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Object: Congenital occipitocervical (OC) instability is uncommon in healthy children but can occur in many children with Down syndrome. A simple morphometric method of evaluating the OC joint in children with OC instability is presented, supported by a qualitative image analysis based on computed tomography (CT)., Methods: Thin-cut CT scans of the OC joint were obtained in eight patients with Down syndrome and one patient with congenital OC instability. These patients' CT scans were compared with those of 15 healthy age-matched control individuals. Morphometric analysis was performed by measuring the depth and length of the superior articular surface (SAS) of C-1, and these values were normalized for a comparison between groups. Qualitative data were acquired using a surface-rendering technique for a visual comparison of the C-1 SAS. Morphometric analysis demonstrated an absence of the concave C-1 SAS anatomy in patients with congenital OC instability compared with age-matched control individuals (0.083 compared with 0.202, p < 0.001). Three-dimensional (3D) image analysis of the C-l SAS supported this finding., Conclusions: Congenital differences in the shape of the OC joint are highly associated with atraumatic OC instability in children with Down syndrome. High-resolution CT imaging combined with 3D rendering techniques and surface mapping provides support for this assessment. It appears that abnormal OC joint shape is a contributing factor to congenital OC instability, especially in patients with Down syndrome.

Objective: Aneurysms of the vertebral artery are rare, comprising less than 5% of all aneurysms. They can present with subarachnoid hemorrhage, medullary compression, and cranial neuropathies. In consideration of their surrounding regional anatomy, they present a formidable surgical challenge to the neurosurgeon using traditional techniques. Recent advances in endoscopic transnasal surgery have provided an additional approach for the treatment of these difficult lesions., Clinical Presentation: We present a case of a large vertebral artery aneurysm causing mass effect on the medulla. Initial treatment consisted of endovascular trapping of the aneurysm; however, because of concerns that the remaining aneurysm and intraluminal thrombus was causing mass effect and continued brainstem compression, a decompressive procedure was required., Intervention: After the endovascular trapping, the patient underwent a completely endoscopic transnasal surgical clipping and aneurysmorrhaphy. After exposure of the aneurysm, distal and proximal clips were applied transnasal, and the aneurysmorrhaphy completed using suction and ultrasonic aspiration., Conclusion: In consideration of their surrounding regional anatomy, aneurysms of the vertebral artery present a formidable surgical challenge to the neurosurgeon. Although endovascular techniques have proven to be extremely valuable for the treatment of these lesions, they are limited when patients have significant mass effect with brainstem compression or cranial neuropathy. Advances in endoscopic transnasal surgery have provided an additional approach for the treatment of these difficult lesions. This case report represents, to our knowledge, the first literature report of a transnasal endoscopic aneurysm clipping and thrombectomy.

Study Design: This is a case report of a patient who survived traumatic atlanto-occipital dislocation with atlantoaxial subluxation., Objective: To describe the useful points of 3-dimensional computerized tomography (CT) and magnetic resonance imaging (MRI) for an evaluation of atlanto-occipital dislocation., Summary of Background Data: Atlanto-occipital dislocation is a severe ligamentous injury that usually results in either a fatal outcome or severe neurologic deficit. To our knowledge, no patient who has survived atlanto-occipital dislocation with atlantoaxial subluxation has yet been reported., Methods: Three-dimensional CT was performed to confirm the diagnosis of atlanto-occipital dislocation and precisely evaluate the magnitude of displacement. MRI clearly showed a disruption of the ligamentous structures, which play a role as the primary stabilizers of the cranium on the cervical spine., Results: As soon as the patient's general condition improved, the posterior spinal fusion with internal fixation was performed to maintain the stability of cervical spine. A significant degree of motor function was regained within 2 years after injury., Conclusions: In this case, the diagnosis was accurately confirmed, and the cervical spine was evaluated in detail using both 3-dimensional CT and MRI as a reliable examination for atlanto-occipital dislocation.

Objective: Tuberculosis of the craniovertebral junction is an uncommon entity and its optimal management remains controversial. In this study, we present the evolution of management protocol of this disease in our institute in the past 3 decades., Methods: A total of 51 patients with craniovertebral junction tuberculosis presenting as atlantoaxial dislocation from 1978 through 2004 were reviewed. The disease was rated from Stage I to Stage III, depending on the radiological findings. All patients received antitubercular treatment for 18 months. In the initial period of this study (1978-1986), all patients (n = 10) underwent surgery, usually a posterior fusion. In the second period (1987-1998), patients with less severe disease (Stages I and II, n = 14) were managed with external rigid immobilization, whereas patients with severe disease (Stage III, n = 11) underwent either a transoral decompression with or without posterior fusion or posterior fusion alone. More recently (1999-2004), all patients (n = 16) in all stages (Stages I-III) have been managed without surgery by a rigid external immobilization., Results: Except for two patients who died (one because of miliary tuberculosis, the other because of acute hydrocephalus), clinical recovery occurred in all. Follow-up imaging demonstrated radiological healing as well, with regrowth of the destroyed bone., Conclusion: The mainstay of management of tuberculosis of the craniovertebral junction is prolonged antitubercular treatment with a rigid external immobilization. Surgery is not necessary, even in patients with advanced stages of disease. Complete clinical and radiological healing occurs in all patients with conservative treatment.

