Deformative stress associated with an abnormal clivo-axial angle: A finite element analysis

Craniocervical instability in patients with Ehlers-Danlos syndromes: outcomes analysis following occipito-cervical fusion

Craniocervical instability (CCI) is increasingly recognized in hereditary disorders of connective tissue and in some patients following suboccipital decompression for Chiari malformation (CMI) or low-lying cerebellar tonsils (LLCT). CCI is characterized by severe headache and neck pain, cervical medullary syndrome, lower cranial nerve deficits, myelopathy, and radiological metrics, for which occipital cervical fusion (OCF) has been advocated. We conducted a retrospective analysis of patients with CCI and Ehlers-Danlos syndrome (EDS) to determine whether the surgical outcomes supported the criteria by which patients were selected for OCF. Fifty-three consecutive subjects diagnosed with EDS, who presented with severe head and neck pain, lower cranial nerve deficits, cervical medullary syndrome, myelopathy, and radiologic findings of CCI, underwent open reduction, stabilization, and OCF. Thirty-two of these patients underwent suboccipital decompression for obstruction of cerebral spinal fluid flow. Questionnaire data and clinical findings were abstracted by a research nurse. Follow-up questionnaires were administered at 5-28 months (mean 15.1). The study group demonstrated significant improvement in headache and neck pain (p < 0.001), decreased use of pain medication (p < 0.0001), and improved Karnofsky Performance Status score (p < 0.001). Statistically significant improvement was also demonstrated for nausea, syncope (p < 0.001), speech difficulties, concentration, vertigo, dizziness, numbness, arm weakness, and fatigue (p = 0.001). The mental fatigue score and orthostatic grading score were improved (p < 0.01). There was no difference in pain improvement between patients with CMI/LLCT and those without. This outcomes analysis of patients with disabling CCI in the setting of EDS demonstrated significant benefits of OCF. The results support the reasonableness of the selection criteria for OCF. We advocate for a multi-center, prospective clinical trial of OCF in this population.

Intraoperative occipital to C2 angle and external acoustic meatus-to-axis angular measurements for optimizing alignment during posterior fossa decompression and occipitocervical fusion for complex Chiari malformation

Background

Excess flexion or extension during occipitocervical fusion (OCF) can lead to postoperative complications, such as dysphagia, respiratory problems, line of sight issues, and neck pain, but posterior fossa decompression (PFD) and OCF require different positions that require intraoperative manipulation.

Objective

The objective of this study was to describe quantitative fluoroscopic morphometrics in Chiari malformation (CM) patients with symptoms of craniocervical instability (CCI) and demonstrate the intraoperative application of these measurements to achieve neutral craniocervical alignment while leveraging a single axis of motion with the Mayfield head clamp locking mechanism.

Methods

A retrospective cohort study of patients with CM 1 and 1.5 and features of CCI who underwent PFD and OCF at a single-center institution from March 2015 to October 2020 was performed. Patient demographics, preoperative presentation, radiographic morphometrics, operative details, complications, and clinical outcomes were analyzed.

Results

A total of 39 patients met the inclusion criteria, of which 37 patients (94.9%) did not require additional revision surgery after PFD and OCF. In this nonrevision cohort, preoperative to postoperative occipital to C2 angle (O-C2a) (13.5° ± 10.4° vs. 17.5° ± 10.1°, P = 0.047) and narrowest oropharyngeal airway space (nPAS) (10.9 ± 3.4 mm vs. 13.1 ± 4.8 mm, P = 0.007) increased significantly. These measurements were decreased in the two patients who required revision surgery due to postoperative dysphagia (mean difference - 16.6°° in O C2a and 12.8°° in occipital and external acoustic meatus to axis angle). Based on these results, these fluoroscopic morphometrics are intraoperatively assessed, utilizing a locking Mayfield head clamp repositioning maneuver to optimize craniocervical alignment prior to rod placement from the occipital plate to cervical screws.

Conclusion

Establishing a preoperative baseline of reliable fluoroscopic morphometrics can guide surgeons intraoperatively in appropriate patient realignment during combined PFD and OCF, and may prevent postoperative complications.

Perioperative opioid-minimization approach as a useful protocol in the management of patients with Ehlers-Danlos syndrome-hypermobility type, craniocervical instability and severe chronic pain who are to undergo occipito-cervical fixation

Patients suffering from connective tissue disorders like Ehlers-Danlos syndrome hypermobility type/joint hypermobility syndrome (EDS-HT/JHS) may be affected by craniocervical instability (CCI). These patients experience myalgic encephalomyelitis, chronic fatigue, depression, extreme occipital-cervical pain, and severe widespread pain that is difficult to relieve with opioids. This complex and painful condition can be explained by the development of chronic neuroinflammation, opioid-induced hyperalgesia, and central sensitization. Given the challenges in treating such severe physical pain, we evaluated all the analgesic methods previously used in the perioperative setting, and updated information was presented. It covers important physiopathological aspects for the perioperative care of patients with EDS-HT/JHS and CCI undergoing occipital-cervical/thoracic fixation/fusion. Moreover, a change of paradigm from the current opioid-based management of anesthesia/analgesia in these patients to the perioperative opioid minimization strategies used by the authors was analyzed and proposed as follow-up considerations from our previous case series. These strategies are based on total-intravenous opioid-free anesthesia, multimodal analgesia, and a postoperative combination of anti-hyperalgesic coadjuvants (lidocaine, ketamine, and dexmedetomidine) with an opioid-sparing effect.

Radiologic Features of Atlas Occipitalization and Its Clinical Implications

STUDY DESIGN

Retrospective radiographic analysis.

OBJECTIVES

Evaluation of the anatomic features of the craniovertebral junction in patients with occipitalization with and without atlantoaxial dislocation (AAD).

SUMMARY OF BACKGROUND DATA

Atlas occipitalization is a common feature of congenital AAD and usually requires surgical intervention. However, not all instances of occipitalization necessarily lead to AAD. No study has specifically examined and compared the craniovertebral bony morphology in occipitalization with, and without, AAD.

MATERIALS AND METHOD

We reviewed computed tomography (CT) scans of 2500 adult outpatients. Occipitalization cases without AAD (ON) were selected. Meanwhile, a series of 20 inpatient occipitalization cases with AAD (OD) were obtained in parallel. Another 20 control cases without occipitalization were also included. Multi-directional reconstructed CT images of all cases were analyzed.

