Disappearance of degenerative, non-inflammatory, retro-odontoid pseudotumor following posterior C1-C2 fixation: case series and review of the literature

Imaging Characteristics of Nonrheumatoid Arthritis Patients With Retro-odontoid Pseudotumor: A Multicenter Case-control Study

STUDY DESIGN

Multicenter case-control study.

OBJECTIVE

To identify imaging characteristics of the cervical spine in patients with retro-odontoid pseudotumor (ROP) without rheumatoid arthritis (RA) and determine the pathogenesis of ROP.

BACKGROUND

ROP results from proliferative changes in the soft tissue of the atlantoaxial junction surrounding the region of the transverse ligament, and is commonly seen in RA patients. However, the pathogenesis of ROP caused by mechanical instability of the upper cervical spine in patients without RA is yet to be explained.

MATERIALS AND METHODS

We collected imaging data [preoperative radiographs, magnetic resonance imaging (MRI), and computed tomography (CT)] of patients who underwent surgery between April 2011 and March 2022 at the three university hospitals for ROP (cases) and cervical spondylotic myelopathy (as age, sex, and institution matched controls). The two groups were compared for different parameters on cervical dynamic radiographs, MRI, and CT.

RESULTS

The ROP group consisted of 42 patients, and the control group comprised 168 patients. C2-C7 range of motion was significantly smaller in the ROP group (25.8 ± 2.6°) compared with the control group (33.0 ± 1.0°). C2-C7 sagittal vertical axis was significantly larger in the ROP group than the control group (39.3 ± 3.6 vs. 32.2 ± 1.3 mm). MRI and CT assessment showed progressive degeneration at all intervertebral levels in the ROP group. A significant positive correlation was observed between the thickness of the soft tissue posterior to the dental process and the atlantodental interval in the flexion position ( r = 0.501).

CONCLUSIONS

The development of ROP was associated with degeneration of facet joints and intervertebral disks in the middle and lower cervical spine. Our findings suggest that decreased mobility of the middle and lower cervical spine may cause instability in the upper cervical spine, leading to the formation of ROP.

Clinical and MR Predictors of Retro-Odontoid Pseudotumor Regression Following Posterior Fixation in Patients with Atlantoaxial Instability

Purpose

To identify clinical and MR predictors of retro-odontoid pseudotumor (ROP) regression after posterior fixation in patients with atlantoaxial instability.

Materials and Methods

We included patients who had undergone posterior fixation for atlantoaxial instability and preoperative and postoperative MR imaging. Patients were classified into two groups according to the degree of ROP regression after posterior fixation: regression (≥ 10% reduction) and no regression (< 10% reduction). Mann-Whitney and Fisher's exact tests were performed to identify the clinical (age and sex) and MR predictors (preoperative ROP thickness, ROP type, MR signal homogeneity of the ROP, spinal cord signal change, spinal cord atrophy, ossified posterior longitudinal ligament, os odontoideum, and atlantodental interval) associated with ROP regression.

Results

We retrospectively assessed 11 consecutive patients (7 female; median age, 66 years [range, 31-84 years]). Posterior fixation induced ROP regression in eight (72.7%) patients. Older age and greater preoperative ROP thickness significantly correlated with ROP regression (p = 0.024 and 0.012, respectively). All patients with preoperative ROP thickness > 5 mm exhibited ROP regression. The other variables were not significantly associated with ROP regression.

Conclusion

Older age and thicker preoperative ROP are associated with ROP regression after posterior fixation in patients with atlantoaxial instability.

Evaluation of the Bone Union Occurring Subsequent to C1-2 Fusion Combined With C1 Laminectomy for the Surgical Treatment of Retro-Odontoid Pseudotumor

Introduction Surgical treatments for retro-odontoid pseudotumors (ROPs) include C1 laminectomies and C1-2 and occipitocervical (OC) fusions. When a C1 laminectomy is combined with a C1-2 fusion, concerns arise regarding an increased risk of pseudarthrosis due to decreased bone grafting space. Extension of the fusion area to the OC region may be considered to ensure an adequate bone graft bed. However, this procedure is associated with a risk of complications. Thus, in this study, we investigated the bone fusion and clinical outcomes of C1-2 fusion combined with a C1 laminectomy. Methods Between January 2017 and December 2022, seven patients with ROPs who had undergone C1-2 fusion combined with a C1 laminectomy were included in the study. All patients were followed up for >1 year. Bone fusion was evaluated by computed tomography (CT) at one year postoperatively, while implant failure was assessed by radiography at the final follow-up. Clinical evaluations included preoperative and one-year postoperative Japanese Orthopaedic Association (JOA) scores and recovery rates. Results This study included five male and two female patients, with an average age of 71.9 years. The average follow-up duration was 3.3 years. The primary anchor choices included the C1 lateral mass screw and the C2 pedicle screw. In one case, the transarticular screw was utilized unilaterally, and in another case, a lamina screw was utilized unilaterally. One year postoperatively, CT revealed bone fusion in three of the seven patients. Fusion occurred at the lateral and median atlantoaxial joints in two cases and one case, respectively. Screw loosening was observed in one case. None of the patients required reoperations. The average JOA recovery rate was 34.6%. Conclusion This surgical technique is useful for stabilizing and decompressing the C1-2 region while preserving mobility at the OC joint. However, further long-term follow-up studies are required.

Comparison of the S8 navigation system and the TINAVI orthopaedic robot in the treatment of upper cervical instability

The objective is to compare the clinical efficacy and safety of the S8 navigation system and the Tinavi orthopaedic surgery robot in the treatment of upper cervical instability. The research methods adopted are as follows. The clinical data of patients with upper cervical instability who underwent surgery from May 2021 to December 2021 were analysed retrospectively. Patients were divided into a navigation group (assisted by the S8 navigation system) and a tinavi group (assisted by the Tinavi robot) according to the auxiliary system used. Computed tomography and digital radiography were performed after the operation. The accuracy of pedicle screw placement was evaluated using the criteria put forward by Rampersaud. Degree of facet joint violation, visual analogue scale score, neck disability index and Japanese orthopaedic association score were recorded and assessed during follow-up examinations in both groups. Record two groups of surgery-related indicators. Record the complications of the two groups. A total of 50 patients were included. 21 patients in the navigation group and 29 in the tinavi group. The results of the study are as follows. The average follow-up time was 12.1 months. There was no significant difference in nail placement accuracy between the navigation and tinavi groups (P > 0.05); however, the navigation group had a significantly higher rate of facet joint violation than that of tinavi group (P < 0.05), and the screws were placed closer to the anterior cortex (P < 0.05). Significantly more intraoperative fluoroscopies were performed in the tinavi group than in the navigation group, and the operation time was significantly longer in the tinavi group than in the navigation group (P < 0.05). The time of single nail implantation, intraoperative blood loss and incision length in navigation group were significantly longer than those in tinavi group. There were no statistically significant differences in other indicators between the two groups (P > 0.05). We come to the following conclusion. The Stealth Station S8 navigation system (Medtronic, USA), which also uses an optical tracking system, and the Tinavi Orthopedic robot have shown the same high accuracy and satisfactory clinical results in the treatment of upper cervical instability. Although the S8 navigation system still has many limitations, it still has good application prospects and is a new tool for spine surgery.

