McRae Line Research Articles

External lumbar drainage for the management of refractory intracranial hypertension in pediatric severe traumatic brain injury: a retrospective single-center case series.

Guidelines for the management of pediatric severe traumatic brain injury (TBI) recommend external ventricular drainage for CSF drainage as a first-tier treatment in the intracranial pressure (ICP) pathway. However, ventriculostomy in children can sometimes be challenging because of the small size of the lateral ventricles. External lumbar drainage (ELD) may be a useful alternative; therefore, the authors analyzed the outcome of a cohort of pediatric patients who underwent ELD to manage intracranial hypertension (ICH). This study retrospectively enrolled pediatric patients with ICH following severe TBI who underwent ELD. Radiological and clinical severity scores (Marshall classification, Rotterdam score, Injury Severity Score, and Pediatric Trauma Score) were noted. ICP and cerebral perfusion pressure (CPP) curves were analyzed 12 hours before and after the procedure. Any change in medical therapy was recorded, as well as the total volume and duration of drainage. Cerebellar tonsillar position according to the McRae line was noted before and after ELD. Glasgow Outcome Scale-Extended score at follow-up was also noted. Thirty patients were included, with a mean age of 8 ± 4.4 years, and a median admission Glasgow Coma Scale score of 7 ± 4 (range 3-13). ELD was performed after a median delay of 1 day (range 0-7 days), mean drainage volume/day was 296 ± 129 ml, and median duration of drainage was 7 ± 5 (range 2-12) days. Forty-three percent of the patients underwent ELD as a part of the first-tier therapy. ICP decreased after ELD (mean difference 13.4 ± 6.2 mm Hg, p < 0.001), whereas CPP increased (mean difference 10.6 ± 6.4 mm Hg, p < 0.001). Fifty-three percent of the cohort did not need any further second-tier therapy after ELD. The study found 1 case of drain revision and 3 cases of cerebellar tonsil herniation. These preliminary data suggest ELD is a valuable option to treat ICH in severely head-injured children, limiting the use of second-tier treatments. This pilot study should lay the foundation for a multicenter prospective trial.

Atlantoaxial facet fixation using cervical facet cage: technical case report and review of the literature.

In 1994, the use of interfacet spacer placement was for joint distraction, reduction, and fusion to supplement atlantoaxial or occipitocervical fixation. Here, we present a unique case of bilateral atlantoaxial interfacet fixation using cervical facet cages (CFC) in a pediatric patient with basilar invagination. In addition, we review the literature on atlantoaxial facet fixation. We present a 12-year-old boy with Wiedemann-Steiner syndrome who presented with multiple episodes of sudden neck jerking, described as in response to a sensation of being shocked, and guarding against neck motion, found to have basilar invagination with cervicomedullary compression. He underwent an occiput to C3 fusion with C1-C2 CFC fixation. We also conducted a literature review identifying all publications using the following keywords: "C1" AND "C2" OR "atlantoaxial" AND "facet spacer" OR "DTRAX." The patient demonstrated postoperative radiographic reduction of his basilar invagination from 6.4 to 4.1mm of superior displacement above the McRae line. There was a 4.5mm decrease in the atlantodental interval secondary to decreased dens retroflexion. His postoperative course was complicated by worsening of his existing dysphagia but was otherwise unremarkable. His neck symptoms completely resolved. We illustrate the safe use of CFC for atlantoaxial facet distraction, reduction, and instrumented fixation in a pediatric patient with basilar invagination. Review of the literature demonstrates that numerous materials can be safely placed as a C1-C2 interfacet spacer including bone grafts, titanium spacers, and anterior cervical discectomy and fusion cages. We argue that CFC may be included in this arsenal even in pediatric patients.