RESULTS

A total of 18 adults with ON were found in all 2500 outpatients (0.7%). Both anterior height and posterior height of C1 lateral mass in the control group were significantly larger than those in both the ON and OD groups, whereas posterior height in the OD group was significantly less than that in the ON group. Three morphologic types of the occipitalized atlas posterior arch were identified: Type I, bilateral sides were unfused with opisthion; Type II, unilateral side was unfused with opisthion, whereas the other side was fused; and Type III, bilateral sides were fused with opisthion. In the ON group, three cases were type I (17%), six cases were type II (33%), and nine cases were type III (50%). In the OD group, all 20 cases were type III (100%).

CONCLUSIONS

Atlas occipitalization with, and without, AAD results from a distinctly different bony morphology at the craniovertebral junction. The novel classification system based on reconstructed CT images may be useful in prognosticating AAD in the setting of atlas occipitalization.

The Design of Brainstem Interfaces: Characterisation of Physiological Artefacts and Implications for Closed-loop Algorithms

Surgical neuromodulation through implantable devices allows for stimulation delivery to subcortical regions, crucial for symptom control in many debilitating neurological conditions. Novel closed-loop algorithms deliver therapy tailor-made to endogenous physiological activity, however rely on precise sensing of signals such as subcortical oscillations. The frequency of such intrinsic activity can vary depending on subcortical target nucleus, while factors such as regional anatomy may also contribute to variability in sensing signals. While artefact parameters have been explored in more 'standard' and commonly used targets (such as the basal ganglia, which are implanted in movement disorders), characterisation in novel candidate nuclei is still under investigation. One such important area is the brainstem, which contains nuclei crucial for arousal and autonomic regulation. The brainstem provides additional implantation targets for treatment indications in disorders of consciousness and sleep, yet poses distinct anatomical challenges compared to central subcortical targets. Here we investigate the region-specific artefacts encountered during activity and rest while streaming data from brainstem implants with a cranially-mounted device in two patients. Such artefacts result from this complex anatomical environment and its interactions with physiological parameters such as head movement and cardiac functions. The implications of the micromotion-induced artefacts, and potential mitigation, are then considered for future closed-loop stimulation methods.

Reference values of four measures of craniocervical stability using upright dynamic magnetic resonance imaging

PURPOSE

To establish reference ranges for four most commonly used diagnostic measures of craniocervical instability (CCI) in three cervical sagittal positions. This necessitated development of a reliable measurement protocol using upright, dynamic MRI (udMRI), to determine differences in the extent of motion between positions, and whether age and sex correlate with these measures.

MATERIALS AND METHODS

Deidentified udMRIs of 50 adults, referred for reasons other than CCI, were captured at three positions (maximal flexion, maximal extension and neutral). Images were analyzed, providing measures of basion-axial interval, basion-axial angle, basion-dens interval (BDI) and the Grabb-Oakes line (GOL) for all three positions (12 measures per participant). All measures were independently recorded by a radiologist and neurosurgeon to determine their reliability. Descriptive statistics, correlations, paired and independent t-tests were used. Mean (± 2 SD) identified the reference range for all four measures at each craniocervical position.

RESULTS

The revised measurement protocol produced inter-rater reliability indices of 0.69-0.97 (moderate-excellent). Fifty adults' (50% male; mean age 41.2 years (± 9.7)) reference ranges for all twelve measures were reported. Except for the BDI and GOL when moving between neutral and full flexion, significant extents of movement were identified between the three craniocervical positions for all four measures (p ≤ 0.005). Only a minor effect of age was found.

CONCLUSIONS

This is the first study to provide a rigorous standardized protocol for four diagnostic measures of CCI. Reference ranges are established at mid and ends of sagittal cervical range corresponding to where exacerbations of signs and symptoms are commonly reported.

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.

Craniocervical instability in patients with Ehlers-Danlos syndrome: controversies in diagnosis and management

Ehlers-Danlos syndrome (EDS) is a rare hereditary condition that can result in ligamentous laxity and hypermobility of the cervical spine. A subset of patients can develop clinical instability of the craniocervical junction associated with pain and neurological dysfunction, potentially warranting treatment with occipitocervical fixation (OCF). Surgical decision-making in patients with EDS can be complicated by difficulty distinguishing from hypermobility inherent in the disease and true pathological instability necessitating intervention. Here we comprehensively review the available medical literature to critically appraise the evidence behind various proposed definitions of instability in the EDS population, and summarize the available outcomes data after OCF. Several radiographic parameters have been used, including the clivo-axial angle, basion-axial interval, and pB-C2 measurement. Despite increasing recognition of EDS by spine surgeons, there remains a paucity of data supporting proposed radiographic parameters for spinal instability among EDS patients. Furthermore, there is a lack of high-quality evidence concerning the efficacy of surgical treatments for chronic debilitating pain prevalent in this population. More standardized clinical measures and rigorous study methodologies are needed to elucidate the role of surgical intervention in this complex patient population.

Craniocervical Instability in Ehlers-Danlos Syndrome-A Systematic Review of Diagnostic and Surgical Treatment Criteria

STUDY DESIGN

Systematic review.

OBJECTIVE

Ehlers-Danlos Syndrome (EDS) comprises a spectrum of connective tissue disorders, which may be associated with cranio-cervical instability (CCI). There is a lack of consensus on diagnostic imaging parameters, indications, and outcomes of surgical treatment.

METHODS

This systematic review analyses the literature on diagnostic methods and/or criteria for CCI, screening the databases Ovid Medline, Embase, Cochrane Library, and PubMed. Articles were included based on the PRISMA guidelines and assessed using the Newcastle-Ottawa Quality Assessment Scale (NOS) and according to their evidence level.

RESULTS

Sixteen articles, including 78 surgical patients, met the inclusion criteria. The main diagnostic measures for CCI were dynamic x-rays and CT imaging. Ten different radiographic parameters were reported, of which 4 were the most frequently applied for surgical decision-making: the clivo-axial angle (CXA), the Harris measurement, the Grabb-Mapstone-Oakes measurement, and the angular displacement of C1 to C2. The evidence level ranged between III and V and the article quality between 4 and 8 out of 9 stars on the NOS Scale.

CONCLUSIONS

There is a lack of high quality, prospective evidence regarding the evaluation of suspected CCI in patients with EDS. Based on our systematic review, we recommend that the CXA, Harris measurement, Grabb-Mapstone-Oakes measurement, and the angular displacement of C1 to C2 be used to evaluate suspected CCI in EDS patients. Surgical fixation of suspected CCI should only be performed in cases with clear radiographic presence of instability and concordant symptoms/signs. Consensus-based guidelines and care pathways are required.