The Impact of Cervical Degeneration and Sagittal Balance on Retro-Odontoid Soft-Tissue Thickness

OBJECTIVE

To investigate whether retro-odontoid soft-tissue thickness (ROSTT) is associated with cervical degeneration, cervical spine mobility, and sagittal balance of cervical spine.

METHODS

The data of 151 patients who presented at our hospital with cervical spondylosis were reviewed. The ROSTT was measured using T1-weighted sagittal cervical magnetic resonance imaging findings. The assessment of the degree of cervical intervertebral disc degeneration (IVDD) was conducted using sagittal T2-weighted imaging. The T1 slope (T1S), C0-C2 angle, C1-C2 angle, C2-C7 angle, C1-C7 sagittal vertical axis and C2-C7 sagittal vertical axis were measured. The range of motion was assessed by measuring the flexion-extension radiographs. According to the ROSTT, those measuring less than 3 mm were classified as normal group and those measuring larger than 3 mm were classified as thickened group.

RESULTS

The thickened group had larger cervical IVDD grade, age, C2-C7 angle, and T1S compared to the normal group (all P < 0.05). Additionally, the C0-C2 angle was significantly smaller in the thickened group than in the normal group (P < 0.05). ROSTT showed a negative correlation with C0-C2 angle (r = -0.181, P < 0.05), but positive correlations with both C2-C7 angle (r = 0.255, P < 0.05) and T1S (r = 0.240, P < 0.05). Furthermore, ROSTT was positively correlated with age (r = 0277, P < 0.05) and cervical IVDD grade (Spearman, r = 0.299, P < 0.05).

CONCLUSIONS

Cervical sagittal balance and cervical degeneration have a significant impact on ROSTT. Patients with a higher T1S and severe cervical degeneration are more likely to result in greater ROSTT.

Acute abducens nerve palsy from a complex retro-odontoid pseudotumor with a protrusion: A case report

Retro-ondontoid pseudotumors represent soft tissue proliferation surrounding the transverse ligament of the atlas, which most commonly results in cervical neck pain or myelopathy due to impingement upon the cervicomedullary junction. The causes of retro-odontoid pseudotumor formation are varied and include metabolic, inflammatory, degenerative, and post-traumatic etiologies. To the best of our knowledge, an abducens nerve palsy as a result of a complex retro-odontoid pseudotumor has never been reported. We discuss a case of a 90-year-old woman who presents with acute lateral gaze palsy with multimodality imaging demonstrating a retro-odontoid pseudotumor with an unusual protrusion which courses superolaterally to the level of the pons and compresses the abducens nerve root entry zone.

Comparative Study of Surgical Outcomes of Occipitocervical and Atlantoaxial Fusion for Retro-Odontoid Pseudotumor

OBJECTIVE

To compare the surgical and radiographic outcomes of occipitocervical fusion (OCF) with those of atlantoaxial fusion (AAF) in patients with cervical myelopathy caused by retroodontoid pseudotumors (ROPs).

METHODS

This retrospective, comparative study included 26 patients; 12 underwent occipitocervical fusion (OCF) (group O) and 14 retroodontoid pseudotumor (AAF) (group A) with a minimum 2-year follow-up. Neurologic outcomes were evaluated using the Japanese Orthopedic Association (JOA) score. Radiologic assessment included the maximum anteroposterior (AP) diameter of the anteroposterior-retroodontoid pseudotumor (AP-ROP), C2-7 angle, O-C2 angle, C1-2 angle, atlantodental interval (ADI), range of motion (ROM) of the ADI, C2-C7 sagittal vertical axis (C2-7 SVA), and T1 slope. Global spinal alignments (pelvic incidence [PI] minus lumbar lordosis [LL] [PI-LL], pelvic tilt, sacral slope, and C7 sagittal vertical axis) were also compared between the groups.

RESULTS

Both groups had equally good clinical outcomes with equal complication rates. Three patients had a three-level fusion, 5 cases had a four-level fusion, and 4 cases had more than five-level fusion in group O. All cases had a single-level fusion in group A. Surgical time was significantly shorter in group A. AP-ROP was significantly downsized postoperatively in both groups and was more prominent in group O. C2-7 SVA was significantly increased and C2-7A ROM was significantly reduced in group O at the final follow-up. The PI-LL showed a significant increase in group O at the final follow-up.

CONCLUSIONS

Although OCF and AAF were similarly effective for cervical myelopathy with ROP, AAF was less invasive, and spinal alignment was better maintained postoperatively in AAF than OCF.

Cervical Myelopathy Caused by Non-Rheumatic Retro-Odontoid Pseudotumor: An Investigation of Underlying Mechanisms and Optimal Surgical Strategy

STUDY DESIGN

Retrospective case-control study.

OBJECTIVE

This study aimed to identify the underlying pathologies of non-rheumatic retro-odontoid pseudotumors (NRPs), which would help establish an appropriate surgical strategy for myelopathy caused by NRP.

METHODS

We identified 35 patients with myelopathy caused by NRP who underwent surgery between 2006 and 2017. An age- and sex-matched control group of 70 subjects was selected from patients with degenerative cervical myelopathy. Radiographic risk factors for NRP were compared between cases and controls. We also assessed surgical outcomes following occipital-cervical (O-C) fusion, atlantoaxial (C1-2) fusion, or C1 laminectomy.

RESULTS

Patients with NRP had significantly lower C1 sagittal inner diameter, C2-7 range of motion (ROM), C2-7 Cobb angle, and C7 tilt, as well as significantly higher C1-2 ROM, atlantodental interval (ADI), and C1-2 to O-C7 ROM ratio. Multivariate regression analysis revealed that ADI, C2-7 ROM, and C7 tilt were independent risk factors for NRP. Neurological recovery and pseudotumor size reduction were comparable among surgical procedures, whereas post-operative cervical spine function was significantly lower in the O-C fusion group than in the other groups.

CONCLUSION

Non-rheumatic retro-odontoid pseudotumor was associated with an increase in ADI, suggesting that spinal arthrodesis surgery is a reasonable strategy for NRP. C1-2 fusion is preferable over O-C fusion because of the high prevalence of ankylosis in the subaxial cervical spine. Given that 29% of patients with NRP have C1 hypoplasia, such cases can be treated by posterior decompression alone. Our study highlights the need to select appropriate surgical procedures based on the underlying pathology in each case.

Factors Associated with Retro-Odontoid Pseudotumor in Long-Term Hemodialysis Patients

OBJECTIVE

Hemodialysis has been reported to be associated with retro-odontoid pseudotumor (ROP), but its clinical characteristics have not been well described. The purpose of the present study was to investigate the factors associated with ROP in hemodialysis patients.

METHODS

A retrospective clinical study of hemodialysis patients was conducted with the evaluation of computed tomography and magnetic resonance imaging of cervical spinal lesions at a single institution from 2012 to 2020. The patients' characteristics and radiographic findings were assessed. A case-control analysis was performed between patients with ROP (ROP group) and patients without ROP (control group).

