The Prevalence and Morphology-Wise Demographic Distribution of Ponticulus Posticus on CT Scans-A Retrospective Observational Study.

Background and Objectives: The ponticulus posticus (PP) is a bony bridge that emerges from the posterior aspect of the superior articular process, to connect the posterior arch of the atlas. It is often associated with neurological symptoms. The aim of this study was to obtain an insight into this malformation, and prevalence in the North East region of the Romanian population. Materials and methods: This anatomical variant was analyzed through an observational and retrospective study which was carried out in St. Spiridon Hospital Iasi. The duration of the study was 10 months and, a number of 487 patients who presented neurological symptoms without cranio-cerebral traumatisms were enrolled and a computed tomography (CT) scan was performed. We proposed a new classification of PP in five types. The prevalence of PP was calculated and Skewness test, ANOVA test with Bonferroni correction, and Student's t-test were used for statistical analysis. Results: Among the sample of 487 patients, PP was found in 170 cases (34.90%) in an age group of 8-90 years (mean age = 59.52 years, SD ± 19.94 years). Type I was found in 11.29%, followed by Type II-8.21%, Type III-5.13%, Type IV-5.54%, and Type V-4.72% (p = 0.347). It was 19.5%, mirroring the incomplete type, whereas the complete type was reported in 15.40% of cases (p = 0.347), the highest prevalence, namely 41.17% was found in the "41 to 60 years" age group, followed by 36.95% in the "21 to 40 years" group (p = 0.00148). The mean age was higher in patients with PP Type III (61.16 years, SD ± 19.98), while patients with PP Type V recorded the lowest mean age (56.48 years, SD ± 22.13). The differences between the comparative average ages on types were not statistically significant (p = 0.411). The gender and age were not good predictors of PP Type V (AUC < 0.600). Conclusion: according to our study, incomplete types of PP were found to be more prevalent as compared to complete types. No difference between males and females was detected. PP is more frequent in adults and young adults than in the elderly population. It is confirmed that gender and age were not good predictors of the bilateral complete type of PP.

Estudio morfológico de pontículus pósticus en telerradiografías laterales / Morphological study of pontículus pósticus in lateral teleradiographies

OBJETIVO establecer la prevalencia de Pontículus Pósticus (PP) en pacientes atendidos en el Servicio de Imagenología de la Universidad Finis Terrae en el periodo 2015-2020. METODOLOGÍA estudio de tipo transversal descriptivo, donde se analizaron 334 telerradiografías laterales (TL) obtenidas del Servicio de Imagenología de la Universidad Finis Terrae entre los años 2015 y 2019 adquiridas mediante el equipo marca SIRONA modelo Orthophos XG, seleccionándolas según criterios de inclusión y exclusión. Se analizó la primera vértebra cervical buscando la presencia de PP consignando: sexo, edad y tipo de osificación según clasificación de Cederberg y Stubbs, asignándoles valores numéricos para posteriormente realizar el análisis estadístico de tipo descriptivo uni y bivariado. RESULTADOS se seleccionaron 320 TL. La prevalencia de PP fue del 31,9% de las TL incluidas, de los cuales el 68,1% correspondió al tipo 1 de la clasificación de Cederberg y Stubbs, el 14,1% al tipo 2, 10,3% al tipo 4 y el 7,5% al tipo 3. La edad media en pacientes con PP presente correspondió a 30,63 años +/­ 15,888 D.E con un mínimo de 12 años y un máximo de 78. En cuanto a la presencia de PP y la variable sexo, el 53,9% correspondió al sexo femenino y el 46,1% al sexo masculino, en donde no se encontró una predilección estadísticamente significativa (p = 0,08). CONCLUSIONES el PP es una variante anatómica de prevalencia variada, siendo levemente mayor en esta población chilena en comparación con otros países. Además, su evidencia es escasa y no existe un consenso sobre su prevalencia y diversas variables como el género y la edad, difiriendo en varios estudios. Es importante conocer e investigar más sobre la epidemiología de esta anomalía y su relación con distintos desórdenes neurológicos

