Partial atlantooccipital assimilation causing atlantoaxial instability and early myelopathy in an adult treated with occipitocervical fusion: A case report

INTRODUCTION & IMPORTANCE

Atlanto-occipital assimilation is a rare congenital abnormality which can cause atlantoaxial instability. Basilar invagination and instability can lead to cord compression and myelopathy in young individuals.

CASE REPORT & DISCUSSION

A 37-year-old male presented with gradually worsening axial neck pain for four years duration His deep tendon reflexes are exaggerated in all four limbs but there is no weakness or imbalance. Following radiological evaluation, he was diagnosed to have partial atlantooccipital assimilation causing atlantoaxial instability, basilar invagination and early myelopathy. He was treated with occipital-cervical fusion after the closed reduction of the atlantoaxial joint.

CONCLUSION

Atlanto-axial assimilation can lead to atlantoaxial instability and subsequently myelopathy. Dynamic radiographs and computed tomography are helpful in the diagnosis. Reducible atlantoaxial instability can be managed with closed reduction and occipitocervical fusion.

An Updated Algorithm for Radiographic Screening of Upper Cervical Instability in Patients With Down Syndrome

STUDY DESIGN

Retrospective evaluation of cervical spine images from 2006-2012 for the purposes of "screening" children with Down syndrome for instability.

OBJECTIVE

To determine whether a full series of cervical spine images including flexion/extension lateral (FEL) radiographs was needed to avoid missing upper cervical instability.

SUMMARY OF BACKGROUND DATA

The best algorithm, measurements, and criteria for screening children with Down syndrome for upper cervical instability are controversial. Many authors have recommended obtaining flexion and extension views. We noted that patients who require surgical stabilization due to myelopathy or cord compression typically have grossly abnormal radiographic measurements on the neutral upright lateral (NUL) cervical spine radiograph.

METHODS

The atlanto-dental interval, space available for cord, and basion axial interval were measured on all films. The Weisel-Rothman measurement was made in the FEL series. Clinical outcome of those with abnormal measurements were reviewed. Sensitivity, specificity, and positive and negative predictive values of NUL and FEL radiographs for identifying clinically significant cervical spine instability were calculated.

RESULTS

A total of 240 cervical spine series in 213 patients with Down syndrome between the ages of 4 months and 25 years were reviewed. One hundred seventy-two children had an NUL view, and 88 of these patients also had FEL views. Only one of 88 patients was found to have an abnormal atlanto-dental interval (≥6 mm), space available for cord at C1 (≤14 mm), or basion axial interval (>12 mm) on an FEL series that did not have an abnormal measurement on the NUL radiograph. This patient had no evidence of cord compression or myelopathy.

CONCLUSIONS

Obtaining a single NUL radiograph is an efficient method for radiographic screening of cervical spine instability. Further evaluation may be required if abnormal measurements are identified on the NUL radiograph. We also propose new "normal" values for the common radiographic measurements used in assessing risk of cervical spine instability in patients with Down syndrome.

LEVEL OF EVIDENCE

Level IV.

Os odontoideum: diagnosis and role of imaging

OBJECTIVE

To elucidate the imaging manifestations of os odontoideum, establish the diagnosis and guide surgical therapy.

METHODS

Clinical and imaging data, including X-ray, CT and MR of 24 patients with os odontoideum, were retrieved and reviewed retrospectively.

RESULTS

Os odontoideum with intact cortex was divided into round, conical and blunt tooth types. Four cases of orthotopic and 20 cases of dystopic os odontoideum were included. There was anterior displacement of the base of the dens in six cases, posterior displacement in nine cases and no displacement in nine cases. A widening of anterior atlanto-axial space was shown in 14 patients with varying degrees. Thickening of the soft tissue posterior to the dens was observed in 19 patients, spinal canal stenosis in 21 patients, cervical myelopathy in 10 patients and craniocervical junction malformation in 9 patients. Posterior C1-C2 pedicle screw fixation and fusion was performed in 12 patients and 4 patients underwent posterior occipito-cervical fixation and fusion.

CONCLUSION

Radiographically, os odontoideum is defined as an independent ossicle of variable size with smooth circumferential cortical margins separated from the axis. Imaging can be used to assess atlanto-axial instability, associated normal or abnormal anatomical structures and guide surgical therapy.