RESULTS

We analyzed 46 patients. The mean duration of hemodialysis (± standard deviation) was 21.5 ± 11.8 years. The mean retro-odontoid soft tissue thickness was 4.3 ± 0.3 mm and was correlated with the duration of hemodialysis (r = 0.46, P < 0.01). Thirty patients (65.2%) were included in the ROP group. The ROP group showed a significantly longer duration of hemodialysis (24.9 ± 11.2 years vs. 15.2 ± 10.3 years, P < 0.01) and a higher incidence of osteolytic lesions in the atlantoaxial joint compared with the control group (60.0% vs. 18.8%, P < 0.01). Logistic regression analysis revealed the atlantoaxial osteolytic lesions are associated with retro-odontoid pseudotumor in hemodialysis patients (odds ratio, 5.1; 95% confidence interval, 1.1-24.2; P = 0.04).

CONCLUSIONS

The existence of ROP in hemodialysis patients was associated with osteolytic lesions in the atlantoaxial joint. The finding of atlantoaxial erosive lesions in long-term hemodialysis patients requires spine surgeons to carefully evaluate the presence of ROP.

Imaging Characterization of Non-Rheumatoid Retro-Odontoid Pseudotumors: Comparison with Atlantoaxial Manifestation of Rheumatoid Arthritis

Backgroundand Objectives: To date, imaging characterization of non-rheumatic retro-odontoid pseudotumors (NRROPs) has been lacking; therefore, NRROPs have been confused with atlantoaxial joint involvement of rheumatoid arthritis (RA). It is important to differentiate these two disease because the treatment strategies may differ. The purpose of this study is to characterize imaging findings of NRROPs and compare them with those of RA. Material and Methods: From January 2015 to December 2019, 27 patients (14 women and 13 men) with NRROPs and 19 patients (15 women and 4 men) with RA were enrolled in this study. We evaluated various imaging findings, including atlantoaxial instability (AAI), and measured the maximum diameter of preodontoid and retro-odontoid spaces with magnetic resonance imaging (MRI) and computed tomography (CT). Results: Statistical significance was considered for p < 0.05. AAI was detected in eight patients with NRROPs and in all patients with RA (p < 0.0001). Seventeen patients with NRROPs and six patients with RA showed spinal cord compression (p = 0.047). Compressive myelopathy was observed in 14 patients with NRROPs and in 4 patients with RA (p = 0.048). Subaxial degeneration was observed in 25 patients with NRROPs and in 9 patients with RA (p = 0.001). Moreover, C2-3 disc abnormalities were observed in 11 patients with NRROPs and in 2 patients with RA (p = 0.02). Axial and longitudinal diameter of retro-odontoid soft tissue and preodontoid and retro-odontoid spaces showed significant differences between NRROP and RA patients (p < 0.0001). Furthermore, CT AAI measurements were differed significantly between NRROP and RA patients (p < 0.05). Conclusions: NRROPs showed prominent retro-odontoid soft tissue thickening, causing compressive myelopathy and a high frequency of subaxial and C2-3 degeneration without AAI.

Operative Technique for Resection of a Ventral Trans-Dural Retro-Odontoid Pannus: A 2-Dimensional Operative Video

Retro-odontoid pseudotumors are rare inflammatory complications of atlantoaxial instability often associated with cervical degenerative disease and rheumatoid arthritis. While propagation of these lesions has been shown to cause spinal cord compression and cervical myelopathy, intradural extension has rarely been reported. In this manuscript and two-dimensional illustrative intra-operative video, we demonstrate cervical decompression, removal of the intradural component, and stabilization with C1-2 instrumentation utilizing a posterior approach. A 71 year old patient presented with progressive cervical myelopathy. Preoperative imaging demonstrated a large retro-odontoid pannus causing severe spinal cord compression and an associated contrast-enhancing intradural lesion, in the absence of obvious C1-2 instability or fractures on CT scan. C1-2 posterior decompression and fusion were performed with maximally safe intradural pannus resection and ventral dural reconstruction. Postoperatively, the patient experienced significant improvement in myelopathic symptoms. Imaging demonstrated good spinal cord decompression with complete intradural pannus resection and debulking of the extradural component. Our outcome in this rare complication suggests a posterior approach may be effective in treating similar patients.

Atlantoaxial stenosis after muscle-preserving selective laminectomy

There are few reports of degenerative atlantoaxial stenosis and new stenosis after cervical decompression. We experienced four cases of atlantoaxial stenosis after muscle-preserving selective laminectomy. We compared these four cases with no stenosis cases after long-term follow-up of selective laminectomy, as well as healthy subjects. A total of 1205 patients who underwent muscle-preserving selective laminectomy due to cervical disorders were included in this study. Postoperative atlantoaxial stenosis, which needed decompression, appeared in 4 cases, and 30 patients did not have radiological stenosis for more than 10 years after surgery. Twenty healthy volunteers were also used as controls. The radiographic parameters measured were C2-C7 angle, C2-C7 sagittal vertical axis (SVA), C2 slope, C7 slope, C2-C5 angle, C5-C7 angle, C1-C2 angle, and atlantodental interval (ADI). We measured the anterior-posterior (AP) diameters of the spinal cord (SC) and dural tube (Dura) at C1/C2 with sagittal MRI. In the cases of atlantoaxial stenosis, the AP of SC and Dura at C1/C2 were smaller preoperatively, and the residual space for SC (SAC) was also smaller. The preoperative ADI was significantly higher in patients with atlantoaxial stenosis, suggesting preoperative instability at C1/C2. Analysis of the ROC curve showed that patients with a preoperative SAC of less than 3.6 mm and an ADI of more than 1.35 mm were more likely to develop postoperative atlantoaxial stenosis. When we perform a muscle-preserving selective laminectomy, decompression of C1/C2 is suggested when the SAC at C1/C2 is less than 3.6 mm and the ADI is more than 1.35 mm.

Retro-Odontoid Intradural Synovial Cyst Decompression via Endoscopic-Assisted Far-Lateral Approach C1-C2 Hemilaminectomy Without Fusion: The Use of Intracranial Denticulate Ligament as Intraoperative Landmark

Purely intradural retro-odontoid synovial cysts are rarely reported in neurosurgical literature, particularly in the absence of associated bony erosions. We present the case of a 57-year-old Native American male with a retro-odontoid synovial cyst and a history of chronic refractory neck pain that was adequately decompressed via an endoscopic-assisted far-lateral approach using a C1-2 hemilaminectomy, obviating the vertebral artery (VA) transposition, bony instability, and the need for instrumented bony fusion. The patient presented to our clinic with several months of refractory nuchal and cervical spine pain and crepitation affecting his activities of daily living (ADL). MRI findings revealed an intradural cyst at the level of C2 behind the odontoid process impinging on the medulla and causing early VA displacement. Both stereotactic neuro-navigation and microsurgical visualization aided in the manipulation of the endoscope and attaining the caudocranial working trajectory. The patient remained neurologically non-lateralizing postoperatively, similar to his preoperative status. This article highlights a less invasive surgical exposure with an endoscope-assisted caudocranial trajectory obtained by a limited unilateral hemilaminectomy to achieve the desired outcome.