OBJETIVE to establish the prevalence of Ponticulus Posticus (PP) in patients attended in Radiology Service of Finis Terrae University between the years 2015 and 2020. METHODOLOGY descriptive cross-sectional study, 334 lateral cephalograms were analyzed obtained from the Radiology Service of Finis Terrae University between the years 2015 and 2020 acquired from SIRONA system model Orthophos XG, selecting them following the inclusion and exclusion criteria. The first cervical vertebrae were analyzed searching for the presence of PP, consigning: Type of ossification by Cederberg and Stubbs classification, Age and Sex, assigning them numerical values to subsequently perform the descriptive statistical analysis uni and bivariate. RESULTS the prevalence of PP found was 31,9% of the 320 included TL, of which 68,1% corresponded to Type 0 of Cederberg and Stubbs classification, 14,1% to Type 1, 10,3% to Type 3 and the 7,5% al Type 2. The average age of present PP patient's was 30,63 years +­ 15,888 S.D with a minimum of 12 years and a maximum de 78. As for the presence of PP and sex variable, 53,9% corresponded to female sex and 46,1% to males, where no statistically significant predilection was found (p = 0,08). CONCLUSIONS PP is an anatomical variant with varied prevalence worldwide, being slightly higher in Chile, compared to other countries. In addition, their evidence is scarce and there is no consensus on its prevalence and various variables such as gender and age, differing in several studies. It is important to know and research more about the epidemiology of this anomaly and its relationship with different neurological disorder

Torticollis, Facial Asymmetry, Local Pain, and Barré-Liéou Syndrome in Connection with One-Sided Ponticulus Posticus: A Case Report and Review of the Literature.

BACKGROUND: Ponticulus posticus (PP) occurs frequently and may cause symptom series, including vertebrobasilar insufficiency, migraine, hearing loss, and Barré-Liéou syndrome. However, few studies to date have described surgical treatment of PP. We report a rare case of a patient who suffered from torticollis, facial asymmetry, localized pain, and Barré-Liéou syndrome in connection with PP. We also review the pertinent literature, focusing on surgical treatment for symptoms due to PP. CASE PRESENTATION: A 23-year-old male presented with the chief complaint of continuous significant dizziness to the point of losing consciousness while rotating his head to the right. Plain radiographs and computed tomography (CT) scans of the cervical spine showed a С1 anomaly with the formation of complete PP on the left (dominant) side, with acute-angled, С-shaped kinking of the vertebral artery. Resection of PP via the posterior midline was performed successfully. The patient had satisfactory postoperative relief from localized pain and Barré-Liéou syndrome, but there were no obvious changes in the torticollis and facial asymmetry observed during the 3-month follow-up period. CONCLUSIONS: This case is a rare presentation of torticollis, facial asymmetry, localized pain, and Barré-Liéou syndrome in connection with one-sided complete PP. This tetrad indicates that PP may affect the patient earlier than expected. In such situations, early diagnosis and timely surgical treatment may significantly improve patients' quality of life and avoid the development of torticollis and face asymmetry.

Isolated atlas-duplication as a manifestation of persistent proatlas: a case report.

PURPOSE: Atlas-duplication is an exceedingly rare dysplasia of the craniocervical junction. To the best of our knowledge, only two cases of atlas-duplication have been reported and these were associated with complete anterior rachischisis and os odontoideum. We aimed to report a case of isolated atlas-duplication of incidental finding and without attributable symptoms which makes it unique. METHODS: Following a normal coronarography for a suspected myocardial infarction, a 60-year-old-man with no significant medical history developed a transient ischemic attack that justified brain computed-tomography angiography. RESULTS: There was no evidence for cerebral ischemic lesion, intracranial occlusion or significant artery disease. Bone analysis revealed eight cervical vertebral segments with an additional vertebral level located between the occiput and the atlas. This vertebra presented all the morphological characteristics of an atlas vertebra except for hypoplasia of the left transverse process. An incomplete anterior rachischisis was associated, and there was no other abnormality of craniocervical junction. The clinical examination revealed no neck pain, no limitation of joint amplitude and no neurological deficit. Apart from preventive treatment of ischemic stroke, no orthopedic or surgical treatment was undertaken. After 1.5 years of radiological monitoring, the patient remains symptom-free. CONCLUSIONS: Atlas-duplication is an exceedingly rare dysplasia of the craniocervical junction that may be found isolated and incidentally. If this variation does not necessarily warrant specific treatment, brain CT angiography is recommended to detect anatomical variations of the vertebral arteries.

The computed tomographic evaluation of bony bridge of C1 as bleeding risk factor at the screw placement.

