Endoscopic transnasal and transoral resection of the odontoid process and C1 combined with occipitocervical fusion for osteoradionecrosis of the upper cervical spine: a case report and literature review.

BACKGROUND: Osteoradionecrosis (ORN) of the upper cervical spine is a rare but severe complication of head and neck cancer radiotherapy. To raise awareness of this condition, we describe a patient with a history of nasopharyngeal carcinoma who developed ORN of the upper cervical spine and review the published literature reporting surgical management. CASE PRESENTATION: A 59-year-old female patient with persistent neck pain for one month and limited range of neck motion who had undergone radiotherapy for nasopharyngeal carcinoma with a total dose of 69.96 Gy 15 years ago presented to our hospital. The patient underwent endoscopic transnasal and transoral resection of the odontoid process and C1 anterior arch, combined with occipitocervical fusion. To better understand surgical management of ORN of the upper cervical spine, the literature published in the PubMed, Ovid MEDLINE, and Embase databases was reviewed. Our patient experienced alleviation of cervical pain and did not exhibit any postoperative complications. Since 2005, 11 cases of surgical management of ORN of the upper cervical spine (including the present case) have been published. Basilar invagination and/or atlantoaxial subluxation were observed in 4 /11 cases. Endoscopic procedures were performed in 4/11 cases, and occipitocervical fusion was performed in 8 /11 cases. CONCLUSION: Endoscopic transnasal and transoral resection of the odontoid process and C1 anterior arch is a safe and effective treatment option for ORN of the upper cervical spine. Occipitocervical fusion is useful in patients with basilar invagination and atlantoaxial subluxation.

MR documented craniocervical ligamentous injury at age 18 months: delayed formation of OS odontoideum. Complex management issues. Case-based review.

OBJECTIVE: There are two separate theories regarding the genesis of os odontoideum: congenital and post-traumatic. Trauma documentation in the past has been the presence of a normal odontoid process at the time of initial childhood injury and subsequent development of the os odontoideum. True MR documentation of craniocervical injury in early childhood and subsequent os odontoideum formation has been very rare. METHODS: An 18-month-old sustained craniocervical ligamentous injury documented on MRI with transient neurological deficit. Chiari I abnormality was also recorded. Subsequent serial imaging of craniocervical region showed the formation of os odontoideum and instability. He became symptomatic from the os odontoideum and the Chiari I abnormality. The patient underwent decompression and intradural procedure for Chiari I abnormality and occipitocervical fusion. Postoperative course was complicated by the failure of fusion and redo. He later required transoral ventral medullary decompression. He recovered. RESULTS: This is an MR documented craniocervical ligamentous injury with sequential formation of os odontoideum with accompanying changes in the atlas. Despite a subsequent successful dorsal occipitocervical fusion, he became symptomatic requiring transoral decompression. CONCLUSIONS: Os odontoideum here is recognized as a traumatic origin with the presence of congenital Chiari I abnormality as a separate entity. The changes of the anterior arch of C1 as well as the os formation were serially documented and give credence to blood supply changes in the os and atlas as a result of the trauma. The recognized treatment of dorsal occipitocervical fusion failed in this case requiring also a ventral decompression of the medulla.

Anterior occipital condyle screw placement through the endonasal corridor: proof of concept study with cadaveric analysis.

PURPOSE: Odontoidectomy for ventral compressive pathology may result in O-C1 and/or C1-2 instability. Same-stage endonasal C1-2 spinal fusion has been advocated to eliminate risks associated with separate-stage posterior approaches. While endonasal methods for C1 instrumentation and C1-2 trans-articular stabilization exist, no hypothetical construct for endonasal occipital instrumentation has been validated. We provide an anatomic description of anterior occipital condyle (AOC) screw endonasal placement as proof-of-concept for endonasal craniocervical stabilization. METHODS: Eight adult, injected cadaveric heads were studied for placing 16 AOC screws endonasally. Thin-cut CT was used for registration. After turning a standard inferior U-shaped nasopharyngeal flap endonasally, 4 mm × 22 mm AOC screws were placed with a 0° driver using neuronavigation. Post-placement CT scans were obtained to determine: site-of-entry, measured from the endonasal projection of the medial O-C1 joint; screw angulation in sagittal and axial planes, proximity to critical structures. RESULTS: Average site-of-entry was 6.88 mm lateral and 9.74 mm rostral to the medial O-C1 joint. Average angulation in the sagittal plane was 0.16° inferior to the palatal line. Average angulation in the axial plane was 23.97° lateral to midline. Average minimum screw distances from the jugular bulb and hypoglossal canal were 4.80 mm and 1.55 mm. CONCLUSION: Endonasal placement of AOC screws is feasible using a 0° driver. Our measurements provide useful parameters to guide optimal placement. Given proximity of hypoglossal canal and jugular bulb, neuronavigation is recommended. Biomechanical studies will ultimately be necessary to evaluate the strength of AOC screws with plate-screw constructs utilizing endonasal C1 lateral mass or C1-2 trans-articular screws as inferior fixation points.

The predictive ability of occipital to C3 angle for dysphagia after occipitocervical fusion in patients with combined C2-3 Klippel-Feil syndrome.

BACKGROUND: Improper occipitocervical alignment after occipitocervical fusion (OCF) may lead to devastating complications, such as dysphagia and/or dyspnea. The occipital to C2 angle (O-C2a), occipital and external acoustic meatus to axis angle (O-EAa) have been used to evaluate occipitospinal alignment. However, it may be difficult to identify the inferior endplate of the C2 vertebra in patients with C2-3 Klippel-Feil syndrome (KFS). The purpose of this study aimed to compare four different parameters for predicting dysphagia after OCF in patients with C2-3 KFS. METHODS: There were 40 patients with C2-3 KFS undergoing OCF between 2010 and 2019. Radiographs of these patients were collected to measure the occipital to C3 angle (O-C3a), O-C2a, occipito-odontoid angle (O-Da), occipital to axial angle (Oc-Axa), and narrowest oropharyngeal airway space (nPAS). The presence of dysphagia was defined as the patient complaining of difficulty or excess endeavor to swallow. Patients were divided into two groups according to whether they had postoperative dysphagia. We evaluated the relationship between each of the angle parameters and nPAS and analyzed their influence to the postoperative dysphagia. RESULTS: The incidence of dysphagia after OCF was 25% in patients with C2-3 KFS. The Oc-Axa, and nPAS were smaller in the dysphagia group compared to non-dysphagia group at the final follow-up (p < 0.05). Receiver-operating characteristic (ROC) curves showed that dO-C3a had the highest accuracy as a predictor of the dysphagia with an area under the curve (AUC) of 0.868. The differences in O-C3a, O-C2a, O-Da, and Oc-Axa were all linearly correlated with nPAS scores preoperatively and at the final follow-up within C2-3 KFS patients, while there was a higher R2 value between the dO-C3a and dnPAS. Multiple linear regression analysis showed that the difference of O-C3a was the only significant predictor for dnPAS (ß = 0.670, p < 0.001). CONCLUSIONS: The change of O-C3a (dO-C3a) is the most reliable indicator for evaluating occipitocervical alignment and predicting postoperative dysphagia in C2-3 KFS patients. Moreover, dO-C3a should be more than - 2° during OCF to reduce the occurrence of postoperative dysphagia.

A novel COL2A1 mutation causing spondyloepiphyseal dysplasia congenita in a Chinese family.

BACKGROUND: Spondyloepiphyseal dysplasia congenita is an autosomal dominant cartilaginous dysplasia characterized by short trunk, abnormal epiphysis, and flattened vertebral body. Skeletal features of SEDC are present at birth and evolve over time. Other features of SEDC include myopia and/or retinal degeneration with retinal detachment and cleft palate. A mutation in the COL2A1 gene located in 12q13.11 is considered as one of the important causes of SEDC. In 2016, Barat-Houari et al. reported a large number of COL2A1 mutations. Among them, a non-synonymous mutation in COL2A1 exon 37, c.2437G>A (p. Gly813Arg), has been reported to cause SEDC in only one patient from France so far. METHODS: We followed up a patient with SEDC phenotype and his family members. The clinical manifestations, physical examination and imaging examination, including X-ray, CT and MRI, were recorded. The whole-exome sequencing was used to detect the patients' genes, and the pathogenic genes were screened out by comparing with many databases. RESULTS: We report a Chinese patient with SEDC phenotype characterized by short trunk, abnormal epiphysis, flattened vertebral body, narrow intervertebral space, dysplasia of the odontoid process, chicken chest, scoliosis, hip and knee dysplasia, and joint hypertrophy. Gene sequencing analysis showed that the patient had a heterozygous mutation (c.2437G>A; p. Gly813Arg) in the COL2A1 gene. No COL2A1 mutation or SEDC phenotype was observed in his family members. This is the first report of SEDC caused by this mutation in an East Asian family. CONCLUSION: This report provides typical clinical, imaging, and genetic evidence for SEDC, confirming that a de novo mutation in the COL2A1 gene, c.2437G>A (p. Gly813Arg), causes SEDC in Chinese population.

