and the presence of congenitally developed free ossicles (n = 22) and of third occipital condyles (n = 3). The largest osteophytes (giant osteophytes) (n = 4) of the anterior arch of the atlas formed osseous contact zones with the basiocciput that were visible histologically as real joints and were designated accessory median atlanto-occipital joints. The third occipital condyles also formed osseous contact zones, visible histologically as real joints, with the anterior arch of the atlas or with the tip of the dens, and were designated accessory atlanto-occipital or occipito-odontoid joints. Frequent free ossicles, incorporated into the accessory joint, were found by histological examination to be covered with hyaline cartilage.

Avulsion Fracture of the Foramen Magnum Treated with Occiput-to-C1 Fusion: Technical Case Report

OBJECTIVE AND IMPORTANCE:

A 31-year-old woman presented with an avulsion fracture of the foramen magnum via bilateral occipital condyles with extension through the inferior aspect of the clivus.

CLINICAL PRESENTATION:

The patient had no neurological deficits and was initially immobilized in a halo brace.

INTERVENTION:

To preserve rotational motion at C1–C2, we performed an occiput-to-C1 fusion with bilateral C1 lateral mass screws attached with rods to occipital keel screws. Postoperatively, the patient remained neurologically intact. Three-month follow-up imaging revealed no abnormal motion. Follow-up computed tomographic scan showed an intact construct and bony fusion.

CONCLUSION:

This rare injury, a bony variant of occipitoatlantal dislocation, was successfully treated with a unique occiput-to-C1 fusion.

Odontoid compression of the brainstem without basilar impression – “ odontoid invagination”

We report five patients with odontoid invagination, in which the odontoid process bulges upward into the foramen magnum and compresses the brainstem without deformity of the occipital bone. Two patients had a craniovertebral abnormality associated with Chiari malformation without instability of the craniovertebral junction (stable odontoid invagination). The other three patients had dislocation of the craniovertebral junction due to iatrogenic destruction of the occipital condyle, rheumatoid arthritis or an anomaly of C2 (unstable odontoid invagination). Patients with stable odontoid invagination underwent a transoral odontoidectomy followed by occipitocervical fixation. Those with unstable odontoid invagination underwent cervical traction followed by posterior fixation in reducible cases, while in irreducible cases odontoidectomy with subsequent occipitocervical fixation was performed. Decompression of the neuraxis together with symptomatic improvement was achieved in all patients and none became unstable or developed new symptoms during follow-up ranging from 3 to 15 years.

Basicranium Malformation With Anterior Dislocation of Right Styloid Process Causing Stylalgia

Differential diagnosis of stylalgia is broad, and many causes should be taken into account, such as temporomandibular joint disorders, carotidynia, compression of nerve fibers by neoplasms, cranial nerve neuralgias, chronic pharyngotonsillitis, pharyngeal or base of tongue tumors and elongation of styloid process, or Eagle syndrome. Basicranium malformation can determine a rare form of stylalgia that is caused by dislocation of styloid process. This can produce a reduction of maxillo-vertebropharyngeal space and irritation of nerve fibers together with stylopharyngeal muscular chronic contraction. This case report illustrates the diagnostic dilemma and surgical strategy experienced in a rare case of stylalgia caused by a dislocation of styloid process produced by a basicranium malformation. Basicranium malformation should be considered in the pathogenesis of stylalgia when a styloid process with normal dimension is encountered.

Tectorial Membrane Injuries in Children

We report three cases of tectorial membrane injury in children. An increased interspinous ratio was identified on cervical spine radiographs. The tectorial membrane injuries were diagnosed by magnetic resonance imaging. The three children were restrained passengers in high-speed motor vehicle accidents, and all sustained polytrauma. Two children with partial tears of the tectorial membrane were immobilized in a halo, and one with a longitudinal tear of the tectorial membrane had an occiput-to-C2 fusion.

