Are Chiari malformation and basilar invagination associated with jugular foramen stenosis?

OBJECTIVE

To compare the diameter of the jugular foramen (JF) between normal individuals and those with the diagnosis of craniovertebral junction abnormalities, such as Chiari malformation type I (CMI) and/or basilar invagination (BI).

METHODS

This cross-sectional analytical study measured the diameter of right and left JF in magnetic resonance imaging of patients that were split into four groups: 68 with combined CMI and BI (CMI+BI), 42 with isolated BI, 45 with isolated CMI, and 102 control cases. The t test determined sex differences, while univariate ANOVA with Tukey's post-hoc test assessed JF differences between groups.

RESULTS

Considering all combinations of laterality and sex, CMI+BI had JF narrower than their respective controls. The JF was bilaterally narrower in BI than the control, only in females. Regardless of laterality, CMI had wider JF than the CMI+BI in males, and it did not differ from the control. In the females of CMI, the right JF did not differ from the control, and it was wider than the CMI+BI; while the left JF was narrower than the control, and it did not differ from the CMI+BI.

CONCLUSION

JF narrowing is associated with CMI and BI when they are found combined in the same patient. When CMI or BI are detected separately, they do not imply evident changes in JF morphometry. It is expected that these findings could bring empiric substrate to support theories that claims a possible role of intracranial pressure disturbances as a triggering factor for CMI.

Release, reduction, and fixation of one-stage posterior approach for basilar invagination with irreducible atlantoaxial dislocation

PURPOSE

We evaluate the efficacy, safety and indications of single stage posterior release, reduction, and fixation of basilar invagination (BI) with irreducible atlantoaxial dislocation (IAAD).

MATERIALS AND METHODS

Seventeen patients with BI and IAAD consecutively underwent one-stage release, reduction, and fixation by a posterior approach from July 2000 to June 2015 were followed up for at least 12 months. There were 8 males. Mean age was 56 35.2 ± 13.8 years (range 12-56). The clinical symptoms and signs of the patients were recorded. Pre- and postoperative imaging examinations were performed. Neurological function was assessed using the Japanese Orthopedic Association (JOA) and Ranawat scores.

RESULTS

Average follow-up time was 47.4 months (12-97 months). The JOA score increased from preoperative 4-10 (8.06 ± 2.52) to postoperative 13-16 (15.20 ± 0.62). The preoperative Chamberlain line, McRae line, Wackenheim line, atlantodens interval, and cervico medullary angle were 12.52 ± 5.17 mm, 6.59 ± 3.04 mm, 6.96 ± 4.32 mm, 9.88 ± 1.93 mm, and 115.35 ± 12.40°, respectively. The postoperative values were 2.0 ± 3.67 mm, -3.06 ± 1.85 mm, -1.76 ± 2.88 mm, 1.17 ± 1.18 mm, and 136.76 ± 11.44°, respectively.

CONCLUSION

One-stage release, reduction, and fixation for patients with BI and IAAD through a posterior approach is safe and efficient.

Evaluation of Craniometric Parameters and Efficacy of Posterior Surgical Intervention Types in Basilar Invagination Patients

OBJECTIVE

Basilar invagination is one of the most frequently observed abnormalities at the craniovertebral junction, in which the odontoid process of C2 prolapses into the foramen magnum.

METHODS

The current study included 27 patients who underwent surgery for basilar invagination between October 2013 and January 2023. The study group was divided into 2 groups according to basilar invagination types; type I (the presence of type A atlantoaxial instability and instability is the main pathology) and type II (the presence of type B and C atlantoaxial instability and skull base dysgenesis is the main pathology). Craniometric parameters included in the study were atlantodental interval, posterior atlantodental interval, Chamberlain's line violation, clivus-canal angle, Welcher's basal angle, and Boogaard angle.

RESULTS

The mean age of the patients was 24.30 ± 14.36 years (5-57 years). Fourteen patients (51.9%) were female, and 13 patients (48.1%) were male. Ten patients (37%) had type I basilar invagination, and 17 patients (63%) had type II basilar invagination. Preoperative and postoperative atlantodental interval and Boogaard angle were significantly higher in type I basilar invagination, as preoperative and postoperative posterior atlantodental interval and clivus-canal angle were significantly higher in type II basilar invagination. There was a positive strong correlation between Chamberlain's line violation and Boogaard angle. Postoperative Chamberlain's line violation was significantly higher in occipitocervical fixation (P = 0.035). C1 lateral mass screw fixation was found more successful in Chamberlain's line violation correction than occipital plates. Occipitocervical fixation was found to be associated with higher postoperative Nurick scores (P = 0.015) and complication rates (P = 0.020). Cages applied to the C1-C2 joint space were found to be associated with higher fusion rates (P = 0.023) and lower complication rates (P = 0.024).

CONCLUSIONS

In the present study, it was found that C1-C2 fixation was more successful in correcting craniometric parameters and had lower complication rates than occipitocervical fixation. In appropriate patients, it was determined that cage application increased the success rates of the operations.

A Global Bibliometric and Visualization Analysis of Craniovertebral Junction Bony Abnormalities Based on VOSviewer and Citespace

OBJECTIVE

Recent years have witnessed a rapidly growing interest in CVJ bony abnormalities, and a qualitative and quantitative analysis of relevant literatures is necessary. This study aims to identify and summarize the published articles related to craniovertebral junction bony abnormalities, to analyze and visualize the current research trends and major contributors.

METHODS

We collected data from Web of Science, excluding certain article types. Two researchers screened articles for relevance. Data were organized with EndnoteX9, and analyzed using VOSviewer and CiteSpace for co-authorship, co-occurrence, keyword burst, and co-citation analyses to identify research trends and collaborations.

RESULTS

A total of 2,776 articles were included, revealing an increasing trend in annual publications of CVJ bony abnormalities. The USA was the leading country. King Edward Memorial Hospital was the most prolific institution, and Seth GS Medical College had the most citations. The Spine is the most popular journal with the highest number of publications and citations. Professor Goel Atul from India emerged as the most influential pioneer in this field. Keyword analysis highlighted surgical techniques, diagnosis, and anatomy as the primary research hotspots and Fixation, Placement, and Basilar invagination gradually become the new research trend. However, there is a relative weakness in basic research and epidemiology.

CONCLUSIONS

This study provides valuable insights into the current research trends and critical contributors in CVJ bony abnormalities, guiding evidence-based decisions and fostering international collaborations to advance knowledge in this field.

Neurological outcome following delayed traction and fixation in severe tetraparesis consecutive to posterior decompression for Chiari malformation: a case report

BACKGROUND

Chiari malformation type 1 (CM1) is a congenital hindbrain malformation characterized by herniation of the cerebellar tonsils below the foramen magnum. The term Chiari type 1.5 is used when herniation of the brainstem under the McRae line and anomalies of the craniovertebral junction are also present. These conditions are associated with several symptoms and signs, including headache, neck pain, and spinal cord syndrome. For symptomatic patients, surgical decompression is recommended. When radiographic indicators of craniovertebral junction (CVJ) instability or symptoms related to ventral brainstem compression are present, CVJ fixation should also be considered.

CASE DESCRIPTION

We report the case of a 13-year-old girl who presented with severe tetraparesis after posterior decompression for Chiari malformation type 1.5, followed 5 days later by partial C2 laminectomy. Several months after the initial surgery, she underwent two fixations, first without and then with intraoperative cervical traction, leading to significant neurological improvement.

DISCUSSION AND CONCLUSION

This case report underscores the importance of meticulous radiological analysis before CM surgery. For CM 1.5 patients with basilar invagination, CVJ fixation is recommended, and C2 laminectomy should be avoided. In the event of significant clinical deterioration due to nonadherence to these guidelines, our findings highlight the importance of traction with increased extension before fixation, even years after initial destabilizing surgery.

C1-C2 intraarticular distraction with anterior cervical cages for basilar invagination realignment: Operative technique nuances and review of literature

Neurosurgical management of basilar invagination (BI) has traditionally been aimed at direct cervicomedullary decompression through transoral dens resection or suboccipital decompression with supplemental instrumented fixation. Dr. Goel introduced chronic atlantoaxial dislocation (AAD) as the etiology in most cases of BI and described a technique for distracting the C1-C2 joint with interfacet spacers to achieve reduction and anatomic realignment. We present our modification to Goel's surgical technique, in which we utilize anterior cervical discectomy (ACD) cages as C1-C2 interfacet implants. A young adult male presented to our institution with BI, cervicomedullary compression, occipitalization of C1, and Chiari 1 malformation. There was AAD of C1 over the C2 lateral masses. This reduced some with preoperative traction. He underwent successful C1-C2 interfacet joint reduction and arthrodesis with anterior cervical discectomy (ACD) cages and concomittant occiput to C2 instrumented fusion. BI can be effectively treated through reduction of AAD and by utilizing ACD cages as interfacet spacers.

