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.

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.

Two-Stage Approach for Unstable Pediatric Craniocervical Junction Anomalies with a Halo Vest and Delayed Occipitocervical Fusion: Technical Note, Case Series, and Literature Review.

OBJECTIVE: Malformations in the craniocervical junction (CCJ) are rare in the pediatric population but often need surgical treatment. We present a pediatric case series of patients treated with a 2-stage surgical approach with a halo vest and occipitocervical fusion and review complications and outcomes. METHODS: A retrospective analysis of a single-center case series was performed. Pediatric patients affected by congenital craniocervical junction anomalies and treated with a 2-stage approach were included. A halo vest was implanted in the first surgery, and ambulatory progressive reduction was performed. When a favorable anatomic situation was observed, arthrodesis was performed. Safety analysis was undertaken by analyzing the incidence of complications in both procedures. Effectivity analysis was carried out analyzing radiologic and clinical outcome (Goel grade and modified Japanese Orthopaedic Association score). Student t test was used for statistical analysis. RESULTS: Sixteen cases were included. Mean age of patients was 9.38 years. Safety analysis showed 2 halo loosenings, 1 pin infection, 2 wound infections, 1 cerebrospinal fluid leak, and 2 delayed broken rods. No major complications were observed. Radiologic analysis showed an improvement in the tip of the odontoid process to the McRae line distance (from -3.26 mm to -6.16 mm), atlantodental interval (from 3.05 mm to 1.88 mm), clival-canal angle (from 134.61° to 144.38°), and cervical kyphosis (from 6.39° to 1.54°). Clinical analysis also showed improvement in mean Goel grade (from 1.75 to 1.44) and modified Japanese Orthopaedic Association score (from 15.12 to 16.41). CONCLUSIONS: The 2-stage approach was a suitable and effective treatment for craniocervical junction anomalies in pediatric patients.

Congenital Fusion of Dens to T3 Vertebra in Klippel-Feil Syndrome.

BACKGROUND: Patients with Klippel-Feil syndrome may present with neurologic complaints such as neck pain, radiculopathy and gait instability. Here we describe surgical management of a patient with congenital fusion of the occipital-cervical region and also block circumferential fusion of dens to T3 with spinal cord compression. This report is the first of its kind with such extensive fusion. CASE DESCRIPTION: Our patient was a 56 year-old female, who presented with neck pain and tingling in all extremities. On exam, she had a short neck, prominent jaw with extremely limited range of motion in neck and features of myelopathy. CT showed fusion of the dens to T3 vertebrae. Patient underwent sub-occipital craniectomy, C1 laminectomy and Occiput to T5 posterior fixation and fusion with neurologic improvement. CONCLUSION: This is the first reported case of Klippel-Feil syndrome with fusion of all cervical vertebrae down to T3. We recommend surgery for advanced cases of myelopathy or radiculopathy due to stenosis and spinal instability.

Familial Os Odontoideum.

BACKGROUND: To add to the confusion in the debate on pathogenesis of os-odontoideum, an additional report of its occurrence in two members of the same family is reported. CASE DESCRIPTION: This is a report of a rare coincidence wherein both father (51 years old) and daughter (25 years old) were diagnosed to have os odontoideum and presented with crippling neurologic deficits. CONCLUSIONS: Following atlantoaxial fixation, both recovered in their symptoms. Investigations revealed no genetic abnormality. Literature on the subject is briefly reviewed.

Medullary Infarction Leading to Locked-In Syndrome Following Lumbar Puncture in a Patient with Basilar Invagination.

BACKGROUND: Lumbar puncture is a common procedure that can be safely performed in most patients. Certain populations may have increased risk for complications following lumbar puncture, but the significance of basilar invagination is often underappreciated. CASE DESCRIPTION: A 45-year-old woman with basilar invagination received multiple lumbar punctures in the workup of acute meningitis. Preprocedural computed tomography was obtained. Following lumbar puncture, the patient developed locked-in syndrome. Magnetic resonance imaging obtained several days later demonstrated severe compression and infarction of the medulla and inferior cerebellum by the odontoid process and ectopic cerebellar tonsils. The patient was transferred but at this point, surgical decompression was not possible. She did not regain significant neurologic function. CONCLUSIONS: Basilar invagination is a risk factor for devastating neurologic complications following lumbar puncture. Awareness of this complication and prompt recognition of its occurrence may prevent future morbidity of lumbar puncture in patients with basilar invagination.