Rheumatic manifestation at the cervical spine occurs in more than 50% of all cases in the natural course of this disease. The first cervical manifestation takes place in the upper cervical spine. The initial involvement of the C1/C2 segment leads to atlantodental subluxation. Progressive destruction can result in vertical instability, which is characterized by cranial subluxation of the odontoid process with the danger of resulting stenosis and cervical myelopathy. The goal of diagnosis has to be the early recognition of these changes to establish an effective treatment protocol. Persistent pain, neurological deficits, and progressive radiological signs for instability are indications for operative stabilizing procedures. These procedures avoid progressive destruction and improve the prognosis regarding pain decrease, regression of neurological deficits, and life expectancy.

Introduction: Traumatic lesions of cervical spine are common, but those of the cervico-occipital junction are less frequent but more serious., Purpose: Evaluate the radiological aspects of cervico occipital Junction traumatisms., Methods: It is a retrospective study of 32 files of cervico occipital junction traumatisms, collected from January 1995 to December 2004. Imaging methods used were: conventional radiography and computed tomography., Results: Cervico occipital junction traumatisms were less common. They account for 12.7% of cervical spine traumatisms and 0.64% of the admissions. Patients mean age was of 36 years with a male predominance of 81%. Main etiologies were public highway accidents (66%), falls (7%), sports accidents (6%). Bone lesions were most frequent, dominated by fractures of the axis (58%), followed by those of the atlas (24%) and of the occipital bone (5%). Dislocations were observed in 10 patients. Basilar print was observed in two patients who deceased. Polytrauma was observed in 34% of the patients., Conclusion: Cervico occipital junction traumatisms are severe and uncommon in hospitals because of their high lethality. CT is most effective for analyzing lesions.

Atlanto-occipital dislocation (AOD) is a devastating condition that frequently results in prehospital cardiorespiratory arrest and accounts for 15% of fatal spinal trauma. Atlanto-occipital dislocation occurs 5 times more commonly in children than adults, and is believed to be caused by hyperextension. Because of improvements in prehospital resuscitation, more victims with AOD now survive to reach the emergency department. Neurologic injury is usually severe secondary to ligamentous disruption that allows the cranium to move with respect to the cervical spine, and associated facial and head injuries are common. There are, however, reports of survivors without neurologic deficits. We present the case of a 46-year-old woman who suffered an AOD after a motor vehicle crash and we discuss the diagnosis of this condition. The signs of AOD are often subtle, and the possibility of this diagnosis must be kept in mind in all patients with a neck injury, even in the absence of neurologic signs. A systematic approach to assessing the cranio-cervical relationship on the lateral cervical x-ray and the appropriate use of CT scanning is essential to identifying AOD. Through this case report we hope to familiarize clinicians with mechanisms of injury and appropriate imaging interpretation that will assist in the diagnosis of AOD.

Study Design: This study examined the extraosseous and intraosseous anomalies of vertebral arteries in patients who underwent surgery of the craniovertebral junction., Objectives: To describe the usefulness of three-dimensional computed tomography angiography for evaluating vertebral artery anomalies before surgery., Summary of Background Data: Previous studies using catheter angiograms have identified anomalous courses of the vertebral artery at the craniovertebral junction. Studies using computed tomography reconstruction also showed deviation of the vertebral artery groove at the C2 isthmus, demonstrating a risk of vertebral artery injury for C1-C2 transarticular screw placement. These analyses provided us with useful information for identifying anomalies of the vertebral artery, but they could not visualize the artery and its circumferential osseous tissue simultaneously, nor could they analyze the reciprocal anatomy of both tissues., Methods: Thirty-one consecutive patients who submitted to surgery at the craniovertebral junction were evaluated before surgery by three-dimensional computed tomography angiography. Eleven of the patients had congenital osseous anomalies at the craniovertebral junction including os odontoideum and ossiculum terminale. Anomalous vertebral arteries at the extraosseous region were visualized by three-dimensional reconstruction images, and the intraosseous deviation of the vertebral artery at the C2 isthmus was evaluated by multiplanar reconstruction images., Results: Extraosseous and/or intraosseous vertebral artery anomalies were detected in 9 cases. Eight of the 9 cases had osseous anomalies at the craniovertebral junction. Abnormal courses of the vertebral artery at the extraosseous region were detected in 4 cases: 2 had fenestration and 2 had persistent first intersegmental artery. Asymmetry of bilateral vertebral arteries was found in 5 cases: the right was dominant in 3 cases and the left in 2 cases. A high-riding vertebral artery at the C2 isthmus was detected in 5 cases. Based on these findings, we modified our surgical approach and the screw placement; consequently, no vertebral artery injury occurred., Conclusions: In patients having osseous anomalies at the craniovertebral junction, the frequency of vertebral artery anomalies at the extraosseous and intraosseous regions is increased. With preoperative three-dimensional computed tomography angiography, we can precisely identify the anomalous vertebral artery and reduce the risk of intraoperative injury to the vertebral artery, in advance.

Study Design: A case of a child with a traumatic atlanto-occipital dislocation (AOD), with unexpected secondary redislocation in a halo vest is presented. An extensive literature review was performed., Objectives: To show the difficulties in diagnosing AOD, to emphasize its intrinsic instability, and to make recommendations for treatment of this condition., Summary of Background Data: AOD is a rare condition that is difficult to diagnose. Because of the high neurologic morbidity, this injury often results in death. Different diagnostic approaches have been evaluated throughout the literature. Also, there are different opinions on how to treat AOD. There is no large trial that compares conservative treatment with surgery., Methods: A 4-year-old child with a longitudinal distraction of the head is described. Because of his tenuous medical condition, initial treatment was in a halo vest. However, redislocation occurred inside the vest, so surgical stabilization was performed as soon as the patient's condition allowed., Results: To diagnose AOD, different measuring techniques can be applied on a lateral cervical spine radiograph. Using a combination of these tools, the sensitivity of the examination can be increased. There are 3 types of dislocation. Type II, which is a longitudinal distraction, is most unstable. Once confirmed, AOD should be immobilized. This can temporarily be performed with a halo-frame, but our case shows that this does not necessarily provide a stable situation, and early surgical reconstruction should be considered., Conclusions: AOD can be an extremely unstable lesion and is difficult to diagnose. Although initial treatment in a halo vest is recommended, redislocation can occur even in the vest. We recommend urgent surgical stabilization.

Study Design: Blinded comparison of 5 methods to diagnose atlanto-occipital dislocation (AOD) on plain radiographs and computerized tomography (CT) of the cervical spine., Objective: To determine the best method to diagnose AOD., Summary of Background Data: Several methods are proposed for the diagnosis of AOD, including the Power's ratio, X-line method, basion-dens interval, condylar gap, and Harris method. No blinded comparison of the results of these methods has been compared to patient outcome, and there is no information available regarding the accuracy of these methods applied to CT scans., Methods: Plain lateral radiographs and CTs of the cervical spine were reviewed in 104 patients, including 6 with AOD. Images underwent a blinded review by a board certified neurosurgeon (D.K.R.), orthopedist (P.A.A.), radiologist (J.C.), and emergency physician (D.B.B.). Each diagnostic method for AOD was applied for determination of sensitivity, specificity, and positive and negative predictive values. The ability to identify relevant anatomic landmarks was also tabulated., Results: Average values for sensitivities, specificities, positive and negative predictive values for each method applied to plain radiographs are: 0.4625-1.0, 0.8933-0.9725, 0.2775-0.45, and 0.975-1.0, respectively. These values for each method applied to CT scans are: 0.7075-1.0, 0.8725-0.9775, 0.3175-1, and 0.98-1.0, respectively. Identification of relevant anatomic landmarks occurred 99.75% of the time when these methods were applied to CT scans compared to 39% to 84% of the time on plain radiographs., Conclusions: Sensitivity, specificity, positive and negative predictive values of these methods improve when applied to CT scans because of better visualization of anatomic landmarks. This result suggests CT scans of the cervical spine may be warranted in all trauma patients suspected of having cervical spine injury.

We report two rare cases of progressive congestive myelopathy caused by dural arteriovenous fistulae (DAVF) at the foramen magnum. The first, a 69-year-old male with a 2-year history of progressive myelopathy, had symptoms unrecognized due to a past history that included spinal caries and congenital dislocation of the hip. The second, a 60-year-old male, had a recurrence of the myelopathy three months after endovascular occlusion of the DAVF feeding artery. Both patients were successfully treated by direct microsurgical interruption of the arterialized medullary vein with functional and radiological improvement. The clinical manifestations of DAVF at the foramen magnum are nonspecific, mimicking those of cervical spondylotic myelopathy or cervical neoplasm. Accurate and early diagnosis followed by complete obliteration of the fistula is mandatory to avoid permanent neurological deficit.

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

The authors describe a new technique of internal atlantooccipital screw fixation involving posterior wiring and fusion for the treatment of traumatic atlantooccipital dislocation, which was performed in a 17-year-old male patient involved in a motor vehicle accident and who suffered from atlantooccipital dislocation without neurological injury. At the 6-month follow-up examination, the patient was neurologically intact with a solid occipitocervical fusion and full range of motion of the neck.

Study Design: A case report of traumatic atlanto-occipital dislocation complicated by the development of anterior and posterolateral pseudomeningoceles and the late development of syringohydromyelia is presented., Objective: To describe a unique post-traumatic and postsurgical course following atlanto-occipital dislocation., Summary of Background Data: Syringomyelia is a significant potential long-term complication in patients recovering from traumatic atlanto-occipital dislocation. Cord enlargement and increased T2 signal can be a marker of abnormal cerebrospinal fluid flow dynamics. This "presyrinx state" can be seen before clinical evidence of neurologic compromise. Pseudomeningocele formation after atlanto-occipital dislocation is rare, with only 3 reported cases. To our knowledge, all reported cases describe retropharyngeal pseudomeningoceles, and posterolateral pseudomeningocele as seen in this case has not previously been described., Methods: A single case is reported with an emphasis on the imaging findings related to the patient's subsequent neurologic deterioration., Results: Following a pedestrian-motor vehicle collision, the patient received initial evaluation and treatment at a local foreign medical facility, where his cervical spine was cleared. Several days following stabilizing treatment and surgery, the patient was transferred to a foreign-based United States military medical facility and ultimately to our institution, where magnetic resonance imaging demonstrated occipitocervical dissociation. The patient was taken to the operating room for surgical stabilization. Four months after his index operation, the patient underwent halo removal. Follow-up magnetic resonance imaging revealed thickening of the cervical spinal cord in conjunction with diffuse high cord T2 signal and a small low cervical segment of syringomyelia. The patient was observed with follow-up magnetic resonance imaging obtained after 1 month. At this time, the low cervical syrinx had enlarged slightly, a small thoracic syrinx was observed, and cine imaging of cerebrospinal fluid flow demonstrated obstruction at the level of the foramen magnum. The patient was taken to the operating room fordecompression of the foramen magnum and posterior fossa and duraplasty. One month later, the patient's clinical condition began to deteriorate, and repeat imaging showed continued enlargement of the patient's syrinx and hydrocephalus. He was admitted for an urgent shunt procedure but unfortunately sustained cardiorespiratory arrest while on the ward awaiting surgery., Conclusions: Atlanto-occipital dislocation is rarely survivable, and delayed diagnosis can negatively affect long-term clinical outcome. This case illustrates how, despite early signs of improvement, post-traumatic syringomyelia may occur months or even years after spinal trauma and should always be considered in patients who experience late neurologic deterioration after atlanto-occipital dislocation.

Background: Tuberculosis of the craniovertebral junction (CVJ) is extremely rare. However, recent evidence suggests that the incidence of this condition may be increasing. The diagnosis is often difficult despite advances in imaging using magnetic resonance imaging. The transoral approach to the anterior CVJ provides excellent access to this region, has low mortality and morbidity, and enables biopsy of lesions and decompression of the neuraxis. Management of associated atlantoaxial instability, with regard to timing and method of stabilization, is controversial., Methods: We report 24 cases of CVJ tuberculosis. Prominent manifestations of the disease included neck pain and stiffness, swelling of the retropharyngeal soft tissues, quadriparesis, osteolytic erosions, and atlantoaxial subluxation. Seven patients had acute presentation. All patients received antituberculous drug treatment for 18 months. Four patients were managed conservatively, 5 underwent only transoral biopsy, 9 patients underwent transoral decompression and posterior fusion, and 6 patients underwent only posterior fusion., Results: Histopathologic analysis of biopsy material revealed abscess only in 5 cases, granulation tissue only in 6, abscess with granulation tissue in 4, granulation tissue with chronic osteomyelitis in 5, and chronic inflammation in 2. All patients improved, with mean improvement in Nurick grading of 1.71. Even patients with spinal cord signal intensity changes on magnetic resonance images showed improvement., Conclusions: Although CVJ tuberculosis is a rare disease, the outcome of treatment is good. Antituberculous drug therapy remains the mainstay of treatment after confirming the diagnosis. The surgical management options include transoral decompression with or without posterior fusion, depending upon the presence and persistence of atlantoaxial instability.

Objective and Importance: More survivors of traumatic atlanto-occipital dislocation (AOD) in adults have recently been reported. Surgical management options are therefore of increasing interest. We present a new technique of posterior C0-C1-C2 fixation., Clinical Presentation: A 29-year-old motorcyclist survived a traumatic vertical AOD of 15 mm. No spinal cord or medullary lesion was present. Brain contusion and diffuse axonal injuries led to a cortical biplegia, which recovered progressively over a period of 6 months. Twelve months after surgery, no neurological deficit was present except for slightly increased deep tendon reflexes., Intervention: Posterior C0-C1-C2 fixation was performed with two bicortical occipital screws, one bicortical lateral mass screw in the atlas, and one monocortical pars screw in the axis on each side, connected to a plate-rod on the right and left sides. Fusion was performed with monocortical bone graft from the posterior iliac crest., Conclusion: The surgical technique described was thought to be safe to perform and resulted in immediate stability without external immobilization. Solid fusion was achieved 6 months after surgery.

The upper cervical spine includes the articulations of the occiput with atlas and the atlas with the axis, as well as the bony structures of the base of the skull, axis, and atlas. The unique anatomy of the upper cervical spine and the typical mechanisms of injury yield a predictable variety of injury patterns. Injuries to this area include occipital condyle fractures, occipitoatlantal dislocations, subluxations and dislocations of the atlantoaxial articulation, atlas fractures, odontoid fractures, and fractures of the arch of the axis. Injuries to this region are relatively common and can be easily overlooked because patients with the upper cervical injury may have an associated head injury, which can alter their level of consciousness and complicate obtaining an accurate history and physical examination. The complex regional anatomy and overlying structures make plain radiographic images difficult to interpret. Delayed recognition can result in significant disability. A thorough understanding of the clinical presentation, radiographic assessment, and mechanisms of injury can minimize morbidity and enhance treatment effectiveness for the more common upper cervical ligamentous and bony injuries.