The role of sphenoid bone in basilar invagination pathophysiology

Basilar invagination (BI) is characterized by rostral dislocation of the cervical spine toward the skull base. The craniometrics of the skull base have shown significant differences among craniocervical junction malformations. The sphenoid bone is the center of the skull base; however, no study has evaluated this bone in cases of BI. This was a cross-sectional study of MRI databanks from two institutions of the author's practice between 1985 and 2020. The craniometrics of the sphenoid bone were measured in BI patients and controls. Fifty-eight MRIs were selected, including 28 BI patients and 30 controls. The mean sphenoid crest-clivus length was 32.66 ± 4.7 mm in the BI group and 29.98 ± 3.0 mm in the control group (p = 0.01). The mean sphenoid planum-top of Dorsum sellae length was 28.53 ± 3.7 mm in the BI group and 26.45 ± 3.2 mm in the control group (p = 0.02). The mean tuberculum sellae-sphenoid floor height was 18.52 ± 4.4 mm in the BI group and 21.32 ± 2.9 mm in the control group (p = 0.00). The mean sella turcica-sphenoid floor height was 10.35 ± 3.8 mm in the BI group and 12.24 ± 3.5 mm in the control group (p = 0.05). The mean clivus length was 29.81 ± 6.3 mm in the BI group and 40.86 ± 4.2 mm in the control group (p = 0.00). The mean sphenoid length was 58.34 ± 7.4 mm in the BI group and 67.31 ± 6.0 mm in the control group (p = 0.00). The mean sphenoid angle was 116.33 ± 8.7° in the BI group and 112.36 ± 6.9° in the control group (p = 0.05). The BI sphenoid bone has shorter vertical dimensions and longer horizontal measures. This morphology promotes a flattening of the sphenoid angle. The sphenoid bone is significantly altered in BI, favoring the congenital hypothesis in the pathophysiology of this disease.

Facet-occiput slope angle: A novel predictor of cage placement feasibility during surgery in basilar invagination patients

Background and aim

Direct posterior reduction and manipulation of the C1-2 joints, accompanied by placement of spacers, is the state-of-the-art technique for treating basilar invagination (BI) and atlantoaxial dislocation (AAD). The hindrance of occiput to reaching up to the true atlantoaxial facets (AAF) during the surgery remains challenging for cage placement. The aim of this study was to explore an objective and precise method of measuring the effect of the hindrance of occiput to reaching up to the true AAF and cage placement during surgery.

Method

We collected the clinico-imaging data of 58 patients with BI and AAD (Group A) who underwent surgery in our hospital, and 78 control cohorts (Group B) were retrieved retrospectively. We measured facet-occiput slope angle (FOSA) in midsagittal CT. Patients were positioned prone for surgery based on preoperative flexion O-C2a, and access to the true AAF was observed intraoperatively. The cut-off value of FOSA for the feasibility of cage placement in BI and AAD patients was appointed when access to the true AAF was impossible due to the hindrance of occiput during surgery.

Results

The cut-off value of FOSA for the feasibility of cage placement was 34o with an area under the curve AUC of 0.800 (95 % CI: 0.672-0.928, P < 0.001) and the Youden index of 0.607. In patients with FOSA >34o, reaching up to the true AAF and 3D-printed cage placement was impossible. FOSA was negative in Group A and positive in Group B, significantly larger in females compared to males in both groups and significantly larger postoperatively in Group A.

Conclusion

FOSA can objectively measure the feasibility of cage placement when the patient is positioned prone per preoperative flexion O-C2a. A FOSA >34o is contraindication for cage placement.

Anatomical Implications of Chiari I and Basilar Invagination (Type B) in the IV Ventricle and Cisterna Magna

OBJECTIVE

To analyze the anatomical changes of the IV ventricle and cisterna magna in the Chiari malformation I (CMI) and basilar invagination (type B).

METHODS

This is a controlled study with 161 exams of magnetic resonance imaging (MRI) of adults grouped into control (n = 37), basilar invagination (BI; n = 31), Chiari malformation I (CMI; n = 37), and CMI+BI (n = 56). The MRIs were analyzed using the visualization software Osirix (Pixmeo, Bernex, Geneva, version 3.8.2). The morphometric variables were: distance from the obex to the McRae line; length of the IV ventricle floor; and the area and volume of the cisterna magna. The univariate ANOVA followed by Tukey's post-hoc test was applied to evaluate the difference between the groups. The difference between sexes was evaluated by the t test for each group.

RESULTS

Alterations in the cisterna magna and IV ventricle were more evident only in the CMI and CMI+BI groups. For both sexes, the CMI and CMI+BI groups showed: a reduction in the CSF space (P < 0.001), cisterna magna with volume reduction (P < 0.001), low position of the obex (P < 0.001), and IV ventricle more elongated (male P = 0.007 and female P < 0.001). The BI group had no significant change in the analysis by sex.

CONCLUSIONS

The CMI (isolated and associated with BI) showed a low obex position and elongation of the IV ventricle due to traction towards the spinal canal. The reduction of cisterna magna volume added to the occupation of the cerebellar tonsils can impact in the cerebrospinal fluid dynamics. The BI when isolated was not related to alterations in the parameters of cerebrospinal fluid spaces studied.

Characteristics and evaluation of C1 posterior arch variation for transpedicular screw placement between patients with and without basilar invagination

BACKGROUND

C1 transpedicular screw (C1TS) placement provided satisfactory pullout resistance and 3D stability, but its application might be limited in patients with basilar invagination (BI) due to the high incidences of the atlas anomaly and vertebral artery (VA) variation. However, no study has explored the classifications of C1 posterior arch variations and investigated their indications and ideal insertion trajectories for C1TS in BI.

PURPOSE

To investigate the bony and surrounding arterial characteristics of the atlas, classify posterior arch variations, identify indications for C1TS, evaluate ideal insertion trajectories for C1TS in BI patients without atlas occipitalization (AO), and compare them with those without BI and AO as control.

METHODS

A total of 130 non-AO patients with and without BI (52 patients and 78 patients, respectively) from two medical centers were included at a 1:1.5 ratio. The posterior arch variations were assessed using a modified C1 morphological classification. Comparisons regarding the bony and surrounding arterial characteristics, morphological classification distributions, and ideal insertion trajectories between BI and control groups were performed. The subgroup analyses based on different morphological classifications were also conducted. In addition, the factors possibly affecting the insertion parameters were investigated using multiple linear regression analyses.

RESULTS

The BI group was associated with significantly smaller lateral mass height and width, sagittal length of posterior arch, pedicle height, vertical height of posterior arch, and distance between VA and VA groove (VAG) than control group. Four types of posterior arch variations with indications for different screw placement techniques were classified; Classifications I and II were suitable for C1TS. The BI cohort showed a significantly lower rate of Classification I than the control cohort. In the BI group, the subgroup of Classification I had significantly larger distance between the insertion point (IP) and inferior aspect of the posterior arch. In addition, it had the narrowest width along ideal screw trajectory, but a significantly more lateral ideal mediolateral angle than the subgroup of Classification II. Multiple linear regression indicated that the cephalad angle was significantly associated with the diagnosis of BI (B = 3.708, P < 0.001) and sagittal diameter of C1 (B = 3.417, P = 0.027); the ideal mediolateral angle was significantly associated with BMI (B = 0.264, P = 0.031), sagittal diameter of C1 (B =  - 4.559, P = 0.002), and pedicle height (B =  - 2.317, P < 0.001); the distance between the IP and inferior aspects of posterior arch was significantly associated with age (B =  - 0.002, P = 0.035), BMI (B =  - 0.007, P = 0.028), sagittal length of posterior arch (B =  - 0.187, P = 0.032), pedicle height (B =  - 0.392, P < 0.001), and middle and lower parts of posterior arch (B = 0.862, P < 0.001).

CONCLUSION

The incidence of posterior arch variation in BI patients without AO was remarkably higher than that in control patients. The insertion parameters of posterior screws were different between the morphological classification types in BI and control groups. The distance between VA V3 segments and VAG in BI cohort was substantially smaller than that in control cohort. Preoperative individual 3D computed tomography (CT), CT angiography and intraoperative navigation are recommended for BI patients receiving posterior screw placement.

Treatment of Chiari malformations with craniovertebral junction anomalies: Where do we stand today?

Background

Chiari malformation type 1 (CM-1) is characterized by cerebellar tonsil herniation through the foramen magnum and can be associated with additional craniovertebral junction anomalies (CVJA). The pathophysiology and treatment for CM-1 with CVJA (CM-CVJA) is debated.

Objective

To evaluate the trends and outcomes of surgical interventions for patients with CM-CVJA.

Methods

A systematic review of the literature was performed to obtain articles describing surgical interventions for patients with CM-CVJA. Articles included were case series describing surgical approach; reviews were excluded. Variables evaluated included patient characteristics, approach, and postoperative outcomes.

Results

The initial query yielded 403 articles. Twelve articles, published between 1998-2020, met inclusion criteria. From these included articles, 449 patients underwent surgical interventions for CM-CVJA. The most common CVJAs included basilar invagination (BI) (338, 75.3%), atlantoaxial dislocation (68, 15.1%) odontoid process retroflexion (43, 9.6%), and medullary kink (36, 8.0%). Operations described included posterior fossa decompression (PFD), transoral (TO) decompression, and posterior arthrodesis with either occipitocervical fusion (OCF) or atlantoaxial fusion. Early studies described good results using combined ventral and posterior decompression. More recent articles described positive outcomes with PFD or posterior arthrodesis in combination or alone. Treatment failure was described in patients with PFD alone that later required posterior arthrodesis. Additionally, reports of treatment success with posterior arthrodesis without PFD was seen.

Conclusion

Patients with CM-CVJA appear to benefit from posterior arthrodesis with or without decompressive procedures. Further definition of the pathophysiology of craniocervical anomalies is warranted to identify patient selection criteria and ideal level of fixation.

Transcervical, retropharyngeal odontoidectomy - Anatomical considerations

Context

Anterior craniocervical junction lesions have always been a challenge for neurosurgeons. Presenting with lower cranial nerve dysfunction and symptoms of brainstem compression, decompression is often required. While posterior approaches offer indirect ventral brainstem decompression, direct decompression via odontoidectomy is necessary when they fail. The transoral and endoscopic endonasal approaches have been explored but come with their own limitations and risks. A novel retropharyngeal approach to the cervical spine has shown promising results with reduced complications.

