Human induced pluripotent stem cell/embryonic stem cell-derived pyramidal neuronal precursors show safety and efficacy in a rat spinal cord injury model.

Nerve regeneration and circuit reconstruction remain a challenge following spinal cord injury (SCI). Corticospinal pyramidal neurons possess strong axon projection ability. In this study, human induced pluripotent stem cells (iPSCs) were differentiated into pyramidal neuronal precursors (PNPs) by addition of small molecule dorsomorphin into the culture. iPSC-derived PNPs were transplanted acutely into a rat contusion SCI model on the same day of injury. Following engraftment, the SCI rats showed significantly improved motor functions compared with vehicle control group as revealed by behavioral tests. Eight weeks following engraftment, the PNPs matured into corticospinal pyramidal neurons and extended axons into distant host spinal cord tissues, mostly in a caudal direction. Host neurons rostral to the lesion site also grew axons into the graft. Possible synaptic connections as a bridging relay may have been formed between host and graft-derived neurons, as indicated by pre- and post-synaptic marker staining and the regulation of chemogenetic regulatory systems. PNP graft showed an anti-inflammatory effect at the injury site and could bias microglia/macrophages towards a M2 phenotype. In addition, PNP graft was safe and no tumor formation was detected after transplantation into immunodeficient mice and SCI rats. The potential to reconstruct a neuronal relay circuitry across the lesion site and to modulate the microenvironment in SCI makes PNPs a promising cellular candidate for treatment of SCI.

Mutational landscape of primary spinal cord astrocytoma.

Primary spinal cord astrocytoma (SCA) is a rare disease. Knowledge about the molecular profiles of SCAs mostly comes from intracranial glioma; the pattern of genetic alterations of SCAs is not well understood. Herein, we describe genome-sequencing analyses of primary SCAs, aiming to characterize the mutational landscape of primary SCAs. We utilized whole exome sequencing (WES) to analyze somatic nucleotide variants (SNVs) and copy number variants (CNVs) among 51 primary SCAs. Driver genes were searched using four algorithms. GISTIC2 was used to detect significant CNVs. Additionally, recurrently mutated pathways were also summarized. A total of 12 driver genes were identified. Of those, H3F3A (47.1%), TP53 (29.4%), NF1 (19.6%), ATRX (17.6%), and PPM1D (17.6%) were the most frequently mutated genes. Furthermore, three novel driver genes seldom reported in glioma were identified: HNRNPC, SYNE1, and RBM10. Several germline mutations, including three variants (SLC16A8 rs2235573, LMF1 rs3751667, FAM20C rs774848096) that were associated with risk of brain glioma, were frequently observed in SCAs. Moreover, 12q14.1 (13.7%) encompassing the oncogene CDK4 was recurrently amplified and negatively affected patient prognosis. Besides frequently mutated RTK/RAS pathway and PI3K pathway, the cell cycle pathway controlling the phosphorylation of retinoblastoma protein (RB) was mutated in 39.2% of patients. Overall, a considerable degree of the somatic mutation landscape is shared between SCAs and brainstem glioma. Our work provides a key insight into the molecular profiling of primary SCAs, which might represent candidate drug targets and complement the molecular atlas of glioma. © 2023 The Pathological Society of Great Britain and Ireland.

The role of clivus and atlanto-occipital lateral mass height in basilar invagination with or without atlas occipitalization.

Basilar invagination (BI) is a common deformity. This study aimed to quantitatively evaluate the height of clivus and atlanto-occipital lateral mass (LM) in patients with BI with or without atlas occipitalization (AOZ). We evaluated 166 images of patients with BI and of controls. Seventy-one participants were control subjects (group A), 68 had BI with AOZ (group B), and 27 had BI without AOZ (group C). Parameters were defined and measured for comparisons across the groups. Multiple linear regression analysis was used to test the relationship between Chamberlain's line violation (CLV) and the clivus height ratio or atlanto-occipital LM height. Based on the degree of AOZ, the lateral masses in group B were classified as follows: segmentation, incomplete AOZ, complete AOZ. From groups A to C, there was a decreasing trend in the clivus height and clivus height ratio. There was a linear negative correlation between the clivus height ratio and CLV in the three groups. Generally, the atlanto-occipital LM height followed the order of group B < group C < group A. The atlanto-occipital LM height was included only in the equations of groups B. There were no cases of atlantoaxial dislocation (AAD) in group C. There was a decreasing trend in LM height from the segmentation type to the complete AOZ type in group B. BI can be divided into three categories: AOZ causes LM height loss; Clivus height loss; Both clivus and LM height loss. The clivus height ratio was found to play a decisive role in both controls and BI group, while the atlanto-occipital LM height loss caused by AOZ could be a secondary factor in patients with BI and AOZ. AOZ may be a necessary factor for AAD in patients with congenital BI. The degree of AOZ is associated with LM height in group B.

Dissection of mendelian predisposition and complex genetic architecture of craniovertebral junction malformation.

The craniovertebral junction (CVJ) is an anatomically complex region of the axial skeleton that provides protection of the brainstem and the upper cervical spinal cord. Structural malformation of the CVJ gives rise to life-threatening neurological deficits, such as quadriplegia and dyspnea. Unfortunately, genetic studies on human subjects with CVJ malformation are limited and the pathogenesis remains largely elusive. In this study, we recruited 93 individuals with CVJ malformation and performed exome sequencing. Manual interpretation of the data identified three pathogenic variants in genes associated with Mendelian diseases, including CSNK2A1, MSX2, and DDX3X. In addition, the contribution of copy number variations (CNVs) to CVJ malformation was investigated and three pathogenic CNVs were identified in three affected individuals. To further dissect the complex mutational architecture of CVJ malformation, we performed a gene-based rare variant association analysis utilizing 4371 in-house exomes as control. Rare variants in LGI4 (carrier rate = 3.26%, p = 3.3 × 10-5) and BEST1 (carrier rate = 5.43%, p = 5.77 × 10-6) were identified to be associated with CVJ malformation. Furthermore, gene set analyses revealed that extracellular matrix- and RHO GTPase-associated biological pathways were found to be involved in the etiology of CVJ malformation. Overall, we comprehensively dissected the genetic underpinnings of CVJ malformation and identified several novel disease-associated genes and biological pathways.

Single-cell transcriptome profiling reveals intra-tumoral heterogeneity in human chordomas.

Chordoma is a rare and aggressive bone tumor. An accurate investigation of tumor heterogeneity is necessary for the development of effective therapeutic strategies. This study aims to assess the poorly understood tumor heterogeneity of chordomas and identify potential therapeutic targets. Single-cell RNA sequencing was performed to delineate the transcriptomic landscape of chordomas. Six tumor samples of chordomas were obtained, and 33,737 cells passed the quality control test and were analyzed. The main cellular populations identified with specific markers were as follows: chordoma cells (16,052 [47.6%]), fibroblasts (6945 [20.6%]), mononuclear phagocytes (4734 [14.0%]), and T/natural killer (NK) cells (3944 [11.7%]). Downstream analysis of each cell type was performed. Six subclusters of chordomas exhibited properties of an epithelial-like extracellular matrix, stem cells, and immunosuppressive activity. Although few immune checkpoints were detected on cytotoxic immune cells such as T and NK cells, a strong immunosuppressive effect was exerted on the Tregs and M2 macrophages. In addition, the cellular interactions were indicative of enhancement of the TGF-ß signaling pathway being the main mechanism for tumor progression, invasion, and immunosuppression. These findings, especially from the analysis of molecular targeted therapy and tumor immune microenvironment, may help in the identification of therapeutic targets in chordomas.

The effect of local intraoperative corticosteroid application on postoperative dysphagia following anterior cervical spine surgery.

Dysphagia is a common complication following anterior cervical spine surgery (ACSS). Although several literatures have reported the potential benefit of local corticosteroid application on dysphagia, its safety and efficacy are still unclear. A systematic review was performed aiming to evaluate the evidence of local corticosteroid application in prevention or treatment of postoperative dysphagia following ACSS. A systematic search was performed in September 2018 in PubMed and Embase database. The following information was extracted: study investigator, year of publication, number of patients, study design, inclusion/exclusion criteria, administration protocol of steroid, type of surgical procedure, number of levels performed, assessment methodology of dysphagia, radiologic assessment of prevertebral soft tissue swelling (PSTS), follow-up time points, outcome of dysphagia, and corticosteroid-related complications. Qualitative synthesis was performed. Finally, 5 studies met the inclusion/exclusion criteria. Four studies found that local corticosteroid application could decrease the incidence and magnitude of postoperative dysphagia while 1 study showed no effect on dysphagia significantly at 6 weeks and 3 months follow-up time. A total of 2325 patients received local corticosteroid intraoperatively; no early corticosteroid-related complication was reported. Totally, 4 adverse events occurred in long-term follow-up time, including 2 bone nonunion at 1.5 and 2.5 years postoperatively, 2 esophageal perforation at 2 months and 11 months of follow-up, respectively. Local corticosteroid application can reduce the incidence and severity of dysphagia following ACSS without increasing early corticosteroid-related complications. But further high-quality study is necessary to analyze potential delayed complications.

Dural ossification associated with ossification of posterior longitudinal ligament in the cervical spine: a retrospective analysis.

OBJECTIVE: Dural ossification (DO) is common in patients with ossification of the posterior longitudinal ligament (OPLL). The existence of DO makes surgery challenging and increases the risk of complications. The aim of this study was to investigate the incidence, distribution and radiological characteristics of DO associated with OPLL. METHODS: From January 2017 to January 2019, 55 patients with cervical OPLL were treated in our single center using an anterior cervical approach microsurgery. Preoperative CT images of decompressed segments were evaluated to identify imaging signs of DO. The 'double-layer sign' (DLS), 'parenthese sign' (PS) and 'hook sign' (HS) were considered to be characteristic imaging findings of DO in OPLL. Two kinds of confusing signs (false double-layer) were identified. RESULTS: Nineteen segments from 15 patients with OPLL had DO related to OPLL. The incidence of DO in OPLL segments was 30.16% (19/63), and the incidence of DO in patients with OPLL was 27.27% (15/55). DO occurred at the intervertebral space level in 14 cases and at the posterior level of the vertebral body in 5 cases. The sensitivity and specificity of imaging diagnosis were 89.47% (17/19) and 81.82% (36/44), respectively. The positive predictive value was relatively low, 68.00% (17/25), due to the false-positive double-layer sign. The negative predictive value was 94.74% (36/38). CONCLUSION: DO was relatively common in cervical OPLL. DLS might be misdiagnosed. PS and HS can vividly and intuitively describe the imaging features of DO and have high diagnostic accuracy.

A novel classification and its clinical significance in Chiari I malformation with syringomyelia based on high-resolution MRI.

BACKGROUND: The existing classification in Chiari I malformation (CM-I) has limited significance for the selection of surgical methods. OBJECTIVE: The purpose of this study was to investigate the surgery of CM-I with syringomyelia based on the high-resolution MR imaging (HRMRI) findings. METHODS: Data from 115 patients were collected and retrospectively analyzed. For those with syringomyelia up to the level of C1, HRMRI was performed and according to the communication status between the fourth ventricle and the syringomyelia, patients can be divided into four types, namely Type A: classic communicating; Type B: partial communicating; Type C: non-communicating; Type D: atrophic. All operations were performed with Foramen magnum and Magendie dredging (FMMD), and all intradural factors that may have induced the obstruction of CSF circulation were recorded. The efficiency of operation on syringomyelia was evaluated by mJOA, imaging findings, and complications in the follow-up periods. RESULTS: The postoperative follow-up period was from 12 to 24 months, with an average of 14.3 months. At 1 year, the mJOA of 115 patients was significantly higher than that before the operations (before surgery 12.1 ± 2.3 vs. after surgery 14. 2 ± 1.4, P < 0.05). In addition, postoperative re-examination showed that the size of the syringomyelia was reduced or completely resolved in patients of Type A, 100% (2/2); Type B, 81% (9/11); Type C, 84% (81/97); and Type D, 20% (1/5). CONCLUSIONS: According to our new classification based on HRMRI, FMMD is the key to surgical treatment, especially for Type A and Type B patients.

Wireless Epidural Electrical Stimulation in Combination With Serotonin Agonists Improves Intraspinal Metabolism in Spinal Cord Injury Rats.

OBJECTIVES: The combination of epidural electrical stimulation (EES) and serotonin agonists (5-HTA) effectively restores rhythmic lower-limb movements and improves intraspinal hemodynamics after spinal cord injury (SCI). Nonetheless, whether EES + 5-HTA improves intraspinal metabolism remains unclear. The present study aimed to evaluate the effects of EES + 5-HTA on intraspinal metabolism in SCI rats. MATERIALS AND METHODS: Wireless EES (WEES) implantation with complete T8 transection was performed in SCI rats. Electrodes were placed at the T12 and L2 vertebral levels. After rest for a week, the SCI rats received 11 weeks of WEES + 5-HTA treatment and treadmill training. WEES was switched off after each daily training. Locomotor function was evaluated by motion capture at week 12. Positron emission tomography-computed tomography was conducted to evaluate basal metabolism when WEES was switched off and assess task metabolism when WEES was switched on. RESULTS: With locomotor recovery after training for 11 weeks, WEES + 5-HTA conjointly improved basal metabolism (vs. each intervention alone; p < 0.05) and linearly modulated task metabolism in a frequency-dependent manner (R2 = 0.8901). Furthermore, 60 Hz of WEES was identified as the threshold for the extensive activation of the spinal cord's task metabolism below the transection plane (p < 0.05). CONCLUSIONS: WEES + 5-HTA could conjointly restore basal metabolism to a healthy level and modulate task metabolism by adjusting the stimulation frequency.