Study Design: Case report of a Down syndrome patient with right vertebral artery fenestration and abnormalities of the craniovertebral junction., Objectives: Describe the utility of 3-dimensional computed tomography angiography for evaluating vertebral artery anomalies before surgery., Summary of Background Data: Previous reviews evaluating catheter angiograms identified various anomalies of vertebral artery at the craniovertebral junction. The frequency of vertebral artery anomalies is increased in patients having osseous anomalies at the craniovertebral junction. Down syndrome is associated with a high incidence of bone abnormalities at the craniovertebral junction, but there have been no published reports of vertebral artery anomalies per se at the craniovertebral junction., Methods: A 16-year-old woman with trisomy 21 presented with gait abnormalities and myelopathy in association with bone abnormalities at the craniovertebral junction, including hypoplastic odontoid and ossiculum terminale. Computed tomography angiography showed that right vertebral artery bifurcated after exiting the C2 transverse foramen with one branch passing through the C1 transverse foramen, whereas the other turned posteromedially and entered the spinal canal between C1 and C2., Results: Occipito-C2 posterior fusion was performed with a rod and screw system. Intraoperatively, the course of the anomalous right vertebral artery was identified by Doppler angiography, and the surgical approach was modified to allow safe pedicle screw insertion while avoiding vertebral artery injury. After surgery, myelopathy resolved within 3 months., Conclusions: Before corrective surgery of craniovertebral junction anomalies in patients with Down syndrome, the possibility of vertebral artery anomalies associated with abnormal craniovertebral junction anatomy should be considered. With preoperative 3-dimensional computed tomography angiography, we can precisely identify the anomalous vertebral artery and modify the surgical approach to reduce the possible risk of intraoperative vertebral artery injury in advance.

Study Design: A retrospective review of 21 patients with spondyloepiphyseal dysplasia congenita (SEDC), including 7 operated patients for atlantoaxial subluxation., Objectives: To clarify the morphological findings of atlantoaxial subluxation in SEDC patients and to evaluate the operative procedures based on these image findings., Summary and Background Data: The presence of atlanto axial sublucation with hypoplasia of the odontoid and/or lax ligaments leads to myelopathy in patients with spondyloepiphyseal dysplasia congenita., Methods: We retropectively reviewed the physical and morphological findings on atlantoaxial images and the clinical findings of myelopathy in 21 patients with SEDC., Results: Myelopathy was found in 9 individuals with severe SEDC who presented with marked short stature and severe coxa vara; of these, 6 had gait disturbances. On the images of the 9 patients with myelopathy, the average sagittal canal diameter (SCD) at the level of the atlas was only 9.2 mm (range, 7-12 mm) with progressive atlantoaxial subluxation. The average atlantodental interval (ADI) was 3.5 mm (range, 2-6 mm) in the presence of a sagittal atlas diameter (SAD) of less than 27.1 mm (range, 22-36 mm). Surgery was performed for 6 of the patients with myelopathy. Since their SADs were small, and the average SCD, at 9.9 mm (8-14 mm), was narrow even at the position of extension (the position of reduction for atlantoaxial subluxation), C1 laminectomy was needed for all these patients, and occipital-cervical posterior fusion was performed. Stability was satisfactory in all cases and the operative outcome for myelopathy was excellent for 1 case, fine for 4, and fair for 2., Conclusion: A small SAD may limit the effectiveness of reducing atlantoaxial subluxation. Persistent narrowing of the SCD may require concomitant C1 laminectomy and occipital-cervical fusion.

The authors report a case of a patient with Down syndrome in whom the abnormal course of the right vertebral artery (VA) at the craniovertebral junction (CVJ) was accurately demonstrated on three-dimensional (3D) computerized tomography (CT) angiography. The patient was a 5-year-old boy, who developed severe myelopathy. Bone abnormalities were also present at the CVJ, including atlantoaxial and occipitoatlantal instabilities, a hypoplastic odontoid process, and ossiculum terminale. Three-dimensional CT angiography revealed that the right VA was duplicated after emerging from the C-2 transverse foramen. One half of the duplication, an artery that was as large as the left VA, turned posteromedially and entered the spinal canal between C-1 and C-2. The other half, a very small artery, ran as usual and passed through the C-1 transverse foramen. The authors performed an occipitocervical posterior fusion and a C-1 laminectomy. Intraoperatively the course of the anomalous VA was identified on Doppler ultrasonography, and the surgical approach and bone excision were undertaken carefully to avoid VA injury. Postoperatively, resolution of myelopathy was marked. In the surgical treatment of patients with Down syndrome, surgeons should consider the possibility that a VA anomaly is present at the CVJ. With preoperative 3D CT angiography, the anomalous VA can be identified precisely and the possible risk of intraoperative VA injury predetermined.

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

We experienced a case of unilateral hypoglossal neuroparalysis, in which the right hypoglossal nerve was compressed by horizontal subluxation in the atlanto-occipital joint, due to rheumatoid arthritis. This report represents a very rare case of unilateral hypoglossal neuroparalysis, in which diagnostic imaging of CT with multiple cross-sectional images (three-dimensional CT) was quite useful for the identification of compression by horizontal subluxation., (Copyright 2003 S. Karger AG, Basel)