Aims

This study aims to explore the feasibility and potential advantages of the anterior retropharyngeal approach for accessing the odontoid process.

Methods and Surgical Technique

To investigate the anatomical aspects of the anterior retropharyngeal approach, a paramedian skin incision was performed below the submandibular gland on two cadaveric specimens. The subcutaneous tissue followed by the platysma is dissected, and the superficial fascial layer is opened. The plane between the vascular sheath laterally and the pharyngeal structures medially is entered below the branching point of the facial vein and internal jugular vein. After reaching the prevertebral plane, further dissection cranially is done in a blunt fashion below the superior pharyngeal nerve and artery. Various anatomical aspects were highlighted during this approach.

Results

The anterior, submandibular retropharyngeal approach to the cervical spine was performed successfully on two cadavers highlighting relevant anatomical structures, including the carotid artery and the glossopharyngeal, hypoglossal, and vagus nerves. This approach offered wide exposure, avoidance of oropharyngeal contamination, and potential benefit in repairing cerebrospinal fluid fistulas.

Conclusions

For accessing the craniocervical junction, the anterior retropharyngeal approach is a viable technique that offers many advantages. However, when employing this approach, surgeons must have adequate anatomical knowledge and technical proficiency to ensure better outcomes. Further studies are needed to enhance our anatomical variations understanding and reduce intraoperative risks.

Congenital atlanto-occipital dislocation in a patient with Down syndrome: a case report

Down syndrome, also known as trisomy 21, is associated with congenital cervical spine abnormalities, including atlantoaxial instability with or without os odontoideum, atlanto-occipital instability, and hypoplasia of the atlas. Herein, we report a case of Down syndrome complicated by congenital atlanto-occipital dislocation. The patient presented with severe cervical myelopathy at 13 years of age after a 10-year follow-up. Radiography and computed tomography revealed os odontoideum protruding into the foramen magnum and congenital anterior atlanto-occipital dislocation. Additionally, a bifurcated internal occipital crest with a thinned central portion of the occipital bone was noted. Magnetic resonance imaging revealed kyphotic alignment of the spinal cord with severe compression at the foramen magnum level. As the neurological impairment was partially improved by halo vest immobilization, we performed in situ O-C2 fusion with an iliac autograft and decompression of the foramen magnum and posterior arch of C1. An improvement was observed immediately after surgery. Two years after surgery, radiography and computed tomography showed solid O-C2 segment fusion. The accumulation of similar cases is essential for determining the prognosis or optimal treatment for this rare congenital condition.

The Morphological Evaluation of the Cervical Muscle in Patients With Basilar Invagination: A Magnetic Resonance Imaging-Based Study

OBJECTIVE

To investigate the characteristics of functional muscle and muscle size in patients with basilar invagination (BI) and explore the effects of atlantoaxial dislocation.

METHODS

Eighty BI patients (BI group) and 80 age- and sex-matched asymptomatic people (control group) were included. Axial T2 magnetic resonance imaging image was used to measure the cross-sectional area (CSA) and functional CSA (FCSA). The sternocleidomastoid (SCM), longus capitis and longus colli (LCap & LC), trapezius (Trap), splenius capitis (SpCap), splenius cervicis (SpC), semispinalis capitis (SSCap), semispinalis cervicis (SSC), multifidus (MS), levator scapulae (LS) and posterior deep layer muscles (PDLM) were evaluated. Correlations between age, atlantodental interval (ADI), Chamberlain distance and muscles were observed.

RESULTS

BI group (39.4 ± 18.4 years; 33 males/47 females) exhibited significantly lower FCSA/CSA ratios than the control group in all extensor and flexor muscles, and presented smaller CSAs on the right and left Trap, SSC, LS, SCM, and left LCap & LC. FCSA/CSA ratios were significantly lower in BI patients with dislocation on the right Trap, SpCap, SpC, SSCap, MS, LS, LCap & LC, and PDLM, and the left SSCap, MS, and LCap & LC than in patients without deformity. Additionally, functional muscles of all parameters decreased with age in BI patients. Excluding children, the Trap, SpC, MS, and LS muscle sizes of BI patients tended to increase with age. ADI and Chamberlain distance tended to correlate negatively with FCSA/CSA ratio.

CONCLUSION

The BI patients, especially those with atlantoaxial dislocation, had less functional muscles compared with the control group. Moreover, their functional muscles decreased with age more obviously.

Modified interfacet technique using shaped autologous occipital bone mass for basilar invagination

PURPOSE

In economically undeveloped areas, surgery for basilar invagination (BI) is still a serious economic burden for people. This study introduces a modified interfacet technique for the treatment of BI using shaped autologous occipital bone mass to reduce BI and to save economical expenditure.

METHODS

The data of 6 patients with BI who underwent modified interfacet technique using shaped autologous occipital bone mass in our hospital from April 2020 to February 2021 were retrospectively analyzed. During the operation, osteotomy at the external occipital protuberance was performed using ultrasonic osteotome, followed by interfacet release and implantation of shaped autologous occipital bone mass to complete vertical reduction. The atlantodental interval (ADI), Chamberlain's line violation (CLV), clivo-axial angle (CXA) and cervico-medullary angle (CMA) were compared before and after surgery. Additionally, we observed implant stability during the follow-up period to assess the long-term success of the modified interfacet technique.

RESULTS

The surgical procedure was successful in all six patients, with no reported incidents of vascular injury, spinal cord injury, or dural tear. Following the operation, improvements were observed in the ADI, CLV, CXA, and CMA. Throughout the follow-up period, the implants remained stable, demonstrating no complications such as bone resorption of the autologous occipital bone mass, implant fracture, or displacement.

CONCLUSION

The utilization of shaped autologous occipital bone mass in atlantoaxial interfacet bone grafting has demonstrated effectiveness and feasibility. This technique offers simplicity, ease of preparation, and cost-effectiveness, making it a viable option for treating BI.

Intra-articular Distraction Versus Decompression to Treat Basilar Invagination Without Atlantoaxial Dislocation: A Retrospective Cohort Study of 54 Patients

OBJECTIVE

The surgical management of basilar invagination without atlantoaxial dislocation (type B basilar invagination) remains controversial. Hence, we have reported the use of posterior intra-articular C1-2 facet distraction, fixation, and cantilever technique versus foramen magnum decompression in treating type B basilar invagination as well as the results and surgical indications for this procedure.

METHODS

This was a single-center retrospective cohort study. Fifty-four patients who underwent intra-articular distraction, fixation, and cantilever reduction (experimental group) and foramen magnum decompression (control group) were enrolled in this study. Distance from odontoid tip to Chamberlain's line, clivus-canal angle, cervicomedullary angle, craniovertebral junction (CVJ) triangle area, width of subarachnoid space and syrinx were used for radiographic assessment. Japanese Orthopedic Association (JOA) scores and 12-item Short Form health survey (SF-12) scores were used for clinical assessment.

RESULTS

All patients in the experimental group had a better reduction of basilar invagination and better relief of pressure on nerves. JOA scores and SF-12 scores also had better improvements in the experimental group postoperation. SF-12 score improvement was associated with preoperative CVJ triangle area (Pearson index, 0.515; p = 0.004), cutoff value of 2.00 cm2 indicating the surgical indication of our technique. No severe complications or infections occurred.

CONCLUSION

Posterior intra-articular C1-2 facet distraction, fixation, and cantilever reduction technique is an effective treatment for type B basilar invagination. As various factors involved, other treatment strategies should also be investigated.

Endoscopic endonasal odontoidectomy for basilar invagination in children: literature review and case report

BACKGROUND

Basilar invagination (BI) is an uncommon clinical condition of the craniocervical junction (CCJ). Surgical management depends on 2 factors: mobility and reducibility; in cases of irreducible dislocation or persistent compression, odontoidectomy should be considered.

CASE DISCUSSION

We present the case of a 13-year-old boy with severe BI, causing cervical myelopathy with progressive gait disorder. The patient underwent cervical traction followed by posterior decompression and occipitocervical fusion. Postoperatively, symptoms initially improved, until new neurological deterioraton set in 4 months later. Follow-up neuroimaging showed compression of the bulbo-medullary junction, with severe brainstem kinking and appearance of a cervical syrinx. Secondary surgery via an endoscopic endonasal approach (EEA) was deemed necessary to relieve the compression. Postoperative course was unremarkable, with steady clinical improvement and a return to independent activities of daily living within 6 months.

LITERATURE REVIEW

A systematic literature review indicated that EEA conserves the palate and oropharynx mucosae, thus causing less airway and swallowing complications than the transoral approach.

CONCLUSION

In selected cases with persistent anterior compression, odontoidectomy on EEA is a safe, effective and valid alternative for managing CCJ pathology.