Circumferential cervical spine surgery in an 18-month-old female with traumatic disruption of the odontoid and C3 vertebrae. Case report and review of techniques. Case report and review of techniques

STUDY DESIGN

A case study of an 18-month-old female with craniovertebral instability and spinal cord compression requiring circumferential stabilization. A review of surgical techniques in upper cervical spine and craniovertebral stabilization for young children is provided.

OBJECTIVES

To describe an interesting surgical approach in a young pediatric patient requiring circumferential stability at the craniovertebral junction.

BACKGROUND DATA

Craniovertebral instability is problematic in the young pediatric population due to the inability to secure hardware for stabilization. We present an interesting case of spinal cord compression with craniovertebral instability in an 18-month-old female requiring circumferential cervical spine and craniovertebral stabilization.

METHODS

The patient presented with acute onset quadriparesis after a fall. Radiographs demonstrated C2-C3 disruption with canal compromise. Magnetic resonance imaging revealed signal changes of the spinal cord at C2-C3. Neurological examination revealed normal muscle volume with strength 1/5 in the upper extremities and 0/5 in the lower extremities. Respirations were normal with normal diaphragmatic function. Cranial nerves were intact.

RESULTS

Halo-traction attempted at 0.453 kg induced occipital-atlantal dislocation. The patient underwent anterior corpectomy of C3 and the base of C2 with autologous rib grafts placed from C2 to C4 and macropore as an anterior plating system. Posteriorly the patient had occiput-C3 fusion with a titanium rod and autologous rib grafts bilaterally. Postoperatively the patient regained normal neurological function with circumferential fusion after 4 months in a halo vest.

CONCLUSIONS

This case demonstrates the ability to achieve circumferential stabilization in the young pediatric patient. Injuries at the odontoid synchondrosis can be difficult to treat and are only complicated by having to achieve a posterior fusion at the craniovertebral junction. We present a successful case of circumferential fusion and offer a surgical technique to achieve spinal cord decompression and fusion of the upper cervical spine and craniovertebral junction in the young pediatric population.

Well-differentiated biphasic synovial sarcoma in the atlanto-occipital joint of a Holstein cow

A 7-year-old Holstein cow developed a large cystic mass in the region between the atlantoaxis and larynx. The mass extended to the synovium in the atlanto-occipital joint. Many villous projections were present on the inner surface of the tumor tissue, and irregular clefts were formed in the inside. Two cell types, epithelioid-like synovioblasts and spindle cells, were present. Immunohistochemical analysis showed that the cells stained positively for cytokeratin (AE1/AE3) and vimentin. Both cells had similar fine structures ultra-structurally. Vacuoles present in the cytoplasm were full of an acid mucous substance. The tumor was diagnosed as a well-differentiated biphasic synovial sarcoma. This is the first report of a rare case of synovial sarcoma, from the viewpoint of its origin.

Vertebral synovial chondromatosis. Report of two cases and review of the literature

Synovial chondromatosis is an uncommon disorder characterized by the formation of multiple cartilaginous nodules within the synovium, most commonly affecting large joints. Its involvement with the spine is rare; only six cases have been reported. The authors describe two patients with synovial chondromatosis involving the cervical spine. In the first case, synovial chondromatosis arose from the left C1-2 facet joint. This patient underwent a two-stage procedure including a posterior approach for tumor resection and occipitocervical fusion as well as a transmandibular circumglossal approach to the anterior craniocervical junction to complete the tumor removal. Interestingly, on histopathological examination, scattered foci of low-grade chondrosarcoma were intermixed within the synovial chondromatosis. To the authors' knowledge, this is the first report of secondary low-grade chondrosarcoma arising in vertebral synovial chondromatosis. In the second case, synovial chondromatosis involved the left C4-5 facet joint. Tumor resection and cervical fusion were performed via a posterior approach. In this report, the authors describe the clinical presentation, radiographic findings, operative details, histopathological features, and clinicoradiological follow-up data obtained in these two patients and review the literature pertaining to this rare entity.

Amyloidoma of the craniovertebral junction

We report a rare case of localized amyloidoma of the craniovertebral junction causing severe myelopathy and respiratory distress and death. The clinical features and the natural history of this rare condition are discussed.