Craniocervical Stabilization After Failed Chiari Decompression: A Case Series of a Population with High Prevalence of Ehlers-Danlos Syndrome

BACKGROUND

In the treatment of Chiari malformation type I (CM-I), posterior fossa decompression is achieved via suboccipital craniectomy (SOC); however, some patients continue to experience symptoms after treatment, which may be due to craniocervical instability (CCI). The purposes of this study were to analyze data from patients who required an occipitocervical fusion (OCF) for the management of CCI after having previously undergone SOC for CM-I to determine if OCF is a safe and effective option and to determine any identifiable risk factors for CCI in these patients.

METHODS

A retrospective review was done on all patients who underwent an OCF performed by the senior author between November 2013 and June 2020 after having previously undergone SOC for CM-I. Demographic, radiographic, perioperative, and outcome data were collected and clivoaxial angles (CXAs) were measured pre- and postoperatively.

RESULTS

Fifteen patients were identified who developed symptomatic CCI after previously undergoing a suboccipital craniectomy for the treatment of CM-I. All 15 patients were treated by OCF with good outcome. Of these, 12 patients had a known diagnosis of Ehlers-Danlos syndrome (EDS). Overall, the CXAs of these patients were found to be corrected to a more anatomical alignment.

CONCLUSIONS

Symptomatic CCI should be recognized as a delayed postoperative complication in the surgical treatment of CM-I, with an underlying connective tissue hypermobility disorder such as EDS serving as a potential risk factor its development. CCI can be managed with OCF as a safe and effective treatment option for this patient population.

Increase in clivo-axial angle is associated with clinical improvement in children undergoing occipitocervical fusion for complex Chiari malformation: patient series

BACKGROUND

The authors analyzed the pre- and postoperative morphometric properties of pediatric patients with complex Chiari malformation undergoing occipitocervical fusion (OCF) to assess clinical outcomes and morphometric properties that might influence postoperative outcomes.

OBSERVATIONS

The authors retrospectively reviewed 35 patients younger than 22 years with Chiari malformation who underwent posterior fossa decompression and OCF with or without endoscopic endonasal odontoidectomy at their institution (13 with and 22 without odontoidectomy). Clivo-axial angle (CXA), pB-C2, atlantodental interval, basion-dens interval, basion-axial interval, and canal diameter at the level of C1 were measured on preoperative and approximately 3-month postoperative computed tomography or magnetic resonance imaging. The authors further stratified the patient cohort into three age groups and compared the three cohorts. The most common presenting symptoms were headache, neck/shoulder pain, and dysphagia; 80% of the cohort had improved clinical outcomes. CXA increased significantly after surgery. When stratified into those who showed postoperative improvement and those who did not, only the former showed a significant increase in CXA. After age stratification, the significant changes in CXA were observed in the 7- to 13-year-old and 14- to 21-year-old cohorts.

LESSONS

CXA may be the most important morphometric predictor of clinical outcomes after OCF in pediatric patients with complex Chiari malformation.

Predicting clinical outcomes using morphometric changes in adults with complex Chiari malformation undergoing occipitocervical fusion with or without ventral decompression: patient series

BACKGROUND

The authors assessed the connection between clinical outcomes and morphometrics in patients with complex Chiari malformation (CM) who have undergone posterior fossa decompression (PFD) and subsequent occipitocervical fusion (OCF) with or without ventral decompression (VD).

OBSERVATIONS

The authors retrospectively reviewed 33 patients with CM aged over 21 years who underwent PFD and OCF with or without endoscopic endonasal odontoidectomy at the authors’ institution (21 OCF only and 12 OCF + VD). Clivoaxial angle (CXA), pB-C2 (perpendicular line to the line between the basion and C2), atlantodental interval (ADI), basion-dens interval (BDI), basion-axial interval (BAI), and C1 canal diameter were measured on preoperative and approximately 3-month postoperative computed tomography or magnetic resonance imaging scans. Common symptoms included headache, paresthesia, and bulbar symptoms. Clinical improvement after surgery was observed in 78.8% of patients. CXA, ADI, and BDI all significantly increased after surgery, whereas pB-C2 and BAI significantly decreased. OCF + VD had a significantly more acute CXA and longer pB-C2 preoperatively than OCF only. Patients who clinically improved postoperatively showed the same significant morphometric changes, but those who did not improve showed no significant morphometric changes.

LESSONS

Patients showing improvement had greater corrections in skull base morphometrics than those who did not. Although there are various mutually nonexclusive reasons why certain patients do not improve after surgery, smaller degrees of morphometric correction could play a role.

Abnormal spinal cord motion at the craniocervical junction in hypermobile Ehlers-Danlos patients

OBJECTIVE

The craniocervical junction (CCJ) is anatomically complex and comprises multiple joints that allow for wide head and neck movements. The thecal sac must adjust to such movements. Accordingly, the thecal sac is not rigidly attached to the bony spinal canal but instead tethered by fibrous suspension ligaments, including myodural bridges (MDBs). The authors hypothesized that pathological spinal cord motion is due to the laxity of such suspension bands in patients with connective tissue disorders, e.g., hypermobile Ehlers-Danlos syndrome (EDS).

METHODS

The ultrastructure of MDBs that were intraoperatively harvested from patients with Chiari malformation was investigated with transmission electron microscopy, and 8 patients with EDS were compared with 8 patients without EDS. MRI was used to exclude patients with EDS and craniocervical instability (CCI). Real-time ultrasound was used to compare the spinal cord at C1-2 of 20 patients with EDS with those of 18 healthy control participants.

RESULTS

The ultrastructural damage of the collagen fibrils of the MDBs was distinct in patients with EDS, indicating a pathological mechanical laxity. In patients with EDS, ultrasound revealed increased cardiac pulsatory motion and irregular displacement of the spinal cord during head movements.

CONCLUSIONS

Laxity of spinal cord suspension ligaments and the associated spinal cord motion disorder are possible pathogenic factors for chronic neck pain and headache in patients with EDS but without radiologically proven CCI.

Atlanto-axial rotary instability (Fielding type 1): characteristic clinical and radiological findings, and treatment outcomes following alignment, fusion, and stabilization

Atlanto-axial instability (AAI) is common in the connective tissue disorders, such as rheumatoid arthritis, and increasingly recognized in the heritable disorders of Stickler, Loeys-Dietz, Marfan, Morquio, and Ehlers-Danlos (EDS) syndromes, where it typically presents as a rotary subluxation due to incompetence of the alar ligament. This retrospective, IRB-approved study examines 20 subjects with Fielding type 1 rotary subluxation, characterized by anterior subluxation of the facet on one side, with a normal atlanto-dental interval. Subjects diagnosed with a heritable connective tissue disorder, and AAI had failed non-operative treatment and presented with severe headache, neck pain, and characteristic neurological findings. Subjects underwent a modified Goel-Harms posterior C1-C2 screw fixation and fusion without complication. At 15 months, two subjects underwent reoperation following a fall (one) and occipito-atlantal instability (one). Patients reported improvement in the frequency or severity of neck pain (P < 0.001), numbness in the hands and lower extremities (P = 0.001), headaches, pre-syncope, and lightheadedness (all P < 0.01), vertigo and arm weakness (both P = 0.01), and syncope, nausea, joint pain, and exercise tolerance (all P < 0.05). The diagnosis of Fielding type 1 AAI requires directed investigation with dynamic imaging. Alignment and stabilization is associated with improvement of pain, syncopal and near-syncopal episodes, sensorimotor function, and exercise tolerance.