Technique of C2 Nerve Root Preservation in the Presence of Anomalous Vertebral Artery in Atlantoaxial Operations

While accessing the C1-C2 joint during posterior atlantoaxial fixation, the C2 nerve root along with its perineural venous plexus remains an obstacle for a panoramic visualization of the entry point of the C1 lateral mass and joint preparation. Therefore, many surgeons frequently advocate its intentional sectioning during this approach, with no related major complications.^1,2 However, this sectioning has at times been associated with symptoms such as hypoesthesia, numbness, dysesthesia, and neuropathic ulcers.³ Thus C2 nerve root preservation during posterior approach for atlantoaxial dislocation (AAD) could potentially avoid such consequences.⁴ Its preservation has been described for AAD cases with relatively normal C1-C2 joint anatomy with no osseovascular abnormalities.² In contrast, attempt at C2 nerve root preservation in patients with congenital AAD harboring bony and vascular anomalies poses a greater challenge owing to a restricted operative space and the potential for perineural venous bleeding during dissection. This is more so for young neurosurgeons in the initial part of their learning curve. Video 1 details the technique of C2 nerve root dissection and preservation in a case of congenital AAD with an anomalous vertebral artery (VA). Computed tomography (CT) of this 30-year-old male patient with spastic quadriparesis showed AAD/basilar invagination with an assimilated C1-arch and right anomalous VA on CT angiography. He underwent C1-C2 joint manipulation and short-segment fixation. At 1-year follow-up, the patient's limb weakness had improved and CT showed good bony fusion. The salient operative steps involve gentle teasing and dissection of perineural soft tissues above and below the nerve root; the key to minimize venous bleeding is to dissect, coagulate, and divide them sequentially. A thorough release of the perineural soft tissues allows adequate nerve root mobilization, which in turn provides clear visualization of the C1-C2 joint space, preventing an undue nerve stretching during the C1-lateral mass screw insertion. The anomalous VA usually lies anterior to the C2 nerve root, and careful imaging evaluation allows its anticipation.³ We do not prefer the easy alternative of C2 nerve root sacrifice because of its inherent complications we noticed in our earlier clinical practice.³.

Chamberlain's Line Violation in Basilar Invagination Patients Compared with Normal Subjects: A Systematic Literature Review and Meta-Analysis

OBJECTIVE

To compare the measured odontoid tip violation above Chamberlain's line described in the literature to diagnose basilar invagination (BI) and to establish the normal placement of the dens tip defining individuals without BI (normal subjects).

METHODS

A systematic literature review was performed to identify clinical or radiological studies that expressed the amount of odontoid violation above Chamberlain's line in patients with a BI diagnosis. In addition, a meta-analysis was performed to evaluate normal subjects' values of Chamberlain's line violation (CLV).

RESULTS

There were 23 studies included (13 radiological and 10 clinical). Most studies used computed tomography and/or magnetic resonance imaging. Eight different cutoff values were used to measure dislocated odontoid apexes above Chamberlain's line regardless of the radiological modality. The mean measured amount of CLV was 3.95 mm (median 5 mm; range, 0-9 mm). The meta-analysis included 8 studies (1233 patients) with a normal sample population with a mean normal CLV of -0.63 mm (below the line) (95% confidence interval [-0.8, 1.18 mm], random effects model).

CONCLUSIONS

Different values were found in the assessed studies used for CLV in BI diagnosis. This variability is especially important for type B BI, as type A BI has other craniocervical diagnostic parameters. Considering the results obtained in this meta-analysis, BI should be diagnosed in the case of any dens violation >1.18 mm.

Interfacet Distraction for Type B-Basilar Invagination Assisted by a Novel Sliding-Traction Head Holder: 2-Dimensional Operative Video

Type B basilar invagination (BI) refers to odontoid process prolapse into skull base without dislocation, which is often associated with Chiari malformation and syringomyelia.¹ Its pathogenesis and treatment are in controversy. Posterior fossa decompression has been introduced to treat the associated Chiari malformation; however, it may not be effective for symptoms with severe ventral nerve compression.² C1-2 in situ fixation has been reported to treat minor instability in type B BI,³ yet the assessment of minor instability has not been widely accepted. We believe that the pathogenesis is chronic ventral compression of the brainstem. Transoral odontoidectomy is a classic surgical procedure to treat the pathogenesis, but it is associated with high risks of infection, velopharyngeal incompetence, and airway obstruction and often requires posterior surgery for fusion.⁴ Thus we use an interfacet distraction technique to move the odontoid process down and relieve ventral brainstem compression.⁵ Therefore interfacet structural support is necessary to maintain the distance of the interfacet. The reason for fixation is that interfacet distraction disrupts atlantoaxial stability. We designed a novel sliding-traction head holder, which can quantitatively tract and stabilize the head without support for the head or face, avoiding the risk of eyeball compression. It adapts to a variety of surgical methods and allows intraoperative changes in the patient's position. Assisted by the device, a satisfied interfacet distraction and a correction of BI were obtained. Video 1 describes how the interfacet distraction technique assisted by a sliding-traction head holder was performed in an illustrative case. The patient consented to the procedure.

Chiari Type 1 Malformation and Syringomyelia in Children: Classification and Treatment Options

Chiari type 1 malformation (CIM) is defined as tonsillar ectopia of >5 mm, while syringomyelia (SM) is defined as a cerebrospinal fluid (CSF)-filled cavity larger than 3 mm dissecting the spinal cord. Over the last decades, our understanding of these pathologies has grown; however, many controversies still exist almost in every aspect of CIM and SM, including etiology, indication for treatment, timing of treatment, surgical technique, follow-up regime, and outcome. This chapter provides a comprehensive overview on different aspects of CIM and SM and on the still existing controversies, based on the evidence presently available. Future directions for clinical research concerning CIM and SM treatment and outcome are elaborated and discussed as well.

Basilar invagination without atlantoaxial dislocation: treatment by correction of clivus canal angle with interfacet distraction and fixation

BACKGROUND

This study reports on the surgical technique used and clinical outcomes obtained during the treatment of basilar invagination (BI) without atlantoaxial dislocation (AAD) through the correction of the clivus canal angle (CCA) using interfacet distraction and fixation.

METHODS

Nineteen cases with BI without AAD treated by the correction of the clivus canal angle were retrospectively analyzed. Pre- and postoperative computed tomography scans and three-dimensional reconstruction views were obtained to measure the size of the CCA, pB-C2 distance, and degree of BI. Chiari malformation and syringomyelia were evaluated by magnetic resonance imaging (MRI). The clinical outcomes for all patients were measured using the Japanese Orthopedic Association (JOA) scale. The CCA was corrected by using interfacet distraction and fixation techniques. The Wilcoxon test was used to compare pre- and postoperative measurements.

RESULTS

All the patients were followed up for 24.95 ± 5.22 months (range 12-36 months); no patient suffered intraoperative nerve or vascular injury. Clinical symptoms improved in 17 patients (89.5%). The mean JOA score increased from 12.32 ± 1.89 to 14.37 ± 1.30 (Z = -3.655, P < 0.001). The mean CCA improved from 129.34 ± 8.52° preoperatively to 139.75 ± 8.86° postoperatively (Z = -3.824, P < 0.001). The mean pB-C2 decreased from 7.47 ± 2.21 to 5.68 ± 3.13 (Z = -3.060, P = 0.002). Syringomyelia was significantly reduced in 10 out of 13 patients by the first follow-up year. All patients achieved bony fusion.

CONCLUSION

Posterior interfacet distraction and fixation to correct the CCA is a feasible and effective method for treating BI without AAD.

Characteristics and Comparisons of Morphometric Measurements and Computed Tomography Hounsfield Unit Values of C2 Laminae for Translaminar Screw Placement Between Patients With and Without Basilar Invagination

OBJECTIVE

Patients with basilar invagination (BI) had high incidences of vertebral variations and high-riding vertebral artery (HRVA) that might restrict the use of pedicle or pars screw and increase the use of translaminar screw on axis. Here, we conducted a radiographic study to investigate the feasibility of translaminar screws and the bone quality of C2 laminae in patients with BI, which were compared with those without BI as control to provide guidelines for safe placement.

METHODS

In this study, a total of 410 patients (205 consecutive patients with BI and 205 matched patients without BI) and 820 unilateral laminae of the axis were included at a 1:1 ratio. Comparisons with regard to insertion parameters (laminar length, thickness, angle, and height) for C2 translaminar screw placement and Hounsfield unit (HU) values for the assessment of the appropriate bone mineral density of C2 laminae between BI and control groups were performed. Besides, the subgroup analyses based on the Goel A and B classification of BI, HRVA, atlas occipitalization, and C2/3 assimilation were also carried out. Furthermore, the factors that might affect the insertion parameters and HU values were explored through multiple linear regression analyses.

RESULTS

The BI group showed a significantly smaller laminar length, thickness, height, and HU value than the control group, whereas no significant difference was observed regarding the laminar angle. By contrast, the control group showed significantly higher rates of acceptability for unilateral and bilateral translaminar screw fixations than the BI group. Subgroup analyses showed that the classification of Goel A and B, HRVA, atlas occipitalization, and C2/3 assimilation affected the insertion parameters except the HU values. Multiple linear regression indicated that the laminar length was significantly associated with the male gender (B = 0.190, p < 0.001), diagnoses of HRVA (B = -0.109, p < 0.001), Goel A (B = -0.167, p < 0.001), and C2/3 assimilation (B = -0.079, p = 0.029); the laminar thickness was significantly associated with the male gender (B = 0.353, p < 0.001), diagnoses of HRVA (B = -0.430, p < 0.001), Goel B (B = -0.249, p = 0.026), and distance from the top of odontoid to the Chamberlain line (B = -0.025, p = 0.003); laminar HU values were significantly associated with age (B = -2.517, p < 0.001), Goel A (B = -44.205, p < 0.001), Goel B (B = -25.704, p = 0.014), and laminar thickness (B = -11.706, p = 0.001).

CONCLUSION

Patients with BI had narrower and smaller laminae with lower HU values and lower unilateral and bilateral acceptability for translaminar screws than patients without BI. Preoperative 3-dimensional computed tomography (CT) and CT angiography were needed for BI patients.