Cerebellar Tonsillar Herniation an Incidental Finding in Asymptomatic Patient

Cerebellar tonsillar herniation, often associated with Chiari malformation, involves the downward displacement of the cerebellar tonsils below the foramen magnum. This condition can lead to significant complications due to the limited intracranial space within the rigid skull. Timely diagnosis is crucial given its potentially fatal nature, with brain structural displacement evident on imaging studies. We present a case of a 27-year-old female with continuous headaches and dizziness, diagnosed with tonsillar herniation through MRI revealing 16 mm of tonsillar descent without associated hydrocephalus or syrinx. Tonsillar herniation, characterized by inferior descent of the cerebellar tonsils, may be congenital or acquired, with measurements typically referenced from the McRae line to the displaced tonsil tip. Complications include brainstem compression, obstruction of cerebrospinal fluid flow, syringomyelia, impaired blood flow, and various neurological and psychological symptoms. Management options vary based on symptom severity and may involve observation, medication, or surgical intervention to alleviate compression and improve cerebrospinal fluid flow. Consultation with a neurologist or neurosurgeon is essential for comprehensive evaluation and tailored management plans aiming to relieve pressure on the brainstem and spinal cord in tonsillar herniation cases.

Retroflexed dens in paediatric Chiari 1 patients and implications: Single centre retrospective study.

Chiari 1 malformation and hind brain hernia can be associated with skull base and craniocervical anomalies. One of the more recently associated anomalies is a retroverted or retroflexed odontoid process or dens. We conducted a retrospective study of our operated symptomatic and conservatively managed asymptomatic Chiari cohort to assess the impact of dens retroflexion on rate of revision or cerebrospinal fluid diversion following primary foramen magnum decompression (FMD). We undertook a retrospective study of all foramen magnum decompression (FMD) cases for Chiari type 1 malformation performed over a 15-year period in a single tertiary paediatric neurosurgical unit. For comparison, non-operated asymptomatic Chiari cases were considered as reference cohort.Information gathered included: demographics, age, sex, length of cerebellar tonsils below McRae's line, pB-C2 distance (a line drawn perpendicular to one drawn between the basion and the posterior aspect of the C2 body), angle of retroflexion (angle formed between a line drawn through the odontoid synchondrosis and its intersection with a line drawn from the tip of the odontoid process) and angle of retroversion (angle formed between the line drawn from the base of C2 and its intersection with a line drawn from the tip of the odontoid process). Grade of retroflexion was measured using pre-operative mid-sagittal MR images and classified as grade 0 (> 90°), grade 1 (85°-89°); grade 2 (80°-84°) and grade 3 (< 80°). The rates for redo surgery or need for cerebrospinal fluid (CSF) diversion were obtained from clinical records and compared in the operated and non-operated groups. One hundred twenty-six Chiari 1 patients were included in this study with adequate imaging. Sixty-five patients were in the non-operated asymptomatic cohort with 61 patients in the operated symptomatic cohort.Mean age of non-operated cohort was 10.2years with M:F ratio (30:35). Mean cerebellar tonsillar length below McRae's line was 10.3mm. 7.7% of this cohort had associated syrinx. Mean angles of retroversion and retroflexion were 76 and 78°, respectively. Retroflexion grades included (9.2% grade 1, 35% grade 2 and 52.3% grade 3). pB-C2 distance was 6.8mm. Mean age of operated cohort was 11.3years, with M:F ratio (21:40). Mean cerebellar tonsillar length below McRae's line was 15mm. 45.9% of this cohort had associated syrinx. Mean angles of retroversion and retroflexion were 73 and 74.5°, respectively. Retroflexion grades included (4.9% grade 1, 16.5% grade 2 and 78.6% grade 3). pB-C2 distance was 6.9mm. No association was identified between retroflexion grade and rate of revision or CSF diversion following primary foramen magnum decompression. The operated Chiari 1 cohort had more retroflexed dens, longer tonsils and associated syrinx compared to the non-operated asymptomatic cohort.