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.

Opioid-free anesthesia for patients with joint hypermobility syndrome undergoing craneo-cervical fixation: a case-series study focused on anti-hyperalgesic approach

Background

Patients with Ehlers-Danlos Syndrome/Hypermobility Type (EDS-HT/JHS) and Craneo-Cervical Instability frequently suffer from severe widespread pain which is difficult to control. Chronic neuroinflammation, opioid-induced hyperalgesia, and central sensitization may explain this painful condition. The aim of this study was to determine if opioid-free anesthesia plus the postoperative administration of lidocaine, ketamine and dexmedetomidine can reduce postoperative pain and the need of methadone rescues in comparison with opioid-based management in these patients undergoing Craneo-Cervical Fixation (CCF). The secondary aim was to assess the needs of opioids at hospital-discharge, incidence of gastrointestinal complications and the requirement of anxiolytic.

Methods

A retrospective, consecutive case series study was designed. 42 patients with EDS-HT/JHS undergoing CCF were enrolled in two groups: an OFA-plus Group that received opioid-free anesthesia with propofol, lidocaine, ketamine and dexmedetomidine, and OP Group, opioid-based anesthesia-analgesia. The main variables: Preoperative Visual Analogue Score (VAS), postoperative VAS on the 1st, 2nd, 4th and 6th days, sufentanil or morphine requirements, need for methadone rescue, and VAS at hospital-discharge. Data was presented by mean ± SD, percentage, median or interquartile range. Chi-squared or Fisher’s test. 95% C.I and P values < 0.05.

Results

Nineteen patients in OFA-plus, and 23 patients in OP group. VAS was lower in OFA-plus on the postoperative days evaluated (p < 0.001).VAS at hospital-discharge was lower in OFA-plus: 4.96 (4.54–5.37) vs. OP 6.39 (6.07–6.71) (p < 0.001). Methadone requirement was lower in the OFA-plus (p < 0.001). 78% of patients in OFA-plus didn’t need methadone rescue. 95% in OP group needed methadone rescues at high doses(> 15 mg/day). No differences regarding equivalent doses of sufentanil or morphine consumption on the 2nd, 4th, and 6th postoperative days were found. OFA-plus decreased ileus, nausea and vomiting (p < 0.001). 60.9% in OFA-plus group decreased opioid requirements at hospital-discharge compared with preoperative values. A 77% reduction of anxiolytics requirements was shown.

Conclusion

OFA-plus management for patients undergoing CCF with EDS-HT/JHS shows significant reduction in postoperative pain and at hospital-discharge compared with opioid-based anesthesia. OFA-plus management decreases the total doses of methadone rescues, reduces anxiolytic requirements and gastrointestinal side-effects, except for constipation. OFA-plus management is a feasible option to improve postoperative pain control, reducing the opioids’ use and their postoperative side-effects in patients undergoing CCF with EDS-HT/JHS.

Ehlers-Danlos syndrome-associated craniocervical instability with cervicomedullary syndrome: Comparing outcome of craniocervical fusion with occipital bone versus occipital condyle fixation

Introduction:

Ehlers–Danlos syndrome (EDS) predisposes to craniocervical instability (CCI) with resulting cranial settling and cervicomedullary syndrome due to ligamentous laxity. This study investigates possible differences in radiographic outcomes and operative complication rate between two surgical techniques in patients with EDS and CCI undergoing craniocervical fusion (CCF): occipital bone (OB) versus occipital condyle (OC) fixation.

Methods:

A retrospective search of the institutional operative database between January 07, 2017, and December 31, 2019, was conducted to identify EDS patients who underwent CCF with either OB (Group OB) or OC (Group OC) fixation. For each patient, pre- and post-operative radiographic measurements and operative complications were extracted and compared between groups (OB vs. OC): pB-C2, clivoaxial angle (CXA), tonsillar descent, C2C7 sagittal Cobb angle, C2 long axis, and operative complications.

Results:

Of a total of 26 patients, 13 underwent OV and 13 underwent OC fixation. Eighty-five percent of the patients underwent OC underwent fusion from occiput to C2, while the remaining 15% fusion from occiput to C3. Radiographic outcome in the OC versus OB group was preoperative measurements were similar between OC and OB group: pB-C2 8.8 mm (1.5, 6–11) versus 8.3 mm (1.7, 4–9.6), P = 0.43; CXA 128.2° (5.4, 122–136) versus 131.9° (6.8,122–141), P = 0.41; tonsillar descent 6.2 mm (4.8, 0–15) versus 2.9 mm (3.4, 0–8), P = 0.05; C2 long axis 75.2° (6.7, 58–85) versus 67.2° (21.4, 1–80), P = 0.21; postoperative change of CXA + 14.4° (8.8, 0–30) versus 16.2° (12.4, −4–38), P = 0.43; change of pB-C2 − 2.6 mm (1.8, −-5.3 to 0) versus − 1.2 mm (4, −4.6–8), P = 0.26; and postoperative C2C7 sagittal Cobb angle − 2.6° (19.5, −43–39) versus − 2.6° (11.4, −21–12). Operative complications were seen in 1 out of 13 patients (8%) versus 2 out of 13 patients (16%), P = 1.

Conclusions:

In EDS, patients with CCI undergoing CCF radiographic and clinical outcome were similar between those with OC versus OB fixation. Both techniques resulted in sufficient correction of pB-C2 and CXA measurements with a low complication rate.

Normal range of clivoaxial angle in adults using flexion and extension cervical magnetic resonance imaging scans

OBJECTIVE

An abnormally decreased clivoaxial angle (CXA) is used during the clinical evaluation for corrective skull base surgery. Published normal ranges of CXA using x-ray, computed tomography, or magnetic resonance imaging (MRI) vary dramatically, especially with neck flexion or extension. The aim of this study was to use high-resolution MRI to determine the normal range of CXA in various neck positions using a reproducible measurement technique.

