Positive and negative predictors for good outcome after decompressive surgery for Chiari malformation type 1 as scored on the Chicago Chiari Outcome Scale

Clinical Outcome Measures in Chiari I Malformation

Chiari malformation type 1 (CM-I) is a common and often debilitating neurologic disease. Reliable evaluation of treatments has been hampered by inconsistent use of clinical outcome measures. A variety of outcome measurement tools are available, although few have been validated in CM-I. The recent development of the Chicago Chiari Outcome Scale and the Chiari Symptom Profile provides CM-I-specific instruments to measure outcomes in adults and children, although validation and refinement may be necessary.

Tonsillar pulsatility before and after surgical decompression for children with Chiari malformation type 1: an application for true fast imaging with steady state precession

INTRODUCTION

We hypothesize that surgical decompression for Chiari malformation type 1 (CM-1) is associated with statistically significant decrease in tonsillar pulsatility and that the degree of pulsatility can be reliably assessed regardless of the experience level of the reader.

METHODS

An Institutional Review Board (IRB)-approved Health Insurance Portability and Accountability Act (HIPAA)-compliant retrospective study was performed on 22 children with CM-1 (8 males; mean age 11.4 years) who had cardiac-gated true-FISP sequence and phase-contrast cerebrospinal fluid (CSF) flow imaging as parts of routine magnetic resonance (MR) imaging before and after surgical decompression. The surgical technique (decompression with or without duraplasty) was recorded for each patient. Three independent radiologists with different experience levels assessed tonsillar pulsatility qualitatively and quantitatively and assessed peritonsillar CSF flow qualitatively. Results were analyzed. To evaluate reliability, