Os odontoideum and craniovertebral junction instability secondary to dystonia: case series and review of the literature.

INTRODUCTION: Os odontoideum refers to a rounded ossicle detached from a hypoplastic odontoid process at the body of the axis. The aetiology has been debated and believed to be either congenital or acquired (resulting from trauma). Os odontoideum results in incompetence of the transverse ligament and thus predisposes to atlantoaxial instability and spinal cord injury. METHODS/RESULTS: Three cases of children with severe dystonic cerebral palsy presenting with myelopathic deterioration secondary to atlantoaxial instability due to os odontoideum are presented. This observation supports the hypothesis of os odontoideum being an acquired phenomenon, secondary to chronic excessive movement with damage to the developing odontoid process. CONCLUSION: In children with cerebral palsy and dystonia, pre-existing motor deficits may conceal an evolving myelopathy and result in delayed diagnosis of clinically significant atlantoaxial subluxation.

Dorsal Atlantoaxial Ligament Hypertrophy as a Cause for Clinical Signs in Dogs with Dens Abnormalities.

The objective of this study is to suggest clinical and subclinical atlantoaxial (AA) instability as a cause for dorsal AA ligament hypertrophy responsible for clinical signs in dogs with dens abnormalities. Clinical information from five dogs with malformed dens and dorsal spinal cord compression at the AA junction was collected. All dogs had neck pain, associated with tetraparesis in three cases. Radiological examination revealed hypoplastic dens in two dogs and a defect in its ossification in the other three. Stress views were able to demonstrate obvious AA instability only in two cases, but it was suspected in the other owing to response to surgical fixation of the joint and the presence of a dorsal compressive band, which was considered an enlarged dorsal AA ligament. Surgical and histopathological examination of compressive tissue confirmed hypertrophy of the ligament. Long-term prognosis in the four operated cases, either by dorsal decompression and ventral fixation or by ventral fixation alone, was excellent. A malformed dens can cause subclinical instability, unnoted in dynamic studies. As instability may lead to hypertrophy of joint ligaments, soft tissue changes (specifically dorsal AA ligament hypertrophy) points out this instability and the need for joint fixation if surgical management is required.

The Rare Anomaly That Can Be Confused With Fracture: Os Odontoideum.

Os odontoideum is a rare anomaly of the second cervical vertebra. The odontoid process is separated by a wide gap from the vertebral body in this anomaly. It can be associated with atlantoaxial instability.

The Relationship Between Basilar Invagination and Chiari Malformation Type I: A Narrative Review.

Basilar invagination (BI) and Chiari malformation type I CM-I) are the most common adult craniovertebral junction malformations, and they are frequently associated with each other and present synchronously. The relationship between BI and CM-I has remained incompletely understood, and the choice of surgical strategy has remained controversial. This brief review focuses on the different aspects of BI and CM-I, and further discusses the relationship between these two concomitant pathologies on the basis of the concepts proposed over the last three decades.

Stability-Sparing Endoscopic Endonasal Odontoidectomy in a Malformative Craniovertebral Junction: Case Report and Biomechanical Considerations.

BACKGROUND: The craniovertebral junction (CVJ) is often involved in a wide range of congenital, developmental and acquired pathologies that can create bony and ligamentous instability or cause direct compression on the medulla and cervical spine cord, resulting in significant impairment. Atlas assimilation is the most common malformation in the CVJ and can be frequently associated with basilar invagination (BI) and Chiari malformation (CM) type I. Posterior atlas assimilation more frequently leads to BI type II with a mass effect on neural structures but usually no signs of biomechanical instability. Operative approaches to the CVJ have undergone a remarkable evolution and can be divided into ventral, lateral and dorsal ones. In this kind of surgery, it is vital to detect and eventually treat any CVJ instability. CASE DESCRIPTION: We present a case of CVJ malformation comprising assimilation of the posterior arch of the atlas, BI type II and CM, treated by endoscopic endonasal odontoidectomy and partial clivus removal to spare CVJ stability. CONCLUSION: Neurological and biomechanical analysis of all CVJ malformations permits stratification and selection of those cases that can be managed by simple, direct, minimally invasive decompression with no need for surgical fusion.

Realignment of Basilar Invagination by C1-C2 Joint Distraction: A Modified Approach to a Paradigm Shift.

BACKGROUND: Distraction of the C1-C2 joint and maintenance thereof by introduction of spacers into the articular cavity can successfully and durably reduce basilar invagination (BI). Thus, with the adjunct of instrumented fusion and decompression, BI-induced myelopathy can be efficiently treated with a one-stage posterior approach. This intervention is technically challenging, and in this paper we describe a procedural variation to facilitate the approach. METHODS AND RESULTS: Through a description of a case of BI, the main anatomopathological alteration underlying and perpetrating the condition of BI is elucidated. A technique of realignment of BI is then described in which this alteration is specifically targeted and neutralized. The result is a single-stage posterior-only approach with decompression, C1-C2 distraction and introduction of poly(methyl methacrylate) (PMMA) into the joint cavity. Instrumented occipitocervical fusion completes the procedure. CONCLUSION: C1-C2 joint distraction is a technically demanding procedure. By providing a modification of the original technique and a detailed description of the crucial steps necessary to successfully and safely carry it out, we hope to make this excellent procedure more approachable.

Torticollis Caused by Nontraumatic Craniovertebral Junction Abnormalities.

Torticollis could be the only symptom and sign of craniovertebral junction (CVJ) abnormality. It could be difficult to identify CVJ abnormality as a cause of torticollis due to their rarity, especially for the subjects with torticollis caused by nontraumatic CVJ abnormalities. There has been no report to focus on nontraumatic CVJ abnormalities as a cause of torticollis. The objective of this study was to report 27 patients of torticollis caused by nontraumatic CVJ abnormalities, with the aim of helping clinicians to identify nontraumatic CVJ abnormalities as a cause of torticollis. This is a retrospective cohort study including 27 subjects who had torticollis caused by nontraumatic CVJ abnormalities. The CVJ was examined in terms of atlanto-occipital angle, atlanto-axial angle, and lateral and anterior atlanto-dens intervals for the evaluation of occipital condylar hypoplasia, rotation of atlanto-axial joint, and lateral and anterior shift of the dens, respectively. Abnormalities of the lower cervical or thoracic spine were also evaluated. Occipital condylar hypoplasia, rotation of atlanto-axial joint, and lateral shift of the dens were the most common CVJ abnormalities. The 18.5% of the subjects had concurrent anomalies of lower cervical or thoracic vertebrae along with CVJ abnormalities. Each subject had 2.22 ±â€Š1.10 types of CVJ abnormalities on average. In conclusion, comprehensive evaluation of CVJ abnormalities is recommended for differential diagnosis of subjects with unexplained torticollis. Once CVJ abnormalities are identified, concurrent abnormalities of other vertebrae need to be evaluated.

Accidental or linked: separated odontoid process fused to the enlarged anterior arch of the atlas associated with atlantoaxial subluxation in a Kashin-Beck disease patient.

PURPOSE: KBD is an endemic disease affecting the epiphyseal growth plate and articular cartilage of multiple joints, resulting in extremities' deformation and skeletal dysplasia. More attention has been paid to the visible deformed extremities instead of inconspicuous spinal condition. There is a lack of reports concerning the spinal radiological features, especially for the atlantoaxial joint. The aim of this paper is to report a case of a Kashin-Beck disease (KBD) patient diagnosed with atlantoaxial subluxation, concomitant with separated odontoid process fused to the enlarged anterior arch of the atlas. METHODS: We report the case of a 60-year-old woman with 54 years' history of KBD complaining of occipitocervical pain, decreasing motor strength and sensory function of both upper and lower extremities. Subsequent radiological examinations of lateral plain radiography, computed tomography scans and magnetic resonance imaging were performed to reveal these rare characteristics of atlantoaxial joint in this patient. Then, we review the associated articles to postulate whether this anomaly is accidental or linked in a KBD patient. RESULTS: She had an extremely rare variant with three aspects of characteristics: atlantoaxial subluxation concurrent with severe spinal canal stenosis and spinal cord compression, odontoid process separating from the body of axis, and the enlarged anterior arch of the atlas fusion with odontoid process. Comparing with the congenital anomaly of atlantoaxial joint, we postulated that this aetiology of anomaly might be linked to the acquired form attributed to the histopathology of KBD, rather than an accidental event. CONCLUSIONS: The anomaly of atlantoaxial joint might occur in KBD patients. Larger numbers of KBD candidates with earlier symptoms are recommended for radiological examinations of atlantoaxial joint, especially for the adolescents. Spinal surgeons are suggested to involve the research of the spinal anatomy and variation for the prevention and earlier therapy for KBD patients.

Os Odontoideum Discovered After Minor Cervical Trauma.

Minor cervical spine injury is a common cause of pediatric emergency department visits. We present a case of a 10-year-old boy with transient paresthesia after minor cervical trauma found to have a rare cervical spine abnormality requiring surgical fusion. We present and discuss the management options for os odontoideum.

Bergmann's ossicle (ossiculum terminale persistens): a brief review and differentiation from other findings of the odontoid process.

PURPOSE: The purpose of this paper was to review the literature on Bergmann's ossicle and provide an overview on its development, etiology, and clinical presentation while also differentiating it from similar structural anomalies. METHODS: A thorough review of the literature available on Bergmann's ossicle was performed. RESULTS: Bergmann's ossicle, also referred to as ossiculum terminale persistens, was defined as a developmental anomaly of the odontoid process in which an ossification center that gives rise to the tip of the dens fails to fuse properly with the body of the axis. CONCLUSION: Bergmann's ossicle is most often a benign condition, although it rarely may present with clinical symptoms such as neck pain and neurological signs. It may be associated with Down's syndrome and contribute to atlantoaxial instability.

Intraoperative electrophysiological monitoring during posterior craniocervical distraction and realignment for congenital craniocervical anomaly.

PURPOSE: Congenital craniocervical segmentation anomaly associated with malalignment of the odontoid process causes progressive spinal cord compression with myelopathy. Recent literatures have reported that ventral decompression could be achieved with posterior craniocervical realignment through posterior instrumented reduction. The purpose of the present study is to show the efficacy of intraoperative electrophysiological monitoring during craniocervical realignment through screws and rod system for congenital craniocervical segmentation anomaly. METHODS: Consecutive ten patients with a congenital craniocervical segmentation anomaly and myelopathy due to a malaligned odontoid process, who underwent posterior craniocervical realignment, were included. Klippel-Feil syndrome (KFS) was combined in four patients. Gait disturbance and motor weakness were the main presentation. Craniocervical realignment was achieved by intraoperative distraction through a rod and screw system. Intraoperative neuromonitoring was performed with transcranial motor-evoked potential (TcMEP) and somatosensory-evoked potential (SSEP). RESULTS: Significant change in TcMEP occurred in two patients with KFS during surgery, but the change was reversed with release of distraction. All patients were awakened without neurological deficit. Motor weakness and gait disturbance were normalized within 6 months in all patients. Postoperative computed tomography scan and/or magnetic resonance imaging showed that the reduction was complete in all patients. CONCLUSIONS: Craniocervical realignment through screws and rod system may be safe and efficacious surgical technique for the treatment of congenital craniocervical anomaly with the help of intraoperative neuromonitoring. However, distraction should be cautiously monitored, especially when Klippel-Feil syndrome is combined.

VACTERL (vertebral defects, anal atresia, tracheoesophageal fistula with esophageal atresia, cardiac defects, renal and limb anomalies) association: disease spectrum in 25 patients ascertained for their upper limb involvement.

OBJECTIVE: To review the clinical characteristics in a series of 25 patients with VACTERL (vertebral defects, anal atresia, tracheoesophageal fistula with esophageal atresia, cardiac defects, renal and limb anomalies) association who were ascertained for upper limb involvement. STUDY DESIGN: The study involved a review of clinical and radiologic data from patients with VACTERL association collected by a hand surgery clinic between 2004 and 2013. RESULTS: Radial axis involvement was found in all 25 patients (100%), with severe thumb function impairment in 79% and complete absence of the radius in roughly 33%. Costovertebral anomalies were the most frequent feature, found in 23 patients (92%). All 3 core features (anal atresia, tracheoesophageal fistula with esophageal atresia, and costovertebral anomalies) were present in only 12% of the patients. Twelve patients (48%) had abnormalities not part of the VACTERL spectrum, showing a specific pattern of non-VACTERL-type malformations, including genitourinary abnormalities (12%), single umbilical artery (8%), and tethered cord (8%). Previously unreported clinical findings were concurrent hypoplasia of both the odontoid process and the coccyx in 2 patients and an isolated sacral dimple in 2 patients. CONCLUSION: Upper limb involvement in VACTERL association is a specific feature of the radial axis that occurs in monolateral form in approximately 75% of cases and, when bilateral, always occurs in a nonsymmetrical fashion. Odontoid and coccygeal hypoplasia and sacral dimple are newly reported malformations of the VACTERL phenotype.

Dysphagia as a primary manifestation of basilar impression: A case report.

Secondary basilar invagination or basilar impression is an anomaly at the craniovertebral junction where the odontoid process prolapses into the foramen magnum with the risk of compressing adjacent structures and obstructing the proper flow of cerebrospinal fluid (CSF). The incidence is less than 1% in the general population and occurs mainly in the first three decades of life when it is associated with malformations of the neuroaxis. In older age, the main aetiologies are diseases that alter bone mineral density. The clinical course is usually progressive and the most common symptoms are asthenia, cervical pain and restricted movement, but also dysphonia, dyspnoea and dysphagia. It is a progressive disease which, if left untreated, can cause severe neurological damage and death. We report the case of a 79-year-old woman with osteoporosis and progressive dysphagia leading to severe malnutrition, which conditioned the decision not to intervene due to the high perioperative risk.

Dens Growth After Surgical Fixation in Children with Morquio-Brailsford Disease.

Mucopolysaccharidosis type IVA is a lysosomal storage disorder caused by a deficiency of the enzyme N-acetyl-galactosamine-6-sulphate sulphatase. Mucopolysaccharidosis type IVA is multisystemic disease with significant spinal involvement and atlantoaxial instability leading to neural compression and significant morbidity. Dens hypoplasia is a common feature of this condition. In this study we demonstrate that after spinal fixation, there is new growth of dens in significant proportion of patients, suggesting atlantoaxial instability as one of the major driving forces of lack of development of dens in this condition.

Congenital axis dysmorphism in a medieval skeleton : secunda a vertendo epistropheus .

PURPOSE: We describe here the axis dysmorphism that we observed in the skeletal remains of a human child dug up from a fifteenth century cemetery located in north-eastern Italy. This bone defect is discussed in the light of pertinent literature. METHODS: We performed macroscopical examination and CT scan analysis of the axis. RESULTS: Axis structure was remarkably asymmetric. Whilst the left half exhibited normal morphology, the right one was smaller than normal, and its lateral articular surface showed horizontal orientation. In addition, the odontoid process appeared leftward deviated and displayed a supplementary articular-like facet situated on the right side of its surface. CONCLUSIONS: These findings suggest a diagnosis of unilateral irregular segmentation of atlas and axis, a rare dysmorphism dependent upon disturbances of notochordal development in early embryonic life. Likewise other malformations of the craniovertebral junction, this axis defect may alter the delicate mechanisms of upper neck movements and cause a complex series of clinical symptoms. This is an emblematic case whereby human skeletal remains may provide valuable information on the anatomical defects of craniovertebral junction.

Surgical treatment of Klippel-Feil syndrome with basilar invagination.

INTRODUCTION: Klippel-Feil syndrome (KFS) is a congenital cervical vertebral union caused by a failure of segmentation during abnormal development and frequently accompanies conditions such as basicranial malformation, atlas assimilation, or dens malformation. Especially in basilar invagination (BI), which is a dislocation of the dens in an upper direction, compression of the spinomedullary junction from the ventral side results in paralysis, and treatment is required. CLINICAL PRESENTATION: We present the case of a 38-year-old male patient with KFS and severe BI. Plane radiographs and computed tomography (CT) images showed severe BI, and magnetic resonance image (MRI) revealed spinal cord compression caused by invagination of the dens into the foramen magnum and atlantoaxial subluxation. Reduction by halo vest and skeletal traction were not successful. Occipitocervical fusion along with decompression of the foramen magnum, C1 laminectomy, and reduction using instruments were performed. Paralysis was temporarily aggravated and then gradually improved. Unsupported walking was achieved 24 months after surgery, and activities of daily life could be independently performed at the same time. CT and MRI revealed that dramatic reduction of vertical subluxation and spinal cord decompression were achieved. CONCLUSION: Reduction and internal fixation using instrumentation are effective techniques for KFS with BI; however, caution should be exercised because of the possibility of paralysis caused by intraoperative reduction.

Navigation-assisted Le Fort I osteotomy with midpalatal split to treat compressive pathologies of the craniovertebral junction.

This report describes the management of the case of an 11-year-old girl with serious compressive pathology of the craniocervical junction using a navigation-guided Le Fort I level maxillotomy and midline split. In this pediatric case, image guidance significantly enhanced intraoperative orientation and helped to determine the correct location of the horizontal osteotomy lines at the Le Fort I level.

Partial midfacial duplication.

A case of craniofacial duplication is presented. Details on this rare form are described, and its treatment is discussed with brief review of the pertinent literature. We excised the duplicate maxilla and also discovered bilateral macrostomia. A year later, a mass appeared again. By CT scan, we found that there was a mass in the skull base extruding to the superior wall of cavitas pharyngis. The mass below the sphenoid bone and the ethmoid bone connected with the skull base. CT scan also showed malformation of the first cervical vertebra and odontoid process had bifurcated. Once again, we excised the mass and found a cranial meningocele on the skull base, repaired the palate cleft, and closed the cerebral meningocele. The patient had a palate fistula after operation. A year later, the palate fistula and macrostomia were repaired. We think the patient should be operated on immediately after she was born so that we could relieve the dyspnea; furthermore, by one well-planned operation, we could repair the palate cleft and other deformity just after we excised the mass.

Transnasal endoscopic removal of malformation of the odontoid process in craniovertebral anomaly: a case report.

The endoscopic endonasal approach is emerging as a feasible alternative to the transoral route for the resection of the odontoid process, when the latter produces a compression of the brainstem and cervicomedullary junction. This type of approach has some advantages, such as excellent prevertebral exposure of the craniovertebral junction in patients with small oral cavities and the possibility to avoid the use of mouth retractors. In this article, we present a typical case of a 12-year-old female patient with a diagnosis of craniovertebral anomaly-basilar invagination into foramen magnum, suffering from an extreme posterior tilt of the odontoid process causing severe anterior compression of the cervicomedullary junction, is presented to stress the potential of this technique. Transnasal endoscopic removal of the odontoid process was performed and resolution of the ventral compression was achieved. This article demonstrates that in selected cases, a multidisciplinary team approach can help our patients.

Ventral compression in adult patients with Chiari 1 malformation sans basilar invagination: cause and management.

BACKGROUND: A small subset of patients with adult Chiari I malformation without basilar invagination (BI) and instability show ventral cervicomedullary distortion/compression and have symptoms pertaining to that. The cause of this ventral compression remains speculative. Additionally, it is unclear if these patients would require ventral decompression with posterior fusion or only posterior decompression would suffice. METHODS: Sixteen adult patients with Chiari I malformation with significant ventral cervicomedullary compression, in the absence of BI, were included in the study. Atlantoaxial dislocation (AAD) was excluded in these patients by flexion-extension craniovertebral junction X-rays and computed tomography (CT). Their clinical profile, especially symptoms pertaining to cervicomedullary compression, i.e. dysphagia, dysarthria and spasticity, were graded. The ventral cervicomedullary compression (VCMC) was quantified using pBC2 (maximum perpendicular distance to the basion-infero posterior point of the C2 body) on sagittal magnetic resonance imaging (MRI) and only those patients with pBC2 ≥9 mm were included. Furthermore, retroversion of dens and retro odonotid tissue thickness was calculated in each patient. Fifteen patients underwent posterior decompression alone and one refused surgery. Follow-up was done every 3 months. Repeat MRI was done at 1 year following surgery to look for pBC2. RESULTS: The mean pBC2 was 11 ± 0.2 mm. Retroversion of dens was responsible for VCMC in three patients and periodontoid crown in 13. There was no correlation between the tonsillar descent, age and the pBC2. All patients improved in symptoms of cervicomedullary compression following surgery. One patient worsened 6 months after initial improvement. The pBC2 did not change, as seen on follow-up MRI done in five patients. CONCLUSIONS: VCMC in adult patients with Chiari I malformation in the absence of BI and/or AAD is due to periodontoid tissue (crown) or retroverted dens. Though a long-term study is required, it appears that all patients with Chiari I malformation, irrespective of the VCMC, can be given a chance with posterior decompression alone. Transoral decompression with posterior fusion may be required in a small subset of patients who fail to improve or worsen following posterior decompression only.