Coexistence of Pseudotumor Cerebri and Chiari Malformation Type 1

Objective: To identify different radiological markers for the diagnosis of the coexistence of pseudotumor cerebri and Chiari malformation type 1. Method: Patients who were clinically suspected to have Chiari malformation type 1 and were referred to the Department of Radiology between 2007 and 2020, and whose diagnosis was radiologically confirmed through magnetic resonance imaging (MRI), were retrospectively evaluated. A total of 49 Chiari malformation type 1 patients with both cervical and cerebral examinations and 49 control subjects of the same age and gender without a diagnosis of Chiari malformation type 1 were included in the study. In Chiari malformation type 1 diagnosed patients, the presence of pseudotumor cerebri, the presence of syringomyelia in cervical spinal MRI images, and the distance of cerebellar tonsils and obex according to McRae line were evaluated in millimeters. Result: In Chiari malformation type 1 clinically and radiologically diagnosed cases, the cerebellar tonsils and obex were located lower in patients with a radiological diagnosis of pseudotumor cerebri compared to those without, and the rate of accompanying syringomyelia appeared to be higher. However, no statistically significant difference was observed between the two groups. Conclusion: The coexistence of pseudotumor cerebri and Chiari malformation type 1 is more common than previously estimated. Different treatment protocols in the coexistence of pseudotumor cerebri and Chiari malformation type 1 emphasize the importance of making this diagnosis. Further radiological imaging studies are needed to identify different radiological markers for the diagnosis of the coexistence of pseudotumor cerebri and Chiari malformation type 1.

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

To analyze the anatomical changes of the IV ventricle and cisterna magna in the Chiari malformation I (CMI) and basilar invagination (type B). This is a controlled study with 161 exams of magnetic resonance imaging (MRI) of adults grouped into control (n= 37), basilar invagination (BI; n= 31), Chiari malformation I (CMI; n= 37), and CMI+BI (n= 56). The MRIs were analyzed using the visualization software Osirix (Pixmeo, Bernex, Geneva, version 3.8.2). The morphometric variables were: distance from the obex to the McRae line; length of the IV ventricle floor; and the area and volume of the cisterna magna. The univariate ANOVA followed by Tukey's post-hoc test was applied to evaluate the difference between the groups. The difference between sexes was evaluated by the t test for each group. Alterations in the cisterna magna and IV ventricle were more evident only in the CMI and CMI+BI groups. For both sexes, the CMI and CMI+BI groups showed: a reduction in the CSF space (P < 0.001), cisterna magna with volume reduction (P < 0.001), low position of the obex (P < 0.001), and IV ventricle more elongated (male P= 0.007 and female P < 0.001). The BI group had no significant change in the analysis by sex. The CMI (isolated and associated with BI) showed a low obex position and elongation of the IV ventricle due to traction towards the spinal canal. The reduction of cisterna magna volume added to the occupation of the cerebellar tonsils can impact in the cerebrospinal fluid dynamics. The BI when isolated was not related to alterations in the parameters of cerebrospinal fluid spaces studied.

A new supportive approach in the diagnosis of Chiari malformation type 1 in pediatric patients.

Chiari malformation type 1 (CM-1) is a posterior fossa anomaly characterized by herniation of the cerebellar tonsils from the foramen magnum (FM). This study compares FM, medulla spinalis (MS), and herniated cerebellar tonsils ratios by making area measurements from axial plane MRI in CM-1 patients and the control group. Our study evaluated 30 pediatric patients with CM-1 and 30 people in the control group. The lengths of the McRae line, twining line, and clivus line were measured on the posterior cranial fossa evaluation. The areas of FM (AFM), MS (AMS), and herniated cerebellar tonsils (ATONSILS) were measured by axial images. As a result of area measurements obtained from axial cross-sectional MRI, a statistically significant difference was found between CM-1 patients and the control group. According to the results of the ROC analysis, if an individual's AMS/AFM value is above 17.9% or the ATONSILS/AFM value is above 18.4%, it can be interpreted as a CM-1 patient. It will be easier to diagnose the patient with the new approach we obtained from axial MR images in addition to sagittal MR images. This method can be a guide in some cases when the surgeons are undecided.

Measuring the shape and dimensions of normal the bony structures in the craniovertebral junction from computed tomography images of the pediatric age group.