Measurement of Deformity at the Craniovertebral Junction: Correlation of Triangular Area and Myelopathy

OBJECTIVE

Diseases of the craniovertebral junction (CVJ) are commonly associated with deformity, malalignment, and subsequent myelopathy. The misaligned CVJ might cause compression of neuronal tissues and subsequently clinical symptoms. The triangular area (TA), measured by magnetic resonance imaging/images (MRI/s), is a novel measurement for quantification of the severity of compression to the brain stem. This study aimed to assess the normal and pathological values of TA by a comparison of patients with CVJ disease to age- and sex-matched controls. Moreover, postoperative TAs were correlated with outcomes.

METHODS

Consecutive patients who underwent surgery for CVJ disease were included for comparison to an age- and sex-matched cohort of normal CVJ persons as controls. The demographics, perioperative information, and pre- and postoperative 2-year cervical MRIs were collected for analysis. Cervical TAs were measured and compared.

RESULTS

A total of 201 patients, all of whom had pre- or postoperative MRI, were analyzed. The TA of the CVJ deformity group was larger than the healthy control group (1.62 ± 0.57 cm2 vs. 1.01 ± 0.18 cm2, p < 0.001). Moreover, patients who had combined anterior odontoidectomy and posterior laminectomy with fixation had the greatest reduction in the TA (1.18 ± 0.58 cm2).

CONCLUSION

In CVJ deformity, the measurement of the cervical TA could indicate the severity of brain stem compression. After surgery, the TA had a varying degree of improvement, which could represent the efficacy of surgery.

The Impact of C1 Anterior Arch Preservation on Spine Stability After Odontoidectomy: Systematic Review and Meta-Analysis

BACKGROUND

Odontoidectomy for symptomatic irreducible ventral brainstem compression at the craniovertebral junction may result in spine instability requiring subsequent instrumentation. There is no consensus on the importance of C1 anterior arch preservation in prevention of iatrogenic instability. We conducted a systematic review of the impact of C1 anterior arch preservation on postodontoidectomy spine stability.

METHODS

PubMed, Embase, Scopus, Web of Science, and Cochrane were searched following the PRISMA guidelines to include studies of patients undergoing odontoidectomy. Random-effect model meta-analyses were performed to compare spine stability between C1 anterior arch preservation versus removal and posttreatment outcomes between transoral approaches (TOAs) versus endoscopic endonasal approaches (EEAs).

RESULTS

We included 27 studies comprising 462 patients. The most common lesions were basilar invagination (73.3%) and degenerative arthritis (12.6%). Symptoms included myelopathy (72%) and neck pain (43.9%). Odontoidectomy was performed through TOA (56.1%) and EEA corridors (34.4%). The C1 anterior arch was preserved in 16.7% of cases. Postodontoidectomy stabilization was performed in 83.3% patients. Median follow-up was 27 months (range, 0.1-145). Rates of spine instability were significantly lower (P = 0.004) when the C1 anterior arch was preserved. Postoperative clinical improvement and pooled complications were reported in 78.8% and 12.6% of patients, respectively, with no significant differences between TOA and EEA (P = 0.892; P = 0.346). Patients undergoing EEA had significantly higher rates of intraoperative cerebrospinal fluid leaks (P = 0.002).

CONCLUSIONS

Odontoidectomy is safe and effective for treating craniovertebral junction lesions. Preservation of the C1 anterior arch seems to improve maintenance of spine stability. TOA and EEA show comparable outcomes and complication rates.

Position-dependent arm dyskinesia due to severe craniocervical malformation

CONTEXT

Spinal-generated movement disorders are a complex group of medical conditions, frequently misdiagnosed, originating in the spinal cord or from combined peripheral and central nervous system involvement. In this case report, we describe a novel form of position-dependent dyskinesia due to severe craniocervical malformation.

FINDINGS

An 83-year-old woman with basilar invagination at the C2 vertebra above the line of Chamberlain, occipitocervical lordosis, platybasia with a short clivus, ankylosis of the C1-C2 complex and fusion of the C1 arch developed an unusual pattern of position-dependent left arm dyskinesia triggered by bending her neck forward with simultaneous contact of the flexed elbow with a flat surface. Symptoms did not improve with anticonvulsants and she progressed and died suddenly.

CONCLUSION/CLINICAL RELEVANCE

A newly described form of position-dependent arm dyskinesia can be associated with severe craniocervical malformation.

Basilar decompression via a far lateral transcondylar approach: technical note

BACKGROUND

Treatments for symptomatic or unstable basilar invagination (BI) include posterior decompression, distraction/fusion, trans-nasal or trans-oral anterior decompression, and combined techniques, with the need for occipitocervical fusion based on the degree of craniocervical instability. Variations of the far lateral transcondylar approach are described in limited case series for BI, but have not been widely applied.

METHODS

A single-institution, retrospective review of consecutive patients undergoing a far lateral transcondylar approach for odontoidectomy (± resection of the inferior clivus) followed by occipitocervical fusion over a 6-year period (1/1/2016 to 12/31/2021) is performed. Detailed technical notes are combined with images from cadaveric dissections and patient surgeries to illustrate our technique using a lateral retroauricular incision.

RESULTS

Nine patients were identified (3 males, 6 females; mean age 40.2 ± 19.6 years). All patients had congenital or acquired BI causing neurologic deficits. There were no major neurologic or wound-healing complications. 9/9 patients (100%) experienced improvement in preoperative symptoms.

CONCLUSIONS

The far lateral transcondylar approach provides a direct corridor for ventral brainstem decompression in patients with symptomatic BI. A comprehensive knowledge of craniovertebral junction anatomy is critical to the safe performance of this surgery, especially when using a lateral retroauricular incision.

Atlantoaxial Joint Distraction and Fusion with DTRAX Intra-Articular Cages: A Cadaveric Feasibility Study and Review of the Pertinent Literature

PURPOSE

Atlantoaxial joint distraction is a key procedure for the treatment of selected patients affected by basilar invagination (BI). In recent years, several authors have reported various techniques of distraction and fixation of the C1-C2 joint using different types of intra-articular spacers, with or without posterior fixation. We review the pertinent literature and propose a feasibility study on the use of a new device for the distraction of the C1-C2 joint aimed to the descent of the dens out of the foramen magnum suggesting its application on selected cases of BI.

METHODS

The GL-DTRAX Cervical Cage-SE is a cage approved by the Food and Drug Administration for distraction and fixation of subaxial cervical spine. Five adult cadaveric specimens were dissected surgically to evaluate the feasibility of DTRAX insertion inside the C1-C2 joint through a posterior approach.

RESULTS

The cages were uneventfully set into the C1-C2 intra-articular space of all samples without the need to sacrifice C2 nerve roots and ganglia. Postoperative cervical computed tomography scanning confirmed the correct fitting of the devices in every sample.

CONCLUSIONS

This cadaveric study highlights the feasibility of the DTRAX cage as a C1-C2 intra-articular device producing a substantial distraction of atlantoaxial complex and suggesting a possible therapeutic role in selected cases of BI.

Posterior two-step distraction and reduction for basilar invagination with atlantoaxial dislocation: a novel technique for precise control of reduction degree without traction

PURPOSE

The pathological changes of basilar invagination (BI) and atlantoaxial dislocation (AAD) include vertical and horizontal dislocations. Current surgical techniques have difficulty in accurately controlling the degree of reduction in these two directions and often require preoperative traction, which increases patients' pain, hospital stay, and medical cost. This study aimed to introduce a novel technique for accurately reducing horizontal and vertical dislocation without preoperative traction and report the radiological and clinical outcomes.

METHODS

From 2010 to 2020, patients with BI and AAD underwent posterior two-step distraction and reduction (TSDR) and occipitocervical fixation. Radiological examination was used to evaluate the reduction degree (RD) and compression. Japanese Orthopedic Association (JOA) score was used to evaluate clinical outcome.

RESULTS

A total of 55 patients with BI and AAD underwent TSDR and occipitocervical fusion. The clinical symptoms of 98.2% of them improved. JOA score increased significantly after the operation. Appropriate (50% ≤ RD < 80%) or satisfactory (RD ≥ 80%) horizontal reduction was achieved in 92.7% of patients, and 90.9% obtained appropriate or satisfactory vertical reduction. Thirty-one patients did not undergo preoperative skull traction. There was no significant difference in radiological outcomes or JOA scores between the traction and non-traction groups. However, the length of hospital stay in the traction group was longer than that in the non-traction group.

CONCLUSION

TSDR enables horizontal and vertical reduction. It is a safe, simple, and effective technique for patients with BI and AAD. Despite the absence of preoperative skull traction, the degree of reduction and clinical outcomes were satisfactory.

Ideal entry point and trajectory for C2 pedicle screw placement in basilar invagination patients with high-riding vertebral artery based on 3D computed tomography

BACKGROUND

C2 pedicle screw placement in patients with basilar invagination (BI) is fraught with risks because of a high incidence of anatomical variations and high-riding vertebral artery (HRVA). However, no study can be found in the literature that attempted to identify the ideal entry point and trajectory through the C2 pedicle in BI patients with HRVA.

PURPOSE

To investigate the parameters of ideal entry point and trajectory for C2 pedicle screw placement in BI patients with HRVA and compare them with those in BI patients without HRVA and patients without BI as control. These parameters would serve as a guide to pedicle screw placement.

STUDY DESIGN

A retrospective comparative study.

PATIENT SAMPLE

A total of 396 patients (198 consecutive BI patients and 198 matched patients without BI as control) and 792 unilateral pedicles from April 2017 to October 2021 at two medical centers were included.

