Diagnosis of Os odontoideum using kinematic magnetic resonance imaging. A case report

Os odontoideum: A comprehensive review

Os odontoideum (OO) is a rare craniocervical anomaly that is characterized by a round ossicle separated from the C2 vertebral body. With a controversial etiology and unknown prevalence in the population, OO may be asymptomatic or present in patients with myelopathic and neurological symptoms. In this literature review, we aimed to investigate epidemiology, embryology, pathophysiology, clinical presentation, and the role of diagnostic radiography in OO. By providing an overview of different management strategies, surgical complications, and postoperative considerations for OO, our findings may guide neurosurgeons in providing proper diagnosis and treatment for OO patients. A literature review was conducted using the PubMed, EMBASE, and Scopus databases. A search using the query "os odontoideum" yielded 4319 results, of which 112 articles were chosen and analyzed for insights on factors such as etiology, clinical presentation, and management of OO. The presentation of OO varies widely from asymptomatic cases to severe neurological deficits. Asymptomatic patients can be managed either conservatively or surgically, while symptomatic patients should undergo operative stabilization. Although multiple studies show different techniques for surgical management involving posterior fusion, the diversity of such cases illustrates how treatment must be tailored to the individual patient to prevent complications. Conflicting studies and the paucity of current literature on OO highlight poor comprehension of the condition. Further understanding of the natural history of OO is critical to form evidence-based guidelines for the management of OO patients. More large-center studies are thus needed to promote accurate management of OO patients with optimal outcomes.

AJ, Soren SK, K. VK. Atlantoaxial Stabilization by Posterior C1 and C2 Screw-Rod Fixation for Various Pathologies: Case Series and Comprehensive Review of Literature

We retrospectively analyzed atlantoaxial dislocation (AAD) of various pathologies, namely, rheumatoid arthritis (RA), os odontoideum, and trauma. Various techniques were discussed in relation to C1-C2 stabilization. The study aims to share our clinical experience in a series of six cases of C1-C2 instability that underwent posterior C1-C2 fusion, with free hand technique and limited fluoroscopy. The clinicoradiological presentation for each patient is described. We reviewed different literatures related to our case vividly and focused on the basic neuroanatomy involved in the atlantoaxial joint. All patients of AAD had evidence of severe canal compromise and chronic compressive spinal cord changes. In our study, the patients age ranged from 28 to 52 years. The study included four males and two females. Out of six patients of AAD, three had history of trauma, two had os odontoideum, and one had chronic inflammatory condition (RA). From our case series, we concluded that the Goel-Harms technique is the most versatile and surgeon friendly technique for C1-C2 fixation. Early recognition and surgical intervention of atlantoaxial joint instability is essential to prevent catastrophic neurological complications.

Dystopic Os Odontoideum Causing Cervical Myelopathy: A Rare Case Report and Review of Literature

Os odontoideum (OO) was first described by Giacomini in 1886 as separation of the odontoid process from the body of the axis. Instability can consequently occurs at this level due to the failure of the transverse atlantal ligament (TAL) and this atlantoaxial instability can be a cause of progressive neurological deficits. It is considered a rare anomaly of the odontoid process. It is a disease with controversial etiology, debatable incidence, and only a partly known natural history owing to the paucity of the literature on this topic. There are insufficient demographic data about the occurrence of the disease, and most of the management is dictated by the isolated case reports and few studies which have been carried out at handful of institutes. OO is classified into two types by Fielding et al. based on the anatomic location: orthotopic and dystopic. Orthotopic OO consists of an ossicle that moves with the anterior arch of the atlas, whereas the dystopic type presents as an ossicle near the basion or one that is fused with the clivus. In one magnetic resonance imaging (MRI) study of odontoid morphology, a 0.7% (1 case of 133 patients) incidence was reported. The spectrum of the clinical presentation varies from completely asymptomatic individuals to patients presenting with features of cervical myelopathy. Here, we present a case of 35-year-old-male with dystopic OO who presented to us with features of gradually progressing cervical myelopathy without any obvious history of neck trauma. On investigations, he was found to have atlantoaxial instability with wide atlanto-dens interval. He was treated with the posterior C1-C2 stabilization and reduction of atlantoaxial instability.

Os Odontoideum: A Comprehensive Clinical and Surgical Review

Os odontoideum (OO) is a rare anomaly of the odontoid process first described by Giacomini in 1886. There is considerable debate about the origin of this anomaly, whether congenital or acquired, though a growing body of evidence favors the latter. Using PubMed, we reviewed the literature on OO with regards to its etiology, clinical presentations, diagnostic modalities, and management. Manuscripts cited in reviews were also searched manually. Because the medical literature on this condition is limited, our understanding of the natural history and management of OO is still vague. The management guidelines for asymptomatic OO are preliminary. Therefore, we need more large-center studies to investigate this condition further.

Acute Traumatic Cervical Cord Injury in Pediatric Patients with os Odontoideum: A Series of 6 Patients

OBJECTIVE

Os odontoideum can lead to instability of the atlantoaxial joint and places the spinal cord at significant risk for acute traumatic catastrophic events or chronic neurologic change. The purpose of this study was to retrospectively review acute cervical cord injury after minor trauma in 6 pediatric patients with os odontoideum.

METHODS

Between 2012 and 2013, 6 pediatric patients with os odontoideum who suffered acute traumatic cervical cord injury were reviewed retrospectively. Their clinical history, neurologic symptoms, radiological investigations, follow-up period, American Spinal Injury Association (ASIA) impairment classification, and motor score were reviewed.