Upper Cervical Compression Myelopathy Caused by the Retro-Odontoid Pseudotumor With Degenerative Osteoarthritis and Calcium Pyrophosphate Dihydrate Disease: A Case Report and Literature Review

The retro-odontoid pseudotumor is often concurrent with atlantoaxial subluxation (AAS). Therefore, the pseudotumor is relatively common in rheumatoid arthritis (RA) but rare in primary osteoarthritis (OA). This is a case report of an elderly male patient suffering from neck pain and compression myelopathy caused by the craniocervical pseudotumor with OA but without atlantoaxial instability. He had long-lasting peripheral and spinal pain treated by nonsteroidal anti-inflammatory drugs. Imaging found upper cervical spondylosis without AAS or dynamic instability but with periodontoid calcifications and ossifications, suggesting calcium pyrophosphate dihydrate (CPPD) crystal deposition. Based on a comprehensive literature search and review, CPPD disease around the atlantodental joint is a possible contributor to secondary OA development and retro-odontoid pannus formation through chronic inflammation, which can be enough severe to induce compression myelopathy in non-RA patients without AAS. The global increase in the aged population advises caution regarding more prevalent upper cervical spine disorders associated with OA and CPPD.

Periodontoid pseudotumoral lesions

Background:

Periodontoid pseudotumoral lesions (PPL) are an uncommon cause of cervical pain and myelopathy. In addition, they may be associated with atlantoaxial instability (AAI).

Case Description:

Two patients over 60 years of age presented with neck pain alone. Their MR scans showed expansive lesions involving the odontoid process. One patient with AAI required an occipitocervical arthrodesis, while the other patient without instability was managed with an external orthosis (Philadelphia collar). Both of them experienced full resolution of pain and remained neurologically intact an average 36 months later (range 24–48).

Conclusion:

Here, we discussed the clinical, MR, and non-surgical (without AAI) versus surgical management (with AAI) for different types of PPL.

Retro-Odontoid Pseudotumor Without Radiographic Instability with Congenital C1 Assimilation and C2-C3 Fusion: A Case Report

CASE

The authors present a case of retro-odontoid pseudotumor (ROP) with congenital C1 assimilation and C2-C3 block vertebra without radiological instability who presented with cervical myelopathy with spastic quadriparesis. The patient was managed with occipitocervical fusion and C1 laminectomy. She had rapid neurological recovery in 3 months postoperatively and at 2 years had complete resolution of the retro-odontoid mass.

CONCLUSION

C1 assimilation without apparent radiographic instability as a cause of ROP is underappreciated. This case report and review of literature highlight that C1 assimilation and C2-C3 fusion can lead to ROP even in the absence of apparent radiographic instability with posterior atlantoaxial fusion alone providing good results.

Comparison of fusion versus non-fusion surgery for retro-odontoid pseudotumor with atlanto-axial subluxation

Background

Due to the limited number of reports comparing posterior fusion with posterior decompression alone for retro-odontoid pseudotumor, there remains no consensus on treatment preference, especially in older patients. This study compared posterior fusion (with or without additional decompression) with posterior decompression alone for treating spinal cord pressure from non-inflammatory retro-odontoid pseudotumor with atlanto-axial subluxation (AAS).

Methods

Forty-one patients (27 male and 14 female; mean age, 73.0 ± 11.4 years) who underwent either posterior cervical fusion or decompression alone for the treatment of non-inflammatory retro-odontoid pseudotumor with AAS and were observed for more than 1 year between September 2009 and July 2019 were enrolled. Thirty-two patients (23 male and 9 female; mean age: 71.8 ± 10.9 years) received posterior fusion surgery (fusion group) and 9 patients (4 male and 5 female; mean age: 77.2 ± 12.5 years) underwent decompression alone (non-fusion group). We compared pre- and postoperative Japanese Orthopaedic Association (JOA) scores and preoperative cervical alignment parameters between the groups.

Results

In the fusion group, the mean preoperative JOA score was significantly improved from 9.0 ± 3.2 points to 11.7 ± 3.2 points at the final follow-up (p = 0.0002). Similarly in the non-fusion group, the mean preoperative and final follow-up JOA scores were 8.2 ± 3.5 points and 11.7 ± 3.8 points, respectively (p = 0.003). The recovery rate at the final follow-up was 22.6% in the fusion group and 43.4% in the non-fusion group, which were statistically comparable (p = 0.23). We observed no remarkable correlations between cervical sagittal spinal alignment parameters and JOA score recovery rate in the cohort, nor was any significant subluxation progression seen.

Conclusion

Compared with fusion surgery, surgical decompression alone may be a suitable and less invasive option for the treatment of non-inflammatory retro-odontoid pseudotumor with AAS, especially in elderly patients.

Surgical Management of Retro-Odontoid Cystic Mass with Cervicomedullary Compression

Retro-odontoid cysts are a rare cause of cervicomedullary compression. The etiology of these lesions is not completely understood. Previous trauma and instability at the cervicomedullary junction may be the precipitating event in the development of retro-odontoid cysts in rare cases. We discussed the neurosurgical evaluation of a patient who presented with progressive and rapid neurological deterioration secondary to cervicomedullary compression. Posterior occipitocervical fusion was performed. The patient made an excellent neurological recovery, and postoperative imaging studies demonstrated resolution of the compression and intramedullary cyst.

The Aging Population Faces Increased Risk for Musculoskeletal Pathologies: The Problematic Atlas-Axis Instability

Spinal cord injury (SCI), particularly of the traumatic variety, is a relatively common condition that disproportionately affects the elderly. Cases of SCI with nontraumatic etiologies in the geriatric population have increased over the last 20 years, however. Pannus formation, resulting from chronic inflammation of the spine, is one such etiology that may progress to SCI and potentially result in rapid neurological degeneration. Here we describe a case of an elderly woman who presented with a sudden onset of quadriplegia without a history of trauma. Radiography revealed upper cervical instability and fracture due to the presence of a large erosive pannus formation. Unfortunately, in the context of severe SCI, the reversibility of neurological decline is not always guaranteed. Additionally, surgical intervention is not always appropriate, especially among the elderly population, where medical management and end-of-life care are more often delivered.

A retro-odontoid pseudotumor treated with fixation and tumor resection by the lateral approach: illustrative case

BACKGROUND

A retro-odontoid pseudotumor is not a condition that requires resection. However, pathological diagnosis is required when a tumor such as a meningeal tumor or chordoma is suspected. The authors report a case of a large lesion treated with posterior fixation and tumor resection using a lateral approach.

OBSERVATIONS

A 77-year-old man visited the authors’ department complaining of neck pain and decreased dexterity of the upper extremities. Magnetic resonance imaging showed a large, beak-shaped lesion behind the dens and severe compression of the spinal cord. Surgery consisted of occipitocervical–C2 fixation, followed by tumor resection with a left lateral approach. The pathological diagnosis was consistent with a retro-odontoid pseudotumor. The tumor was resected to a relatively large extent and shrank over time, leading to complete disappearance.

LESSONS

Pathological examination is also possible with a posterior approach if the tumor can be reached through the lateral edge of the dura. In that situation, the amount of resection is limited, and there is a risk of spinal cord compression. Intradural dissemination of tumors is a concern with the transdural approach. If tumor resection by the posterior approach is difficult, the lateral approach can facilitate tumor resection.

