Surgical management of Chiari I malformation based on different cerebrospinal fluid flow patterns at the cranial-vertebral junction

An autologous duraplasty in situ technique in the treatment of Chiari malformation Type I: a prospective study

OBJECTIVE

Our study aims to prospectively compare an autologous duraplasty in situ technique (IS group) with the synthetic dural graft duraplasty (SDG group) to clarify the effectiveness and superiority of the former in the treatment of patients with Chiari malformation type 1 (CM-I).

METHOD

29 patients with CM-I were randomly assigned to either IS or SDG group. In both groups, a dissection from the occipital bone was performed. All procedures were performed by the same surgeon. The two duraplasty methods were compared in terms of surgical factors and complications. Data analysis was done for the baseline material, the neurological outcome and MRI-documented syrinx size at the 6 month follow-up.

RESULT

29 patients were enrolled in this study, 14 in the IS group and 15 in the SDG group. The results showed no significant difference in operation time (P = 0.916), amount of bleeding (P = 0.120), operation complications, hospitalization time (P = 0.854) and prognosis between the two groups. The hospitalization cost of IS group was 15,125 yuan less than that of SDG group (P < 0.05).

CONCLUSION

The autogenous duraplasty in situ technique is a novel, simple, effective and economical surgical management for patients with CM-I.

Reliability and validity of the pediatric adaptation of the mJOA scale for evaluating cervical spine disorders

PURPOSE

The study aimed to evaluate the validity and reliability of the pediatric adaptation of the Japanese Orthopedic Association (mJOA) scale in pediatric patients with various cervical spine pathologies.

METHODS

Initial assessments were performed by a neurosurgeon, followed by an independent evaluation by a neurologist within 1-2 days to test inter-rater reliability. The same clinician assessed the same group of children using the adapted mJOA scale at different point in time (between 1 month and 1 year after the initial assessment) to test intra-rater reliability. For known-groups validity, the pediatric mJOA scale assessments were compared between two groups of pathologies with different prognosis. Concurrent validity was assessed against the McCormick scale, and convergent validity was tested by reassessing patients using the adult mJOA scale two or more years after the initial assessment by pediatric one.

RESULTS

A cohort of 169 pediatric patients aged 6 months to 18 years (mean age: 10 ± 4.6 years) with various cervical spine pathologies was recruited. Pathologies included atlanto-axial rotatory fixation (AARF), Chiari type I anomaly, congenital cervical spine scoliosis, atlanto-axial dislocation (AAD) and instability (AAI), cervical spine stenosis and trauma, and congenital cervicothoracic dislocations. The majority of patients underwent cervical spine surgery and were followed up for an average of 6.9 ± 2.97 years. The pediatric mJOA scale demonstrated high inter-rater reliability (r = 0.99, p < 0.0001) and strong intra-rater reliability (r = 0.82, p < 0.0001). Significant differences in pediatric mJOA scores were observed between patients with expected-intact neurological status and those with expected-pathological neurological status (p < 0.0001). The pediatric mJOA scale showed a strong correlation with the McCormick grading system (r = 0.97, p < 0.001) and good correlation with the adult mJOA scale during long-term follow-up (r = 0.82, p < 0.0001).

CONCLUSIONS

The pediatric version of the mJOA scale is a reliable and valid tool for assessing pediatric patients with cervical spine disorders. Its high reliability and validity support its use in both clinical practice and research.

Magnetic Resonance Imaging-Related Anatomic and Functional Parameters for the Diagnosis and Prognosis of Chiari Malformation Type I: A Systematic Review and Meta-analysis

OBJECTIVE

Imaging parameters of Chiari malformation type I (CMI) development are not well established. This study aimed to collect evidence of general or specific imaging measurements in patients with CMI, analyze indicators that may assist in determining the severity of CMI, and guide its diagnosis and treatment.