The aim of this study is to contribute to the literature by determining the morphometric reference values of the bony structures in the craniovertebral junction (CVJ) from computer tomography (CT) images of the pediatric age group. In this study, CT's of 151 simple trauma patients aged between 3 and 15 years between 2016 and 2020 were evaluated. All CT examinations were performed using a 32-slice CT and included images of the skull base and C1-C2 junction. A total of 10 measurements were obtained from these images, including Wachenheim clivus canal angle (WCA), Welcher basal angle (WBA), Cran-iocervical tilt angle (CCT), power ratio (PR), Atlantodens interval, McRae Line (MRL), McRae - Dens distance, basion-dens interval (BDI), basion-axis interval (BAI), and atlantooccipital measurement (AOM). In comparison between gender groups, MRL (p=0.011) and AOM (p<0.001) measurements were found to be significantly higher in males. McRae-Dens distance, BDI, and AOM were significantly higher in patients aged 3-9 years (respectively, p=0005, p=0.003, p<0.001), and BAI (p=0.001) was significantly higher in patients aged 10-15 years. The McRae - Dens distance (p=0.119) was similar between patients with and without terminal ossicle in odontoid apex. But BDI of patients without terminal ossicle was significantly higher (p=0.048). All parameters, except the WCA, WBA, CCT, and PR, were statistically significantly correlated with the patient age (respectively, p=0.21, p=0.13, p=0.70, p=0.99). In this study, the morphometric reference values of the bone structures at the CVJ were determined from the CT images of the pediatric age group.

Surgical, Clinical, and Radiological Outcomes Analysis of Craniovertebral Junction Anomalies Cases: An Institutional Experience.

Objective The aim of this study was to evaluate the clinical and radiological outcomes analysis of craniovertebral junction (CVJ) anomalies cases. Materials and Methods Retrospective analysis of 43 CVJ anomalies cases, which were surgically managed at Uttar Pradesh University of Medical Sciences, Saifai, Etawah, Uttar Pradesh, India, from period between June 2015 and June 2019. They were analyzed for age, sex, clinical characteristics, radiological diagnosis, and treatment given. Patient's clinical and radiological status was assessed pre- and postoperatively during time of discharge and at 6 months of follow-up. For clinical assessment we used visual analogue scale (VAS) and Nurick grading system. Radiological assessment was done by atlantodental interval (ADI), craniobasal angle, and craniometric lines. Overall outcomes were depicted as favorable, stabilized, and mortality at 6 to 18 months (mean 12.69 ± 3.77) of follow-up. Results The age range of our cases was 7 to 71 years (mean 29.93 ± 17.39). Male-to-female ratio was 2.91:1. Majority of the cases were presented with neck pain ( n = 38; 88.37%), motor weakness ( n = 35; 81.40%), and sensory deficits ( n = 25; 58.14%). Congenital atlantoaxial dislocation ( n = 31; 72.09) was the most common CVJ anomaly. Clinically, there were significant improvements in VAS ( p = 0.001) and Nurick grade ( p = 0.007) postoperatively. Radiologically, ADI ( p = 0.003) had decreased, clivus canal angle ( p = 0.005) become less acute, and odontoid process ( p = 0.003 for McRae's line) goes downwards in postoperative period. Bony fusion was achieved in 41 (95.35%) cases. Out of 43, 73% cases had favorable outcomes, 21% were stabilized, and mortality was seen in 2.33% cases at 6 months (mean ± standard deviation = 12.69 ± 3.77) of follow-up. Conclusion Proper preoperative evaluation and selection of individualized surgical technique was the key for excellent clinical and radiological outcomes with minimal complications.

Direct intraoperative two-step distraction and reduction for basilar invagination with atlantoaxial dislocation

Objective: To assess the clinical impact of direct two-step distraction reduction (TSDR) for basilar invagination (BI) with atlantoaxial dislocation (AAD). Methods: Retrospective analysis was conducted on the clinical data of patients who underwent TSDR and occipitocervical fusion in West China Hospital between October 2013 and March 2021. Depending on whether the preoperative decrease was greater than 50% on preoperative hyperextension X-rays, the patients were split into two groups. The neurological function [Japanese Orthopedic Association (JOA) score], atlantodens interval (ADI), the distance of odontoid process beyond McRae Line (ML) and Wackenheim Line (WL), cervicomedullary angle (CMA), O-C2 angle (OC2A), and complications incidence were compared between two groups preoperatively and postoperatively. Results: There were 12 men and 23 women among the 35 patients with BI and AAD, and the age ranged from 28 to 71 years, with an mean age of (52.0±13.4) years. In the preoperative reduction ≥50% group, there were 4 males and 9 females with an average age of (54.0±13.8) years; in the preoperative reduction <50% group, there were 8 males and 14 females with a mean age of (50.9±13.4) years. All the patients were followed-up for a mean time of (23.3±13.4) months. There was no significant difference in age, gender, bleeding, length of hospital stay and follow-up time between the two groups (all P>0.05). The JOA score, ADI, WL, ML and CMA of 35 patients were significantly improved when compared with those before operation (all P<0.05). The reduction degree of ADI, ML and WL was more than 80% in 31 cases (88.57%), 30 cases (85.71%) and 31 cases (88.57%), respectively. There was no significant difference in postoperative ADI, ML and WL between the two groups (all P>0.05). All patients had no incision infection, no loosening or breakage of the internal fixators. Dysphagia occurred in 3 patients, non-fusion happened in 1 patient, but no instability in X-ray of cervical dynamic position was found, no loosening or displacement occurred in internal fixators, and partial spontaneous fusion occurred between atlantoaxial lateral mass joints. Conclusions: For BI with AAD without atlantoaxial bony connection or serious atlantoaxial facet joint inclination, TSDR could obtain satisfactory reduction degree. The reduction degree on preoperative hyperextension X-ray doesn't affect the degree of intraoperative reduction.