Posterolateral epidural supra-C2-root approach (PESCA) for biopsy of lesions of the odontoid process in same sitting after occipitocervical fixation and decompression-perioperative management and how to avoid vertebral artery injury.

This study aims to describe the posterolateral epidural supra-C2-root approach (PESCA), which might be a good alternative to the transoral, anterolateral, and other posterolateral approaches for biopsy of lesions of the odontoid process (OP). The preoperative planning of PESCA included computerized tomography (CT), CT-angiography, and three-dimensional reconstruction (if possible, even with three-dimensional print) to analyze the angle of the trajectory and the anatomy of the vertebral artery (VA). For PESCA, the patient is positioned under general anesthesia in prone position. In case of an osteolytic lesion with fracture of the OP, an X-ray is performed after positioning to verify anatomic alignment. In the first step, in case of instability and compression of the spinal cord, a craniocervical fusion and decompression is performed (laminectomy of the middle part of the C1 arc and removal of the lower part of the lateral C1 arc). The trajectory is immediately above the C2 root (and under the upper rest of the lateral part of C1 arc). Even if the trajectory is narrowed, it is possible to perform PESCA without relevant traction of the spinal cord. The vertical segment of V3 of the VA at the level of C2 is protected by the vertebral foramen, and the horizontal part of V3 is protected by the remnant upper lateral part of the C1 arc (in case of normal variants). PESCA might be a good choice for biopsy of selected lesions of the OP in same sitting procedure after craniocervical stabilization and decompression.

Surgical treatment for basilar invagination with irreducible atlantoaxial dislocation: transoral atlantoaxial reduction plate fixation vs occipitocervical fixation.

BACKGROUND: Transoral atlantoaxial reduction plate (TARP) fixation or occipitocervical fixation (OF) is an effective treatment for basilar invagination (BI) with irreducible atlantoaxial dislocation (IAAD). But, all current clinical studies involved a single surgical procedure. The clinical effects of TARP and OF operation for BI with IAAD have yet to be compared. We therefore present this report to compare the treatment of TARP and OF procedure for BI with IAAD. METHODS: Fifty-six patients with BI with IAAD who underwent TARP or OF operation from June 2011 to June 2017 were retrospectively analyzed. Among these, 35 patients underwent TARP operation (TARP group), and 21 patients underwent OF operation (OF group). We compared the difference of clinical, radiological, and surgical outcomes between the TARP and OF groups postoperatively. RESULTS: Compared with OF group, the operative time and blood loss in TARP group were lower. There was no statistical difference in the atlantodental interval (ADI), clivus canal angle (CCA), cervicomedullary angle (CMA), distance between the top of the odontoid process and the Chamberlain line (CL) and Japanese Orthopaedic Association (JOA) score between the TARP and OF groups preoperatively, but the improvements of these parameters in the TARP group were superior to those in the OF group postoperatively. The fusion rates were higher in the TARP group than those in the OF group at the early stage postoperatively. CONCLUSIONS: TARP and OF operations are effective surgical treatment for BI with IAAD, but the performance of reduction and decompression and earlier bone fusion rates of TARP procedure are superior to those of OF.

Post-operative regression of retro-odontoid pseudotumors treated with and without fusion.

PURPOSE: Retro-odontoid pseudotumor is common in elderly people and is a cause of cervical myelopathy. The goal of the study was to investigate surgical procedures, outcomes, and post-operative spontaneous regression of posterior cervical retro-odontoid pseudotumors. METHODS: The subjects were 29 patients who underwent surgery for myelopathy due to a retro-odontoid pseudotumor around the craniocervical region at 9 facilities and were followed-up for an average of 54 months (range 12-96 months). Data were collected in a multicenter review of a retrospective database. Comparisons were performed between cases treated with and without fusion. RESULTS: The JOA recovery rate at final follow-up did not differ significantly between the fusion (n = 17, including all 15 patients with atlantoaxial subluxation) and non-fusion (n = 12) groups. However, pseudotumor regression was significantly more frequent in the fusion group (100% vs. 42%, p < 0.01). In all patients, regression cases had significantly higher rates of contrast enhancement of the pseudotumor on pre-operative T1 gadolinium-enhanced MRI (68% vs. 14%, p = 0.013) and of JOA recovery (50% vs. 30%, p < 0.01). CONCLUSIONS: Regression of pseudotumor occurred in all cases treated with fusion surgery. There was a significant difference in pseudotumor regression with or without fusion, and regression was significantly related to gadolinium enhancement on MRI. Therefore, it is preferable to use fusion surgery for a retro-odontoid pseudotumor that shows contrast enhancement, even if there is no apparent instability pre-operatively. These slides can be retrieved under Electronic Supplementary Material.