PURPOSE: To investigate the prevalence and morphological characteristics of ponticulus posticus (PP) and ponticulus lateralis (PL) using computed tomography (CT) images on a large study sample of the Anatolian population. The presence of the PP and PL bridges can limit gap available for placement procedure through the bony elements of C1. Routine screw techniques are contraindicated because of high risk of fatal bleeding of vertebral artery (VA). METHODS: The CT images of 1000 subjects (500 males, 500 females) were examined for the morphological characteristics and presence of PP and PL. The anteroposterior diameter, superoposterior (transverse) diameter, surface area, and central thickness of the bony bridge of the PP, PL, and transverse foramina (TF). RESULTS: The prevalence of PP was 14.8%, and bilateral complete PP was the most common PP type at 6.8%. The prevalence of PL was 4.1% and left-side complete PL was the most common PL type at 1.2%. The prevalence of both PP and PL was more common in males and bilateral complete PP were more predominant in males (p = 0.004, p = 0.038, and p = 0.010, respectively). The surface area of PP and PL were determined to be smaller than the surface area of the ipsilateral TF (p < 0.001 and p = 0.042, respectively). CONCLUSION: PP is not an uncommon anatomic anomaly and PL is even less frequently encountered. The prevalence of PP and PL was more common in males and bilateral complete PP was more predominant in males. Detailed information about the prevalence and morphometry of the PP and PL obtained in the present study could guide the clinicians dealing with neurosurgery, physical medicine and rehabilitation, and radiology in their practice.

Arterial Vascular Structures Running Through Retrotransverse Foramen and Retrotransverse Groove of the Atlas Vertebrae.

OBJECTIVE: Retrotransverse foramen (RTF) and retrotransverse groove (RTG) are anatomic variations of the atlas (C1) vertebrae. RTF contains an anastomotic vein connecting atlanto-occipital and atlanto-axodian venous sinuses. The purpose of this study was to analyze the arterial vascular structures running though the RTF and RTG. METHODS: Three-dimensional volume rendered computed tomography angiography (3D VR CTA) images of 427 patients (264 men, 163 women; age 17-87 years) were reviewed and evaluated using the RadiAnt DICOM Viewer (version 5.0.2; Medixant, Poznan, Poland). The incidence of RTF or RTG, the incidence of the V3 segment of vertebral artery variants, and the artery vascular structures inside the RTF and RTG anatomic variation of C1 were analyzed. RESULTS: Fifty (11.7%) atlases presented RTF anatomical variant; 113 (26.5%) atlases presented RTG anatomical variants. The incidence of the V3 segment of vertebral artery variants was 0.94% (4 of 427). Three (0.7%) were persistent first intersegmental artery and 1 (0.2%) was the fenestration of the vertebral artery on left side. In 4 cases of C1 vertebral artery V3 segmental variants, there were no RTF and RTG. No artery vascular structure was found in RTF or RTG. CONCLUSIONS: The RTF or RTG of C1 was a common anatomical variant. No arterial vascular structure runs though the RTF or RTG. The presence of C1 RTF and RTG variants had no effect on the V3 segmental course of the vertebral artery. Preoperative understanding of these variations using 3D CTA are helpful for the safe execution of the upper cervical posterior approach surgeries.

Multiple Fractures of Cervical Vertebrae Combined with Arcuate Foramen and Vertebral Artery Occlusion: A Case Report and Literature Review.

BACKGROUND: The arcuate foramen is a complete or partial bony bridge over the vertebral artery groove of atlas. The mechanism of the arcuate foramen is not clearly understood. Omission of the arcuate foramen sometimes causes lethal iatrogenic injury during spinal surgery. CASE PRESENTATION: We describe a patient who was diagnosed with multiple fractures of the cervical vertebrae, arcuate foramen, and right vertebral artery occlusion based on clinical and radiological exams. After conservative treatment, he resumed a normal and productive life. CONCLUSIONS: Arcuate foramen is a common variation that causes symptoms such as dizziness, headache, and migraine. If the patient does not develop severe symptoms, conservative treatment can achieve very good results without the necessity to remove the bone bridge. When serious symptoms occur, surgical treatment to resect the bony ridges can relieve the symptoms dramatically.

Population-level assessment of atlas occipitalization in artificially modified crania from pre-Hispanic Peru.