Reliability and Agreement in the Cerebellar Tonsil Tip Localization: Two Methods Using the McRae Line Concept in MRI

The cerebellar tonsil tip position (TP) is a common parameter used for the radiologic diagnosis of Chiari malformation type 1 (CM1). However, these paramedian structures are usually not properly visualized in the midsagittal section. Such mismatch may be a source of bias in TP measurements based on the McRae line (ML) traced between median craniometric points. This study aims to evaluate the intraoperator and interoperator reliability and agreement of 2 protocols to trace the ML in magnetic resonance imaging (MRI) for the cerebellar tonsil tip localization, adding a 3-dimensional multiplanar reconstruction (MPR) approach to the midsagittal plane. Sixty-two T1-weighted head MRIs were obtained for 32 CM1 patients and 30 controls. Two operators independently applied 2 TP measurement protocols, one considering only the visualization of the sagittal plane and the other using MPR. The intraclass correlation coefficient was used to assess intraoperator and interoperator reliability, and the Bland-Altman graphical method was used to evaluate the agreement between the measurement protocols. The sagittal method significantly underestimated ML and tonsillar herniation when compared with the MPR method. The MPR method provided better reliability of the ML measurement when compared to the sagittal method, but this did not influence the reliability of the TP. Analysis of the Bland-Altman plot showed that the limits of agreement were close to acceptable for the ML, but not for measures of TP. The standardization of the LM tracing by the MPR method improves the acquisition of data regarding the position of the tonsils.

Possible predictive clinical and radiological markers in decision making for surgical intervention in patients with Chiari Malformation type 1

ABSTRACT Background The first aim of this study was to compare the clinical data and posterior fossa morphometry obtained during the admission to the hospital between control group individuals (who had not Chiari Malformation (CM) type 1) and CM type 1 patients treated surgically or not. The second aim was to create a valid and reliable scale that can predict the decision-making for surgical intervention simply and easily in these patients. Materials Medical data and radiological images of 70 CM type 1 patients during their admission to the hospital were compared with the data of 69 control group individuals. Results Conservative treatment and/or follow-up was applied to 58 (82.9%) patients, and 12 (17.1%) patients underwent surgery. ROC analysis showed that the presence of myelopathy, tonsillar herniation >8 mm, Chamberlain line >84 mm, McRae line >44.50 mm, and odontoid process-McRae line angle <10.50 degrees could be used as predictive markers in decision-making for surgical intervention (p < 0.05). Logistic Regression analysis revealed that symptoms severity, and McRae line value would be the ‘best parameters’ in decision-making for surgical intervention (p < 0.05). A scale named the CHIASURG scale developed using this study’s parameters showed that the parameters of ‘depth of tonsillar herniation’, ‘Chamberlain line’, and ‘McRae line’ could predict the surgical intervention risk. Conclusion It was found that symptoms severity and McRae line value could be used as predictive markers in decision-making for surgical intervention. Additionally, it was concluded that a new scale called CHIASURG could predict surgical intervention risk validly and reliably.