[Conventional intubation and laryngeal tube in cervical spine instability : Changes in the width of the dural sac in unfixed human body donors]

BACKGROUND

Airway management in patients with an unstable cervical spine requires a cautious approach if secondary damage is to be prevented but the question regarding the optimum method remains unresolved. The primary aim of the study was to investigate whether there were differences between intubation by conventional Macintosh laryngoscopy and placement of a laryngeal tube (LTS-D) with respect to dural sac compression on an unfixed human cadaver model with unstable injuries of the upper cervical spine. Secondary parameters that could be relevant in patients with unstable spinal injuries were also investigated.

MATERIAL AND METHODS

Orotracheal intubation by conventional direct laryngoscopy using a Macintosh blade and placement of a laryngeal tube (LTS-D) were performed in six fresh human cadavers. The dural sac was filled with contrast dye to allow continuous myelography by lateral fluoroscopy. Changes in the width of the dural sac at the cervical segments (C) C0/C1 and the C1/C2 levels as well as secondary parameters (angulation, distraction, intervention time) were assessed in the intact spine as well as in the presence of combined atlanto-occipital dislocation and atlanto-axial instability. The intubation methods were considered independent and examined using the Mann-Whitney U‑test.

RESULTS

At the C0/C1 level in the intact spine, conventional laryngoscopy caused less reduction of the width of the dural sac than placement of the LTS-D (0.33 mm vs. 0.46 mm, p = 0.035); however, in the presence of combined atlanto-occipital dislocation and atlanto-axial instability, placement of the LTS-D caused less reduction in the width of the dural sac than conventional intubation (1.18 mm vs. 0.68 mm, p = 0.005). At the C1/C2 level no differences were found with respect to changes in the width of the dural sac, neither in the intact spine nor in combined atlanto-occipital dislocation and atlanto-axial instability. Conventional intubation caused more angulation than placement of the LTS-D at both levels measured. Both methods did not cause distraction. The intervention times for placement of the laryngeal tube were shorter.

CONCLUSION

In an unfixed human cadaver model with combined atlanto-occipital dislocation and atlanto-axial instability, placement of the LTS-D caused less reduction in the width of the dural sac than conventional intubation at the level of the craniocervical junction. The LTS-D also caused less angulation and could be placed faster. It could therefore also be advantageous over conventional intubation in living patients with an unstable cervical spine.

Bicortical facet screws as a new option for posterior C2 fixation: anatomical study and clinical experience

PURPOSE

C2 fixation is a demanding procedure, particularly in patients with variants of C1-C2 anatomy. The inferior articular process (IAP) of the axis can be an alternative for screw placement. We report the results of a CT study of C2 IAP anatomy and we present the clinical experience of 28 patients operated with this technique.

METHODS

Anatomical study: 50 CT angiographies of the vertebral arteries (VA) were used for this study and, therefore, 100 IAPs were considered. We measured on the axial and sagittal planes the length, height and width of the facet, the distance between the anterior cortex and the VA and the distance between the screw entry point and the VA. We also measured the angle between the sagittal plane and the external tangent line of the VA.

CLINICAL REPORT

28 patients were treated with C2 IAP screws at the Spine Surgery Department of the University Hospital in Lyon, France, from January 2014 to January 2016.

RESULTS

Anatomical study: the mean length of C2 IAP was 12 ± 2 mm, the mean distance between the anterior cortical layer and the VA was 5.2 ± 1.4 mm, and the mean angle we found was 0.2° ± 5.3°.

CLINICAL REPORT

16 of the 28 patients presented post-traumatic C1-C2 instability, 8 patients presented degenerative disease, 1 patient was treated for pseudoarthrosis, 1 for tumour, 1 for OPLL and 1 for rheumatoid arthritis. All the screws were correctly positioned and there was no VA injury.

CONCLUSION

IAP screws can represent a safe alternative option for C2 fixation.