OUTCOME MEASURES

The insertion parameters of mediolateral angle, surface distance, cephalad angle, and vertical distance from the superior border of the lamina were the primary outcome measures for the reference of C2 pedicle screw placement. Furthermore, factors that affect the primary insertion parameters were assessed via multiple linear regression analyses.

METHOD

According to the diagnosis of BI and HRVA, the unilateral pedicles were assigned into HRVA of BI, non-HRVA of BI, HRVA of control, and non-HRVA of control groups. Subgroup analyses based on Goel types A and B were also performed. Moreover, vertebral artery (VA) anomalies that might result in potentially serious complications were identified and systematically compared.

RESULTS

The measurements of insertion parameters in BI patients with HRVA indicated a mean mediolateral angle of 27.42°, a mean cephalad angle of 43.02°, a mean surface distance of 9.74 mm, and a mean vertical distance from the superior border of the lamina of 3.85 mm. Compared with that in BI patients without HRVA, the measurements suggested that the entry point in BI patients with HRVA should be shifted upward by 0.38 mm and the trajectory should be angled cephalad by 6.05° and medially by 4.78°. In the control group, changes in the insertion parameters between HRVA and non-HRVA showed a similar trend to the BI group. Multiple linear regression showed that mediolateral angle was significantly associated with the male gender (B=-0.930, p=.017) and the diagnoses of HRVA (B=6.964, p<.001), Goel type A (B=-1.656, p=.003), and Goel type B (B=0.981, p=.030). Moreover, cephalad angle was significantly associated with the length of lateral mass (B=-0.319, p=.001) and the diagnoses of HRVA (B=3.254, p<.001) and Goel type A (B=6.924, p<.001). The VA anomalies were significantly higher in the BI group than in the control group.

CONCLUSIONS

The insertion parameters of the ideal entry point and trajectory for C2 screw placement in BI patients with HRVA were remarkably different from those of non-HRVA of BI, HRVA of control, and non-HRVA of control cohorts. Preoperative 3D computed tomography (CT) and CT angiography are highly recommended in such patients to improve intraoperative safety and reduce postoperative complications.

Transoral Odontoidectomy - Our Experience in A Limited-Resource Setup

BACKGROUND

Although posterior procedures are used for most cases of basilar invagination, transoral decompression is an important tool in complex deformities with severe degeneration and neural compression.

METHODS

Consecutive patients who underwent transoral odontoidectomy for basilar invagination and atlantoaxial dislocation at the neurosurgical unit of Lady Reading Hospital Peshawar between June 2016 and January 2022 were retrospectively included. Preoperative and postoperative neurological, clinical, and radiological parameters were recorded and compared.

RESULTS

Of the 33 patients included in this study, 22 were men and 11 were women. The mean age was 23.4 years ±8.4 years (mean ± standard deviation). The most common presenting symptoms were gait abnormalities and neck pain. A total of 28 patients were treated for the first time, while 5 patients had prior posterior fusion. The mean distance of the tip of the dens above the chamberlain line was 8.9 ± 4.2 mm, while the mean anterior atlantodental interval was 6.5 ± 2.1 mm. Seven patients had an anomalous course of vertebral artery on at least one side. A total of 28 patients improved significantly, while 5 patients did not improve at the follow-up. The mean follow-up was 8.5 months ±6.3 (mean ± standard deviation). The mean Nurick and Modified Japanese Orthopedic Association scores improved postoperatively (P < 0.05). Three patients underwent reoperation including one with vertebral artery injury. Three patients underwent tracheostomy.

CONCLUSIONS

With proper patient selection, transoral odontoidectomy can be safely performed in a limited-resource setting.

Anatomical analysis of the C2 pedicle in patients with basilar invagination

PURPOSE

To evaluate and describe the morphologic features of the C2 pedicle in patients with basilar invagination (BI) for informing the placement of pedicle screws. C2 pedicle screw placement is an important surgical technique for the treatment of atlantoaxial instability in patients with BI. However, no systematic and comprehensive anatomical study of the C2 pedicle in patients with BI has been reported.

METHODS

The data from 100 patients diagnosed with BI (BI group) and 100 patients without head or cervical disease (control group) were included in the study. Radiographic parameters, including the pedicle width, length, height, transverse angle, lamina angle, and superior angle, were measured and analyzed on CT images. After summary analysis, the effect of C2-3 congenital fusion on C2 pedicle deformity in patients with BI was also investigated.

RESULTS

The width, length, and height of the C2 pedicle of the BI patients were smaller than those of the control group. The pedicle cancellous bone was smaller in the BI group, while no significant difference in cortical bone was observed. In total, 44% of the pedicles were smaller than 4.5 mm in the BI group. Patients with C2-3 congenital fusion presented with smaller pedicle transverse angles and larger pedicle superior angles than those without fusion. Wide variations in the left and right angles of the pedicle were observed in the BI group with atlantoaxial dislocation or atlantooccipital fusion.

CONCLUSION

The C2 pedicle in the BI group was thinner than that in the control group due to a smaller cortical bone. Cases of C2-3 congenital fusion, atlantoaxial dislocation, and atlantooccipital fusion displayed variation in the angle of the C2 pedicle.

Evaluating craniovertebral stability in Chiari malformation coexisting with Type II basilar invagination: an observational study based on kinematic computed tomography and its clinical application

BACKGROUND

Treatment of Chiari malformation (CM) is controversial, especially when it coexists with "stable" or Type II basilar invagination (CM+II-BI). Precise evaluation of craniovertebral junction (CVJ) stability is crucial in such patients; however, this has never been validated. This study aimed to dynamically evaluate atlanto-condyle and atlantoaxial stability by kinematic computed tomography (CT) and report its surgical treatment.

METHODS

The study recruited 101 patients (control, CM, and CM+II-BI groups: 48, 34, and 19 patients, respectively). During kinematic CT, the CVJ stability-related parameters were measured and compared between the three groups. The surgical strategy for treating CM+II-BI was based on these results. Pre- and postoperative images were acquired, and functional scores were used to assess the outcome.

RESULTS

Among the three groups, the length of the clivus and the height of the condyle were the shortest in the CM+II-BI group, which was accompanied by the greatest rotation of the atlas and atlanto-condyle facet movement on cervical flexion and extension. Moreover, in such patients, increased Chamberlain's baseline violation indicated the aggregate invagination of the odontoid in the flexed position, and asymmetric displacement of atlantoaxial facets was observed. Seventeen CM+II-BI patients underwent surgical treatment with atlantoaxial distraction and occipitocervical fusion. The syringomyelia width and tonsillar herniation decreased significantly, and functional scores indicated symptom relief and good outcomes.

CONCLUSIONS

CVJ instability, especially the ultra-movement of atlanto-condyle facets, commonly exists in II-BI as evaluated using kinematic CT. The surgical strategy of atlantoaxial distraction and occipitocervical fusion should be considered to treat such patients.

Basilar invagination: a tilt of the foramen magnum

OBJECTIVES

Congenital basilar invagination (BI) is a craniocervical deformity marked by odontoid prolapse into the skull base. The foramen magnum angle (FMA), which is formed by Chamberlain's line and McRae's line has not been fully studied. The study aimed to investigate the FMA and its relationship with other craniocervical parameters.

METHODS

Participants were divided into controls, type A BI and type B BI. Parameters included Chamberlain line violation (CLV), atlantodental interval, clivus height, clivus anteroposterior dimension, FMA, basal angle, clivo-axial angle, head and neck flexion angle, Boogard's angle, and subaxial cervical spine lordosis angle. Comparision of these parameters among the three groups and correlation analysis between FMA and other parameters was performed. The significance level was set at P<0.05.

RESULTS

A total of 111 controls, 111 type A BI patients, and 62 type B BI patients were enrolled. The FMAs in the control, type A BI, and type B BI groups were 6.21 (3.67,8.71), 22.16±6.61, and 22.39 (17.27, 31.08) °, respectively. Correlation analysis revealed correlations between the FMA and other variables. In the two BI subgroups, FMA was significantly correlated with CLV, clivus height, clivus anteroposterior dimension, basal angle, clivo-axial angle, and Boogard's angle.

CONCLUSION

The FMA in patients with BI was approximately 22° and approximately 6° in controls, indicating that the FM in BI had a greater tilt. As a pathological condition, FMA can reflect the degree of BI. Clivus hypogenesis is a reason for excessive tilt of the FM.

Influence of clivo-axial angle on outcome after foramen magnum decompression in adult symptomatic Chiari type 1 malformation

OBJECTIVE

A significant number of patients with Chiari type 1 malformation (CM1) have abnormal clivo-axial angle (CXA) without other radiographic indicators of basilar invagination or craniovertebral junction (CVJ) instability. This study aimed to investigate whether abnormal CXA alone influences postoperative outcomes among patients who underwent foramen magnum decompression (FMD).

METHODS

A total of 44 adult patients with symptomatic CM1 undergoing FMD without CVJ fixation were enrolled. Preoperative clinical characteristics and radiographic measurement include the CXA as well as the radiographic indicators of basilar invagination and instability were recorded. The univariate and multivariate binary logistic regression tests were used to identify the potential prognostic factors for favorable outcomes.

RESULTS

Eighteen patients (41%) and 26 patients (59%) were divided into unfavorable and favorable outcome groups, respectively. Baseline demographic and imaging characteristics were similar between the two patient groups. The mean CXA was 132.3 ± 15.8 and 145 ± 13.6 degrees in the unfavorable and favorable groups, respectively (P = 0.091). In the favorable outcome group, the proportion of patients with CXA > 135 degrees was significantly higher than that of the unfavorable outcome group (77% vs. 44%; P = 0.05). The CXA > 135 degrees was found to be the only independent predictor associated with favorable outcomes (adjusted risk ratio 2.16; 95% CI 1.01-4.76; P = 0.047).