METHODS

The CXA was measured in 10 healthy volunteers on sagittal T2 SPACE c-spine MRI in supine and prone positions and with the neck both neck and extended. CXA is strictly defined as the angle between a line along the inferior third of the dorsal clival cortex and a line from the superior/posterior cortex of the dens to the posterior/inferior corner of the C2 body. Statistical analysis was performed in all positions and included mean CXA, range, standard deviation (SD), inter-reader agreement, and group comparisons.

RESULTS

The mean CXA overall was 156.92° (SD=4.23°; range 134-179°). The mean value for extension CXA was 169.20° (SD=5.81°), and the mean value for flexion CXA was 144.73° (SD=5.71°), the difference being statistically significant (p<0.0001) regardless of supine or prone position. Concordant correlations of reader measurements showed substantial agreement in the supine position at 0.96, with lower agreement in the prone position at 0.87.

CONCLUSIONS

We report normal ranges for CXA in various neck positions based on 3D T2-weighted MRI, using a reproducible measurement method. There was a significant difference in the CXA values between neck extended and neck flexed positions but not between supine and prone positions.

Refractory Syncope and Presyncope Associated with Atlantoaxial Instability: Preliminary Evidence of Improvement Following Surgical Stabilization

BACKGROUND

The proclivity to atlantoaxial instability (AAI) has been widely reported for conditions such as rheumatoid arthritis and Down syndrome. Similarly, we have found a higher than expected incidence of AAI in hereditary connective tissue disorders. We demonstrate a strong association of AAI with manifestations of dysautonomia, in particular syncope and lightheadedness, and make preliminary observations as to the salutary effect of surgical stabilization of the atlantoaxial motion segment.

METHODS

In an institutional review board-approved retrospective study, 20 subjects (16 women, 4 men) with hereditary connective tissue disorders had AAI diagnosed by computed tomography. Subjects underwent realignment (reduction), stabilization, and fusion of the C1-C2 motion segment. All subjects completed preoperative and postoperative questionnaires in which they were asked about performance, function, and autonomic symptoms, including lightheadedness, presyncope, and syncope.

RESULTS

All patients with AAI reported lightheadedness, and 15 had refractory syncope or presyncope despite maximal medical management and physical therapy. Postoperatively, subjects reported a statistically significant improvement in lightheadedness (P = 0.003), presyncope (P = 0.006), and syncope (P = 0.03), and in the frequency (P < 0.05) of other symptoms related to autonomic function, such as nausea, exercise intolerance, palpitations, tremors, heat intolerance, gastroesophageal reflux, and sleep apnea.

CONCLUSIONS

This study draws attention to the potential for AAI to present with syncope or presyncope that is refractory to medical management, and for surgical stabilization of AAI to lead to improvement of these and other autonomic symptoms.

Craniometric parameters for the evaluation of platybasia and basilar invagination on magnetic resonance imaging: a reproducibility study

Objective

The present study aims to perform a reproducibility study of the clivus-canal angle (CCA), Welcker’s basal angle (WBA), and the distance from the odontoid process to Chamberlain’s line (DOCL) on magnetic resonance imaging (MRI).

Materials and Methods

Two medical students and two radiologists respectively evaluated 100 and 50 consecutive MRI scans of adult skulls, selected randomly. Each examiner, working independently and blinded to the previous results, performed readings for each patient on two different occasions. Measurements were performed in T1-weighted sequences acquired in the midsagittal plane. The levels of intraobserver reproducibility and interobserver agreement were evaluated by calculating the intraclass correlation coefficients (ICCs) and the corresponding 95% confidence intervals.

Results

The mean values obtained by the examiners were 150º for the CCA, 130º for the WBA, and 2.5 mm for the DOCL. The ICC for interobserver agreement was 0.980, 0.935, and 0.967, for the CCA, WBA, and DOCL, respectively, for the students, compared with 0.977, 0.941, and 0.982, respectively, for the radiologists, and 0.980, 0.992, and 0.990, respectively, for all of the examiners together. In the analysis of intraobserver agreement, the ICC ranged from 0.929 to 0.959 for the CCA, from 0.918 to 0.964 for the WBA, and from 0.918 to 0.981 for the DOCL.

Conclusion

The measurement of the CCA, WBA, and DOCL appears to show excellent intraobserver reproducibility and interobserver agreement on MRI.

Anatomical evaluation of the craniovertebral junction on cone-beam computed tomography images

INTRODUCTION

There are many craniometric measurements that are used in evaluating craniovertebral junction (CVJ) pathologies such as basilar invagination, atlantoaxial dislocation and platybasia. Therefore, it is important to determine the normal reference range of the craniometric measurements. This study aims to determine the morphometric reference values of the bony structures in the CVJ from cone-beam computed tomography (CBCT) images of a group of South Eastern Anatolian population.

MATERIALS AND METHODS

The CBCT images of 300 individuals were retrospectively evaluated. 14 parameters on midsagittal and 2 parameters on the coronal plane were studied. The data were statistically evaluated.

RESULTS

Measurement results were found as follows; the distances between odontoid process (OP) and McGregor line as 0.31 ± 3.22 mm, OP and Chamberlain line 1.06 ± 3.22 mm, OP and McRae line 5.30 ± 1.59 mm, OP and Fischgold digastric line 8.70 ± 4.12 mm, OP and Fischgold bimastoid line - 5.15 ± 4.86 mm, length of McRae line 35.58 ± 2.52 mm, atlantodental interval 1.28 ± 0.48 mm, posterior atlantodental interval 19.54 ± 2.24 mm, basion axial interval 4.01 ± 1.83 mm, basion dental interval 4.92 ± 1.77 mm, length of Modified Ranawat line 28.66 ± 2.38 mm, length of Redlund-Johnell line 35.11 ± 4.09 mm, clivus canal angle 157.62° ± 11.85°, Welcher basal angle 130.83° ± 6.29°, craniocervical tilt 126.98° ± 12.24° and Powers ratio as 0.72 ± 0.06.

CONCLUSION

In this study, the morphometric values were evaluated according to age and gender in individuals who did not have any radiologic anomalies. The normal reference ranges may be useful for researchers who are researching pathology in this region. It is recommended to conduct further studies with different populations to determine the normal reference range.

Optimizing Alignment Parameters During Craniocervical Stabilization and Fusion: A Technical Note

Proper craniocervical alignment during craniocervical reduction, stabilization, and fusion optimizes cerebrospinal fluid (CSF) flow through the foramen magnum, establishes the appropriate “gaze angle”, avoids dysphagia and dyspnea, and, most importantly, normalizes the clival-axial angle (CXA) to reduce ventral brainstem compression. To illustrate the metrics of reduction that include CXA, posterior occipital cervical angle, orbital-axial or “gaze angle”, and mandible-axial angle, we present a video illustration of a patient presenting with signs and symptoms of the cervical medullary syndrome along with concordant radiographic findings of craniocervical instability as identified on dynamic imaging and through assessment of the CXA, Harris, and Grabb-Oakes measurements.