Retro-Odontoid and Retro-C2 Body Pseudotumor, Pannus, and/or Cyst. A Study Based on Analysis of 63 Cases

OBJECTIVE

The potential significance of relationship of atlantoaxial instability with retro-odontoid pseudotumor, pannus, and/or cyst (RPC) is analyzed.

METHODS

We searched the database of patients with craniovertebral junction-related instability treated by atlantoaxial fixation from January 2000 to March 2020. We identified 63 patients in whom there was an RPC in the region posterior to the odontoid process or posterior to the posterior aspect of the C2 body.

RESULTS

The RPC was solid in 10 patients, predominantly cystic in 39 patients, and had both solid and cystic components in 14 patients. The vertical dimension of the RPC varied from 4.5 to 10.5 mm (average, 7.9 mm) and the transverse dimension ranged from 2 to 5.2 mm (average, 3.4 mm). In 51 patients, the RPC was in the midline and in 9 patients, it was eccentric in location. In 38 patients, there was erosion of the C2 body adjoining the RPC. Analysis of investigations showed that in 100% of patients, the dome of the RPC was in line with the most susceptible point of potential bone compression of neural structures. The RPC was eccentric in location in 9 patients presenting with torticollis. RPC indicated the presence of atlantoaxial instability even when there were no other positive and validated radiologic indicators. After atlantoaxial stabilization, the RPC spontaneously regressed or disappeared. Direct resection of the RPC was neither performed nor was necessary in any case.

CONCLUSIONS

RPCs are secondary consequences of atlantoaxial instability and need not be primarily addressed by surgical resection. Their location suggests that they might have a neural protective function.

Nonrheumatoid Retro-Odontoid Pseudotumors: Characteristics, Surgical Outcomes, and Time-Dependent Regression After Posterior Fixation

Objective

Although a retro-odontoid pseudotumor associated with rheumatoid arthritis is a well-known clinical entity, little is known about retro-odontoid pseudotumors not associated with rheumatoid arthritis due to their rarity.

Methods

Between 2006 and 2019, consecutive patients with nonrheumatoid pseudotumors were included and retrospectively compared with patients with rheumatoid pseudotumors.

Results

Nineteen patients had nonrheumatoid pseudotumors (mean age, 73 ± 6 years; male, 53%). All had cervical lesions including ossified anterior and posterior longitudinal ligaments with a history of cervical surgery in 5. The mean thickness of the pseudotumors at diagnosis was 8.1 mm (range, 4.2–17.2 mm). Pseudotumor thickness had a significant negative correlation with the atlantodental interval (p = 0.008) and the subaxial range of motion (p = 0.049). In comparison with 7 rheumatoid pseudotumor patients, nonrheumatoid pseudotumor patients were older (p = 0.042), had a higher proportion of males (p = 0.023), had a smaller atlantodental interval (p = 0.007), and had larger pseudotumors at diagnosis (p = 0.030). Of the 19 patients, 18 received posterior fixation with or without C1 laminectomy, while the other received C1 laminectomy alone. The percent pseudotumor thickness at follow-up to those at diagnosis was 91%, 77%, 68%, 46%, 58%, and 49% at 1, 3, 6, 12, 24, and 36 months after surgery, respectively.

Conclusion

This study revealed markedly clinical and radiological differences between nonrheumatoid and rheumatoid pseudotumors. The main etiology for nonrheumatoid pseudotumors was subaxial cervical degeneration and ossified lesions. There were good outcomes following posterior fixation and time-dependent pseudotumor regression within 12 months.

A Case Report of Complete Dislocation of Atlantoaxial Joint due to a Traumatic and Pathological Axial Lesion

BACKGROUND

Atlantoaxial dislocation usually results in sudden death. The patient had never found any axial lesion before, and the atlantoaxial joint dislocation was caused by rotation of the neck due to discomfort of the neck. The patient was given surgical treatment after the rescue of respiratory and cardiac arrest during transportation, which was extremely rare and rarely reported.

METHODS

A 62-year-old male patient presented with limited cervical mobility after a violent rotation of the neck due to neck discomfort. X-ray and computed tomography (CT) scan suggested atlantoaxial dislocation. Sudden respiratory and cardiac arrest during transportation was immediately followed by continuous cranial traction and successful occipital and neck fusion operation.

RESULTS

After the successful rescue of endotracheal intubation, the patient was given continuous cranial traction. After the completion of CT scan, the patient was given occipital neck fusion, and 6 days after the surgery, the patient wore the skull-neck-thorax brace and walked freely.

CONCLUSION

Continuous cranial traction and posterior occipitocervical fusion are effective methods for treating axial pathological fracture with atlantoaxial dislocation.

LEVEL OF EVIDENCE

5.

Kinematic MRI Analysis of Reducible Atlantoaxial Dislocation for Decompression

Background

Many doctors ignored the possibility that there is still a spinal cord compression (SCC) need for decompression after atlantoaxial reduction. Reduction can be achieved on kinematic magnetic resonance imaging (MRI); thus, we want to analyze the role of kinematic MRI in reducible atlantoaxial dislocation and make a preoperative decision whether to perform decompression.

Methods

36 patients with atlantoaxial reduction on preoperative kinematic MRI in extension postures were enrolled retrospectively. Grouping was based on the condition of SCC after atlantoaxial reduction preoperatively. Group A: patients with SCC after atlantoaxial reduction on dynamic cervical MRI were treated with C1 laminectomy for decompression and atlantoaxial fixation. Group B: patients with no significant SCC, according to dynamic MRI, underwent only atlantoaxial fixation. Clinical outcomes were evaluated using JOA score for spinal cord function. Radiological outcomes were assessed by measuring spinal cord diameter on MRI.

Results

The mean follow-up time was 17.1 months. Postoperative JOA score and percentage of SCC in both groups were significantly better than its preoperative score. There were no significant statistical differences in the JOA score at 12 months after surgery and the JOA improvement rate between two groups. All patients in the two groups had a lower percentage of SCC on preoperative extension MRI, compared with neutral MRI. No significant statistical differences in the spinal decompression improvement rate were observed between the two groups.

Conclusions

Decompression should be performed in patients who still have significant SCC on preoperative kinematic MRI. Kinematic MRI could be used to assess SCC and decide whether to perform decompression preoperatively.

Retro-Odontoid Pseudotumor Formation in the Context of Various Acquired and Congenital Pathologies of the Craniovertebral Junction and Surgical Techniques

Retro-odontoid pseudotumor formation consists of an abnormal growth of granulation tissue typically posterior to the odontoid process, resulting as a manifestation of atlantoaxial instability. This instability can occur as a result of conditions ranging from severe mechanical trauma to metabolic disease or autoimmune conditions such as rheumatoid arthritis. A pseudotumor may impinge on the spinal nerves or even the spinal cord and brainstem, manifesting symptoms from severe neck pain to cervicomedullary compression or myelopathy, and in some cases even sudden death. The objective of this review is to consolidate the findings in published case reports and relevant prior literature reviews regarding the formation of retro-odontoid pseudotumor. We address the pathophysiology involved in acquired and congenital pseudotumor formation, including those associated with rheumatoid arthritis (panni). Additionally, we discuss past and current operative techniques designed to curtail and ultimately regress a retro-odontoid pseudotumor and pannus. Surgical techniques that are addressed include ventral decompression (both transoral and transnasal), dorsal decompression, and indications for posterior instrumentation in pannus formation, particularly in cases that may be sufficiently treated in lieu of an anterior approach. Finally, we will examine the role of external orthoses as both a method of conservative treatment as well as a potential adjunct to the aforementioned surgical procedures.