CONCLUSION

The preoperative CXA of greater than 135 degrees was identified as a prognostic factor associated with a favorable outcome at one-year follow-up after FMD among adult patients with symptomatic CM1 without basilar invagination or CVJ instability. This factor should be incorporated into preoperative considerations.

Morphometric and volumetric analysis of the posterior cranial fossa in adult Chiari malformation type I with and without group B basilar invagination

BACKGROUND

The frequent association of basilar invagination (BI) makes the understanding of the pathogenesis of Chiari malformation type I (CMI) difficult. The influence of group B type of BI (the BI without obvious atlantoaxial instability) on the skeletal morphology has not been thoroughly studied. The objective of this study is to evaluate the skeletal alterations in the posterior cranial fossa (PCF) of adult CMI cases with and without group B BI.

METHODS

Fifty-four adult CMI without BI cases (CMI-only group) and 30 adult CMI with group B BI cases (CMI-BI group) were retrospectively studied. Fifty-six adult patients with unruptured intracranial aneurysms were included as the controls. Several linear and angular variables, and the bony volume of the PCF were analyzed based on thin-slice computed tomography data.

RESULTS

Morphological analysis revealed a significant difference in several variables from controls compared to CMI-only, and CMI-BI patients. The clivus and occipital bone, shortened and elevated in CMI-only patients, were further flattened in BI-associated CMI patients. Furthermore, although out of the scope for the diagnostic threshold of BI, the CMI-only cases also had a tendency to form BI. The association of BI modified several variables, without further reducing the bony PCF volume.

CONCLUSIONS

These findings indicate that the variables associated with group B BI tend to be a continuum of the same pathological abnormalities that originate from the same pathological alterations in CMI patients.

Craniocervical abnormalities in osteogenesis imperfecta type V

Craniocervical abnormalities in osteogenesis imperfecta (OI) such as basilar invagination or cervical kyphosis can cause severe neurological morbidity. These abnormalities may be more frequent in OI type V compared with other OI subtypes of similar disease severity, underlining the importance of screening in this group.

INTRODUCTION

Craniocervical abnormalities in osteogenesis imperfecta (OI) can cause severe neurological morbidity. Although radiological cranial base abnormalities in OI have been well described in the literature, there are limited data on these abnormalities in OI type V and their association with clinical sequelae.

METHODS

A retrospective case series on patients with craniocervical abnormalities in OI type V at our institution.

RESULTS

Craniocervical abnormalities were present in 7 of 37 patients with OI type V (19%). For 5 patients (age at last follow-up: 5 to 26 years; 2 females), sufficient information was available for inclusion in the case series. All had genetically confirmed OI type V. Age range at diagnosis of the craniocervical abnormality was 1 day to 18 years. Basilar invagination was present in 3 patients; 2 had cervical kyphosis. Dysplasia of upper cervical vertebrae or base of skull was seen in 3 patients. The severity of the craniocervical abnormality did not clearly correlate with the severity of the OI phenotype. Three patients required surgical intervention (ages 7, 11, and 26 years) due to compression of the spinal cord or brainstem. Craniocervical abnormalities were detected incidentally or on screening in 3 patients, and only 2 had significant positive findings on neurological examination.

CONCLUSION

A variety of craniocervical abnormalities are seen in OI type V including dysplasia of the cervical vertebrae. These cases highlight the importance of screening patients with OI type V with lateral skull and cervical spine x-rays throughout childhood and after skeletal maturity.

A combined approach for stabilization and endoscopic/ endonasal odontoid and clivus resection for treatment of basilar invagination

Background:

Basilar invagination (BI) is a complex condition characterized by prolapse of the odontoid into the brain stem/upper cervical cord. This lesion is often associated with Chiari malformations, and rheumatoid arthritis (RA). Treatment options for BI typically include cervical traction, an isolated anterior transoral odontoidectomy, anterior endonasal odontoidectomy, an isolated posterior fusion, or combined anterior/ posterior surgical approach.

Case Description:

A 45-year-old female with a Chiari I malformation and RA underwent a combined posterior C0-C5 posterior decompression/fusion, followed by an anterior odontoidectomy (i.e. endoscopic/endonasal under neuronavigation). Postoperatively, the patient’s symptoms and neurological signs resolved.

Conclusion:

BI in was successfully managed with a combined posterior C0-C5 decompression/fusion followed by an anterior endoscopic/endonasal odontoidectomy performed under neuronavigation.

C2 Nerve Root Preservation During Posterior Fixation for Instability Secondary to Congenital Craniovertebral Junction Anomalies: Feasibility Factors and Related Outcomes

OBJECTIVE

Patients with instability because of congenital craniovertebral anomalies often have complex C1-C2 osseovascular anomalies. C2 nerve root sacrifice has been described to address such difficult anatomy during posterior C1-C2 fixation and has its own downsides. Its preservation as a recent alternative poses greater surgical challenge, and the considerations differ from other causes of craniovertebral junctional instability; the pertaining outcomes have been scarcely studied. The objective of this study was to prospectively determine the feasibility and outcomes related to C2 nerve root preservation in patients with congenital atlantoaxial dislocation (CAAD) after posterior C1-C2 fixation.

METHODS

In this observational study, 63 patients (126 nerve roots) with CAAD after posterior fixation were prospectively assessed. Underlying osseovascular anomalies affecting the feasibility of C2 nerve root preservation, and C2 nerve-related dysfunction at 12 months follow-up were analyzed.

RESULTS

The overall C2 nerve root preservation rate was 89.7%. Even in the presence of extreme joint obliquity/spondyloptosis and anomalous vertebral artery, it was feasible in about three fourths. After preservation, 28.3% patients developed new-onset C2 nerve root dysfunction: neuralgia in 2, dysesthesia in 6, and hypoesthesia/paresthesia in 9. The symptoms were not disabling in most patients.

CONCLUSIONS

In most patients with CAAD, C2 nerve root preservation is feasible despite an aberrant bony and vascular anatomy. A few patients after nerve root preservation develop related symptoms that are conservatively manageable, with no significant adverse consequences. Given the controversy in the literature on C2 nerve sacrifice-related outcomes, we favor an attempt at C2 nerve root preservation.

Transarticular Fixation Following Mobilization of "High-Riding" Vertebral Artery

BACKGROUND AND IMPORTANCE

The article identifies the feasibility of transarticular screw fixation after mobilizing the vertebral artery in cases where it is in a "high-riding" location.

CLINICAL PRESENTATION

A 42-yr-old male patient had a 4-yr history of progressive quadriparesis. Investigations revealed severe basilar invagination. There was assimilation of atlas and C2-3 fusion. The vertebral artery was "high-riding" into the pedicle-facet of C2 vertebra on both sides. Vertebral artery loop was exposed and mobilized inferiorly on both sides after careful drilling of pedicular bone on the posterior aspect of the dome of the artery. C2 facetal bone on the anterior face of the vertebral artery dome was now available for screw insertion. The C1-2 facets and the articulation were directly in line, making transarticular screw fixation relatively straightforward. The wide bone space available permitted insertion of 2 screws in a transarticular fashion on both sides. The patient had satisfactory clinical improvement. Imaging after 22 mo showed bone fusion across the facets.

CONCLUSION

Mobilization of the high-riding vertebral artery loop can help salvage the surgical procedure of lateral mass stabilization.

A Safe and Effective Posterior Intra-Articular Distraction Technique to Treat Congenital Atlantoaxial Dislocation Associated With Basilar Invagination: Case Series and Technical Nuances

BACKGROUND

The management of atlantoaxial dislocation (AAD) associated with basilar invagination (BI) is challenging, and traditional posterior-only approaches lack the ability to release the anterior soft tissue resulting in unsatisfactory reduction. Furthermore, vertebral artery anomalies and deformed anatomy increase surgical risks.

OBJECTIVE

To introduce a safe and efficient technique to reduce congenital AAD and BI through a single-stage posterior-only approach.

METHODS

A total of 65 patients with AAD and concomitant BI who had congenital osseous abnormalities were retrospectively analyzed. All patients had anterior soft tissue released through a posterior-only approach, followed by intra-facet cages implantation, cantilever correction, and instrumentation. Clinical results were measured using the Japanese Orthopedic Association (JOA) scale, and radiographic measurements included the atlanto-dental interval, the distance of odontoid tip above Chamberlain's line, clivus-canal angle (CCA), and syrinx length. Paired t-tests were used to compare preoperative and postoperative measurements.

RESULTS

The mean JOA score increased from 10.98 to 14.40 at 1-yr follow-up. Complete reduction of AAD and BI was achieved in 48 patients (73.8%). The mean CCA improved from 115° preoperatively to 129° postoperatively. Reduction of syrinx size was observed in 14 patients at 1 wk and in 35 patients 1 yr after surgery. All patients achieved bony fusion.

CONCLUSION

Posterior intra-articular distraction followed by cage implantation and cantilever correction can achieve complete reduction in most cases of congenitally anomalous AAD associated with BI.

Foramen Magnum Angle: A New Parameter for Basilar Invagination of Type B

OBJECTIVE

To describe the foramen magnum angle (FMA) as a new parameter for basilar invagination (BI) type B.

METHODS

The FMA was performed on sagittal slice of magnetic resonance imaging (MRI) as a line from the hard palate to the opisthion (angle vertex), and another line from the opisthion to the basion. The MRIs from 31 participants with BI type B and 96 controls were used. Intraclass correlation coefficient, descriptive data, and receiver operating characteristic (ROC) curve were used for statistical analysis at the 95% confidence interval.