Cervical medullary syndrome secondary to craniocervical instability and ventral brainstem compression in hereditary hypermobility connective tissue disorders: 5-year follow-up after craniocervical reduction, fusion, and stabilization

A great deal of literature has drawn attention to the "complex Chiari," wherein the presence of instability or ventral brainstem compression prompts consideration for addressing both concerns at the time of surgery. This report addresses the clinical and radiological features and surgical outcomes in a consecutive series of subjects with hereditary connective tissue disorders (HCTD) and Chiari malformation. In 2011 and 2012, 22 consecutive patients with cervical medullary syndrome and geneticist-confirmed hereditary connective tissue disorder (HCTD), with Chiari malformation (type 1 or 0) and kyphotic clivo-axial angle (CXA) enrolled in the IRB-approved study (IRB# 10-036-06: GBMC). Two subjects were excluded on the basis of previous cranio-spinal fusion or unrelated medical issues. Symptoms, patient satisfaction, and work status were assessed by a third-party questionnaire, pain by visual analog scale (0-10/10), neurologic exams by neurosurgeon, function by Karnofsky performance scale (KPS). Pre- and post-operative radiological measurements of clivo-axial angle (CXA), the Grabb-Mapstone-Oakes measurement, and Harris measurements were made independently by neuroradiologist, with pre- and post-operative imaging (MRI and CT), 10/20 with weight-bearing, flexion, and extension MRI. All subjects underwent open reduction, stabilization occiput to C2, and fusion with rib autograft. There was 100% follow-up (20/20) at 2 and 5 years. Patients were satisfied with the surgery and would do it again given the same circumstances (100%). Statistically significant improvement was seen with headache (8.2/10 pre-op to 4.5/10 post-op, p < 0.001, vertigo (92%), imbalance (82%), dysarthria (80%), dizziness (70%), memory problems (69%), walking problems (69%), function (KPS) (p < 0.001). Neurological deficits improved in all subjects. The CXA average improved from 127° to 148° (p < 0.001). The Grabb-Oakes and Harris measurements returned to normal. Fusion occurred in 100%. There were no significant differences between the 2- and 5-year period. Two patients returned to surgery for a superficial wound infections, and two required transfusion. All patients who had rib harvests had pain related that procedure (3/10), which abated by 5 years. The results support the literature, that open reduction of the kyphotic CXA to lessen ventral brainstem deformity, and fusion/stabilization to restore stability in patients with HCTD is feasible, associated with a low surgical morbidity, and results in enduring improvement in pain and function. Rib harvest resulted in pain for several years in almost all subjects.

Anterior Retropharyngeal Cage Distraction and Fixation for Basilar Invagination: "The Wedge Technique"

OBJECTIVE

Surgery is indicated for basilar invagination (BI) in symptomatic patients. In many patients, symptoms and signs occur due to an upward-migrated and malaligned odontoid with fixed or mobile atlantoaxial instability. Posterior distraction and fixation of the atlantoaxial joints has evolved to become the standard of care, but has some inherent morbidity. In this study, we propose that the unilateral anterior submandibular retropharyngeal approach with customized wedge-shaped titanium cages inserted into both atlantoaxial joints and anterior atlantoaxial fixation with a plate screw construct is a safer and easier option in many cases of BI.

METHODS

From February 2014 to February 2019, 52 patients (age range, 15-78 years; 40 males and 12 females) with symptomatic BI with atlantoaxial dislocation and minimal sagittal facetal inclination and only mild Chiari malformation without syringomyelia were offered anterior submandibular retropharyngeal atlantoaxial distraction and fixation surgery.

RESULTS

Neurological improvement occurred in 80% of patients, while the neurological status of 20% remained unchanged. No patients worsened, and no major complications or mortality was observed.

CONCLUSION

In properly selected cases of symptomatic BI, anterior wedge cage distraction with anterior atlantoaxial fixation is a safe and simple option.

Cervical Spine and Cord Angle Mismatch in the Pathogenesis of Myelopathy

BACKGROUND

Cervical myelopathy is a complex pathology and dynamic compression of the tethered cervical cord, which may be responsible for clinical symptoms.

METHODS

Patients with cervical canal stenosis who had magnetic resonance imaging in flexion and extension positions were retrospectively reviewed. All cases were evaluated in Nurick grade. The cervical parameters-cervical cord (CC) angle, cervical lordosis, and spine/cord (S/C) angle ratio-were measured on the magnetic resonance imaging. Mean values of these parameters were compared between nonmyelopathic (Nurick grade 0) and myelopathic groups (Nurick grades 1-5). A multinomial ordinal logistic regression was used to predict outcome for Nurick grade using the CC angle, the cervical lordosis angle, and the S/C angle ratio as independent variables.

RESULTS

A total of 65 patients (35 men) with the mean age of 58.6 ± 11.4 years were analyzed. A comparison of means between Nurick grade 0 against each of myelopathic grades 1-5 revealed significant differences only for the S/C angle ratio. A cumulative comparison between nonmyelopathic and myelopathic grades for the S/C angle ratio showed significant difference of 0.29 (1.16 ± 0.5 vs. 1.45 ± 0.6, respectively; P < 0.05). Cumulative comparison for the CC angle difference in flexion and extension lordosis did not show substantial differences. The S/C angle ratio was the only significant parameter in the prediction of the Nurick grade with an odds ratio of 2.63 (95% confidence interval 2.11-2.79).

CONCLUSIONS

A positive correlation between Nurick grade and cervical spine and cord angle mismatch was found.

Improvement of severe myalgic encephalomyelitis/chronic fatigue syndrome symptoms following surgical treatment of cervical spinal stenosis

Background

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a potentially disabling disorder. Little is known about the contributors to severe forms of the illness. We describe three consecutive patients with severe ME/CFS whose symptoms improved after recognition and surgical management of their cervical spinal stenosis.

Methods

All patients satisfied clinical criteria for ME/CFS and orthostatic intolerance, and were later found to have cervical spinal stenosis. Overall function was assessed before and after surgery using the Karnofsky score and the SF-36 physical function subscale score.

Results

Neurological findings included > 3+ deep tendon reflexes in 2 of 3, a positive Hoffman sign in 2 of 3, tremor in 2 of 3, and absent gag reflex in 1 of 3. The cervical spine canal diameter in the three patients ranged from 6 to 8.5 mm. One had congenital cervical stenosis with superimposed spondylosis, and two had single- or two-level spondylosis. Anterior cervical disc replacement surgery in two patients and a hybrid anterior cervical disc fusion and disc replacement in the third was associated with a marked improvement in myelopathic symptoms, resolution of lightheadedness and hemodynamic dysfunction, improvement in activity levels, and improvement in global ME/CFS symptoms.