Basilar Invagination: A Tilt of the Foramen Magnum

Congenital basilar invagination (BI) is a craniocervical deformity marked by odontoid prolapse into the skull base. The foramen magnum angle (FMA), which is formed by the Chamberlain's line and McRae's line, has not been fully studied. The study aimed to investigate the FMA and its relationship with other craniocervical parameters. Participants were divided into control, type A BI, and type B BI groups. Parameters included Chamberlain line violation, atlantodental interval, clivus height, clivus anteroposterior dimension, FMA, basal angle, clivo-axial angle, head and neck flexion angle, Boogard's angle, and subaxial cervical spine lordosis angle. A comparison of these parameters among the 3 groups and correlation analysis between FMA and other parameters were performed. The significance level was set at P < 0.05. A total of 111 controls, 111 type A BI patients, and 62 type B BI patients were enrolled. The FMAs in the control, type A BI, and type B BI groups were 6.21° (3.67°, 8.71°), 22.16° ± 6.61°, and 22.39° (17.27°, 31.08°), respectively. Correlation analysis revealed correlations between the FMA and other variables. In the 2 BI subgroups, FMA was significantly correlated with Chamberlain line violation, clivus height, clivus anteroposterior dimension, basal angle, clivo-axial angle, and Boogard's angle. The FMA in patients with BI was approximately 22° and approximately 6° in controls, indicating that the foramen magnum in BI had a greater tilt. As a pathological condition, FMA can reflect the degree of BI. Clivus hypogenesis is a reason for the excessive tilt of the FM.

Comparison of posterior cranial fossa morphometric measurements in Chiari type I patients with and without syrinx cavity on magnetic resonance imaging.

To compare the posterior fossa measurements of Chiari type I malformation (CHM1) patients with and without syrinx and with a control group. The patients with syrinx were divided into 2 groupd according to syrinx width/cord width (S/C) ratios: group 1 - S/C ratio < 50%; group 2 - S/C ratio > 50%. The length of the clivus, the AP length of the foramen magnum, the AP length of the posterior fossa, the perpendicular distance between the McRae line and (a) the splenium of corpus callosum, (b) the pons, and (c) the fastigium of the 160 patients and of the 160 control patients were statistically compared. In addition, the measurements of the patients with and without syrinx, according to the S/C ratio, were statistically compared. Syrinx was present in 59 (36.8 %) of the 160 patients. The S/C ratio was < 50% in 30 (50.9 %) of them, and S/C ratio > 50% in 29 (49.1%) of them. All the measurements in the patient group, except of the AP length of the foramen magnum, were statistically significantly lower than in the control group (p = 0.001). There was no significant difference in the measurements of the patients with syrinx group 1 and the patients without syrinx, but the AP length of posterior fossa was statistically significantly lower in the patients with syrinx group 2 than the patients without syrinx (p = 0.03). The S/C ratio can be a guide to the underlying aetiology.

BASILAR INVAGINATION: IMPORTANCE OF CRANIOMETRIC MEASUREMENT

<h3>BACKGROUND</h3> Basilar invagination (BI) is a congenital or degenerative craniovertebral junction abnormality that results from the odontoid process prolapsing into the foramen magnum. Even though the acquired form is frequently seen with rheumatoid arthritis, BI commonly presents in many congenital conditions such as in people with Chiari malformation. In another type, it has been classified as those in which the odontoid process invaginates into the foramen magnum, resulting in cranio-cervical instability (Type 1) and those with flattened base of cranium that is not associated with instability (Type 2). Clinical presentations include chronic headaches, limited neck motion, and acute neurologic deterioration. <h3>CASE REPORT</h3> A 31-year-old male patient presented for treatment of a sleep-related breathing disorder. Cone beam computed tomography (CBCT) was completed for airway evaluation. Standard radiographic parameters described by Chamberlain were used to assess the craniovertebral junction. Osseous fusion of the C1/C2 joint and extension of the odontoid process approximately 10.5 mm above the Chamberlain line were noted. BI is diagnosed once the tip of the odontoid is 5 mm or more above this line. <h3>DISCUSSION/CONCLUSIONS</h3> The diagnosis of BI relies on radiographic evaluation and various radiographic reference lines such as the Chamberlain line, McGregor line, or McRae line. However, the radiographic interpretation of the cervical vertebrae is often challenging and results in missing important findings. This case report aimed to demonstrate the characteristic radiographic features of BI as seen on CBCT and the use of craniometric measurements to assist health care providers in diagnosing and managing this condition. It is important for oral and maxillofacial radiologists to pay attention to this anatomically critical junction on every study that captures it and perform an assessment so they do not miss BI-related anomalies in asymptomatic patients.