METHODS

A comprehensive search was conducted across various databases including the Cochrane Library, PubMed, MEDLINE, Scopus, and Embase, covering the period from January 2002 to October 2023, following predefined inclusion criteria. Meta-analyses were performed using RevMan (ver. 5.4). We performed a quantitative summary and systematic analysis of the included studies. This study was registered in the PROSPERO (International Prospective Register of Systematic Reviews) prior to initiation (CRD42023415454).

RESULTS

Thirty-three studies met our inclusion criteria. The findings indicated that out of the 14 parameters examined, 6 (clivus length, basal angle, Boogard's angle, supraocciput lengths, posterior cranial fossa [PCF] height, and volume) exhibited significant differences between the CMI group and the control group. Furthermore, apart from certain anatomical parameters that hold prognostic value for CMI, functional parameters like tonsillar movement, obex displacement, and cerebrospinal fluid dynamics serve as valuable indicators for guiding the clinical management of the disease.

CONCLUSION

We collated and established a set of linear, angular, and area measurements deemed essential for diagnosing CMI. However, more indicators can only be analyzed descriptively for various reasons, particularly in prognostic prediction. We posit that the systematic assessment of patients' PCF morphology, volume, and other parameters at a 3-dimensional level holds promising clinical application prospects.

Is foramen magnum decompression for acquired Chiari I malformation like putting a finger in the dyke? - A simplistic overview of artificial intelligence in assessing critical upstream and downstream etiologies

Background

Missed diagnosis of evolving or coexisting idiopathic (IIH) and spontaneous intracranial hypotension (SIH) is often the reason for persistent or worsening symptoms after foramen magnum decompression for Chiari malformation (CM) I. We explore the role of artificial intelligence (AI)/convolutional neural networks (CNN) in Chiari I malformation in a combinatorial role for the first time in literature, exploring both upstream and downstream magnetic resonance findings as initial screening profilers in CM-1. We have also put together a review of all existing subtypes of CM and discuss the role of upright (gravity-aided) magnetic resonance imaging (MRI) in evaluating equivocal tonsillar descent on a lying-down MRI. We have formulated a workflow algorithm MaChiP 1.0 (Manjila Chiari Protocol 1.0) using upstream and downstream profilers, that cause de novo or worsening Chiari I malformation, which we plan to implement using AI.

Materials and Methods

The PRISMA guidelines were used for "CM and machine learning and CNN" on PubMed database articles, and four articles specific to the topic were encountered. The radiologic criteria for IIH and SIH were applied from neurosurgical literature, and they were applied between primary and secondary (acquired) Chiari I malformations. An upstream etiology such as IIH or SIH and an isolated downstream etiology in the spine were characterized using the existing body of literature. We propose the utility of using four selected criteria for IIH and SIH each, over MRI T2 images of the brain and spine, predominantly sagittal sequences in upstream etiology in the brain and multiplanar MRI in spinal lesions.

Results

Using MaChiP 1.0 (patent/ copyright pending) concepts, we have proposed the upstream and downstream profilers implicated in progressive Chiari I malformation. The upstream profilers included findings of brain sagging, slope of the third ventricular floor, pontomesencephalic angle, mamillopontine distance, lateral ventricular angle, internal cerebral vein-vein of Galen angle, and displacement of iter, clivus length, tonsillar descent, etc., suggestive of SIH. The IIH features noted in upstream pathologies were posterior flattening of globe of the eye, partial empty sella, optic nerve sheath distortion, and optic nerve tortuosity in MRI. The downstream etiologies involved spinal cerebrospinal fluid (CSF) leak from dural tear, meningeal diverticula, CSF-venous fistulae, etc.

Conclusion

AI would help offer predictive analysis along the spectrum of upstream and downstream etiologies, ensuring safety and efficacy in treating secondary (acquired) Chiari I malformation, especially with coexisting IIH and SIH. The MaChiP 1.0 algorithm can help document worsening of a previously diagnosed CM-1 and find the exact etiology of a secondary CM-I. However, the role of posterior fossa morphometry and cine-flow MRI data for intracranial CSF flow dynamics, along with advanced spinal CSF studies using dynamic myelo-CT scanning in the formation of secondary CM-I is still being evaluated.