Predictors of mortality in patients with primary spinal cord glioblastoma.

PURPOSE: Primary spinal cord glioblastoma (GBM) is a rare and devastating disease. Little attention was ever paid to this rare disease. As a result, the standard treatment protocol and prognostic factors of primary spinal cord GBM were not well established. The aim of this study was to determine the predictors associated with survival in patients with primary spinal cord GBM. METHODS: A total of 122 patients with primary spinal cord GBM from Surveillance, Epidemiology, and End Results database and our institution were included in this retrospective analysis. Information about age, sex, race, tumor invasion, extent of resection, radiation, chemotherapy and year of diagnosis was collected. Univariate and multivariate accelerated failure time (AFT) regression model was performed to identify prognostic factors. RESULTS: Of the 122 patients, 102 (83.6%) expired at the time of data collection. Overall survival at 1 year, 2 years, 3 years and 5 years was 48.4%, 22.8%, 17.1% and 8.4%, respectively, and median survival time was 12 months. Only radiation was found to be associated with survival in the AFT regression model (time ratio 1.94, 95% CI 1.01-3.72, p < 0.05). Radiotherapy could improve survival slightly; patients who received RT survived approximately two times as long as patients who did not receive RT, but the advantage was short term. CONCLUSION: The survival of primary spinal cord GBM is poor in the current treatment strategy. Radiotherapy was associated with better survival, but the advantage was short term.

Vertebral artery dissection caused by atlantoaxial dislocation: a case report and review of literature.

BACKGROUND: Atlantoaxial dislocation (AAD) is the most common craniovertebral junction malformation (CVJm) which are anomalies of the bones and soft tissues surrounding the foramen magnum. It usually leads to neurologic abnormalities because of instability of this mobile area. But vertebral artery dissection (VAD) caused by AAD is uncommon. CASE REPORT: We report a 15-year-old boy who presented with acute onset of bilateral VAD leading to posterior circulation ischemic stroke (PCIS). Computed tomography angiography (CTA) indicated dissection and occlusion of bilateral intracranial vertebral arteries and AAD with os odontoideum. After antithrombotic treatment for 3 months, the patient got complete revascularization and received posterior C1-C2 fusion. DISCUSSION: There have only been tens of cases of PCIS caused by CVJm. We reviewed these relevant literatures and suggested that more attention should be paid to vascular impairment for patients with CVJm.

Effectiveness of posterior reduction and fixation in atlantoaxial dislocation: a retrospective cohort study of 135 patients with a treatment algorithm proposal.

PURPOSE: Surgical procedures on atlantoaxial dislocation remain controversial. The aim of this observational retrospective study was to investigate the treatment algorithm of surgical procedures. METHODS: According to CT and intraoperative evaluation during direct posterior reduction, 135 AAD cases were categorized into three groups: Group I: reducible dislocation; Group II: irreducible dislocation (Group IIa: effective decompression achieved after posterior reduction; Group IIb: no effective decompression after posterior reduction); and Group III: fixed dislocation. Group III presented with extensive bony fusions. Group I and Group IIa were treated with direct posterior reduction and fixation. Group IIb underwent posterior fixation and transoral odontoidectomy. Group III underwent transoral odontoidectomy alone. Japanese Orthopedic Association scores (JOA) were assessed to evaluate clinical status before and 6, 12 months after surgery. RESULTS: Our study included 118 Group I cases, 16 Group II cases (Group IIa: 11 cases; Group IIb: 5 cases), and one Group III case. Follow-up ranged from 12 to 36 months. PRIMARY OUTCOME: Anatomic atlantoaxial reduction was achieved in 118 of 135 patients (87.4%). Clinical improvements were seen in 96.3% (130/135) all the patients. Solid atlantoaxial fusion was shown in 134 patients. Secondary outcome: The overall complication rate was 3.7% (5/135). For Group I, the mean postoperative 6-month JOA was 14.5 versus 12.2 in preoperative patients (paired Student's t test, P < 0.01). CONCLUSIONS: This article proposes a clinical procedure that assists with therapeutic decision making and indicates the severity and difficulty of reduction of the atlantoaxial joint. These slides can be retrieved under Electronic Supplementary Material.