[Rheumatoid atlanto-axial dislocation: a surgical approach]. / Atlantoaksial'nye dislokatsii revmatoidnogo geneza: khirurgicheskaia taktika.

Pathological processes in the craniovertebral region (CVR) are usually accompanied by dislocation complications leading to gross neurological disorders. One of the diseases that affect the CVR and lead to atlanto-axial dislocation (AAD) is rheumatoid arthritis. Errors in the diagnosis of rheumatoid disease and in the choice of a treatment approach may cause adverse outcomes. OBJECTIVE: To define the approach for surgical treatment of AAD associated with rheumatoid disease of the CVR, with allowance for the rigidity of deformity. MATERIAL AND METHODS: Five patients with rheumatoid AAD, 4 females and 1 male, aged 54 to 73 years underwent surgery. All dislocations were anterior ones. Three patients had mobile pannus-associated dislocation. In 2 cases, AAD was rigid and combined with odontoid invagination into the foramen magnum (FM). RESULTS: In all mobile AAD cases, decompression of the brainstem and restoration of the normal anatomical relationships in the CVR were achieved by dislocation correction and atlanto-axial fusion performed from the posterior approach, avoiding transoral interventions. In this case, spontaneous resorption of the pannus occurred within several months after surgery. In the postoperative period, all patients achieved significant regression of pain and neurological disorders. Complications in the form of wound infection developed in 1 case. CONCLUSION: A decision algorithm for choosing a surgical treatment option was based on the degree of deformity stability. Mobile AADs serve as an indication for indirect decompression using instrumental correction of dislocation and atlantoaxial fixation from the posterior approach. In the case of fixed AAD, posterior fixation is complemented by anterior decompression via the transoral approach.

Anterior transoral atlantoaxial release and posterior instrumented fusion for irreducible congenital basilar invagination.

PURPOSE: Recently, it has been demonstrated that anterior release of tight structures via a transoral approach can assist posterior distraction-reduction technique in restoring the cranio-cervical anatomy in irreducible atlantoaxial dislocations. Our aim was to evaluate the radiological and clinical outcome of anterior release and posterior instrumentation for irreducible congenital basilar invagination. METHODS: A consecutive series of 15 patients (2007-2009) with irreducible congenital basilar invagination were treated with anterior release using transoral approach. A retrospective chart review was performed. All patients presented with myelopathy. Dislocation was treated as irreducible if acceptable reduction was not achieved with traction under general anesthesia and neuromuscular paralysis. The anterior release comprised of transverse sectioning the longus colli and capitis, C1-C2 joint capsular release and intra-articular adhesiolysis with or without anterior C1 arch excision. Cantilever mechanism using posterior instrumentation was used to correct any residual malalignment. RESULTS: Mean age was 21.4 (10-50) years. Average duration of follow-up was 28 (24-40) months. The average preoperative JOA score was 11.4 (8-16), which improved to 15.4 (10-18) after surgery. Anatomical reduction was achieved in thirteen patients. Fusion was documented in all patients. Complications included persistent nasal phonation in one, and superficial wound dehiscence in one. CONCLUSION: We believe that a significant number of irreducible dislocations can be anatomically reduced with this procedure thus avoiding odontoid excision. Encouraging results from this short series have given us a new perspective in dealing with these challenging problems.

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.

Radiographic Prediction of the Occipito-C2 Angle Variation with Changes in Distance between the Mandible and Cervical Vertebrae: A Preliminary Study.