A Novel Craniocervical Junction Compression Severity Index-Based Grading System for Multidirectional Quantification of the Biomechanics at Foramen Magnum of Chiari Malformation Type I

Objective  This study aimed to establish a novel grading system, based on the craniovertebral junction compression severity index (CVJCSI) for multidirectional quantification at the foramen magnum plane for Chiari malformation type I (CMI). Methods  The CVJCSI grading system was established to stratify patients based on the ventral (modified clivoaxial angle < 138°), dorsal (tonsil herniation), and central (brainstem herniation) CVJ (craniovertebral junction) compression, the CVJCSI grading system was established to stratify patients. The optimal surgical method for each grade was recommended by intragroup comparisons regarding the efficacy of the three operations. Finally, according to the CVJCSI grading system, a prospective validation trial was performed and surgically treated for internal validation. Results  Based on the retrospective study ( n  = 310), the CVJCSI included six grades: I: syrinx alone without compression; II: dorsal compression; III: dorsal and central compression; IV: ventral compression; V: dorsal and ventral compression; and VI: ventral, dorsal, and central compression. Among all available variables, only the CVJCSI and surgical methods significantly affected the CCOS. The CCOS scores, overall and for each CVJCSI grade, increased in the prospective cohort ( n  = 42) compared with that in the retrospective analysis. Conclusions  The CVJCSI can be used to stratify CMI patients. The higher the CVJCSI grade, the more severe the CVJ compression and the worse posterior fossa deformity. Meanwhile, the CVJCSI was negatively correlated with the CCOS. The lower the CVJCSI grade, the better the response to surgery, and the less-invasive surgical procedures were warranted. Finally, the prospective cohort study validated the proposed CVJCSI-based surgical protocols.

A long-term follow-up study of adults with Chiari malformation type I combined with syringomyelia

Background

There is a considerable amount of controversy regarding the treatment and prognosis of adult patients with Chiari malformation type I (CM-I) at home and abroad; furthermore, no large-sample, long-term, follow-up studies have examined CM-I patients with syringomyelia (SM) comparing posterior fossa decompression with resection of tonsils (PFDRT) vs. posterior fossa decompression with duraplasty (PFDD).

Objective

This study retrospectively analyzed the factors affecting the treatment and long-term prognosis of adults with CM-I combined with SM.

Methods

We retrospectively analyzed data from 158 adult CM-I patients combined with SM who underwent PFDRT or PFDD, including 68 patients in group PFDRT and 90 patients in group PFDD. We examined the clinical manifestations, imaging features, and follow-up data of patients. Clinical outcomes were assessed using the Chicago Chiari Outcomes Scale (CCOS), and radiographic outcomes were indicated by the syrinx remission rate. Multivariate logistic regression analysis and multiple linear regression analysis were used to explore the relevant factors affecting the long-term prognosis of patients.

Results

This study showed that compared with preoperative patients in the PFDRT group and PFDD group, the sensory impairment, cough-related headache, and movement disorder were significantly improved (p < 0.01); meanwhile, the diameter of the syrinx and the volume of the syrinx decreased significantly (p < 0.001). Additionally, the study found that there were significant differences in the syrinx remission rate (p = 0.032) and the clinical cure rates (p = 0.003) between the two groups. Multivariate logistic regression analysis showed that age (p = 0.021), cerebellar-related symptoms (p = 0.044), preoperative cisterna magna volume (p = 0.043), and peak systolic velocity (p = 0.036) were independent factors for clinical outcomes. Multiple linear regression analysis showed that different surgical procedures were positively correlated with the syrinx remission rate (p = 0.014), while preoperative syrinx diameter (p = 0.018) and age (p = 0.002) were negatively correlated with the syrinx remission rate.