Objective: To present a detailed description of a dog with atlanto-occipital (A-O) luxation, including results of the neurologic examination, diagnostic imaging, and treatment by closed reduction., Study Design: Clinical case report., Sample Population: One adult intact male German shepherd dog., Results: Neurologic signs included nonambulatory tetraparesis and neck pain. An apparent hypoglossal nerve deficit was consistent with a lesion at the peripheral part of the nerve in the region of the craniocervical junction. Radiographic examination revealed a left-sided luxation of the A-O joint, and fractures were excluded with the aid of computed tomography (CT). Closed reduction of the luxated articulation resulted in a stable A-O joint, and complete neurologic recovery occurred within 4 weeks., Conclusions: Hypoglossal nerve deficits may be associated with A-O luxation., Clinical Relevance: Closed reduction of a unilateral, traumatic luxation of the A-O joint is a therapeutic option in dogs. CT imaging, especially 3-dimensional reconstruction, was considered helpful in excluding fractures as well as defining treatment options., (Copyright 2003 by The American College of Veterinary Surgeons)

We present four patients who had sustained a traumatic dislocation of the atlanto-occipital joint. The diagnosis was initially missed in two patients. One patient, who was neurologically intact, was treated non-operatively. The remaining three recovered neurologically after an occipitocervical fusion. Early recognition of the injury, especially in multiply-injured patients with head injuries, and timely management may improve survival and neurological recovery.

Object: Stabilization of the craniocervical junction (CCJ) remains a significant challenge. In this multicenter study, the authors present the results of an evaluation of a precontoured titanium implant, the Ohio Medical Instruments (OMI) Loop, for craniocervical fixation., Methods: In this multicenter retrospective study the authors evaluated 30 patients (16 female, 14 male; mean age 53.8 years) with rheumatoid arthritis (15 cases), traumatic occipitoatlantoaxial instability (six cases), congenital vertebral anomalies (two cases), instability due to basilar invagination in the setting of Chiari malformation (two cases), or Down syndrome (one case), tumor (one case), os odontoideum (two cases), and pseudarthrosis/other (one case), who underwent OMI Loop-assisted occipitocervical reconstruction. The mean follow-up period was 25.4 months (range 6-60 months). A solid reconstruction was achieved in 29 of 30 cases; there was only one case of hardware failure requiring reoperation. Noncritical hardware failure occurred in two patients in whom partial occipital screw backout occurred but did not necessitate reoperation. There were no perioperative neurological complications. One patient (3.3%) experienced a delayed postoperative worsening of myelopathy at 1 year that resolved with further surgery. Postoperatively, in 66.6% of patients the degree of myelopathy remained stable (as measured by American Spinal Injury Association [ASIA] scores), whereas 30% improved by one or more ASIA grade. The rate of osseous fusion was 96.6% at a mean follow-up period of 25.4 months., Conclusions: The authors found that the OMI Loop is a versatile precontoured occipitocervical fixation device that can be applied to a wide range of CCJ lesions. It provides excellent immediate rigid fixation of the CCJ, a high rate of osseous fusion, and a low rate of hardware failure.

We present a case of progressive atlanto-occipital dislocation, recognized by a new onset of positive neurologic findings. We discuss the anatomic relationship of the lower four cranial nerves to the foramen magnum and the atlanto-occipital joint. The importance of careful assessment of the cranial nerves prior to choosing a treatment algorithm is emphasized.

Object: The authors compared the biomechanical stability resulting from the use of a new technique for occipitoatlantal motion segment fixation with an established method and assessed the additional stability provided by combining the two techniques., Methods: Specimens were loaded using nonconstraining pure moments while recording the three-dimensional angular movement at occiput (Oc)-C1 and C1-2. Specimens were tested intact and after destabilization and fixation as follows: 1) Oc-C1 transarticular screws plus C1-2 transarticular screws; 2) occipitocervical transarticular (OCTA) plate in which C1-2 transarticular screws attach to a loop from Oc to C-2; and (3) OCTA plate plus Oc-C1 transarticular screws. Occipitoatlantal transarticular screws reduced motion to well within the normal range. The OCTA loop and transarticular screws allowed a very small neutral zone, elastic zone, and range of motion during lateral bending and axial rotation. The transarticular screws, however, were less effective than the OCTA loop in resisting flexion and extension., Conclusions: Biomechanically, Oc-C1 transarticular screws performed well enough to be considered as an alternative for Oc-C1 fixation, especially when instability at C1-2 is minimal. Techniques for augmenting these screws posteriorly by using a wired bone graft buttress, as is currently undertaken with C1-2 transarticular screws, may be needed for optimal performance.

Atlantooccipital dislocation (AOD) injuries are highly unstable, and usually result in significant neurological injury and death. Recently the postinjury survival period has increased. In a review of the literature the authors found 41 cases in which survival was greater than 48 hours. This is likely due to improved on-scene resuscitation, spinal immobilization, transportation, new diagnostic techniques, and a higher index of suspicion. Diagnosis is usually made with plain cervical radiographs, but there are shortcomings associated with this modality in the pediatric population. Diagnosis is aided by high-resolution computerized tomography and magnetic resonance imaging. Infants and toddlers may undergo orthotic immobilization alone, whereas older children usually undergo early occipital cervical fusion. Those with incomplete AOD may be managed successfully with orthotic immobilization.