Is there a morphometric cause of Chiari malformation type I? Analysis of existing literature.

Although many etiologies have been proposed for Chiari malformation type I (CM-I), there currently is no singular known cause of CM-I pathogenesis. Advances in imaging have greatly progressed the study of CM-I. This study reviews the literature to determine if an anatomical cause for CM-I could be proposed from morphometric studies in adult CM-I patients. After conducting a literature search using relevant search terms, two authors screened abstracts for relevance. Full-length articles of primary morphometric studies published in peer-reviewed journals were included. Detailed information regarding methodology and symptomatology, craniocervical instability, syringomyelia, operative effects, and genetics were extracted. Forty-six studies met inclusion criteria, averaging 93.2 CM-I patients and 41.4 healthy controls in size. To obtain measurements, 40 studies utilized MRI and 10 utilized CT imaging, whereas 41 analyzed parameters within the posterior fossa and 20 analyzed parameters of the craniovertebral junction. The most commonly measured parameters included clivus length (n = 30), tonsillar position or descent (n = 28), McRae line length (n = 26), and supraocciput length (n = 26). While certain structural anomalies including reduced clivus length have been implicated in CM-I, there is a lack of consensus on how several other morphometric parameters may or may not contribute to its development. Heterogeneity in presentation with respect to the extent of tonsillar descent suggests alternate methods utilizing morphometric measurements that may help to identify CM-I patients and may benefit future research to better understand underlying pathophysiology and sequelae such as syringomyelia.

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

Purpose We evaluate the efficacy, safety and indications of single stage posterior release, reduction, and fixation of basilar invagination (BI) with irreducible atlantoaxial dislocation (IAAD). Materials and methods Seventeen patients with BI and IAAD consecutively underwent one-stage release, reduction, and fixation by a posterior approach from July 2000 to June 2015 were followed up for at least 12 months. There were 8 males. Mean age was 56 35.2 ± 13.8 years (range 12–56). The clinical symptoms and signs of the patients were recorded. Pre- and postoperative imaging examinations were performed. Neurological function was assessed using the Japanese Orthopedic Association (JOA) and Ranawat scores. Results Average follow-up time was 47.4 months (12–97 months). The JOA score increased from preoperative 4–10 (8.06 ± 2.52) to postoperative 13–16 (15.20 ± 0.62). The preoperative Chamberlain line, McRae line, Wackenheim line, atlantodens interval, and cervico medullary angle were 12.52 ± 5.17 mm, 6.59 ± 3.04 mm, 6.96 ± 4.32 mm, 9.88 ± 1.93 mm, and 115.35 ± 12.40°, respectively. The postoperative values were 2.0 ± 3.67 mm, −3.06 ± 1.85 mm, −1.76 ± 2.88 mm, 1.17 ± 1.18 mm, and 136.76 ± 11.44°, respectively. Conclusion One-stage release, reduction, and fixation for patients with BI and IAAD through a posterior approach is safe and efficient.

Two-Stage Approach for Unstable Pediatric Craniocervical Junction Anomalies with a Halo Vest and Delayed Occipitocervical Fusion: Technical Note, Case Series, and Literature Review

Malformations in the craniocervical junction (CCJ) are rare in the pediatric population but often need surgical treatment. We present a pediatric case series of patients treated with a 2-stage surgical approach with a halo vest and occipitocervical fusion and review complications and outcomes. A retrospective analysis of a single-center case series was performed. Pediatric patients affected by congenital craniocervical junction anomalies and treated with a 2-stage approach were included. A halo vest was implanted in the first surgery, and ambulatory progressive reduction was performed. When a favorable anatomic situation was observed, arthrodesis was performed. Safety analysis was undertaken by analyzing the incidence of complications in both procedures. Effectivity analysis was carried out analyzing radiologic and clinical outcome (Goel grade and modified Japanese Orthopaedic Association score). Student t test was used for statistical analysis. Sixteen cases were included. Mean age of patients was 9.38 years. Safety analysis showed 2 halo loosenings, 1 pin infection, 2 wound infections, 1 cerebrospinal fluid leak, and 2 delayed broken rods. No major complications were observed. Radiologic analysis showed an improvement in the tip of the odontoid process to the McRae line distance (from-3.26 mm to-6.16 mm), atlantodental interval (from 3.05 mm to 1.88 mm), clival-canal angle (from 134.61° to 144.38°), and cervical kyphosis (from 6.39° to 1.54°). Clinical analysis also showed improvement in mean Goel grade (from 1.75 to 1.44) and modified Japanese Orthopaedic Association score (from 15.12 to 16.41). The 2-stage approach was a suitable and effective treatment for craniocervical junction anomalies in pediatric patients.