Conclusion

In conclusion, this study suggested that, in a long-term follow-up, although both surgical procedures are effective in treating patients with CM-I and SM, PFDRT is better than PFDD; age and cerebellar-related signs independently affect the patient's prognosis. Additionally, an effective prognosis evaluation index can be developed for patients, which is based on imaging characteristics, such as preoperative cisterna magna volume, preoperative syrinx diameter, and preoperative cerebrospinal fluid (CSF) hydrodynamic parameters to guide clinical work.

Congress of Neurological Surgeons Systematic Review and Evidence-Based Guidelines for Patients With Chiari Malformation: Diagnosis

BACKGROUND

Chiari I malformation (CIM) is characterized by descent of the cerebellar tonsils through the foramen magnum, potentially causing symptoms from compression or obstruction of the flow of cerebrospinal fluid. Diagnosis and treatment of CIM is varied, and guidelines produced through systematic review may be helpful for clinicians.

OBJECTIVE

To perform a systematic review of the medical literature to answer specific questions on the diagnosis and treatment of CIM.

METHODS

PubMed and Embase were queried between 1946 and January 23, 2021, using the search strategies provided in Appendix I of the full guidelines.

RESULTS

The literature search yielded 567 abstracts, of which 151 were selected for full-text review, 109 were then rejected for not meeting the inclusion criteria or for being off-topic, and 42 were included in this systematic review.

CONCLUSION

Three Grade C recommendations were made based on Level III evidence. The full guidelines can be seen online at https://www.cns.org/guidelines/browse-guidelines-detail/1-imaging .

A valuable subarachnoid space named the occipito-atlantal cistern

The cisterna magna has been defined as the space between the inferior margin of the cerebellar vermis to the level of the foramen magnum, while an enlarged dorsal subarachnoid space at the occipito-cervical junction extending from the foramen magnum to the upper border of the axis (C2) is still ignored. Recently, the myodural bridge complex is proved to drive the cerebral spinal fluid flowing via this region, we therefore introduce the "occipito-atlantal cistern (OAC)" to better describe the subarachnoid space and provide a detailed rationale. The present study utilized several methods, including MRI, gross anatomical dissection, P45 sheet plastination, and three-dimensional visualization. OAC was observed to be an enlarge subarachnoid space, extending from the foramen magnum to the level of the C2. In the median sagittal plane, OAC was a funnel shape and its anteroposterior dimensions were 15.92 ± 4.20 mm at the level of the C0, 4.49 ± 1.25 mm at the level of the posterior arch of the C1, and 2.88 ± 0.77 mm at the level of the arch of the C2, respectively. In the median sagittal plane, the spino-dural angle of the OAC was calculated to be 35.10 ± 6.91°, and the area of OAC was calculated to be 232.28 ± 71.02 mm². The present study provides OAC is a subarachnoid space independent from the cisterna magna. Because of its distinctive anatomy, as well as theoretical and clinical significance, OAC deserves its own name.

Potential association among posterior fossa bony volume and crowdedness, tonsillar hernia, syringomyelia, and CSF dynamics at the craniocervical junction in Chiari malformation type I

Objective

The characteristic morphological parameters (bony posterior fossa volume (bony-PFV), posterior fossa crowdness, cerebellar tonsillar hernia, and syringomyelia) and CSF dynamics parameters at the craniocervical junction (CVJ) in Chiari malformation type I (CMI) were measured. The potential association between these characteristic morphologies and CSF dynamics at CVJ was analyzed.

Methods

A total of 46 cases of control subjects and 48 patients with CMI underwent computed tomography and phase-contrast magnetic resonance imaging. Seven morphovolumetric measures and four CSF dynamics at CVJ measures were performed. The CMI cohort was further divided into "syringomyelia" and "non-syringomyelia" subgroups. All the measured parameters were analyzed by the Pearson correlation.