The Retroverted Dens: A Review of its Anatomy, Terminology, and Clinical Significance.

BACKGROUND: Little attention has been given to the retroverted dens within the existing medical literature. However, this finding can have a clinical impact, especially in patients with Chiari malformation type I (CM1), as it can have consequences for further treatment. METHODS: Using standard search engines, we performed a literature review of anatomical, radiologic, and clinical studies as well as pathologic and surgical considerations related to the retroverted dens. Key words for our search included retroverted dens; retroflexed dens; odontoid retroflexion; posterior inclination; and tilted dens. RESULTS: A retroverted dens is most commonly found in the pediatric population in relation to CM1. Research has demonstrated that high degree of dens angulation can result in significant anterior brain stem compression with the need for both anterior and posterior decompression in patients with symptomatic CM1. CONCLUSIONS: A greater degree of dens angulation can lead to neurologic symptoms secondary to spinomedullary compression. Therefore, correct measurements are essential as such findings can influence presurgical planning.

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.

Elongated Clivus with Deficient Anterior Atlantal Arch and Congenital Posterior Atlantooccipital Dislocation: Pathoembryology and Management Nuances of a Rare Form of Proatlas Segmentation Anomaly.

BACKGROUND: Proatlas segmentation anomalies represent a rare subset of congenital craniovertebral junction anomalies. In this condition, the structures originating from the proatlas, such as the clivus, occipital condyles, foramen magnum rim, and odontoid tip, may demonstrate congenital anomalies, usually without any spinal instability. Elongated clivus, as a result of nonsegmentation of the odontoid tip from the rest of the proatlas, has been reported before to cause ventral spinal cord compression. We report such a case with certain unreported other associations and explore the pathoembryology and management options of such complex anomalies. CASE DESCRIPTION: An 8-year old girl presented with a 2-year history of progressive spastic quadriparesis. On neuroimaging, the anterior arch of the atlas was deficient, the odontoid process was foreshortened, and the clivus was elongated, encroaching into the spinal canal leading to ventral spinal cord compression. Additionally, there was rotatory posterior dislocation of the occipital condyles onto the posterior atlantal arch and vertebral artery anomaly. This patient underwent transoral decompression followed by occipitocervical fusion using rods and screws with satisfactory results. CONCLUSIONS: Proatlas anomalies are rare, varied, and often subtle enough to go unrecognized. Knowledge of the embryology and its aberrations is necessary to understand these anomalies. Our case describes a rare form of bony anomalies pertaining to the fate of the proatlas with accompanying atlanto-occipital dislocation.

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.

Cranio-vertebral transition assessment by magnetic resonance imaging in a sample of a northeast Brazilian population.

METHODS: Cross-sectional analysis of craniometric parameters from individuals submitted to magnetic resonance at an outpatient imaging center between 2011 and 2012. RESULTS: Of 181 analyzed cases, the Welcker basal angle averaged 128.96º (SD 6.51), median distance between apex of the odontoid and Chamberlain's line was 2.27 mm (IQR -1.23-4.47) and the median clivus-canal angle was 150.5º (IQR 143.2-157.3). The Welcker basal angle was inversely correlated to the clivus-canal angle, and correlated to the distance between the apex of the odontoid and Chamberlain's line. CONCLUSION: There was a tendency to platibasia, basilar invagination and narrowing of the cranio-vertebral transition.