Objective: We describe a series of seven consecutive patients treated with endoscopically assisted transoral surgery for decompression of high cervical and clival abnormalities., Methods: Seven endoscopically assisted transoral procedures were performed at the University of Florida from September 1999 to April 2000 for irreducible compression at the cervicomedullary junction. The abnormalities encountered were primary basilar invagination from congenital craniovertebral junction malformation (two cases), irreducible rheumatoid cranial settling (one case), secondary basilar invagination caused by migration of odontoid fracture fragments (one case), pseudogout granulation mass (one case), clivus chordoma (one case), and Chiari malformation with associated basilar invagination (one case)., Results: Successful decompression was achieved in all seven patients. There were no adverse neurological sequelae. One patient died from a perioperative myocardial infarction. At a mean clinical follow-up of 6.16 months, neurological status was noted to be stable or improved in all remaining patients., Conclusion: Endoscopically assisted transoral surgery represents an emerging alternative to standard microsurgical techniques for transoral approaches to the anterior cervicomedullary junction. Used in conjunction with intraoperative fluoroscopy, it provides a safe method for anterior decompression of the cervicomedullary junction without the need for extensive soft palate splitting, hard palate resection, or extended maxillotomy. Experience is required with greater numbers of patients and long-term follow-up to further validate this promising technique.

Unlabelled: We examined the reliability of an airway evaluation test to assess the occipitoatlantoaxial (OAA) extension capacity described by Bellhouse et al. (Bellhouse test) in 20 adult volunteers with normal cervical spines. Each subject sat upright with the head in the neutral position and was then asked to extend the head maximally while attempting to move the neck as little as possible. The angle from the neutral position to the extreme extension was measured using the goggle-goniometer. Lateral cervical radiographs were taken in these positions, and the OAA extension angle was radiographically measured. Median values for OAA extension measured radiographically and extension of the head measured with the Bellhouse test were 21.5 degrees and 30 degrees, respectively. Extension of 9.5 degrees occurred at the subaxial regions, which could not be detected by inspecting surface contours of the neck. The extent of the subaxial extension was almost consistent with the degree of overestimation of the OAA extension capacity by the Bellhouse test. Because the subaxial extension occurred independent of the degree of the OAA extension, a strong relationship between the angle measured with the goggle-goniometer and the OAA extension angle measured radiographically was not established (P < 0.01, r(2) = 0.44). These findings mean that the test is not always accurate to evaluate the OAA extension capacity and will fail to detect a reduction of the OAA extension capacity if the subaxial regions are normal. Therefore, these problems derived from the Bellhouse test offer a potential for missing a prediction of difficult tracheal intubations because reduced OAA extension is one of the important factors that make intubation difficult., Implications: The Bellhouse test was not always accurate to evaluate the actual occipitoatlantoaxial extension capacity because of the inevitable occurrence of the subaxial extension. This may mean that some difficult endotracheal intubations will be unpredictable.

Purpose: Survival after atlanto-axial-occipital ligamentous injury is uncommon and experience with the immediate clinical management of these patients is similarly low. There has been considerable work published recently with respect to airway management in similar patients and a review of this material was undertaken., Methods: Medline searches were performed to seek out the English language literature using the key words and phrases: cervical spinal injury; atlanto-occipital dislocation; atlanto-occipital disarticulation; and airway management after spinal injury. The titles were culled for materials relevant particularly to upper cervical spinal injury, these were obtained and reviewed. The bibliographies of these articles were searched to ensure that the review would be complete., Relevant Findings: The majority of cervical spinal movement occurring during direct laryngoscopy is concentrated in the upper cervical spine. The magnitude of movement during airway management rarely exceeds the physiological limits of the spine. Movement is reduced by in-line immobilization but traction forces cause clinically important distraction and should be avoided. Indirect techniques for tracheal intubation cause less cervical movement than does the direct laryngoscope. Survival after severe upper ligamentous injury is uncommon but intact survival occurs. Missed diagnosis is common and associated with a high incidence of severe secondary injury. Failure to immobilize the spine is deemed to be the most relevant factor in secondary injury., Conclusions: Patients who survive severe upper cervical ligamentous injury and present to hospital are uncommon. However, of those who do, both intact survival and survival with limited neurological sequelae do occur. Meticulous airway care with maintenance of alignment and provision of continuous cervical immobilization are an integral component of care in these patients.

In this review a new interpretation of the origin of bony developmental malformations affecting the craniocervical junction and the cervical spine is presented based on recent advances in the understanding of embryonic development of the spine and its molecular genetic control. Radiographs, CT and MRI scans or CT myelograms of patients with Klippel-Feil syndrome were used for demonstration. Detailed clinical and radiological analysis of these patients was published earlier [David KM, Stevens JM, Thorogood P, Crockard HA. The dysmorphic cervical spine in Klippel-Feil syndrome: interpretations from developmental biology. Neurosurg Focus 1999;6(6):1.]. Homeotic transformation due to mutations or disturbed expression of Hox genes is a possible mechanism responsible for Cl assimilation. Notochordal defects and/or signalling problems, that result in reduced or impaired Pax-1 gene expression, may underlie vertebral fusions. This, together with asymmetrical distribution of paraxial mesoderm cells and a possible lack of communication across the embryonic mid-line, could cause the asymmetrical fusion patterns. The wide and flattened shape of the fused vertebral bodies, their resemblance to the embryonic cartilaginous vertebrae and the process of progressive bony fusion with age suggest that the fusions occur before or, at the latest, during chondrification of vertebrae. The authors suggest that the aforementioned mechanisms are likely to be, at least in part, responsible for the origin of the bony developmental malformations affecting the craniocervical junction and the cervical spine.

