Considerations on "Endoscopic endonasal approach to the craniocervical junction: the importance of anterior C1 arch preservation or its reconstruction"

Os odontoideum associated with a retro-odontoid cyst treated with posterior C1-C3 fixation: A case report and literature review

Background

Os odontoideum is a rare abnormality of the upper cervical spine, and os odontoideum associated with a retro-odontoid cyst has been described as a marker of local instability.

Case description

This paper reports a case of a 52-year-old female patient who was diagnosed with os odontoideum associated with a retro-odontoid cyst. The patient underwent posterior C1-C3 fixation without surgical removal of the cyst. Magnetic resonance imaging (MRI) two days later revealed that the retro-odontoid cyst was still present and that there were no significant changes to it when compared with the preoperative MRI.

Conclusion

Retro-odontoid cysts associated with unstable os odontoideum can lead to symptomatic spinal cord compression. Posterior C1-C3 fixation can restore atlantoaxial stability by allowing the gradual resorption of the cyst and ensuring spinal cord decompression. Fixation can also avoid the surgical risk associated with a high-riding vertebral artery.

Biomechanical evaluation of the craniovertebral junction after odontoidectomy with anterior C1 arch preservation: A finite element study

OBJECTIVE

Odontoidectomy with preservation of the anterior C1 arch can be increasingly achieved by an endoscopic endonasal approach. It is controversial whether preservation of the anterior C1 arch after odontoidectomy can prevent instability of the craniovertebral junction （CVJ） and avoid posterior fixation. The aim of this research was to investigate the biomechanical effect of the preserved anterior C1 arch after odontoidectomy.

METHODS

A validated finite element model of a whole cervical spine (occipital bone to T1) was constructed to study the biomechanical changes due to traditional odontoidectomy (TO) and odontoidectomy with preservation of the anterior C1 arch (OPC1).

RESULTS

The greatest biomechanical changes in the cervical spine model after TO and OPC1 occurred at C0-C1 and C1-C2. At C0-C1 and C1-C2, the motion changes of the TO and OPC1 models had no significant difference in flexion, extension and lateral bending. Compared with the intact model, motion increases of the two surgical models were both extremely significant at C1-C2 in extension (128.2% vs. 128.1%) and lateral bending (178% vs. 156%). In axial rotation, the TO approach produced more motions than the OPC1 approach, especially at C1-C2(90.3° under TO approach, and 74.6° under OPC1 approach).

CONCLUSIONS

Preservation of the anterior C1 arch after odontoidectomy can preserve the axial rotational motion at C0-C1 and C1-C2, whereas the motions in extension and lateral bending continue to have an extremely abnormal increase at C1-C2. Thus, instability of the CVJ still exists, and posterior internal fixation may also be required after OPC1.

Multidisciplinary approach to the craniovertebral junction. Historical insights, current and future perspectives in the neurosurgical and otorhinolaryngological alliance

Historically considered as a nobody’s land, craniovertebral junction (CVJ) surgery or specialty recently gained high consideration as symbol of challenging surgery as well as selective top level qualifying surgery. The alliance between Neurosurgeons and Otorhinolaringologists has become stronger in the time. CVJ has unique anatomical bone and neurovascular structures architecture. It not only separates from the subaxial cervical spine but it also provides a special cranial flexion, extension, and axial rotation pattern. Stability is provided by a complex combination of osseous and ligamentous supports which allows a large degree of motion. The perfect knowledge of CVJ anatomy and physiology allows to better understand surgical procedures of the occiput, atlas and axis and the specific diseases that affect the region. Although many years passed since the beginning of this pioneering surgery, managing lesions situated in the anterior aspect of the CVJ still remains a challenging neurosurgical problem. Many studies are available in the literature so far aiming to examine the microsurgical anatomy of both the anterior and posterior extradural and intradural aspects of the CVJ as well as the differences in all the possible surgical exposures obtained by 360° approach philosophy. Herein we provide a short but quite complete at glance tour across the personal experience and publications and the more recent literature available in order to highlight where this alliance between Neurosurgeon and Otorhinolaringologist is mandatory, strongly advisable or unnecessary.

Why the Craniovertebral Junction?

The craniovertebral junction (CVJ) has unique anatomical bone and neurovascular structure architecture. It not only separates the skull base from the subaxial cervical spine but also provides a special cranial flexion, extension and axial rotation pattern. Stability is provided by a complex combination of osseous and ligamentous supports, which allow a large degree of motion. Perfect knowledge of CVJ anatomy and physiology allows us to better understand instrumentation procedures of the occiput, atlas and axis, and the specific diseases that affect the region. Therefore, a review of the vascular, ligamentous and bony anatomy of the region, in relation to all possible surgical approaches to this anatomically unique segment of the cervical spine, appears to be absolutely mandatory in order to preview and to overcome possible anatomy-related complications of CVJ surgery; moreover, knowledge of the basic principles of instrumentation and of the kinematics of the region, since they interact with the anatomy, seems to be strategic in preoperative planning.Historically considered a no man's land, CVJ surgery, or the CVJ specialty, has recently attracted strong consideration as a symbol of challenging surgery as well as selective top-level qualifying surgery.Although many years have passed since the beginning of this pioneering surgery, managing lesions situated in the anterior aspect of the CVJ still remains a challenging neurosurgical problem. Many studies are available in the literature, aiming to examine the microsurgical anatomy of both the anterior and posterior extradural and intradural aspects of the CVJ, as well as the differences in all possible surgical exposures obtained by the 360° approach philosophy. In this paper the author provides a short but quite complete at-a-glance tour of personal experience and publications and the more recent literature available.