Results

Compared with the control, the posterior cranial fossa (PCF) area, bony-PFV, and CSF net flow were significantly smaller (P < 0.001) in the CMI group. Otherwise, the PCF crowdedness index (PCF CI, P < 0.001) and the peak velocity of CSF (P < 0.05) were significantly larger in the CMI cohort. The mean velocity (MV) was faster in patients with CMI with syringomyelia (P < 0.05). In the correlation analysis, the degree of cerebellar tonsillar hernia was correlated with PCF CI (R = 0.319, P < 0.05), MV (R = -0.303, P < 0.05), and the net flow of CSF (R = -0.300, P < 0.05). The Vaquero index was well correlated with the bony-PFV (R= -0.384, P < 0.05), MV (R = 0.326, P < 0.05), and the net flow of CSF (R = 0.505, P < 0.05).

Conclusion

The bony-PFV in patients with CMI was smaller, and the MV was faster in CMI with syringomyelia. Cerebellar subtonsillar hernia and syringomyelia are independent indicators for evaluating CMI. Subcerebellar tonsillar hernia was associated with PCF crowdedness, MV, and the net flow of CSF at CVJ, while syringomyelia was associated with bony-PFV, MV, and the net flow of CSF at the CVJ. Thus, the bony-PFV, PCF crowdedness, and the degree of CSF patency should also be one of the indicators of CMI evaluation.

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.

Outcome evaluation of decompression surgery combined with cerebellar tonsillectomy compared without cerebellar tonsillectomy for Chiari type I malformation patients

BACKGROUND

Surgical intervention is an important treatment option to improve the prognosis for Chiari type I malformation (CM-I) patients. However, there is no consensus about surgical strategies. The article intends to evaluate the effect of decompression combined with or without cerebellar tonsillectomy in the treatment of CM-I.

METHOD

Following PRISMA's principles, Embase, PubMed, Web of Science, and Cochrane databases and references to relevant articles were searched to include only original articles on decompression combined with or without cerebellar tonsillectomy in CM-I patients. Through meta-analysis, the data on clinical improvement, radiological improvement, and complications were pooled.

RESULTS

Nine articles, including 399 CM-I patients undergoing decompression alone and 343 undergoing decompression with cerebellar tonsillectomy, meet the inclusion standard. In comparison, the improvement rate of clinical symptoms or signs in patients with cerebellar tonsillectomy is higher and statistically significant (RR: 0.85, 95% CI: 0.75-0.95; P = 0.006). However, decompression with cerebellar tonsillectomy is also significantly higher in the incidence of postoperative complications (RR: 0.54, 95% CI: 0.36-0.80; P = 0.002). No statistical difference is discovered between the two groups in the improvement rate of syringomyelia (RR: 0.77, 95% CI: 0.57-1.03; P = 0.08).

CONCLUSIONS

Although decompression with cerebellar tonsillectomy is superior than decompression alone in clinical improvement for CM-I patients, it also faces a higher risk of postoperative complications. The reduction of syringomyelia in the two groups can be considered equally effective without significant differences. In the future, the results of the research require multicenter and large-scale randomized controlled trials to verify in clinical practice.

TRIAL REGISTRATION

CRD42022321750 (PROSPERO).

Headache and Other Symptoms in Chiari Malformation Type I Are Associated with Cerebrospinal Fluid Flow Improvement After Decompression: A Two-Institutional Study

OBJECTIVE

Chiari malformation type I (CMI) is a common neurologic condition and surgery is the standard treatment. We aim to establish the cerebrospinal fluid (CSF) flow change as a potential objective indicator of surgical efficacy to improve symptoms.

METHODS

We performed a retrospective 2-center analysis of surgically treated patients with CMI. Qualitative CSF flow studies obtained preoperatively and postoperatively were analyzed by the neuroradiologist, seeking improvement in CSF flow. Symptom status, including headache and neck pain, were recorded.