Conclusions

The prompt post-surgical restoration of more normal function suggests that cervical spine stenosis contributed to the pathogenesis of refractory ME/CFS and orthostatic symptoms. The improvements following surgery emphasize the importance of a careful search for myelopathic examination findings in those with ME/CFS, especially when individuals with severe impairment are not responding to treatment.

Utility of the clivo-axial angle in assessing brainstem deformity: pilot study and literature review

There is growing recognition of the kyphotic clivo-axial angle (CXA) as an index of risk of brainstem deformity and craniocervical instability. This review of literature and prospective pilot study is the first to address the potential correlation between correction of the pathological CXA and postoperative clinical outcome. The CXA is a useful sentinel to alert the radiologist and surgeon to the possibility of brainstem deformity or instability. Ten adult subjects with ventral brainstem compression, radiographically manifest as a kyphotic CXA, underwent correction of deformity (normalization of the CXA) prior to fusion and occipito-cervical stabilization. The subjects were assessed preoperatively and at one, three, six, and twelve months after surgery, using established clinical metrics: the visual analog pain scale (VAS), American Spinal InjuryAssociation Impairment Scale (ASIA), Oswestry Neck Disability Index, SF 36, and Karnofsky Index. Parametric and non-parametric statistical tests were performed to correlate clinical outcome with CXA. No major complications were observed. Two patients showed pedicle screws adjacent to but not deforming the vertebral artery on post-operative CT scan. All clinical metrics showed statistically significant improvement. Mean CXA was normalized from 135.8° to 163.7°. Correction of abnormal CXA correlated with statistically significant clinical improvement in this cohort of patients. The study supports the thesis that the CXA maybe an important metric for predicting the risk of brainstem and upper spinal cord deformation. Further study is feasible and warranted.

Neurological and spinal manifestations of the Ehlers-Danlos syndromes

The Ehlers-Danlos syndromes (EDS) are a heterogeneous group of heritable connective tissue disorders characterized by joint hypermobility, skin extensibility, and tissue fragility. This communication briefly reports upon the neurological manifestations that arise including the weakness of the ligaments of the craniocervical junction and spine, early disc degeneration, and the weakness of the epineurium and perineurium surrounding peripheral nerves. Entrapment, deformation, and biophysical deformative stresses exerted upon the nervous system may alter gene expression, neuronal function and phenotypic expression. This report also discusses increased prevalence of migraine, idiopathic intracranial hypertension, Tarlov cysts, tethered cord syndrome, and dystonia, where associations with EDS have been anecdotally reported, but where epidemiological evidence is not yet available. Chiari Malformation Type I (CMI) has been reported to be a comorbid condition to EDS, and may be complicated by craniocervical instability or basilar invagination. Motor delay, headache, and quadriparesis have been attributed to ligamentous laxity and instability at the atlanto-occipital and atlantoaxial joints, which may complicate all forms of EDS. Discopathy and early degenerative spondylotic disease manifest by spinal segmental instability and kyphosis, rendering EDS patients prone to mechanical pain, and myelopathy. Musculoskeletal pain starts early, is chronic and debilitating, and the neuromuscular disease of EDS manifests symptomatically with weakness, myalgia, easy fatigability, limited walking, reduction of vibration sense, and mild impairment of mobility and daily activities. Consensus criteria and clinical practice guidelines, based upon stronger epidemiological and pathophysiological evidence, are needed to refine diagnosis and treatment of the various neurological and spinal manifestations of EDS. © 2017 Wiley Periodicals, Inc.

Craniometric Analysis of the Hindbrain and Craniocervical Junction of Chihuahua, Affenpinscher and Cavalier King Charles Spaniel Dogs With and Without Syringomyelia Secondary to Chiari-Like Malformation

OBJECTIVES

To characterize and compare the phenotypic variables of the hindbrain and craniocervical junction associated with syringomyelia (SM) in the Chihuahua, Affenpinscher and Cavalier King Charles Spaniel (CKCS).

METHOD

Analysis of 273 T1-weighted mid-sagittal DICOM sequences of the hindbrain and craniocervical junction from 99 Chihuahuas, 42 Affenpinschers and 132 CKCSs. The study compared 22 morphometric features (11 lines, eight angles and three ratios) of dogs with and without SM using refined techniques based on previous studies of the Griffon Bruxellois (GB) using Discriminant Function Analysis and ANOVA with post-hoc corrections.

RESULTS

The analysis identified 14/22 significant traits for SM in the three dog breeds, five of which were identical to those reported for the GB and suggest inclusion of a common aetiology. One ratio, caudal fossa height to the length of the skull base extended to an imaginary point of alignment between the atlas and supraoccipital bones, was common to all three breeds (p values 0.029 to <0.001). Associated with SM were a reduced occipital crest and two acute changes in angulation i) 'sphenoid flexure' at the spheno-occipital synchondrosis ii) 'cervical flexure' at the foramen magnum allied with medulla oblongata elevation. Comparing dogs with and without SM, each breed had a unique trait: Chihuahua had a smaller angle between the dens, atlas and basioccipital bone (p value < 0.001); Affenpinschers had a smaller distance from atlas to dens (p value 0.009); CKCS had a shorter distance between the spheno-occipital synchondrosis and atlas (p value 0.007).

CONCLUSION

The selected morphometries successfully characterised conformational changes in the brain and craniocervical junction that might form the basis of a diagnostic tool for all breeds. The severity of SM involved a spectrum of abnormalities, incurred by changes in both angulation and size that could alter neural parenchyma compliance and/or impede cerebrospinal fluid channels.

Correlation of clivoaxial angle to skeletal malocclusions: A prescreening for future risk of neurodegenerative disorders

Objectives

To find out if there exists any correlation between clivoaxial angle (CXA) and skeletal malocclusions.

Materials

and Methods: Lateral cephalograms of 33 filipino patients equally divided in three types of skeletal malocclusions were traced, and cephalometric parameters CXA, BaSN, ANB, SNMPA, FMA, MMPA, and Y-axis were traced. Data underwent bivariate correlation and curve estimation analysis in SPSS 17.0 statistical software at confidence interval of 95% and 0.05 significance level.

Results

A highly significant (P = 0.003) strong negative correlation was revealed in Class III patients between CXA and BaSN.

Conclusion

Class III patients seem to have higher chances of craniocervical junction anomalies and thus might be at risk of developing neurodegenerative disorders in future.