The Occipito (O) -C2 angle reflects the correct craniocervical spine alignment; however, the poor image quality of standard intraoperative fluoroscopy at times lead to inaccurate measurements. Herein, we preliminarily investigated the relationship between the O-C2 angle and the Gonion-C2 distance, which is based on the positioning of the mandible and the cervical spine. We enrolled patients who underwent cervical spine radiography in neutral, flexion, and extension positions from January 2020 to October 2020. The difference by posture changes for each parameter was defined as the Δ value, and the Spearman's rank correlation coefficient was determined. Furthermore, we determined the cutoff value of the ΔGonion-C2 distance to predict a decrease of > 10° in the ΔO-C2 angle, which is reported to be related to dysphagia and dyspnea. Seventy-four patients were included. Spearman's rank correlations for the neutral, flexion, and extension positions were 0.630 (P < 0.001), 0.471 (P < 0.001), and 0.625 (P < 0.001), respectively, while the cutoff values of the ΔGonion-C2 distance for predicting > 10° in the ΔO-C2 angle were 9.3 mm for the neutral flexion change (sensitivity: 0.435, specificity: 0.882) and 8.3 mm for the extension-neutral change (sensitivity: 0.712, specificity: 0.909). The O-C2 angle and Gonion-C2 distances correlated; however, this correlation was weaker in the flexed position. Nevertheless, the ΔGonion-C2 distance can be used as a warning sign for postoperative complications after posterior occipital bone fusion surgery, because a decrease of > 10° in the ΔO-C2 angle can be predicted with high specificity.

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.

Neurosurgical management of patients with Ehlers-Danlos syndrome: A descriptive case series.

Introduction: Ehlers-Danlos syndrome (EDS) is a connective tissue disorder that has been linked to several neurological problems including Chiari malformations, atlantoaxial instability (AAI), craniocervical instability (CCI), and tethered cord syndrome. However, neurosurgical management strategies for this unique population have not been well-explored to date. The purpose of this study is to explore cases of EDS patients who required neurosurgical intervention to better characterize the neurological conditions they face and to better understand how neurosurgeons should approach the management of these patients. Methods: A retrospective review was done on all patients with a diagnosis of EDS who underwent a neurosurgical operation with the senior author (FAS) between January 2014 and December 2020. Demographic, clinical, operative, and outcome data were collected, with additional radiographic data collected on patients chosen as case illustrations. Results: Sixty-seven patients were identified who met the criteria for this study. The patients experienced a wide array of preoperative diagnoses, with Chiari malformation, AAI, CCI, and tethered cord syndrome representing the majority. The patients underwent a heterogeneous group of operations with the majority including a combination of the following procedures- suboccipital craniectomy, occipitocervical fusion, cervical fusion, odontoidectomy, and tethered cord release. The vast majority of patients experienced subjective symptomatic relief from their series of procedures. Conclusions: EDS patients are prone to instability, especially in the occipital-cervical region, which may predispose these patients to require a higher rate of revision procedures and may require modifications in neurosurgical management that should be further explored.

C1 Lateral Mass Screw Placement Through Endonasal Corridor for Purpose of O-C1 Fusion: Morphometric Analysis in Cadaveric Specimens.

BACKGROUND: Odontoidectomy may pose some risks for O-C1 and/or C1-C2 instability, with previous authors reporting techniques for endonasal C1-C2 fusion. However, no technique for endonasal O-C1 fusion currently exists. We sought to describe the feasibility of endonasal anterior C1 (AC1) screw placement for endonasal O-C1 fusion. METHODS: Seven adult cadaveric heads were studied for endonasal placement of 14 C1 screws. Using thin-cut computed tomography (CT)-based "snapshot" neuronavigation assistance, 4 mm x 22 mm screws were placed in the C1 lateral mass using a 0° driver. Post-placement CT scans were obtained to determine site-of-entry measured from C1 anterior tubercle, screw angulation in axial and sagittal planes, and screw proximity to the central canal and foramen transversarium. RESULTS: Average site-of-entry was 16.57 mm lateral, 2.23 mm rostral, and 5.53 mm deep to the anterior-most portion of the C1 ring. Average axial angulation was 19.49° lateral to midline, measured at the C1 level. Average sagittal angulation was 13.22° inferior to the palatal line, measured from the hard palate to the opisthion. Bicortical purchase was achieved in 11 screws (78.6%). Partial breach of the foramen transversarium was observed in 2 screws (14.3%), violation of the O-C1 joint space in 1 (7.1%), and violation of the central canal in 0 (0%). Average minimum screw distances from the unviolated foramen transversaria and central canal were 1.97 mm and 4.04 mm. CONCLUSIONS: Navigation-assisted endonasal placement of AC1 screws is feasible. Additional studies should investigate the biomechanical stability of anterior C1 screw-plating systems, with anterior condylar screws as superior fixation point, compared to traditional posterior O-C1 fusion.