Signs of Intracranial Hypertension, Hypermobility, and Craniocervical Obstructions in Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

The pathophysiology of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is unknown. In this study, we test the hypothesis that hypermobility, signs of intracranial hypertension (IH), and craniocervical obstructions may be overrepresented in patients with ME/CFS and thereby explain many of the symptoms. Our study is a retrospective, cross-sectional study, performed at a specialist clinic for referred patients with severe ME/CFS as defined by the Canada Consensus Criteria. The first 272 patients with ME/CFS were invited to participate, and 229 who provided prompt informed consent were included. Hypermobility was assessed using the Beighton Score. IH was assessed indirectly by the quotient of the optic nerve sheet diameter (ONSD)/eyeball transverse diameter on both sides as measured on magnetic resonance imaging (MRI) of the brain. We also included assessment of cerebellar tonsil position in relation to the McRae line, indicating foramen magnum. Craniocervical obstructions were assessed on MRI of the cervical spine. Allodynia was assessed by quantitative sensory testing (QST) for pain in the 18 areas indicative of fibromyalgia syndrome (FMS). A total of 190 women, mean age 45 years, and 39 males, mean age 44 years, were included. Hypermobility was identified in 115 (50%) participants. MRI of the brain was performed on 205 participants of whom 112 (55%) had an increased ONSD and 171 (83%) had signs of possible IH, including 65 (32%) who had values indicating more severe states of IH. Cerebellar tonsils protruding under the McRae line into the foramen magnum were identified in 115 (56%) of the participants. MRI of the cervical spine was performed on 125 participants of whom 100 (80%) had craniocervical obstructions. Pain at harmless pressure, allodynia, was found in 96% of the participants, and FMS was present in 173 participants or 76%. Compared to a general population, we found a large overrepresentation of hypermobility, signs of IH, and craniocervical obstructions. Our hypothesis was strengthened for future studies on the possible relation between ME/CFS symptoms and hypermobility, IH, and craniocervical obstructions in a portion of patients with ME/CFS. If our findings are confirmed, new diagnostic and therapeutic approaches to this widespread neurological syndrome should be considered.

Ventrolateral Tonsillar Position Defines Novel Chiari 0.5 Classification

Cervicomedullary compression in young children has been described in the context of Chiari type 1 malformation, with symptoms associated with the extent of tonsillar herniation below McRae line. Historically, Chiari type 1 malformation has been defined by tonsillar herniation of at least 5 mm. However, in certain populations, including very young children, Chiari symptoms may be present without this finding. A new Chiari classification is thus necessary. Cases involving patients up to 5 years of age evaluated for possible posterior fossa decompression were retrospectively reviewed. Preoperative symptoms, magnetic resonance imaging findings, surgical management, and short- and long-term outcome and follow-up were recorded. Tonsillar descent and presence of ventral herniation (VH) were recorded. We define VH as the tonsils crossing a line that bisects the caudal medulla at the level of the foramen magnum, thus creating a novel entity, Chiari type 0.5 malformation. Patients with ventrally herniated tonsils were compared with patients exhibiting more typical Chiari morphology. Of 41 cases retrospectively reviewed, 20 met criteria for VH. These differed from cases without VH because of the predominance of medullary symptoms. In the VH cohort, 11 patients underwent surgical decompression with symptom resolution; 9 were initially managed conservatively, but 3 subsequently required surgery. We define a novel Chiari entity, Chiari type 0.5 malformation, characterized by ventral tonsillar wrapping around the medulla in young children in the absence of classic Chiari type 1 malformation imaging findings. These patients are more likely to present with medullary symptoms than patients without VH. They are also more likely to require surgical decompression and respond favorably to intervention.