RESULTS

There were 2 male and 4 female subjects ranging in age from 4 to 18 years (mean 11.8 years). Before the traumatic injury, 2 cases were asymptomatic and 4 complained of myelopathic feature with unsteadiness on feet. Falls were the most common injury (n = 5), followed by a minor motor vehicle accident (n = 1). Atlantoaxial instability and cord compression were presented in all cases with dynamic cervical lateral radiographs and magnetic resonance imaging. Most patients presented with spinal cord thinning and hyperintensity on T2-weighted sequences in magnetic resonance imaging. Spinal cord compression was anterior in 2 cases and both anterior and posterior in 4. Two patients was classified as ASIA B, 1 as ASIA C, and 3 as ASIA D category on admission. Two patients presented with respiratory failure with mechanical ventilation for over 2 weeks in perioperative period. Postoperatively, all patients improved neurologically and clinically after underwent posterior atlantoaxial fixation and fusion.

CONCLUSIONS

Pediatric patients with asymptomatic or myelopathic atlantoaxial instability secondary to os odontoideum are at risk for acute spinal cord injury even after minor traumatic injury. Sufficient fixation and fusion should be undertaken as prophylactic treatment of developing myelopathy and to improve neurologic symptoms with acute traumatic cervical cord injury in pediatric patients with os odontoideum.

Dynamic CT scan of the craniovertebral junction: a role in the management of os odontoideum

Os odontoideum is an uncommon abnormality of the cranio-vertebral junction (CVJ) that exists as a separate ossicle apart from a hypoplastic dens. Its genesis and natural history have been debated, and its proper treatment remains uncertain. A 48-year-old woman complained of persistent upper neck pain and paraesthesia of her left side. Magnetic resonance imaging of the CVJ demonstrated an os odontoideum. Dynamic computed tomography scan of the CVJ showed a reduction of the space available for the spinal cord to 50% from extended to flexed position. The patient underwent posterior spinal fusion of C1-C2 using a sublaminar titanium hook and rods fixed in moderate extension. We discuss the usefulness of the dynamic computed tomography (CT) scan in the evaluation of atlantoaxial motion and the management of this pathology.

Decision making

INTRODUCTION

The craniocervical junction is affected by numerous pathological processes. This involves congenital, developmental, and acquired abnormalities. It can result in neurological deficit secondary to neurovascular compression, abnormal cerebrospinal fluid dynamics, and craniovertebral instability. A physiological approach based on an understanding of the craniovertebral junction dynamics, the site of encroachment and stability was formulated in 1977 and has stood the test of time. The author has reviewed 5,300 patients with neurological symptoms and signs secondary to an abnormality of the craniocervical junction. This includes 2,100 children.

TREATMENT OF CRANIOVERTEBRAL JUNCTION ABNORMALITIES

The factors that influence the specific treatment are: (1) reducibility of the lesion, (2) mechanics of compression and the direction of encroachment, (3) the presence of abnormal ossification centers and epiphyseal growth plates, and (4) the cause of the pathological process.

STABILITY AT THE CRANIOCERVICAL JUNCTION

Instability at the craniocervical junction is considered when the predental space is more than 5 mm in children below the age of 8, when the separation of the lateral atlantal masses is more than 6 mm where the cruciate ligament is felt to be disrupted, and if there is vertical translation of more than 2 mm between the clivus and the odontoid process signifying occipital instability. The gap between the occipital condyle and the lateral atlas facet should never be visible on lateral cervical radiographs. Present day magnetic resonance imaging can visualize disrupted transverse cruciate ligament, alar ligaments, tectorial membrane, and bony malalignment. The primary aim of treatment is to relieve compression at the cervicomedullary junction. Hence, stabilization is paramount in reducible lesions to maintain neural decompression. Irreducible lesions require decompression at the site where the compression has occurred; these were divided into ventral and dorsal compression states. In the former compression state, the operative procedure was a ventral decompression through a palatopharyngeal route, LeForte dropdown maxillotomy, or the lateral extrapharyngeal approach. In dorsal or dorsolateral compression states, a posterolateral decompression is required. If instability is present after decompression, posterior fixation is mandated.

Discrepancies of MRI findings between recumbent and upright positions in atlantoaxial lesion. Report of two cases

Two cases of atlantoaxial (A-A) instability that showed different MRI findings between supine and upright positions are presented. The upright MRI represented the findings corresponding to their symptoms. In A-A lesions, conventional MR images taken in the supine position do not always explain the pathophysiological consequences. The MR images taken in the upright position disclose the actual spinal pathophysiology with gravitational effects.

Anomalies of the odontoid process discovered as incidental findings on cephalometric radiographs

Two patients with unusual developmental anomalies of the odontoid process of the axis are presented. These anomalies were discovered as incidental findings on the cephalometric radiographs obtained as part of orthodontic treatment. Both patients had severe instability of the cervical spine at the articulation between the first and second cervical vertebrae that required referral to a medical specialist. When this was discovered, both patients were asymptomatic, with normal neurologic findings. Surgical stabilization of the spine was considered but deferred because the patients had no neurologic signs or symptoms. To protect them from head injury, the patients were advised to refrain from contact sports and strenuous exercise, and follow-up evaluations were recommended. These cases emphasize the need to evaluate head and neck structures shown on cephalometric radiographs, independent of the traditional morphometric analysis.