Carotid Artery-Related Perioperative Stroke Following Anterior Cervical Spine Surgery: A Series of 3 Cases and Literature Review.

BACKGROUND: Vascular complications following anterior cervical spine surgery are rare but potentially devastating. Complications associated with the carotid artery are even more disastrous but largely anecdotal, with no more than 4 reported cases. MATERIALS AND METHODS: We report 3 new cases of carotid artery-related perioperative stroke following anterior cervical spine surgery. All 3 patients had carotid artery atherosclerosis and the time of intraoperative carotid artery retraction was longer than 1 hour. One patient underwent hypotension during surgery. Risk factors as well as prevention and management protocols of carotid artery-related perioperative stroke based on the literature review and our clinical experience are discussed. CONCLUSIONS: Carotid artery-related perioperative stroke following anterior cervical spine surgery is extremely rare. Prolonged traction, carotid artery atherosclerosis, and intraoperative hypotension can produce cerebral hypoperfusion and cause ischemic stroke. Preoperative risk assessment, adequate perioperative manipulation, and postoperative management can minimize overall morbidity and mortality.

Is anterior release and cervical traction necessary for the treatment of irreducible atlantoaxial dislocation? A systematic review and meta-analysis.

PURPOSE: To compare the clinical and radiographic outcomes of irreducible atlantoaxial dislocation (IAAD) treated with posterior fusion after anterior release and direct posterior reduction of the dislocation. METHODS: Online databases were searched for articles describing IAAD published from 1999 to 2015. Five studies (105 patients) described treatment with posterior fusion after periodontoid tissue release, and five studies (113 patients) described treatment with direct posterior reduction of the dislocation. The primary outcomes in this study were the complete reduction rate, Japanese Orthopedic Association score, perioperative morbidity, perioperative mortality, complications, vascular injury, and infection. Standard meta-analysis techniques were used to compare the outcomes. RESULTS: Of 319 citations examined, 10 articles involving 218 participants were eligible. Overall, there were no significant differences between the anterior release and posterior fixation (ARPF) group and direct posterior reduction and fixation (DPRF) group in the complete reduction rate, neurologic recovery rate, perioperative morbidity, perioperative mortality, vascular injury, or infection. However, the complication rate in the DPRF group was much lower than that in the ARPF group. CONCLUSIONS: Compared with posterior fusion after anterior release, direct posterior reduction of the dislocation showed no significant differences in terms of the complete reduction rate, neurologic recovery rate, or fusion rate; however, it was a simpler process associated with less surgical trauma and a shorter operation time. Because of the limitations of the small sample in this study, whether direct posterior reduction of the dislocation is more effective and safer than posterior fusion after anterior release remains unclear. LEVEL OF EVIDENCE: III. These slides can be retrieved under Electronic Supplementary Material.

Minimally invasive versus open Transforaminal lumbar Interbody fusion in obese patients: a meta-analysis.

BACKGROUND: Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) has been employed in increasing cases compared with open TLIF (Open-TLIF). However, it is uncertain whether the advantages of MI-TLIF can also be specifically applied in obese patients. Therefore, the current study was thereby carried out aiming to compare the outcomes of MI-TLIF with those of Open-TLIF in obese patients with lumbar degenerative diseases. METHODS: Electronic databases were systemically retrieved from construction to May 2017. Meanwhile, the odds ratio (OR), mean difference (MD) and 95% confidence intervals (CI) were determined. RESULTS: A total of 7 observational cohort studies were enrolled into the current meta-analysis. The results indicated that, compared with Open-TLIF group, MI-TLIF could remarkably reduce the operative time (P = 0.002), intraoperative blood loss (P < 0.001), postoperative drainage (P = 0.01), length of stay (P < 0.001) and incidence of complications (P < 0.001). In addition, MI-TLIF could also lead to markedly lower early back pain-Visual Analog Scale (BP-VAS) score than that of Open-TLIF (P < 0.001), but no statistically significant differences were found in Oswestry Disability Index (ODI), late BP-VAS, early leg pain-VAS (LP-VAS) and late LP-VAS scores. CONCLUSION: MI-TLIF may be a more preferred choice for obese patients undergoing spinal surgery. However, differences in the long-term functional and pain outcomes between MI-TLIF and Open-TLIF remain a source of controversy, which should be further verified in future randomized-control trials.