RESULTS

Forty-nine patients were identified between 2010 and 2017. The average age was 36 years, with 47 females. After decompression, CSF flow was improved in 41 patients (group A) and unchanged in 8 (group B). Group A and B had a mean age of 34 and 42 years (P < 0.05) and an average tonsillar herniation of 8.3 and 8.5 mm (P = 0.40), respectively. Group A had improved clinical outcomes, compared with group B (P = 0.024), more specifically, in headache (50% vs. 37%), neck pain (66% vs. 33%), dizziness (78% vs. 50%), vision symptoms (84% vs. 80%), and weakness (100% vs. 66%), respectively. Group B had the only patient who did worse on clinical follow-up.

CONCLUSIONS

Patients with CMI often present with a constellation of symptoms. We showed a significant association between improved CSF flow after decompression and symptom alleviation. Further, our study suggests that the presence of improved CSF flow postoperatively could represent an objective indicator for improved patient outcomes.

Chiari Type 1 malformation: CSF flow dynamics and morphology in the posterior fossa and craniocervical junction and correlation of these findings with syrinx formation

BACKGROUND

Chiari type 1 malformation (CMI) is a disorder in which cerebellar tonsils descend below the foramen magnum. Although syringomyelia associated with CMI thought to be caused by hypoplastic posterior fossa and stenosis at the craniocervical junction; it has characteristic neurological and radiological features and the exact mechanism of syringomyelia remains unknown.

PURPOSE

The purposes of this study were to gain insight into morphological changes in posterior fossa and to find whether there is a difference in aqueductal stroke volume (ASV) between CMI with syrinx and without syrinx which may be an underlying mechanism of syrinx development.

MATERIALS AND METHODS

We consecutively evaluated 85 patients with Chiari malformation between January 2017 and December 2019 who had undergone phase-contrast MRI examination for CSF flow and between 18-60-years-old. We divided patients into two groups as subjects with syrinx (n=19) and without syrinx (n=66). After evaluating morphological changes, peak and average velocity (cm/s), forward and reverse flow volume (μl), net forward flow volume (μl), ASV (aqueductal stroke volume) (μl), aqueductus Sylvi (AS) area (mm²), and prepontine cistern diameter to AS diameter ratio (PPC/AS) were calculated. Distribution of variables from two groups was evaluated by using Shapiro-Wilk normality test. Independent t test was used for groups comparison.

RESULTS

The forward and reverse volumes were statistically significantly higher in patients with syrinx (P=0.021, P=0.005 respectively). ASV was significantly increased in patients with syringomyelia (P=0.014). The PPC/AS was significantly lower in patients with syrinx compared to those without (P <0.001). AS area was significantly larger in those with syrinx. (P=0.022). The diameter of foramen magnum was significantly lower in patients with syrinx than those without (P <0.0001). The diameter of the herniated tonsilla at the foramen magnum level was found to be significantly lower in those with syrinx (P=0.011).

CONCLUSION

Foramen magnum diameter, ASV, diameter of herniated tonsil, and PPC/AS ratio are important factors in syrinx development.

Enhanced Safety of Pedicle Subtraction Osteotomy Using Intraoperative Ultrasound

BACKGROUND

Pedicle subtraction osteotomy (PSO) can improve sagittal alignment but carries risks, including iatrogenic spinal cord and nerve root injury. Critically, during the reduction phase of the technique, medullary kinking or neural element compression can lead to neurologic deficits.

METHODS

We describe 3 cases of thoracic PSO and evaluate the feasibility, findings, and utility of intraoperative ultrasound in this setting.

RESULTS

Intraoperative ultrasound can provide a visual assessment of spinal cord morphology before and after PSO reduction and influences surgical decision making with regard to the final amount of sagittal plane correction. This modality is particularly useful for confirming ventral decompression of disc-osteophyte complex before reduction and also after reduction maneuvers when there is kinking of the thecal sac but uncertainty about the underlying status of the spinal cord. Intraoperative ultrasound is a reliable modality that fits well into the technical sequence of PSO, adds a minimal amount of operative time, and has few limitations.

CONCLUSIONS

We propose that intraoperative ultrasound is a useful supplement to standard neuromonitoring modalities for ensuring safe PSO reduction and decompression of neural elements.

