Management of Chiari malformations: opinions from different centers-a review

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

Background

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

Objective

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

Methods

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

Results

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

Conclusion

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

Postural control in Chiari I malformation: protocol for a paediatric prospective, observational cohort - potential role of posturography for surgical indication

INTRODUCTION

Chiari I malformation (CM1) is an anatomical abnormality characterised by the cerebellar tonsils descending at least 5 mm below the foramen magnum. CM1 causes obstruction of cerebrospinal fluid (CSF) circulation as well as direct compression on the brainstem, thus causing typical consequences (syringomyelia), and typical clinical features (characteristic headaches and neurological impairment). Surgery is the only available treatment, indicated when symptomatology is present. However, sometimes patients have atypical complaints, which are often suggestive of otolaryngological (ears, nose and throat, ENT) involvement. This may be difficult for a neurosurgeon to explain. Our study aims to investigate the relationship between one of these atypical symptoms, for example, postural instability, in a paediatric population using a Computerised Dynamic Posturography (Equitest, NeuroCom, Clackamas, OR). To our knowledge, there are no previously published studies carried out on children with CM1, using dynamic posturography.

METHODS AND ANALYSIS

Forty-five children aged 6-18 years old presenting with radiologically confirmed CM1 and presenting ENT clinical complaints will be included in the study for a duration of 3 years. As primary endpoint, posturographic results will be described in the population study. Second, posturographic results will be compared between patients with and without indication for surgery. Finally, preoperative and postoperative posturographic results, as well as CSF circulation quality at foramen magnum level, syringomyelia, sleep apnoea syndrome, scoliosis and behaviour will be compared in the operated patient group.

ETHICS AND DISSEMINATION

This protocol received ethical approval from the Clinical Research Delegation of Nancy University Hospital, in accordance with the National Commission on Informatics and Liberties (Commission Nationale de l'Informatique et des Libertés) (protocol number 2019PI256-107). Our data treatment was in accordance with the Methodology of reference Methodology Reference-004 specification for data policy. The study findings will be disseminated via peer-reviewed publications and conference presentations, especially to the Neurosphynx's rare disease healthcare network.

TRIAL REGISTRATION NUMBER

NCT04679792; Pre-results.

Incorporating patient-centered quality-of-life measures for outcome assessment after Chiari malformation type I decompression in a pediatric population: a pilot study

OBJECTIVE

Optimal management of pediatric Chiari malformation type I (CM-I) is much debated, chiefly due to the lack of validated tools for outcome assessment, with very few tools incorporating patient-centered measures of health-related quality of life (HRQOL). Although posterior fossa decompression (PFD) benefits a subset of patients, prediction of its impact across patients is challenging. The primary aim of this study was to investigate the role of patient-centered HRQOL measures in the assessment and prediction of outcomes after PFD.

METHODS

The authors collected HRQOL data from a cohort of 20 pediatric CM-I patients before and after PFD. The surveys included assessments of selected Patient-Reported Outcomes Measurement Information System (PROMIS) health domains and were used to generate the PROMIS preference (PROPr) score, which is a measure of HRQOL. PROMIS is a reliable standardized measure of HRQOL domains such as pain, fatigue, depression, and physical function, which are all relevant to CM-I. The authors then compared the PROPr scores with Chicago Chiari Outcome Scale (CCOS) scores derived from time-matched clinical documentation. Finally, the authors used the PROPr scores as an outcome measure to predict postsurgical HRQOL improvement at 1 year on the basis of patient demographic characteristics, comorbidities, and radiological and physical findings. The Wilcoxon signed-rank test, Mann-Whitney U-test, and Kendall's correlation were used for statistical analysis.

RESULTS

Aggregate analysis revealed improvement of pain severity after PFD (p = 0.007) in anatomical patterns characteristic of CM-I. Most PROMIS domain scores trended toward improvement after surgery, with anxiety and pain interference reaching statistical significance (p < 0.002 and p < 0.03, respectively). PROPr scores also significantly improved after PFD (p < 0.008). Of the baseline patient characteristics, preexisting scoliosis was the most accurate negative predictor of HRQOL improvement after PFD (median -0.095 vs 0.106, p < 0.001). A correlation with modest magnitude (Kendall's tau range 0.19-0.47) was detected between the patient-centered measures and CCOS score.

CONCLUSIONS

The authors observed moderate improvement of HRQOL, when measured using a modified panel of PROMIS question banks, in this pilot cohort of pediatric CM-I patients after PFD. Further investigations are necessary to validate this tool for children with CM-I and to determine whether these scores correlate with clinical and radiographic findings.