Posterior Hemi-/Laminectomy and Facetectomy Approach for the Treatment of Dumbbell-Shaped Schwannomas in the Subaxial Cervical Spine: A Retrospective Study of 26 Cases.

OBJECTIVE: It is difficult to completely and safely remove a tumor that is located in the subaxial cervical spine by using the posterior approach because of the anatomical characteristics. Previous reports regarding the total removal of subaxial schwannomas using the one-stage posterior approach are still limited. This study was to evaluate the feasibility and efficacy of treating the dumbbell-shaped schwannomas in the subaxial cervical spine using the one-stage posterior approach. METHODS: Patients with dumbbell-shaped schwannomas in the subaxial cervical spine were treated using the one-stage posterior approach. Surgical profile, clinical outcomes, MRI and X-ray images, and complications were investigated. Japanese Orthopaedic Association (JOA) score and McCormick functional schema score were obtained. RESULTS: The average follow-up was 21.5 ± 5.1 months, with a range of 12-31 months. Twenty-six patients were enrolled in the study. Total resection was achieved in all patients using the one-stage posterior approach with hemi- or laminectomy and facetectomy. All cases underwent lateral mass screw fixation and fusion. JOA improved significantly (p < 0.01). The McCormick score improved significantly (p < 0.05) after the surgery. No mortality, morbidity, or tumor recurrence was observed during the follow-up period. CONCLUSION: Our technique was feasible and effective for the treatment of dumbbell schwannomas in the subaxial cervical spine. The tumor could be totally removed in most cases safely.

The changes of syrinx volume after posterior reduction and fixation of basilar invagination and atlantoaxial dislocation with syringomyelia.

PURPOSE: The purpose of this study focuses on the changes of the syrinx volume after posterior reduction and fixation of the basilar invagination (BI) and atlantoaxial dislocation (AAD) with syringomyelia. METHODS: We retrospectively analyzed the clinical outcome and syrinx volume changes in 71 patients with BI, AAD and syringomyelia treated with the posterior reduction and fixation technique. RESULTS: Clinical improvement was observed in 64 (90.1 %) patients postoperatively; 5 (7.0 %) were stable and 2 (2.8 %) were clinically aggravated. The postoperative Atlantodental interval became normal in 61 patients (86.0 %); showed reduction that was greater than 50 % but not complete in 5 patients (7.0 %); and reduction which was less than 50 % in 5 patients (7.0 %). The size of the syrinx was reduced postoperatively in 66 patients (93.0 %) while no change in the remaining 5 patients (7.0 %). CONCLUSIONS: Posterior reduction and fixation of the AAD and BI can effectively enlarge the foramen magnum, improve the cerebrospinal fluid circulation and consequently reduce the volume of the syrinx.

Retrocerebellar arachnoid cyst resulting in syringomyelia in a patient without tonsillar herniation: successful surgical treatment with reconstruction of CSF flow in the foramen magnum region.

A retrocerebellar arachnoid cyst causing syringomyelia is extremely rare without tonsillar herniation. The authors present a 44-year-old woman with symptoms of foramen magnum compression and syringomyelia. Magnetic resonance imaging demonstrated a large retrocerebellar arachnoid cyst with a large cervicothoracic syrinx but no signs of tonsillar herniation or hydrocephalus. The patient underwent a foramen magnum decompression with C1 laminectomy, microsurgical fenestration of the cyst, and duraplasty. After successful reconstruction of CSF flow, the patient experienced a relief of symptoms and a significant reduction of the syrinx. The intraoperative findings support the theory of a piston mechanism in the development of syringomyelia. Additional arachnoidal adhesions may also obstruct the CSF flow around the craniocervical junction. We recommend the surgical treatment should consist of an adequate decompression of the foramen magnum, wide microsurgical arachnoidal debridement, and duraplasty with autologous grafts sutured in a watertight way.

A case of fourth atlanto-axial facet joint: anatomical description.

PURPOSE: To report a rare fourth atlanto-axial joint. METHODS: A cadaveric specimen of a young male adult from occiput to C4 was dissected for anatomical study of craniocervical region. A true fourth atlanto-axial joint was confirmed. Its morphological characteristics were described. RESULTS: The fourth atlantoaxial joint is rarely seen. The possible embryogenesis is discussed. This case raises an anatomical possibility of a new variant in this region. CONCLUSIONS: A unique case with an anatomically proven fourth atlantoaxial joint is reported. This anomaly can lead to misdiagnosis. CT scan coupled with MRI can facilitate accurate diagnosis.