Posterior midline approach to odontoidectomy: A novel method to treat basilar invagination.

Background: Basilar invagination (BI) is a common malformation of the craniocervical region where the odontoid process protrudes into the foramen magnum. Surgery in this region is difficult because of the complex anatomy of the craniocervical junction. Serious life-threatening complications have been observed with previously described approaches. Therefore, we conceived a novel surgical approach that can be implemented by neurosurgeons with different skill levels to facilitate better outcomes. Methods: We describe a new surgical technique for the treatment of BI that we used in two patients in whom cervical myelopathy and direct ventral compression of the cervicomedullary junction were confirmed through clinical and radiological findings. We present the technique of posterior odontoidectomy in a step-by-step, didactic, and practical manner with surgical tips and tricks. Results: The resection was completed without intraoperative or postoperative complications in both cases. The patients experienced substantial neurological improvements, and full recovery was observed during the 9-month and 12-month follow-up visits after discharge. Compared with the transoral approach, our technique provides a larger decompression area. Conclusions: We describe a novel method for the treatment of BI that was applied in two patients and suggest that the posterior approach might be a safe and effective method for ventral decompression of the craniocervical junction. Posterior odontoidectomy followed by craniocervical fixation helped achieve complete cervicomedullary decompression.

[Research on effectiveness of occipito-odontoid angle in predicting dysphagia after occipitocervical fusion in patients with C 2, 3 Klippel-Feil syndrome].

Objective: To introduce a new occipitocervical angle parameter, occipito-odontoid angle (O-Da), for predicting dysphagia after occipitocervical fusion (OCF) in patients with C 2, 3 Klippel-Feil syndrome (KFS) and analyze its effectiveness. Methods: A total of 119 patients met selective criteria between April 2010 and November 2019 were retrospectively included as the study subjects. There were 56 males and 63 females. The age ranged from 14 to 76 years, with a median age of 51 years. There were 44 cases of basilar invagination and 75 cases of atlantoaxial subluxation. Forty patients were combined with C 2, 3 KFS. Seven patients underwent anterior decompression combined with posterior OCF and 112 patients underwent posterior OCF. The fixed segments were O-C 2 in 36 cases, O-C 3 in 51 cases, O-C 4 in 25 cases, and O-C 5 in 7 cases. All patients were followed up 21-136 months, with a median time of 79 months. The lateral cervical X-ray films before operation and at last follow-up were used to measure the occipital to C 2 angle (O-C 2a), the occipital and external acoustic meatus to axis angle (O-EAa), the occipital protuberance to axial angle (Oc-Axa), the O-Da, and the narrowest oropharyngeal airway space (nPAS). The differences of the above parameters between the last follow-up and the preoperative values were calculated (represented as dO-C 2a, dO-EAa, dOc-Axa, dO-Da, and dnPAS). Patients were divided into two groups according to whether they suffered dysphagia after operation, and the differences in clinical data and radiographic parameters were compared between the two groups. The correlation between occipitocervical angle parameters and nPAS in 40 patients with C 2, 3 KFS was analyzed respectively. In addition, sensitivity and specificity analyses were used to assess the effectiveness of dO-Da≤-5° for the prediction of postoperative dysphagia. Results: Thirty-one patients (26.1%) suffered dysphagia after OCF (dysphagia group), including 10 patients with C 2, 3 KFS; no dysphagia occurred in 88 patients (non-dysphagia group). There was no significant difference in age, follow-up time, fixed segment, proportion of patients with rheumatoid arthritis, proportion of patients with atlantoaxial subluxation, and proportion of patients with C 2, 3 KFS between the two groups ( P>0.05). The proportion of female patients was significantly higher in dysphagia group than in non-dysphagia group ( χ 2=7.600, P=0.006). The difference in preoperative O-C 2a between the two groups was significant ( t=2.528, P=0.014). No significant differences were observed in preoperative O-EAa, Oc-Axa, O-Da, and nPAS ( P>0.05). There was no significant difference in dO-C 2a, dO-EAa, dOc-Axa, dO-Da, and dnPAS between the two groups ( P>0.05). The dO-C 2a, dO-EAa, dOc-Axa, and dO-Da were positively correlated with dnPAS in 40 patients with C 2, 3 KFS ( r=0.604, P<0.001; r=0.649, P<0.001; r=0.615, P<0.001; r=0.672, P<0.001). Taking dO-Da≤-5° as the standard, the sensitivity and specificity of dO-Da to predict postoperative dysphagia in patients with C 2, 3 KFS were 80.0% (8/10) and 93.3% (28/30), respectively. Conclusion: The dO-Da is a reliable indicator for predicting dysphagia after OCF in patients with C 2, 3 KFS.