Atlas occipitalization (AO) is a spinal anomaly, characterized by the fusion of the first cervical vertebra and occipital bone, with a complex etiology that can arise from congenital and environmental causes. AO has been reported in three regions of pre-Hispanic Peru in skeletal remains with artificial cranial modification (ACM), which involves the use of compression devices to permanently alter cranial shape and may have affected the fusion of the atlas and occipital bone. The aims of this study were to gain insights into AO's etiology by testing correlations between AO and ACM presence/type and geographic region as well as to characterize morphological variation associated with AO. We investigated the geographic distribution of AO and its potential relationship to ACM in a large sample of human crania from eight coastal and highland regions of pre-Hispanic Peru, held at the Smithsonian's National Museum of Natural History (n = 608, 1300-1500 CE). Eleven cases of AO were observed in three coastal regions-including two previously unreported regions-at an overall frequency of 1.8%. The frequency of AO did not differ significantly between crania with and without ACM, in general or by type, suggesting that ACM is not an etiological factor that influences AO in this sample. AO was observed at a significantly higher rate in the southern coastal region of Arequipa than in any other region. Genetic, dietary, and epidemiological conditions are evaluated as factors possibly shaping the geographic distribution of AO along the central and southern coasts of Peru.

Rare anatomic variation on a 10,000-year-old South American skeleton: the case of Iuzu, Toca dos Coqueiros, Piauí State, Brazil.

PURPOSE: A skeleton named Iuzu has been unearthed from an exceptional middle Holocene burial in Toca dos Coqueiros site, in Serra da Capivara National Park (UNESCO World Heritage Site, Piauí State, Brazil). During a bioarchaeological analysis of its remains, we discovered that Iuzu was suffering from rare vertebral malformations. A double foramen transversaria, the agenesis of a foramen on the atlas and the hypoplasia of the transverse process of the axis have been highlighted. We aimed to deduce the clinical consequences of the malformation on the patient's health. METHODS: We proceeded to macroscopic observation and radiography of the bones, then we search for other examples of such a pathology in archaeological litterature. RESULT: The malformation caused vascular insufficiency that may have led to neurological lesions leading to various pains and troubles. The very rare malformations Iuzu presented have not been found on a paleoindian skeleton from South America so far. CONCLUSION: This case allowed us to examine the conditions of selection of individuals buried in southern Piauí during the Middle Holocene, during which time this rite does not seem to predominate.

Aplasia del arco lateral del atlas como hallazgo incidental en un estudio 18F-FDG PET/TC / Incidental diagnosis of atlas aplasia in an 18F-FDG PET/CT study

No disponible

A Juvenile Case of Bow Hunter's Syndrome Caused by Atlantoaxial Dislocation with Vertebral Artery Dissecting Aneurysm.

BACKGROUND: Bow hunter's syndrome (BHS) is caused by posterior circulation insufficiency that results from the occlusion or compression of the vertebral artery (VA) during neck rotation. Owing to its rarity, there is no guideline to support the decision of selecting a conservative or a surgical approach. Management of BHS is dependent on each patient. CASE DESCRIPTION: A 13-year-old girl presented with transient visual disturbance, hypoesthesia, and paralysis of the left side of the body. Magnetic resonance imaging revealed an acute cerebral infarction in the right thalamus, and magnetic resonance angiography demonstrated occlusion of the right posterior cerebral artery and dilation of V3 of the left VA. Digital subtraction angiography revealed a left VA dissecting aneurysm at V3 and left VA occlusion at the level of C1-C2 during neck rotation to the right. A dynamic x-ray suggested atlantoaxial joint instability, and three-dimensional computed tomography revealed aplasia of C1 lamina and atlantoaxial rotatory dislocation. BHS with left VA dissecting aneurysm caused by atlantoaxial rotatory dislocation was diagnosed. We performed C1-C2 posterior fusion by the Goel-Harms technique. Stroke did not recur, and computed tomography angiography obtained 8 months postoperatively demonstrated a decrease in the dissecting aneurysm. CONCLUSIONS: To our knowledge, this is the first case of BHS with VA dissecting aneurysm and aplasia of C1 lamina. Based on this case, we suggest that C1-C2 posterior fusion is effective for BHS with VA dissecting aneurysm.

Static Leukoencephalopathy Associated with 17p13.3 Microdeletion Syndrome: A Case Report.