Biomechanics of the effect of subaxial cervical spine degeneration on atlantoaxial complex in idiopathic retro-odontoid pseudotumor development

OBJECTIVES

Retro-odontoid pseudotumor (ROP), with no rheumatoid arthritis, atlantoaxial instability, or other primary diseases, is defined as idiopathic retro-odontoid pseudotumor (IROP). Cervical spine degeneration is associated with IROP development. This study aims to evaluate the effect of cervical spine degeneration on the atlantoaxial complex and find the possible biomechanical mechanism of IROP development.

METHODS

This study was performed using a three-dimensional (3D) finite element (FE) analysis. A degenerated FE model (FEM) and five operation FEMs (C1-C2 fusion, C0-C2 fusion, C0-C3 fusion, C0-C4 fusion, and C1 posterior arch resection) were established based on a normal 3D FEM of the cervical spine including C0-T1 with the main ligaments and muscles. The parameters, including the C1-C2 range of motions (ROMs) and odontoid-related ligaments' stresses in degenerated and operation FEMs, were obtained and compared with those in normal FEM.

RESULTS

Compared to normal FEM, degenerated FEM had reduced C3-C7 ROMs and increased C1-C2 ROMs and odontoid-related ligaments' stresses. After internal fixation, C1-C2 ROMs and most odontoid-related ligaments' stresses were greatly decreased, but with no significant differences among C0-C2, C0-C3, C0-C4, and C1-C2 fusion models. For the C1 posterior arch resection model, C1-C2 ROMs and most odontoid-related ligaments' stresses increased, compared with normal FEM.

CONCLUSIONS

Cervical spine degeneration plays an important part in IROP development in biomechanics. Atlantoaxial complex compensates for cervical spine degeneration, with increased C1-C2 ROMs and odontoid-related ligaments' stresses. Atlantoaxial fusion or short segmental occipitocervical fusion can effectively reduce the stress and should be considered in IROP treatment.

Retro-odontoid pseudotumor: a poorly recognized alteration of the craniocervical junction

INTRODUCTION

Retro-odontoid pseudotumor (ROP) is a rare disease that affects the atlantoaxial joint and, in general, is associated with local biomechanical alterations that may or may not cause instability.

METHODS

Descriptive study of the literature available in databases MEDLINE/PubMed, LILACS, and Scopus. The research was conducted in April 2019.

DISCUSSION

ROP is, possibly, a syndromic designation that encompasses a significant variety of diseases of the atlantoaxial joint. There are different pathophysiological mechanisms implicated in its genesis. The patients, almost in their entirety, present with severe myelopathy, and most of them are treated surgically, with the posterior decompression being the most commonly used method, with or without arthrodesis. Evolution is usually favorable.

CONCLUSION

The ROP is still poorly recognized as a differential diagnosis between the diseases of the cranial-cervical junction. The information available in the literature analyzed was based mainly on the study of reports or case series; therefore, it is insufficient to define conducts with a high level of scientific evidence.

Regression of Retro-odontoid Pseudotumor Using External Orthosis without Atlantoaxial Fusion: A Case Report

CASE

We treated an 87-year-old woman with noninflammatory retro-odontoid pseudotumor induced by atlantoaxial instability (AAI) using only a Philadelphia collar. Because of perioperative risk factors, fusion surgery was canceled; nevertheless, the neurological symptoms improved gradually. After 11 months of nonoperative treatment, the follow-up magnetic resonance imaging demonstrated that the pseudotumor's size was obviously diminished. Orthosis was applied for 2 years, and after its removal, the pseudotumor's size remained the same at the final 7-year follow-up.

CONCLUSIONS

External orthosis is one treatment option for pseudotumor with AAI, especially in patients with significant comorbidities for whom surgical procedures are relatively contraindicated.

Retro-odontoid pseudotumor (pannus) with Forestier’s disease presenting with severe tetraparesis: A case report and literature review

Background:

A retro-odontoid pannus is often associated with inflammatory diseases. It can also have a noninflammatory cause due to chronic atlantoaxial instability.

Case Description:

Here, we report a patient with diffuse idiopathic skeletal hyperostosis and a severe noninflammatory retro-odontoid pannus who rapidly improved after posterior craniocervical decompression and arthrodesis.

Conclusion:

Transoral resection of the pannus, followed by posterior stabilization, is a common treatment for this condition. The pannus can, however, also reduce after posterior stabilization alone (e.g., craniocervical decompression).

The posterior cervical transdural approach for retro-odontoid mass pseudotumor resection: report of three cases and discussion of the current literature

OBJECTIVE

The treatment of a retro-odontoid pseudotumor mass associated with severe spinal cord compression is challenging due to the complex regional anatomy. Here, we present an attractive treatment option involving a single-stage posterior transdural microsurgical resection followed by instrumented cervical reconstruction.

METHODS

We describe three patients presenting with clinical signs of cervical myelopathy and an imaging finding of mucoid and fibrous soft or semi-soft retro-odontoid pseudotumor mass with significant spinal cord compression at the C1/C2 level. Given the severity of the symptoms, surgical decompression was planned and fusion was necessitated by the severe degenerative osteoarthritis seen at the C1/C2 level with signs of instability. Using a standard posterior approach to the spine, a suboccipital decompression by craniectomy and laminectomy of C1, C2 and C3 was performed. The masses were visualized and confirmed with ultrasound imaging, and intraoperative neurosurgical monitoring was applied. The dura was then opened from the level of C0-C2. Exiting C2-C3 nerve roots were identified and protected throughout the procedure, and the dentate ligament was cut to facilitate access. Incision of the anterior dura provided easy access to the lesion for resection without any spinal cord retraction. Multiple intraoperative samples were sent to pathology for tissue diagnosis. The dura was closed with sutures and an overlay of fibrin sealant with collagen matrix sponge. The fusion procedures were performed using a standard occipital cervical plate and screws technique with contoured titanium rods.

CONCLUSIONS

The posterior cervical transdural approach is a safe alternative procedure for mucoid and fibrous soft or semi-soft retro-odontoid pseudotumor mass removal. Preoperative CT scan can evaluate tissue characteristics and distinguish between a soft or ossified mass in front of the spinal cord. Local anatomical conditions facilitate less bleeding and adhesions, together with less spinal cord traction, in the intradural space. Cranio-cervical and suboccipital stabilization can be easily and safely performed with this exposure.