Cranio-vertebral transition assessment by magnetic resonance imaging in a sample of a northeast Brazilian population / Avaliação da transição crânio-vertebral por ressonância magnética em uma amostra da população do nordeste brasileiro

ABSTRACT Platybasia and basilar invagination are important alterations of the cranial-vertebral transition. Neuroimaging-based platybasia parameters include the Welcker basal angle, distance between the apex of the odontoid and Chamberlain's line, and the clivus-canal angle. This study aimed to measure and correlate these parameters in a sample from northeast Brazil. Methods Cross-sectional analysis of craniometric parameters from individuals submitted to magnetic resonance at an outpatient imaging center between 2011 and 2012. Results Of 181 analyzed cases, the Welcker basal angle averaged 128.96º (SD 6.51), median distance between apex of the odontoid and Chamberlain's line was 2.27 mm (IQR -1.23-4.47) and the median clivus-canal angle was 150.5º (IQR 143.2-157.3). The Welcker basal angle was inversely correlated to the clivus-canal angle, and correlated to the distance between the apex of the odontoid and Chamberlain's line. Conclusion There was a tendency to platibasia, basilar invagination and narrowing of the cranio-vertebral transition.

RESUMO Platibasia e invaginação basilar são importantes alterações da transição craniovertebral. Existem parâmetros importantes obtidos pela neuroimagem, como o ângulo basal de Welcker, distância do ápice do odontoide à linha de Chamberlain e o ângulo clivo-canal. Este estudo procurou medir e correlacioná-los em uma amostra do Nordeste Brasileiro. Métodos Estudo transversal com medidas de indivíduos submetidos a ressonância magnética craniana em um centro de diagnóstico por imagem entre 2011 e 2012. Resultados Dos 181 casos analisados, o ângulo basal de Welcker teve média 128.96º (DP 6.51), a distância do ápice do odontoide à linha de Chamberlain obteve mediana 2.27 mm (IIQ -1.23-4.47) e o ângulo clivo-canal mediano foi 150.5º (IIQ 143.2-157.3). O ângulo basal de Welcker foi inversamente correlacionado com o ângulo clivo-canal e diretamente correlacionado com a distância do ápice do odontoide à linha de Chamberlain. Conclusão Houve uma tendência a platibasia, invaginação basilar e estreitamento da transição craniovertebral, que poderiam ser influenciados pela natureza multirracial e por fatores antropológicos da população estudada.

The Corona Dentis: Description of an Anatomic Variant with Technical Implications for Anterior Odontoid Screw Placement.

BACKGROUND: Type 2 odontoid fractures are the most common cervical fractures among the elderly. Neurologic deficit is usually caused by myelopathy as a result of posterior dens migration. Direct anterior screw placement provides stabilization and can preserve C1-C2 movement. The presence of a bony excrescence on the anterior superior tip of the dens may lead to placement of a screw of incorrect length. METHODS: Twenty C2 dry specimens were examined for the presence of a corona dentis, which is a bony excrescence in the coronal plane near the apex of the dens. When identified, measurements of the corona dentis were performed using calipers and a ruler. In addition, anteroposterior (AP) and lateral fluoroscopy was performed on all specimens found to have a corona dentis. RESULTS: A corona dentis was found on 20% of our C2 specimens and had an average width of 9 mm and an average height of 4.5 mm. The average width of the dens did not vary as the normal tip of the dens transitioned into the coronae. In no specimen did the corona dentis seem to be composed of trabecular bone and it was seen as a superior projection of cortical bone on fluoroscopy. On fluoroscopy, the corona dentis could be identified on a true AP projection. In angulated AP views, fluoroscopic images overestimated the length of the corona dentis. CONCLUSIONS: We describe a new entity termed the corona dentis because of its crownlike feature. It is a superior cortical bone protrusion and should be noted as a variant of the dens during anterior odontoid screw placement. Its propensity to increase the height of the dens markedly can lead to higher rates of neurologic deficits during type 2 odontoid fractures if not appreciated. A true AP view is critical for correct screw size placement.

First Gross Anatomic Findings of an Os Odontoideum.

BACKGROUND: Os odontoideum is an uncommon abnormality of the craniovertebral junction where the tip of the odontoid process lacks continuity with the body of C2. The clinical presentation is variable, but severe neurologic impairment can result. CASE DESCRIPTION: We report the gross and radiologic findings of a cadaver found to harbor an os odontoideum. CONCLUSIONS: To our knowledge, there are no cadaveric reports in the literature regarding an os odontoideum. Such a case allows a rare window into the anatomy and relationships of this pathologic structure.

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.