Two children who were 13 months and 3 years old and who had suffered traumatic atlantooccipital dislocation were each treated by being placed in a halo orthosis for 10 weeks. Because of a continued loss of reduction due to the poor fit of the halo vest, a dual-strap augmentation was developed. This strap augmentation allowed consistent reduction to be maintained. Both children were therefore successfully treated nonsurgically with a halo vest. One child remained neurologically intact and the other had improvement in motor strength. There were no complications from the use of strap augmentation for halo vest fixation.

We report the case of a trauma child who developed a cardiac arrest due to atlanto-occipital luxation of the cervical spine. The occurrence of a rapidly reversible cardiac arrest in a trauma patient should alert physicians about cervical trauma. Adequate resuscitation of these patients require endotracheal intubation with concomitant full immobilisation of the cervical spine, plasma expansion to prevent arterial hypotension and immobilisation of the cervical spine during transport. Thorough application of these resuscitation techniques should increase the survival rate on admission to trauma centres of paediatric patients presenting with such a severe condition. Nevertheless, atlanto-occipital luxation is a major cause of paediatric cervical trauma mortality and our patient did not survive this condition.

The purpose of this study was to evaluate ultrasonographic imaging as a means of easy and noninvasive diagnosis of articular and periarticular structures of the atlanto-occipital articulation in the horse; and to find a safe approach to the atlanto-occipital joint. Ultrasonographic investigations were performed on 6 healthy horses and 16 specimens from horses humanely destroyed age 2-17 years (mean 9.56 years). Preliminary examinations included anatomical studies and preparation of cross-sections. On 4 horse specimens, puncture of the atlanto-occipital joint under ultrasonographic guidance was performed and a new lateral approach undertaken. For ultrasonographic investigations, the neck was divided into 4 zones according to anatomical and clinical modalities: 1) insertion of the funiculus nuchae; 2) tuberculum dorsale of the atlas; 3) atlanto-occipital joint and 4) region above the foramen alare. Each zone was examined in transverse and longitudinal planes proceeding from cranial to caudal. Ultrasonography was found to be useful for soft tissue imaging of this region and was performed down to the atlanto-occipital joint of which the joint surfaces, joint capsule and collateral ligament could be delineated in both planes. We conclude that ultrasonography of the neck is a useful technique, representing an easy to use and safe method. However, further studies are indicated which should be performed on live subjects.

Objective: To provide an overview of atlanto-occipital dislocation and associated occipital condyle fracturcs so as to alert physicians to this rare injury and potentially improve patient outcome. The pertinent anatomy, mechanism of injury, clinical and radiologic evaluation and the management of these rare injuries are discussed in an attempt to alert physicians to this type of injury and to improve outcome., Data Sources: The data were obtained from a MEDLINE search of the English literature from 1966 to 1999 and the experience of 4 spine surgeons at a quaternary care acute spinal cord injury unit., Study Selection: Detailed anatomic and epidemiologically sound radiology studies were identified and analyzed. Only small retrospective studies or case series were available in the literature., Data Extraction: Valid anatomic, biomechanical and radiologic evaluation was extracted from studies. Clinical data came from limited studies and expert opinion., Data Synthesis: Early diagnosis is essential and is facilitated by a detailed clinical examination and strict adherence to an imaging algorithm that includes CT and MRI scanning. When the dislocation is identified, timely gentle reduction and prompt stabilization throuigh nonoperative or operative means is found to optimize patient outcome., Conclusions: Atlanto-occipital dislocation should be suspected in any patient involved in a high speed motor vehicle or pedestrian collision. Once suspected, proper imaging and appropriate management of these once fatal injuries can improve survival and neurologic outcome.

A 21-year-old woman presented with mild neck pain following a scooter accident. Conventional cervical radiographs showed a lateralisation of the dens axis to the left in relation to the foramen magnum. A subsequent CT with a multiplanar reconstruction revealed an atlanto-occipital dislocation that was repositioned under fluoroscopic control. The patient had an uneventful recovery; a mild loss of strength in the left arm remained. The atlanto-occipital dislocation without neurological deficit is rare.

Traumatic atlanto-occipital dislocation is a rarely seen clinical entity, because it is too often fatal. The case of an 8-year-old boy is presented with an anterior atlanto-occipital dislocation. He suffered from multiple injuries: severe head injury and coma, fractures of both femurs and one tibia. He was considered an incomplete spinal cord injury on admission. The diagnosis was suspected 4 days after admission, and a minimal cervical traction was applied for 4 weeks. At 5 years follow-up, clinical and radiologic status was normal. This case is compared with the 28 survivor children reported in the literature: 79% had incomplete neurologic lesions, and only 12 were normal at follow-up. Every report pointed out difficulties of initial clinical and radiologic diagnosis. Treatment is varied and controversial but, in children's cases, mild traction may be indicated in anterior and posterior displacement as initial management, and surgical stabilization performed early in longitudinal dislocation and deferred in displacement that remains unstable.