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

BACKGROUND

The existing classification in Chiari I malformation (CM-I) has limited significance for the selection of surgical methods.

OBJECTIVE

The purpose of this study was to investigate the surgery of CM-I with syringomyelia based on the high-resolution MR imaging (HRMRI) findings.

METHODS

Data from 115 patients were collected and retrospectively analyzed. For those with syringomyelia up to the level of C1, HRMRI was performed and according to the communication status between the fourth ventricle and the syringomyelia, patients can be divided into four types, namely Type A: classic communicating; Type B: partial communicating; Type C: non-communicating; Type D: atrophic. All operations were performed with Foramen magnum and Magendie dredging (FMMD), and all intradural factors that may have induced the obstruction of CSF circulation were recorded. The efficiency of operation on syringomyelia was evaluated by mJOA, imaging findings, and complications in the follow-up periods.

RESULTS

The postoperative follow-up period was from 12 to 24 months, with an average of 14.3 months. At 1 year, the mJOA of 115 patients was significantly higher than that before the operations (before surgery 12.1 ± 2.3 vs. after surgery 14. 2 ± 1.4, P < 0.05). In addition, postoperative re-examination showed that the size of the syringomyelia was reduced or completely resolved in patients of Type A, 100% (2/2); Type B, 81% (9/11); Type C, 84% (81/97); and Type D, 20% (1/5).

CONCLUSIONS

According to our new classification based on HRMRI, FMMD is the key to surgical treatment, especially for Type A and Type B patients.

The 270° Circumferential Microsurgical Decompression of the Foramen Magnum in Adult Chiari Malformation Type I: Single Surgeon Series of 130 Patients with Syringomyelia, Neurologic, and Headache Outcomes

OBJECTIVE

Chiari malformation type I (CM-I) is a craniocervical junction disorder associated with descent of the cerebellar tonsils >5 mm. The prevalence of CM-I is common, including 0.5%-3.5% in the general population, 0.56%-0.77% on magnetic resonance imaging, and 0.62% in anatomic dissection studies. We sought to measure our surgical outcomes related to resolution/improvement of headaches, neurologic outcomes, and syringomyelia compared with reported adult CM-I studies from 2000-2019.

METHODS

From December 2003 to June 2018, the first author (K.I.A.) performed 270° circumferential decompression on adult (>18 years) patients with CM-I. At admission and follow-up, all parameters were numerically evaluated; headaches were self-reported on the visual analog scale, neurologic condition was evaluated using Karnofsky Performance Status and European Myelopathy Score, and syrinx width (if present) was measured on magnetic resonance imaging by grades I-IV. All parameters were analyzed, compared, and statistically tested. We compared results with our previously reported and updated systematic review of operative adult CM-I studies (studies from 2000 to 2019).

RESULTS

In our series, 118/121 (98%) experienced headache improvements and 100% experienced neurologic improvements. Complete syrinx resolution was experienced by 35/43 (81%); 8 (19%) showed significant improvement. In data from reported studies (2000-2019), only 79% experienced headache resolution, 77% improvement of neurologic status, and 74% resolution/improvement of syrinx (mean).

CONCLUSIONS

Our modified 270° circumferential microsurgical foramen magnum decompression for adult CM-I appears to be beneficial in improvement of outcomes, namely in resolution of the syrinx, neurologic symptoms, and headaches. We also confirm the association of body mass index with CM-I. Further studies are needed to confirm our results.

The Perplexity Surrounding Chiari Malformations - Are We Any Wiser Now?

Chiari malformations are a diverse group of abnormalities of the brain, craniovertebral junction, and the spine. Chiari 0, I, and 1.5 malformations, likely a spectrum of the same malformation with increasing severity, are due to the inadequacy of the para-axial mesoderm, which leads to insufficient development of occipital somites. Chiari II malformation is possibly due to nonclosure of the caudal end of the neuropore, with similar pathogenesis in the rostral end, which causes a Chiari III malformation. There have been significant developments in the understanding of this complex entity owing to insights into the pathogenesis and advancements in imaging modalities and neurosurgical techniques. This article aims to review the different types and pathophysiology of the Chiari malformations, along with a description of the various associated abnormalities. We also highlight the role of ante- and postnatal imaging, with a focus on the newer techniques in the presurgical evaluation, with a brief mention of the surgical procedures and the associated postsurgical complications.