Computed tomography evaluation of the normal craniocervical junction craniometry in 100 asymptomatic patients

OBJECT

Most of the craniometric relationships of the normal craniocervical junction (CCJ), especially those related to angular craniometry, are still poorly studied and based on measurements taken from simple plain radiographs. In this study, the authors performed a craniometric evaluation of the CCJ in a population without known CCJ anomalies. The purpose of the study was to evaluate the normal CCJ craniometry based on measurements obtained from CT scans.

METHOD

The authors analyzed 100 consecutive CCJ CT scans obtained in adult patients who were admitted at their tertiary hospital for treatment of non-CCJ conditions between 2010 and 2012. A total of 17 craniometrical measurements were performed, including the relation of the odontoid with the cranial base, the atlantodental interval (ADI), the clivus length, the clivus-canal angle (CCA)-the angle formed by the clivus and the upper cervical spine, and the basal angle.

RESULTS

The mean age of the 100 patients was 50.6 years, and the group included 52 men (52%) and 48 women (48%). In 5 patients (5%), the tip of the odontoid process was more than 2 mm above the Chamberlain line, and in one of these 5 patients (1% of the study group). it was more than 5 mm above it. One patient had a Grabb-Oakes measurement above 9 mm (suggesting ventral cervicomedullary encroachment). The mean ADI value was 1.1 mm. The thickness of the external occipital protuberance ranged from 7.42 to 22.36 mm. The mean clivus length was 44.74 mm, the mean CCA was 153.68° (range 132.32°-173.95°), and the mean basal angle was 113.73° (ranging from 97.06°-133.26°).

CONCLUSIONS

The data obtained in this study can be useful for evaluating anomalies of the CCJ in comparison with normal parameters, potentially improving the diagnostic criteria of these anomalies. When evaluating CCJ malformations, one should take into account the normal ranges based on CT scans, with more precise bone landmarks, instead of those obtained from simple plain radiographs.

The Role of the Craniocervical Junction in Craniospinal Hydrodynamics and Neurodegenerative Conditions

The craniocervical junction (CCJ) is a potential choke point for craniospinal hydrodynamics and may play a causative or contributory role in the pathogenesis and progression of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, MS, and ALS, as well as many other neurological conditions including hydrocephalus, idiopathic intracranial hypertension, migraines, seizures, silent-strokes, affective disorders, schizophrenia, and psychosis. The purpose of this paper is to provide an overview of the critical role of the CCJ in craniospinal hydrodynamics and to stimulate further research that may lead to new approaches for the prevention and treatment of the above neurodegenerative and neurological conditions.

Correction of clivoaxial angle deformity in the setting of suboccipital craniectomy: technical note

A subset of patients with Chiari Type I malformation may develop neurological dysfunction secondary to an abnormally obtuse clivoaxial angle (CXA) and clivoaxial deformity causing deformative stress injury to the neural axis. Clivoaxial deformity can occur after initial standard suboccipital craniectomy, duraplasty, and C-1 laminectomy for brainstem compression, or severe clivoaxial deformity may be present in conjunction with a Chiari malformation. Clivoaxial deformity and abnormal CXA can be treated with an occipitocervical fusion (OCF). Performing OCF in the setting of a cranial defect can be challenging with currently available instrumentation. The authors describe their recent experience and outcomes in 3 consecutive pediatric patients using the "inside-out" technique for treating clivoaxial deformity and abnormal CXA in the setting of a craniectomy defect to restore stability to the craniocervical junction, while correcting the CXA.

Basilar invagination: Surgical results

Introduction:

Basilar invagination (BI) is a congenital craniocervical junction (CCJ) anomaly represented by a prolapsed spine into the skull-base that can result in severe neurological impairment.

Materials and Methods:

In this paper, we retrospective evaluate the surgical treatment of 26 patients surgically treated for symptomatic BI. BI was classified according to instability and neural abnormalities findings. Clinical outcome was evaluated using the Nürick grade system.

Results:

A total of 26 patients were included in this paper. Their age ranged from 15 to 67 years old (mean 38). Of which, 10 patients were male (38%) and 16 (62%) were female. All patients had some degree of tonsillar herniation, with 25 patients treated with foramen magnum decompression. Nine patients required a craniocervical fixation. Six patients had undergone prior surgery and required a new surgical procedure for progression of neurological symptoms associated with new compression or instability. Most of patients with neurological symptoms secondary to brainstem compression had some improvement during the follow-up. There was mortality in this series, 1 month after surgery, associated with a late removal of the tracheal cannula.

Conclusions:

Management of BI requires can provide improvements in neurological outcomes, but requires analysis of the neural and bony anatomy of the CCJ, as well as occult instability. The complexity and heterogeneous presentation requires attention to occult instability on examination and attention to airway problems secondary to concomitant facial malformations.

Complex Chiari malformations in children: an analysis of preoperative risk factors for occipitocervical fusion

OBJECT

Chiari malformation Type I (CM-I) is a congenital anomaly often treated by decompressive surgery. Patients who fail to respond to standard surgical management often have complex anomalies of the craniovertebral junction and brainstem compression, requiring reduction and occipitocervical fusion. The authors hypothesized that a subgroup of "complex" patients defined by specific radiographic risk factors may have a higher rate of requiring occipitocervical fusion.

METHODS

A retrospective review was conducted of clinical and radiographic data in pediatric patients undergoing surgery for CM-I between 1995 and 2010. The following radiographic criteria were identified: scoliosis, syringomyelia, CM Type 1.5, medullary kinking, basilar invagination, tonsillar descent, craniocervical angulation (clivoaxial angle [CXA] < 125°), and ventral brainstem compression (pB-C2 ≥ 9 mm). A multivariate Cox regression analysis was used to determine the independent association between occipitocervical fusion and each variable.

RESULTS

Of the 206 patients who underwent CM decompression with or without occipitocervical fusion during the study period, 101 had preoperative imaging available for review and formed the study population. Mean age at surgery was 9.1 years, and mean follow-up was 2.3 years. Eighty-two patients underwent suboccipital decompression alone (mean age 8.7 years). Nineteen patients underwent occipitocervical fusion (mean age 11.1 years), either as part of the initial surgical procedure or in a delayed fashion. Factors demonstrating a significantly increased risk of requiring fusion were basilar invagination (HR 9.8, 95% CI 2.2-44.2), CM 1.5 (HR 14.7, 95% CI 1.8-122.5), and CXA < 125° (HR 3.9, 95% CI 1.2-12.6).

CONCLUSIONS

Patients presenting with basilar invagination, CM 1.5, and CXA < 125° are at increased risk of requiring an occipitocervical fusion procedure either as an adjunct to initial surgical decompression or in a delayed fashion. Patients and their families should be counseled in regard to these findings as part of a preoperative CM evaluation.