Thinking beyond pannus: a review of retro-odontoid pseudotumor due to rheumatoid and non-rheumatoid etiologies

Retro-odontoid pseudotumor, or mass-like retro-odontoid soft tissue thickening, is an uncommon but important imaging finding that may be associated with rheumatoid arthritis, crystal deposition diseases, as well as non-inflammatory conditions such as cervical degenerative changes and mechanical alterations. Retro-odontoid pseudotumor is commonly associated with atlantoaxial microinstability or subluxation. MRI and CT have an important role in the detection and diagnosis of retro-odontoid pseudotumor. However, due to a wide range of imaging characteristics and ambiguous etiology, it is a frequently misunderstood entity. The purpose of this article is to review relevant anatomy of the craniocervical junction; describe various imaging appearances, pathophysiology and histology in both rheumatoid and non-rheumatoid etiologies; and discuss differential diagnosis of retro-odontoid pseudotumor in order to help guide clinical management.

Transnasal and Transoral Approaches to Atlantoaxial Synovial Cysts: Report of 3 Cases and Review of the Literature

BACKGROUND

Synovial cysts are cystic masses lined with pseudostratified columnar cells and containing clear or xanthochromic fluid. Although they are commonly encountered in the lumbar spine, synovial cysts infrequently occur in the cervical spine and rarely involve the odontoid process. The causes of synovial cysts of the odontoid process are unknown, but growth of synovial rests, proliferation of multipotent mesenchymal cells, atlantoaxial instability, and trauma are thought to play a role.

CASE DESCRIPTION

We present 3 cases of atlantoaxial cysts with the associated radiographic features, surgical management, and clinical outcomes. No patient had rheumatoid arthritis. In all cases, preoperative differential diagnosis included neoplastic pathologic changes. Two patients underwent odontoidectomy through either an endonasal or a transoral approach, followed by posterior occipitocervical fusion. The third patient underwent an endoscopic transsphenoidal approach for cyst decompression.

CONCLUSIONS

Tissue diagnosis is important in confirming pathologic analysis because synovial cysts have radiographic characteristics similar to those of a wide variety of neoplasms of the craniovertebral junction.

Atlanto-axial Pannus in Patients with and without Rheumatoid Arthritis

Objective.

Pannus formation in the atlanto-axial joint is a well-recognized complication of rheumatoid arthritis (RA). Occasionally, atlanto-axial pannus is reported when patients without a history of RA undergo magnetic resonance imaging (MRI) of the cervical spine. We sought to further characterize these patients.

Methods.

The Partners HealthCare Research Patient Data Registry was free-text searched for “atlanto-axial” AND “pannus” in cervical spine MRI reports from 2001 to 2015. Cases with MRI reports describing pannus were reviewed. Clinical data were extracted by chart review in cases with confirmed atlanto-axial pannus (n = 105).

Results.

Twenty-nine patients (27.6%) had RA, all of whom except one carried this diagnosis at the time of the MRI scan. Only 1 of 77 patients without a history of RA was subsequently diagnosed with RA (1.3%, 95% CI 0.1–7.0%, median followup 3.6 yrs). Non-RA patients were significantly older (median age 79 vs 63 yrs, p < 0.0001), less frequently female (55% vs 86%, p = 0.0032), and more likely to have undergone prior cervical spine surgery (18% vs 0%, p = 0.016) compared with RA patients. Thirty-four non-RA patients (44.7%) either had a clinical diagnosis of calcium pyrophosphate dihydrate disease (CPPD) or imaging evidence for tissue calcification. There were no significant differences in age or sex between the CPPD subgroup and other non-RA patients. Twenty-eight patients (26.7%) underwent cervical spine surgery.

Conclusion.

Patients without RA diagnosis and incidental atlanto-axial pannus on cervical spine MRI are unlikely to have previously unrecognized RA. Degenerative disease and tissue calcification may contribute to pannus formation in these patients.

Traumatic Atlantoaxial Lateral Subluxation With Chronic Type II Odontoid Fracture: A Case Report

Background

We report a case of an elderly patient who was diagnosed with lateral atlantoaxial subluxation with type II odontoid fracture, an extremely uncommon upper cervical spine injury that has not been previously reported in the literature to the knowledge of the authors.

Methods

An 87-year-old male reported to the emergency room following a syncopal episode after sustaining a fall. He complained of dizziness, fatigue, disruption of vision and audition, and worsening neck pain. Computed tomographic scans were positive of partial dislocation of the C1 relative to C2 and chronic fracture of dens classified as type II according to the Anderson and D'Alonzo classification system. Magnetic resonance imaging further revealed large fracture pannus tissue at the level of the dens, reducing the space in the spinal cord. There was no evidence of spinal cord injury. Atlas-axis fusion with instrumentation was performed to manage the injury. A review of the classification, occurrence, and management of upper cervical spine surgeries was performed.

Results

An acute injury to a previously unrecognized type II odontoid fracture with partial C1-C2 dislocation was identified as a rare upper cervical spine injury and classified based on the Anderson and D'Alonzo and Fielding and Hawkins classification systems. The decision was made to perform instrumented spinal fusion by inserting mass screws into C1, pars screws into C2, and locking rods to realign the vertebral bodies and address the atlantoaxial instability. Follow-up scans indicated good postsurgical reduction and fixation, including resolution of the pannus overgrowth without direct intervention.

Conclusions

Lateral atlantoaxial subluxation with chronic type II fracture of the dens constitutes a rare injury of the upper cervical vertebrae. Posterior instrumented spinal fusion was used to effectively manage the injury, leading to reabsorption of retro-odontoid pannus tissue.

Retro-odontoid Degenerative Pseudotumour Causing Spinal Cord Compression and Myelopathy: Current Evidence on the Role of Posterior C1-C2 Fixation in Treatment

BACKGROUND

A retro-odontoid pseudotumour compressing the spinal cord and causing myelopathy is often associated with an inflammatory condition such as rheumatoid arthritis. A degenerative non-inflammatory retro-odontoid pseudotumour responsible for clinically relevant spinal cord compression is a rare condition described in small clinical series and is likely associated with craniovertebral junction hypermobility or instability-like conditions. For several years, direct removal of the lesion through an anterior or lateral approach has been advocated as the best surgical option. However, in the last decade the posterior approach to the craniovertebral junction, to perform C1-C2 fixation and C1 laminectomy without removal of the retro-odontoid tissue, has demonstrated its efficacy in reducing retro-odontoid pannus as well as in obtaining improvement of myelopathy.

METHODS

In this paper we analyse the clinical and radiological outcomes of seven patients (five males and two females) treated with posterior C1-C2 fixation and C1 laminectomy for a degenerative non-inflammatory retro-odontoid pseudotumour responsible for spinal cord compression. C1 laminectomy provided immediate spinal cord decompression. We also review the relevant literature focusing on associated cervical degenerative conditions that may contribute to triggering or acceleration of atlantoaxial hypermobility or 'instability', causing formation of the retro-odontoid tissue.

RESULTS

The mean follow-up period (of six followed-up patients) was 55.8 months (range 10-96 months). In all cases the Nurick score at the latest follow-up visit demonstrated clinical improvement; magnetic resonance imaging during follow-up demonstrated progressive reduction of the retro-odontoid pseudotumour in all but one patient, who died of surgery-unrelated disease in the early postoperative period. No vascular or neural damage secondary to C1-C2 fixation was observed.