Hemodynamic stroke: A rare pitfall in cranio cervical junction surgery

Surgical C1C2-stabilization may be complicated by arterial-arterial embolism or arterial injury. Another potential complication is hemodynamic stroke. The latter might be induced in patients with poor posterior fossa collateralization (risk factor 1) when the vertebral artery (VA) is compressed during reduction (risk factor 2). We report a clinical case where this rare situation occurred: A 72-year old patient was undergoing C1C2-stabilization for subluxation due to rheumatoid arthritis. Preoperative computed tomography angiography (CTA) had shown poor collaterals in the posterior fossa. Furthermore, intraoperative Doppler ultrasound (US) detected unilateral VA occlusion during reduction. It appeared to be a high-risk situation for hemodynamic stroke. Surgical inspection of the VA found osteofibrous compressing elements. Arterial decompression was performed resulting in the normal flow as detected by US. Subsequently, C1C2-stabilization could be realized. The clinical and radiological outcome was very favorable. In C1C2-stabilization precise analysis of preoperative CTA and intraoperative US are important to detect risk factors of hemodynamic stroke. Using these data may prevent this rare, but potentially life-threatening complication.

Posterior occipito-axial fixation applied C2 laminar screws for pediatric atlantoaxial instability caused by Down syndrome: Report of 2 cases

Background

Upper cervical spine instability is one of the most critical orthopedic problems in patients with Down syndrome. However, arthrodesis of the upper cervical spine in these patients can be very difficult to achieve and has a high complication rate because of mental retardation and accompanying various medical conditions of the vital organs. Even now, surgeries in such patients, especially pediatric cases, are challenging and the optimal operative procedure remains unsettled. The purpose of this study was to report 2 cases of pediatric atlantoaxial instability due to Down syndrome in which posterior occipito-axial fixation with C2 laminar screws was performed.

Methods

Case 1 was a girl aged 6 years 10 months who had atlantoaxial rotatory fixation with os odontoideum. Atlantoaxial rotatory fixation was incompletely reduced by halo traction, and it was not maintained without halo-ring and -vest fixation. Posterior occipito-axial fixation with bilateral C2 laminar screws was then performed. Case 2 was a boy aged 10 years 7 months who had atlantoaxial subluxation with os odontoideum. He also had incomplete quadriplegia, so he could neither walk nor have a meal by himself. Posterior occipito-axial fixation with right C2 pedicle and left C2 laminar screws was then carried out.

Results

In case 1 bone union was obtained at 3 months after surgery and the patient's symptoms were resolved. In case 2 bone union was obtained at 3 months after surgery and the paralysis was improved.

Conclusions/level of evidence

In cases of atlantoaxial instability due to Down syndrome, symptomatic patients often present between ages 5 and 15 years and mental retardation interferes with postoperative cervical immobilization. C2 laminar screws can be safely applied for the pediatric axis and biomechanically accomplished rigid fixation. The C2 laminar screw is one of the most useful options to achieve stability of the pediatric atlantoaxial complex without the risk of vertebral artery injuries (level IV case series).

Management of traumatic atlanto-axial instability: A retrospective study of eight cases

BACKGROUND

C1 lateral mass-C2 transpedicular fixation is an accepted surgical procedure of choice in a large number of cases with traumatic atlanto-axial instability. However, bony and vascular anomalies can predispose to unacceptably high risk with this procedure, And hence are the contraindications for this procedure. The purpose of this study is to analyze the clinical and radiological results in such cases for which only unilateral fixation has been performed in cases where bilateral fixation could not be performed due to various reasons.

MATERIALS AND METHODS

Eight patients (7 males, 1 female) with a mean age of 41.12 years (range 12-68 years), who presented with traumatic atlanto-axial instability and in whom bilateral fixation could not be performed, were treated with unilateral C1 lateral mass-C2 transpedicular fixation. Of these cases, preoperative vertebral artery occlusion was noted in one case, iatrogenic vertebral artery injury in two cases and bony anomalies or fractures in the remaining of five cases. All patients were evaluated clinically with the American Spinal Injury Association (ASIA) scale and radiologically with computed tomography scans and serial X-ray using criteria to evaluate stability.

RESULTS

All cases were evaluated at 6 months followup with mean followup of 2 years and one month (range 6 months to 4 years). All eight patients showed adequate stability and fusion at 6 months; clinically there was no significant restriction of neck movement in any of the patient. There was no neurological deterioration in any of the patient at their last follow-up.

CONCLUSION

Unilateral C1 lateral mass-C2 transpedicular fixation could be considered a viable option in cases of traumatic atlanto-axial instability where vascular and osseous anomalies contradict a bilateral fixation.