BACKGROUND: Leukoencephalopathy associated with dysmorphic features may be attributed to chromosomal abnormalities such as 17p13.3 microdeletion syndrome. CASE: A 19-year-old female patient was referred to our hospital for diagnostic evaluation of her leukoencephalopathy. She demonstrated moderate intellectual disability, minor dysmorphic features, and short stature. Serial brain magnetic resonance images obtained within a 16-year interval revealed prolonged T2 signals in the deep cerebral white matter with enlarged Virchow-Robin spaces. A nonsymptomatic atlas anomaly was also noted. Using microarray-based comparative genomic hybridization, we identified a 2.2-Mb terminal deletion at 17p13.3, encompassing YWHAE, CRK, and RTN4RL1 but not PAFAH1B1. CONCLUSION: Except for atlas anomaly, the patient's clinical and imaging findings were compatible with the diagnosis of 17p13.3 microdeletion syndrome. The white matter abnormality was static and nonprogressive. The association between the atlas abnormality and this deletion remains elusive. We note the importance of exploring submicroscopic chromosomal imbalance when patients show prominent but static white matter abnormalities with discrepantly mild and stable neurological signs.

Change of Anatomical Location of the Internal Carotid Artery Relative to the Atlas with Congenital Occipitalization and the Relevant Clinical Implications.

INTRODUCTION: The occipitalization of the atlas (OA) is always associated with multiplanar dislocation and olisthy of the C1 over C2 facets, which may change the anatomical relationship between the internal carotid artery (ICA) and the atlas. The purpose of this current study is to identify the location of the ICA relative to the anterior aspect of the atlas in patients with OA and define the clinical implications for screw placement. METHODS: We retrospectively reviewed the computed tomography angiography data of 86 patients with OA and 86 control subjects. Several parameters were also measured to quantitatively evaluate the mutual relationship. RESULTS: In the OA group, 25.6% of ICAs were located in area 3 and 74.4% in area 2, whereas the percentages were 57.4% and 42.6%, respectively, in the control group. There were 73 (42.4%) ICAs in which the shortest distance between the dorsal surface of the ICA and the ventral cortex of the atlas was less than 4 mm in the OA group and only 50 (29.1%) in the control group. The ideal angulation of C1 screw trajectory was about 5 degrees more medial in the OA group than that in the control group (P < 0.01). CONCLUSIONS: The risk of ICA injury is much higher in OA patients than in non-OA patients during the C1 screw placement. A mean medial angulation about 20 degrees will permit a long and safe screw purchase, but should be individualized. We recommend careful preoperative computed tomography angiography evaluation in all patients before surgery.

Three-Dimensional Evaluation and Classification of the Anatomy Variations of Vertebral Artery at the Craniovertebral Junction in 120 Patients of Basilar Invagination and Atlas Occipitalization.

BACKGROUND: Patients with basilar invagination and atlas occipitalization usually present abnormal anatomy of the vertebral arteries (VAs) at the craniovertebral junction (CVJ). OBJECTIVE: To describe and further classify different types of VA variations at the CVJ with 3D visualization technology. METHODS: One hundred twenty patients with basilar invagination and atlas occipitalization who had undergone 3-dimensional computed tomographic angiography (3D-CTA) were retrospectively studied. Imaging data were processed via the separating, fusing, opacifying, and false-coloring-volume rendering technique. Abnormal anatomy of the VA at the CVJ was categorized and related anatomic parameters were measured. RESULTS: Seven different types were classified. Type I, VAs enter the cranium after leaving VA groove on the posterior arch of atlas (26.7% of 240 sides); Type II, VAs enter an extraosseous canal created in the assimilated atlas lateral mass-occipital condyle complex before reaching the cranium (53.3%); Type III, VA courses above the axis facet or curves below the atlas lateral mass then enter the cranium (11.7%); Type IV, VAs enter the spinal canal under the axis lamina (1.3%); Type V, high-riding VA (31.3%); Type VI, fenestrated VA (2.9%); Type VII, absent VA (4.2%). Distance from the canal of Type II VA to the posterior facet surface of atlas lateral mass (5.51 ± 2.17 mm) means a 3.5-mm screw can be safely inserted usually. Shorter distance from the midline (13.50 ± 4.35) illustrates potential Type III VA injury during exposure. Decreased height and width of axis isthmus in Type V indicate increased VA injury risks. CONCLUSION: Seven types of VA variations were described, together with valuable information helpful to minimize VA injury risk intraoperatively.

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.