RESULTS

The interobserver agreement of the FMA was 0.952. Patients with BI type B had a FMA significantly greater (25.9° ± 9.3°) than control participants (11.6° ± 4.9°) (P < 0.001). The area under the ROC curve showed a diagnostic value of 0.947. The FMA showed sensitivity 0.900 and specificity 0.854 for the cutoff criterion 17° (P < 0.001).

CONCLUSIONS

The FMA had an optimal diagnostic value that provided complementary evidence to investigate BI type B.

The enigma of acute worsening after a latent interval in post-operative patients of craniovertebral junction instability

OBJECTIVE

For reasons that are poorly understood and still undocumented, few patients of craniovertebral junction (CVJ) anomalies with instability/atlantoaxial dislocation (AAD) in our practice have been seen to suffer unprecedented acute neurological deterioration with respiratory compromise about 48-72 h post-surgery. This has been specifically observed after an uneventful, stable clinical condition in the immediate postoperative period. This study attempts to elucidate the factors and outcomes related to such latent worsening.

PATIENTS AND METHODS

The 4-year surgical data of 268-patients with CVJ instability (AAD/basilar-invagination) who underwent C1-C2 fixation were retrospectively studied. The relevant factors of 17 patients who showed such deterioration were compared with that of the remaining in a multivariate model.

RESULTS

Seventeen patients had acute neurological worsening with respiratory arrest after a latent period. Ten improved at follow-up. Contrary to the general expectation, poor preoperative neurological score or severe dislocation that needed considerable manipulation did not influence such worsening. Dural injury in patients with associated Chiari malformation and vertebral arterial (VA) injury emerged as independent factors (p < 0.01) associated with this pattern of delayed neurological decline.

CONCLUSIONS

We report our management and outcomes of a unique subset of AAD with neurological worsening in the postoperative period after 48-72 h. Such a subgroup was not previously identified in literature. Dural lacerations in AAD with Chiari, and VA injury seem to predispose to such complications and should be prevented at best. Close observation, and caution regarding early extubation (<72 h) is recommended in this subset despite an apparently uneventful immediate postoperative neurological status.

Basilar Invagination: Surgical Treatment by Novel Anterior Implant

Introduction

Anterior retropharyngeal realignment, distraction, and atlantoaxial fixation are an option for the treatment of symptomatic basilar invagination (BI). The anterior implants for distraction and fixation for atlantoaxial joints are still evolving. We share our experience using a novel implant which can easily, safely, and rigidly fix both lateral masses to the body of the axis.

Methods

After exposing both the atlantoaxial joints anteriorly, the joints were prepared, distracted with wedge shaped autologous tricorticate bone grafts and realigned to correct the cervicomedullary strain. The atlantoaxial joints were fixed using a novel titanium plate by passing screws upwards and laterally into the lateral masses of the atlas and centrally into the body of the axis. Post-operative imaging showed effective correction of BI and atlantoaxial dislocation. Post-operative dynamic X-ray images confirmed maintenance of rigid fixation at 6 months.

Conclusion

This new plate screw construct is safe, easy, cost-efficient, and biomechanically appealing option for the treatment of symptomatic BI.

Role of Atlas Assimilation in the Context of Craniocervical Junction Anomalies

Atlas assimilation (AA) may be associated with atlantoaxial dislocation, Chiari malformation (CM), and basilar invagination. The importance of AA in the context of craniocervical junction (CVJ) anomalies is unclear. Considering this context, this study's objective is to discuss the role of AA in the management of CVJ anomalies, especially in CM. A comprehensive literature review was performed. In addition, some illustrative cases were discussed on the basis of our review. Finally, we propose a theoretic algorithm to evaluate patients with AA and CM. AA is a proatlas segmentation anomaly that may be complete or incomplete. It may be totally asymptomatic or symptomatic as the result of transferred shifted forces onto the C1-2 joints, leading to clear instability (atlantoaxial dislocation) or mild C1-2 instability. Cautious surgical planning may be required due to associated vertebral artery anomalies. AA with concomitant C2-C3 segmentation failure is highly associated with late C1-C2 instability. CVJ decompression failure was reported in patients with CM and a low clivus canal angle (<130-135 degrees). Patients with assimilated anterior C1 arches usually have evident AAD. CM patients with AA generally have type 1 BI or type 2 BI and are reported with higher rates of CVJ instabilities when compared with those "pure" CM. Dynamic examinations may provide additional evidence of atlantoaxial instability. Although AA per se is not considered an unstable configuration, further and detailed evaluations of patients with CM associated with AA are necessary. Some associated unstable configurations required concomitant CVJ fixation.

A novel surgical protocol for safe and accurate placement of C1 lateral mass screws in patients with atlas assimilation, basilar invagination and atlantoaxial instability: technical details, accuracy assessment and perioperative complications

PURPOSE

To introduce a novel surgical protocol for safe and accurate placement of C1 lateral mass screws in patients with atlas assimilation, basilar invagination and atlantoaxial instability, and to categorize the screw accuracy and perioperative complications regarding this technique in a large case series.

METHODS

Between January 2015 and January 2020, patients who had atlas assimilation, basilar invagination and atlantoaxial instability, and underwent atlantoaxial fixation using C1 lateral mass screws were reviewed. C1 lateral mass screws were placed with a novel surgical protocol following a series key steps, including posterior para-odontoid ligament release, panoramic exposure of the invaginated lateral mass, and diligent protection of the abnormal VA. Screw accuracy and related complications were specifically evaluated.

RESULTS

A total of 434 C1 lateral mass screws were placed. Fifteen screws (3.5%) were classified as unacceptable, 54 screws (12.4%) were classified as acceptable, and 365 screws (84.1%) were classified as ideal. Overall, 96.5% of screws were deemed safe. There were no cases of vascular injury or permanent neurological defects. One patient with an unacceptable screw presented with hypoglossal nerve paralysis and recovered after an immediate revision surgery. Thirty-seven patients complained about occipital neuralgia and were successfully managed with medication.

CONCLUSION

Placement of C1 lateral mass screws in patients with atlas assimilation, basilar invagination and atlantoaxial instability following this surgical protocol is safe and accurate. Thorough para-odontoid ligamental release, wide exposure of the invaginated lateral mass, and diligent protection of the vertebral artery are critical to maximize the chances of successful screw placement.

Basilar invagination: A mimicker of bulbar-onset amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is characterized by progressive onset motor deficits with heterogenous presentations ranging from dysarthria to foot drop. Approximately 20% of the patients present with focal bulbar symptoms, in which some may remain restricted to bulbar region (isolated bulbar palsy), and the remaining eventually spreads to involve other body regions (classical ALS). Without accompanying upper and lower motor neurons signs elsewhere, differential diagnoses for isolated bulbar symptoms are extensive, include ALS variants as well as potentially treatable mimics. Therefore, it is important to take heed on every possible aetiology that may disrupt the hypoglossal nucleus, nerve, or lingual muscle itself. Herein, we illustrated a rare presentation of Group A basilar invagination, which mimicked bulbar-onset ALS.

A Universal Craniometric Index for Establishing the Diagnosis of Basilar Invagination

Objective

The conventional criteria for defining the basilar invagination (BI) focus on the relationship of odontoid tip to basion and opisthion, landmarks that are intrinsically variable especially in presence of occipitalised atlas. A universal single reference line is proposed that helps in unequivocally establishing the diagnosis of BI, may be relevant in establishing both Goel types A and B BI, as well as in differentiating a ‘very high’ from ‘regular’ BI.

Methods

Study design – case-control study. In 268 patients (group I with BI [n = 89] including Goel type A BI [n = 66], Goel type B BI [n = 23], and group II controls [n = 179]), the perpendicular distance between odontoid tip and line subtended between posterior tip of hard palate-internal occipital protuberance (P-IOP line) was measured. Logistic regression analysis determined factors influencing the proposed parameter (p < 0.05).

Results

In patients with a ‘very high’ BI (n = 5), the odontoid tip intersected/or was above the P-IOP line. In patients with a ‘regular’ BI (n = 84), the odontoid tip was 6.56 ± 3.9mm below the P-IOP line; while in controls, this distance was 12.53 ± 4.28 mm (p < 0.01). In Goel type A BI, the distance was 7.01 ± 3.78 mm and in type B BI, it was 5.07 ± 4.19 mm (p = 0.004). Receiver-operating characteristic curve analysis identified 9.0 mm (8.92–9.15 mm) as the cut-point for diagnosing BI using the odontoid tip-P-IOP line distance as reference.

Conclusion

The odontoid tip either intersecting the P-IOP line (very high BI) or being < 9 mm below the P-IOP line (Goel types A and B BI) is recommended as highly applicable criteria to establish the diagnosis of BI. This parameter may be useful in establishing the diagnosis in all varieties of BI.

Craniovertebral junction anomaly with kissing carotids

Background:

“Kissing carotids” typically involves the lower C4-C6 retropharyngeal space. Here, we describe a case of “kissing carotids” observed at the C1-C2 level in conjunction with basilar invagination (BI).

Case Description:

A 34-year-old-male presented with congenital atlantoaxial dislocation and BI. The initial surgical plan was for a transoral decompression (TOD). However, this approach was abandoned when the preoperative computed tomography angiography (CTA) documented “kissing carotids” lying anteriorly at the C1-C2 level.

Conclusion:

Obtaining a CTA before performing a TOD for BI is essential to prevent an intraoperative catastrophic hemorrhage due to the laceration of “kissing carotids.”