Chiari Malformation in Children

Chiari malformation type 1 (CM1) is often found incidentally. However, patients with symptoms or signs referable to CM1 or an associated syrinx will likely benefit from surgical intervention. Patients who are not symptomatic from CM1 at presentation are unlikely to become symptomatic at follow-up.

Interlayer dural split technique for Chiari I malformation treatment in adult-Technical note

OBJECTIVE

To present an alternative surgical technique in treating cases of Chiari I Malformation with mild-to-moderate syringomyelia after decompressive suboccipital craniectomy: incising only the outer layer of the dura mater, then dissecting it from the inner layer without opening the latter.

PATIENTS AND METHODS

We utilized this technique in a short series of three cases who were admitted to our department for mild symptoms such as intermittent headache and dissociated sensory loss in the upper limbs, caused by a Chiari Malformation Type I. The patients were placed in the sitting position. We performed a reduced median suboccipital craniectomy and resection of the posterior arch of C1 adapted to the level of tonsil descent, from a limited superior half to complete resection. Afterward, we incised the outer dural layer, while sparing the inner one. Using a fine dissector, we then split apart the outer and inner layers to the margin of the craniectomy. Through the transparency of the inner layer and the arachnoid, the cerebellum and the medulla were visible and pulsating. An autologous fascia duraplasty was then performed.

RESULTS

The postoperative course was favorable in all cases, the patients being discharged without any deficits and with complete symptom resolution. Follow-up at 3, 6, and 12 months after surgery revealed a significant reduction in brainstem compression and syringomyelia.

CONCLUSIONS

Interlayer dural split technique can be used effectively in treating symptomatic cases of type I Chiari malformation in adults, with mild-to-moderate syringomyelia. It is less invasive than opening the dura and possibly more effective than decompressive craniectomy and C1 laminectomy alone. This technique must be validated in a larger case-control series.

Spontaneous syrinx resolution in patient with Chiari I malformation: illustrative case

BACKGROUIND

Chiari malformations include a spectrum of congenital hindbrain herniation syndromes. In patients with the most common subtype, Chiari malformation Type I, 50% to 75% develop a syrinx. The pathogenesis of syringomyelia is not well understood, with multiple theories outlined in the literature. Although the presence of a syrinx in a patient with Chiari malformation is generally accepted as an indication for surgical intervention, there are documented cases of spontaneous resolution that support a more conservative approach to management.

OBSERVATIONS

The authors reported a case of spontaneous resolution of a cervical syrinx in an adult with an unchanged Chiari malformation.

LESSONS

Given the possibility of spontaneous resolution over time, the authors believe a more conservative approach of observation with periodic surveillance, magnetic resonance imaging, and neurological examination should be considered in the management of a patient with a Chiari malformation and associated syringomyelia.

Long-term outcomes for children with an incidentally discovered Chiari malformation type 1: what is the clinical significance?

OBJECTIVES

Chiari malformation type 1 (CM1) is an increasingly common incidental finding on magnetic resonance imaging (MRI). The proportion of children with an incidentally discovered CM1 who upon further evaluation require operative intervention for previously unrecognized signs and symptoms of neurological compromise or significant radiographic findings (syringomyelia) is unclear. An extensive long-term single-institution patient series was evaluated to better clarify the likelihood of surgery in patients who present with an incidentally discovered CM1.

METHODS

This study was conducted using prospective data for patients up to 18 years old that were evaluated for a CM1 at a large tertiary pediatric neurosurgery clinic between February 2009 and June 2019. Patients were excluded if they did not have an incidentally discovered CM1 and at least 12 months of clinical follow-up.

RESULTS

A total of 218 consecutive patients were included in this study. The mean age at the initial neurosurgical evaluation was 6.5 years (range 5 months to 18.4 years), and the mean duration of clinical follow-up was 40.6 months (range 12 to 114 months). Initial MR imaging was most commonly obtained for the evaluation of seizures (15.1%), nonspecific headaches (not occipital or tussive) (14.7%), trauma (9.6%), and developmental delay (7.8%). Of the patients studied that eventually required surgery, we identified two groups: those operated before 6 months since presentation and those operated after 6 months. A total of 36 patients (16.5%) underwent a decompression with 22 patients (61.1%) receiving surgery within 6 months and the remaining 14 patients (38.9%) beyond 6 months. Patients undergoing early surgery (10.1%) initially presented with a significant syrinx or were noted to have an occult neurological dysfunction, whereas a smaller subset of patients (6.4%) eventually required surgery over time due to the development of new symptoms or a de novo syrinx. Only the presence of syringomyelia was statistically significant for the need of a surgical intervention, while age, sex and degree of tonsillar herniation were not.