Traumatic posterior atlantoaxial dislocation without fracture of the odontoid process: illustrative case.

BACKGROUND: Traumatic posterior atlantoaxial dislocation without fracture of the odontoid process is extremely rare. Only 24 cases have been documented since the first patient was reported by Haralson and Boyd in 1969. Although various treatment strategies are reported, no consensus has been yielded. OBSERVATIONS: A 58-year-old man experienced loss of consciousness and breathing difficulties after being struck by a car from behind. An immediate computed tomography scan showed subarachnoid hemorrhage, a posterior atlantoaxial dislocation without C1-2 fracture, and a right tibiofibular fracture. After the patient's respiration and hemodynamics were stabilized, closed reduction was attempted. However, this strategy failed due to unbearable neck pain and quadriplegia, resulting in surgical intervention with transoral odontoidectomy and posterior occipitocervical fusion. The patient developed postoperative central nervous system infection. After anti-infective and drainage treatment, the infection was controlled. At 1-year follow-up, the patient did not complain of special discomfort and was generally in good condition. LESSONS: The authors report their experience with transoral odontoidectomy and concomitant posterior occipitocervical fusion in a case of posterior atlantoaxial dislocation without related fracture. Although these procedures are highly feasible and effective, particular attention should be paid to their complications, such as postoperative infection.

Staged Repositioning in Endoscopic Endonasal Odontoidectomy Maximizes Decompression While Allowing Preservation of the C1 Anterior Arch: A Technical Note.

BACKGROUND: Preservation of the anterior arch of C1 in endoscopic endonasal odontoidectomy has been proposed as an alternative to complete C1 arch resections, potentially affording less destabilization of the craniocervical junction. Nonetheless, this approach may limit the decompression achieved. In this case, intraoperative repositioning allowed maximal decompression while preserving the anterior arch of C1. METHODS: A 79-year-old woman presented with suboccipital pain caused by an expansile and compressive mass centered on the dens. Notably, the mass occluded both vertebral arteries resulting in small cerebellar strokes. An endoscopic endonasal approach for diagnosis and decompression was performed followed by posterior fixation. RESULTS: Given the significant compression, the patient was initially positioned in slight cervical extension. After rhinopharyngeal flap harvest, the top half of the anterior arch of C1 was resected, maintaining its structural integrity. The odontoidectomy was completed flush to the superior border of the reduced C1 arch. After an intraoperative computed tomography (CT) scan, performed in a neutral position, the patient was then repositioned with cervical flexion. This maneuver presented the residual odontoid above the C1 arch, but, given the partial removal of the dens, it did not result in any change in neuromonitoring. Further odontoid resection was then completed and follow-up CT scan revealed maximal dens removal, extending below the C1 anterior arch in neutral position. CONCLUSIONS: In cases of odontoid/atlantoaxial pathology causing significant neural compression, staged intraoperative repositioning can safely maximize the odontoidectomy, while affording preservation of the structural integrity of the anterior arch of C1.

Resolution of retro-odontoid cyst in a patient with atlanto-occipital assimilation after occipitocervical fixation.

BACKGROUND: Fusion of the atlas with the lower part of the occiput is clinically known as atlanto-occipital assimilation (AOA) or atlas occipitalization. This can be either partial or complete depending on the extent of fusion. AOA is one of the most common congenital anomalies of the craniovertebral junction and is usually asymptomatic. CASE DESCRIPTION: An 80-year-old female presented with a retro-odontoid cyst in conjunction with AOA. Following posterior occipitocervical fixation without resection of the cyst, the patient improved, and the postoperative MR documented cyst resolution. CONCLUSION: Patients with AOA and a retro-odontoid cyst may be successfully managed with occipitocervical fixation without resection of the cyst. However, we would recommend preoperative computed tomography angiography to document whether the vertebral artery follows an anomalous course to avoid an intraoperative neurovascular injury.