non rheumatoid retro-odontoid pannus, secondary to C1-C2 instability


Senior Member
Eur Spine J. 2013 Nov; 22(Suppl 6): 879–888.

Disappearance of degenerative, non-inflammatory, retro-odontoid pseudotumor following posterior C1–C2 fixation: case series and review of the literature
Giuseppe M. V. Barbagallo, Francesco Certo, Massimiliano Visocchi, Stefano Palmucci, Giovanni Sciacca, and Vincenzo Albanese

Retro-odontoid pseudotumor, not related to inflammatory or traumatic conditions, is an uncommon pathology. Atlanto-axial instability has been advocated to explain the pathophysiology of retro-odontoid pseudotumor’s formation and growth. Despite pseudotumor direct removal through transoral or lateral approach represented the main surgical strategy for a long time, in the last decade several authors highlighted the possibility to treat retro-odontoid pseudotumor by occipito-cervical or C1–C2 fixation without removal of the intracanalar tissue. The goal of this study is to analyze the data collected in a series of patients suffering from cervical myelopathy due to non-inflammatory, degenerative retro-odontoid pannus and treated by posterior C1–C2 fixation. The relevant literature is also reviewed.
Five patients, not suffering from inflammatory diseases, were treated between 2009 and 2012. Abnormalities of cranio-cervical junction and/or lower cervical spondylotic degeneration were observed in all patients. No evidence of atlanto-axial instability was demonstrated. Clinical and radiological evaluation included pre- and post-operative Nurick score as well as pre- and post-operative X-rays, CT and MRI. In one case, CT scan highlighted an eggshell calcification of the pannus. All patients underwent either a C1–C2 fixation (C1 lateral mass and C2 isthmus-pedicle screws) or occipito-cervical fixation (2 patients) in cases of C0–C1 fusion.
Follow-up ranges from 22 to 45 months (mean 32) in four patients. One patient died of surgery-unrelated disease.
Nurick score changes suggest a clinical improvement in four cases.
Neuro-radiological evaluation shows a progressive but incomplete reduction of thickness of retro-odontoid pseudotumor in one patient, and its disappearance in the other three cases. A second-stage transoral or posterior lateral approach was not required.
Although the etiopathogenesis of non-inflammatory, i.e., degenerative, retro-odontoid pseudotumor is still controversial, our series (the second largest on degenerative retro-odontoid pannus in the literature) confirms that a posterior approach may be sufficient and transoral surgery is not required.


Senior Member
I give back to cesar what belongs to cesar :

Retro-odontoid mass: An evidence of craniovertebral instability
Atul Goel 2015
Author information
Department of Neurosurgery, King Edward Memorial Hospital and Seth Gordhandas Sunderdas Medical College, Mumbai, Maharashtra, India
Corresponding author: Prof. Atul Goel, Department of Neurosurgery, King Edward Memoria Hospital and Seth Gordhandas Sunderdas Medical College, Parel, Mumbai - 400 012, Maharashtra, India. E-mail: moc.liamtoh@26leogluta

Retro-odontoid “bony” or “cartilagenous” mass has been referred to by various names including pseudotumor, inflammatory granulation tissue, degenerative fibrochondral-like tissue, and cystic deterioration.

The lesion can sometimes grow in size, and imaging shows severe compression of the craniocervical cord. The lesion was earlier considered to be a kind of tumor, and surgical efforts were concentrated on methods and techniques that would be able to best resect this mass.

Transoral surgery, lateral cervical approach, and similar such approaches have been designed to resect the lesion.

Goel suggested for the first time that retro-odontoid tissue is a manifestation of atlantoaxial instability and need not be directly addressed, and the surgical efforts should be focused on atlantoaxial fixation.[1,2]

Subsequently, several authors have performed atlantoaxial fixation for such lesions and have even demonstrated resolution of the retro-odontoid mass.[3]


The retro-odontoid tissue is a result of buckling of the posterior longitudinal ligament that results from reduction in the joint space laterally in the facets.

We speculated earlier that instability manifested at the facets is the primary point of pathogenesis of spondylotic spinal disease. Instability at the facets that is the only true joint of the spine is secondary to weakness of the muscles of the nape of the neck related to muscle abuse or disuse.

We had proposed a similar hypothesis in the formation of retro-odonoid pannus in cases with rheumatoid arthritis.[1,2]
.... We have reported immediate post-operative regression of the “pannus” following surgery that involves distraction of the facets, stabilization, and aiming at arthrodesis.[4]

The instability in spinal degenerative problems is subtle, long standing, and several secondary ligaments, disc, and bone changes are apparent when the diagnosis is made.
Essentially it means that instability is the primary event and other physical, morphological musculoskeletal, disc, and even neural alterations are secondary effects. The primary pathology is instability that may not be obvious in the subaxial spine due to oblique profile of the facets and the difficulty in radiologically viewing them. However, the facets of atlas and axis are large and are horizontal in their lay and can be relatively easily visualized.

In the presence of retro-odontoid mass, the instability of the atlantoaxial joint is relatively subtle.

The atlantoaxial instability can be visualized on dynamic flexion-extension images.

The movements of the odontoid process and the increase in atlantodental interval may not be as wide as seen in cases with congenital atlantoaxial dislocations.

The dislocation is more often subtle.

In cases where the odontoid process related instability is not obvious, attention should be directed towards instability of facets. Frequently, the instability of the facets can be visualized on sagittal imaging.

We recently presented an alternative classification of atlantoaxial dislocation on the basis of facetal alignment.[10]
Type II facetal dislocation is when the facet of atlas is dislocated posterior to the facet of axis.
In Type III facetal dislocation, the facets are in alignment, but their instability can be clearly appreciated during surgery that involves facetal handling.

In cases with retro-odontoid osteophyte, Type II facetal dislocation is frequent and should be evaluated. Type B instability can be a frequent indicator of instability of the region and suggests the need for surgical stabilization.
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Senior Member
It looks like Cesar is not Dr Goel but Dr Grob (Switzerland) who first proposed pannus as a result of C1-C2 instability in rheumatoid arthritis...

1997 Jul
Atlantoaxial fusion and retrodental pannus in rheumatoid arthritis.
Grob D1, Würsch R, Grauer W, Sturzenegger J, Dvorak J.

1Schulrhess Klinik, Spine Unit, Zürich, Switzerland.
This study analyzed the influence of atlantoaxial fusion in rheumatoid arthritis patients on inflammatory retrodental pannus.
To determine the value of fusion on the magnitude of pannus as a compressive structure on the spinal cord.
Transverse and vertical instability may lead to neurologic deficits from spinal cord compression. Increased size of the retrodental pannus can exacerbate the neurologic deterioration. Anterior removal of dens and pannus followed by posterior fusion has been proposed in such situations as a method to relieve spinal cord compression.
Twenty-two patients with atlantoaxial instability and verified pannus on magnetic resonance imaging underwent posterior fusion of the upper cervical spine. These patients were followed 12 to 75 months after surgery by clinical, radiologic, and magnetic resonance imaging evaluations. The size of the pannus was compared before and after surgery.
In all patients, the retrodental pannus had significantly decreased or disappeared postoperatively.
Pannus reduction occurred even in patients whose disease was active or progressing, supporting the hypothesis that the pannus is more a reactive fibrous tissue resulting from instability rather than a direct consequence of the inflammatory process itself.

at that time, there was commentaries...