CONCLUSION

Evaluation of a large group of patients with an incidentally discovered Chiari malformation demonstrated that most patients may be managed conservatively, especially in the absence of syringomyelia. However, there is a subset of patients who will go on to develop a de novo syrinx or neurological symptoms that are new or progressive during follow-up, which should be evaluated by imaging of the brain and spinal cord. The presence of syringomyelia was associated with need for early surgical intervention. However, for patients without syringomyelia, surgical intervention is uncommon but may be delayed up to several years after presentation; therefore, long-term clinical follow-up is recommended.

Type I Chiari Malformation Without Concomitant Bony Instability: Assessment of Different Surgical Procedures and Outcomes in 73 Patients

OBJECTIVE

Posterior fossa decompression is the treatment of choice in type 1 Chiari malformation (CM-1) without bony instability. Although surgical fixation has been recommended by a few authors recently, comparative studies to evaluate these treatment strategies using objective outcome tools are lacking.

METHODS

Seventy-three patients with pure CM-1 (posterior fossa bony decompression [PFBD], n = 21; posterior fossa bony and dural decompression [PFBDD], n = 40; and posterior fixation [PF], n = 12) underwent a postoperative outcome assessment using Chicago Chiari Outcome Score (CCOS). Logistic regression analysis detected predictors of an unfavorable outcome.

RESULTS

Minimally symptomatic patients generally underwent a PFBD while most of the clinically severe patients underwent a PFBDD (p = 0.049). The mean CCOS score at discharge was highest in the PF (12.0 ± 1.41) and lowest in PFBDD group (10.98 ± 1.73, p = 0.087). Patients with minimal preoperative clinical disease severity (adjusted odds ratio [AOR], 4.58; 95% confidence interval [CI], 1.29-16.31) and PFBDD (AOR, 7.56; 95% CI, 1.70-33.68) represented risks for an unfavorable short-term postoperative outcome. Though long-term outcomes (CCOS) did not differ among the 3 groups (p = 0.615), PFBD group showed the best long-term improvements (mean follow-up CCOS, 13.71 ± 0.95), PFBDD group improved to a comparable degree despite a poorer short-term outcome while PF had the lowest scores. Late deteriorations (n = 3, 4.1%) occurred in the PFBDD group.

CONCLUSION

Minimally symptomatic patients and PFBDD predict a poor short-term postoperative outcome. PFBD appears to be a durable procedure while PFBDD group is marred by complications and late deteriorations. PF does not provide any better results than posterior fossa decompression alone in the long run.

Prognostic significance of C1-C2 facet malalignment after surgical decompression in adult Chiari malformation type I: a pilot study based on the Chicago Chiari Outcome Scale

OBJECTIVE

The authors assessed the prognostic significance of various clinical and radiographic characteristics, including C1-C2 facet malalignment, in terms of surgical outcomes after foramen magnum decompression of adult Chiari malformation type I.

METHODS

The electronic medical records of 273 symptomatic patients with Chiari malformation type I who were treated with foramen magnum decompression, C1 laminectomy, and duraplasty at Mayo Clinic were retrospectively reviewed. Preoperative and postoperative Neurological Scoring System scores were compared using the Friedman test. Bivariate analysis was conducted to identify the preoperative variables that correlated with the patient Chicago Chiari Outcome Scale (CCOS) scores. Multiple linear regression analysis was subsequently performed using the variables with p < 0.05 on the bivariate analysis to check for independent associations with the outcome measures. Statistical software SPSS version 25.0 was used for the data analysis. Significance was defined as p < 0.05 for all analyses.

RESULTS

Fifty-two adult patients with preoperative clinical and radiological data and a minimum follow-up of 12 months were included. Motor deficits, syrinx, and C1-C2 facet malalignment were found to have significant negative associations with the CCOS score at the 1- to 3-month follow-up (p < 0.05), while at the 9- to 12-month follow-up only swallowing function and C1-C2 facet malalignment were significantly associated with the CCOS score (p < 0.05). Multivariate analysis showed that syrinx presence and C1-C2 facet malalignment were independently associated with the CCOS score at the 1- to 3-month follow-up. Swallowing function and C1-C2 facet malalignment were found to be independently associated with the CCOS score at the 9- to 12-month follow-up.

CONCLUSIONS

The observed results in this pilot study suggest a significant negative correlation between C1-C2 facet malalignment and clinical outcomes evaluated by the CCOS score at 1-3 months and 9-12 months postoperatively. Prospective studies are needed to further validate the prognostic value of C1-C2 facet malalignment and the potential role of atlantoaxial fixation as part of the treatment.