CONCLUSION

C1-C2 fixation associated with C1 laminectomy is an effective surgical option to treat myelopathy secondary to a degenerative retro-odontoid pseudotumour. In these cases, direct removal of intracanalar tissue compressing the spinal cord is not required, as C1-C2 fixation is sufficient to cause its disappearance.

Dysphagia following C1 laminectomy and posterior atlantoaxial fixation for retro-odontoid pseudotumor: a case report

Purpose: Although dysphagia is known potential complication of cervical spine surgery, it rarely occurs after a posterior approach. We describe an unusual case of a retro-odontoid pseudotumor that suffered dysphagia following a C1 laminectomy and posterior atlantoaxial fixation.Materials and methods: A 79-year-old man presented with progressive tetraparesis and bladder and bowel dysfunction due to severe compression to cervical cord at C1 from a retro-odontoid pseudotumor. After C1 laminectomy and atlantoaxial fixation, the symptoms improved, but dysphagia and aspiration developed, associated with pharyngeal and esophageal stases on videofluoroscopy.Results and conclusions: Possible explanations for postoperative dysphagia include limitation of cervical spine motion, and cervical cord reperfusion injury in addition to the baseline anterior osteophyte and aging. This is the first case of dysphagia developing after laminectomy and posterior atlantoaxial fixation not involving the occipital bone.

Retro-Odontoid Pseudotumor without Radiologic Atlantoaxial Instability: A Systematic Review

BACKGROUND

Retro-odontoid pseudotumor (RP) can be caused by several diseases, especially rheumatoid arthritis, and is usually associated with the presence of atlantoaxial instability. On the other hand, a different group of patients have been identified in whom RP is observed without radiologic findings of atlantoaxial instability. The pathophysiology, clinical characteristics, and prognosis of this latter group of patients are not well described in the literature.

METHODS

A PubMed and Scopus search adhering to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines was performed to include studies reporting patients with RP without radiologic instability (RPWRI). The data gathered from this review were analyzed to characterize RPWRI.

RESULTS

The search yielded 36 articles with a total of 62 patients. All studies were case reports and small case series. Different characteristics of RPWRI are described, including causes, pathophysiology, and treatment.

CONCLUSIONS

The results of this review show that RPWRI has different causes such as hypermobility, deposition of substances, and perhaps disc herniation. Depending on the cause of RPWRI, the pathophysiologic mechanism is different. Treatment should be tailored based on the primary cause of RP and the degree of compression of the cervicomedullary junction. Different degrees of improvement are usually observed after surgical treatment in these patients regardless of the treatment used, but a higher rate of mass regression was observed in those patients in whom the atlantoaxial joint was stabilized.

Retro-Odontoid Pseudotumor in a Patient with Atlanto-Occipital Assimilation

A retro-odontoid pseudotumor is an uncommon non-neoplastic mass. They are mostly associated with rheumatoid arthritis and atlanto-axial subluxation. The pathogenesis is degeneration of the transverse ligament due to chronic mechanical stress. In this case report, an atlanto-occipital assimilation altered the biomechanics of the cervical spine, causing chronic mechanical stress on the transverse ligament and subsequently the development of a retro-odontoid pseudotumor. This is in accordance with previous studies that have attributed the development of retro-odontoid pseudotumor to a loss of mobility of the cervical spine, in cases without associated rheumatoid arthritis or atlanto-axial subluxation.

Retroodontoid Pseudotumor Related to Development of Myelopathy Secondary to Atlantoaxial Instability on Os Odontoideum

Retroodontoid pseudotumor (ROP) is a nonneoplasic lesion of unknown etiology, commonly associated with inflammatory conditions, and the term of pannus is usually used. Less frequently, ROP formation can develop with other noninflammatory entities, with atlantoaxial instability as most accepted pathophysiological mechanism for posttraumatic or degenerative ROP. As it can clinically and radiologically mimic a malignant tumor, it is paramount for the radiologist to know this entity. Magnetic resonance imaging is the modality of choice to reveal the possible severe complication of ROP in the form of a compressive myelopathy of the upper cervical cord. The purpose of the surgical treatment is the regression or complete disappearance of ROP, with posterior decompression by laminectomy and posterior C1-C2 or occipitocervical fixation. We present the case of an elderly patient with retroodontoid soft tissue mass secondary to a chronic atlantoaxial instability on os odontoideum, an extremely rare cause of ROP. The patient developed a posttraumatic cervical myelopathy related to the decompensation of this C1-C2 instability responsible for the formation of a compressive ROP. We will overview the retroodontoid pseudotumor and its differential diagnosis.

Transdural approach to resection of retro-odontoid cysts in elderly patients: report of 3 cases

Retro-odontoid cysts that arise from the tectorial membrane are uncommon lesions that can occur in elderly patients. They arise secondary to degenerative changes, including calcium pyrophosphate deposition within the ligaments. Surgical treatment is indicated when these lesions result in intractable pain, instability, and/or myelopathy. Several surgical techniques to treat this condition exist, but the optimal approach in elderly patients with comorbidities remains controversial. Here, the authors present a case series of 3 patients who underwent successful resection of a retro-odontoid lesion performed through a transdural approach.

The patients were 70, 81, and 74 years old and presented with symptoms of cervical myelopathy. In consideration of their advanced age and the location of their lesion, resection via a posterior approach was considered. A 1- to 2-cm suboccipital craniectomy and C-1 and partial C-2 laminectomy were performed. These lesions could not be accessed via an extradural posterolateral approach, and so a transdural approach was performed. In the first 2 patients, a preexisting deformity prompted an instrumented fusion. In the third patient, only a lesion resection was performed. In each case, the dural opening was made using a paramedian ipsilateral-sided incision, and the lesion was resected through an incision in the anterior dura mater. Only the posterior dura was closed primarily. MR imaging evidence of excellent spinal cord decompression was evident in follow-up examinations.

Transdural resection of retro-odontoid cysts is a viable option for treating asymmetrical ventral extradural cysts. Results from this case series suggest that such an approach is safe and feasible and can provide an alternative to open or endoscopic anterior transpharyngeal approaches.

Mineralization of the transverse ligament of the atlas causing compressive radiculopathy

Objective: To describe a case of a Boxer dog with radiculopathy due to mineralization of the transverse ligament of the atlas and subsequent resorption and resolution of clinical signs after atlantoaxial arthrodesis and odontoidectomy.

Case Report: A five-year-old neutered female Boxer dog was presented with a four-month history of cervical hyperaesthesia refractory to medical management. Neurological examination and magnetic resonance imaging indicated a diagnosis of radiculopathy due to cervical nerve root impingement by dystrophic mineralization of the transverse ligament of the atlas. Odontoidectomy was performed by a ventral approach and atlantoaxial arthrodesis was achieved with a ventral composite polymethylmethacrylate and pin fixation.

Results: Atlantoaxial arthrodesis and progressive resorption of the mineralization following stabilization facilitated indirect decompression. The radioclinical diagnosis and response to arthrodesis was considered ana -logous to retro-odontoid pannus in the human.

Clinical relevance: A clinical condition similar to retro-odontoid pannus may exist in the canine and may be amenable to atlantoaxial arthrodesis.