Persistent Syringomyelia After Posterior Fossa Decompression for Chiari Malformation

BACKGROUND

Chiari malformation (CM) is often comorbid with syringomyelia. The treatment of CM via posterior fossa decompression (PFD) may not improve syringomyelia in up to 40% of patients, based on historical cohorts. Management of these patients is problematic, as both reoperation and syrinx shunting have high failure rates in the long term.

METHODS

We retrospectively reviewed our cases in which patients with CM type 1 or 1.5 and syringomyelia underwent PFD without postoperative improvement in syringomyelia. Symptomatology and radiographic measurements were collected at presentation and on the first and latest available postoperative scans and analyzed. We present 2 cases to illustrate the challenges in the management of these patients.

RESULTS

Our cohort consisted of 48 consecutive patients with CM and syringomyelia who underwent PFD. Of these, 41 patients had postoperative improvement in or resolution of syringomyelia. We subsequently studied the cohort of 7 patients who underwent PFD with (n = 5) or without (n = 2) durotomy and demonstrated worsening of syringomyelia following surgery. This cohort had mean (±SEM) preoperative syrinx area of 23.9 ± 10.0 mm². Postoperatively, the mean syrinx area increased to 40.5 ± 9.6 mm² and 57.3 ± 12.5 mm² on the first and latest postoperative scans available (P = 0.02), for an increase of 106.9% ± 94.4% and 186.0% ± 107.4% (P = 0.04). Presenting symptoms included occipital headache, paresthesias, visual deterioration, and paraspinal pain. On last follow-up (mean 13.9 ± 4.9 months), the majority of symptoms were resolved in this cohort, despite persistence of syringomyelia.

CONCLUSIONS

In this small cohort of unique patients, syrinx resolution was not achieved via decompression surgery. Despite "radiographic failure," good symptom control was achieved, with most patients remaining or becoming asymptomatic postoperatively, thus supporting our rationale for what has largely been a conservative approach in this population.

Outcomes and complications for individual neurosurgeons for the treatment of Chiari I malformation at a children's hospital

PURPOSE

The aim of this study was to evaluate the outcomes and complications for individual surgeons at British Columbia Children's Hospital for the treatment of Chiari I Malformation (CMI) in children.

METHODS

This was a retrospective review of patients with CMI who had surgery from 1986 to 2015. We assessed the Chicago Chiari Outcome Scores (CCOS) and complication rates by surgeon.

RESULTS

Seventy patients, 38 males and 32 females, underwent posterior fossa decompression including 14 extradural and 56 intradural approaches. Syringomyelia was present in 74.3%. Most syringomyelia improved with no difference between intradural and extradural surgeries. After initial surgery, 13 patients (18.6%) had complications including 2/14 (14.3%) of extradural and 11/56 (19.6%) of intradural surgeries. Two patients required surgical intervention for complications whereas 11 had transient complications. The complication rate by surgeon ranged from 11 to 20% for extradural (2 surgeons only) and 10.5 to 40% for intradural surgeries (4 surgeons). The CCOS ranged from 12 to 15 for extradural and 6 to 16 for intradural. The CCOS ranges for surgeons 1 and 2 were 12-15 and 13-15 respectively for extradural. The CCOS ranges for surgeons 1, 2, 3, and 4 were 12-16, 6-15, 12-16, and 12-16 respectively for intradural. Thirteen patients had a second surgery for CMI. The final CCOS was good in 86% and moderate in 14%.

CONCLUSION

There was variability in surgeries performed at BCCH by different surgeons, with variations in CCOS and complication rates. This information is important during decision making, consent process, and for quality improvement.