Agenesis of the posterior arch of the atlas: an incidental finding in a polytraumatized patient / Agenesia de arco posterior de atlas: um achado acidental em um paciente politraumatizado / Agenesia del arco posterior del atlas: un hallazgo incidental en un paciente politraumatizado

ABSTRACT The first cervical vertebra is subject to numerous anatomical variations. One of these is posterior arch agenesis, which is classified into five distinct morphological types. Together, all types of posterior arch agenesis comprise only 4% of atlas variations. Furthermore, complete agenesis of the posterior arch associated with the presence of the posterior tubercle is rare. This work reports a case of posterior arch agenesis with the presence of the posterior tubercle in a 33 year-old male victim of a motor vehicle collision. Despite being asymptomatic, this anatomical variation can present with headaches and neck pain. It is mostly found as an incidental finding in imaging studies performed by the emergency team and, as a result, it is often misdiagnosed as a C1 fracture. Knowledge of the variations relating to the first cervical vertebra is therefore essential to avoid delays in diagnosis and treatment of polytraumatized patients. Level of evidence V; Case report.

RESUMO A primeira vértebra cervical é alvo de inúmeras variações anatômicas. Uma destas inclui a agenesia do seu arco posterior, que é classificada em cinco tipos morfológicos distintos. Apesar de uma incidência de 4% na população em geral, a agenesia completa do arco posterior, associada à presença do tubérculo posterior do atlas, é rara. Objetivou-se no presente trabalho relatar a agenesia completa do arco posterior com a presença do tubérculo posterior da primeira vértebra cervical em um paciente de 33 anos de idade, que sofreu um acidente automobilístico. Em geral, essa condição é assintomática, porém, essa variação anatômica pode causar sintomas como dores de cabeça. Na maioria dos casos, é um achado acidental em exames de imagem realizados pela equipe de emergência. Como resultado, a agenesia de arco posterior de atlas pode ser interpretada erroneamente como uma fratura. Portanto, o conhecimento das variações anatômicas da primeira vértebra cervical é essencial para evitar erro no diagnóstico e tratamento de pacientes politraumatizados. Nível de Evidência V; Relato de caso.

RESUMEN La primera vértebra cervical puede presentar numerosas variaciones anatómicas. Una de ellas es la agenesia del arco posterior, que se clasifica en cinco tipos morfológicos distintos. En conjunto, todos los tipos de agenesia del arco posterior comprenden solo el 4% de las variaciones del atlas. Además, la agenesia completa del arco posterior asociada con la presencia del tubérculo posterior es rara. Este trabajo relata un caso de agenesia del arco posterior con presencia del tubérculo posterior en un paciente del sexo masculino de 33 años de edad que sufrió un accidente automovilístico. A pesar de ser asintomática, esta variación anatómica puede causar dolores de cabeza y cuello. Se encontra principalmente como hallazgo incidental en pruebas de imagen realizadas por el equipo de emergencia y como resultado, a menudo se diagnostica erróneamente como una fractura de C1. El conocimiento de las variaciones anatómicas de la primera vértebra cervical es, por lo tanto, esencial para evitar retrasos en el diagnóstico y tratamiento de pacientes politraumatizados. Nivel de Evidencia V; Relato de caso.

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.

Morphometric Measurements of the C1 Lateral Mass with Congenital Occipitalization of the Atlas.

OBJECTIVE: Unfamiliarity with the morphometry of the assimilated C1 lateral mass (C1LM) could make screw placement dangerous. In the present study, we defined the morphometric dimensions of the occipitalized C1LM to provide surgeons with valuable information for preoperative planning. METHODS: Thin-slice computed tomography scanning data from 131 patients with occipitalization of the atlas (OA) and 50 control cases were imported into Mimics software for analysis. The widths and heights of the C1LM were fully measured in the different planes. The ideal inward angulation and the safe maximum cephalic angulation of C1 screw trajectory were evaluated. RESULTS: Except for the medial height, all the widths and heights of C1LM were significantly shorter in the OA group than those in the control group. The ideal inward angle (α) was significantly larger in the OA group (23.8° ± 8.3°) than that (15.3° ± 3.8°) in the control group; the corresponding screw length was also significantly longer in the OA group (20.9 ± 2.9 mm). The safe maximum cephalic angles (ß) of the screw trajectory did not reach a significant difference between the 2 groups. All the widths and heights were shorter in the females than those in the males. The α angle also did not reach a significant difference between the sexes; however, the ß angles in the males (35.9° ± 10.4°) was significantly larger than that in the females (32.0° ± 9.4°). CONCLUSIONS: Although the hypoplastic C1LM brings limitations to screw insertion to some extent, it is still broad enough to accommodate a screw safely in both female and male patients. Considering the irregularity of the C1LM in patients with OA, the preoperative imaging assessment is critical, and C1LM screw placement should be performed individually.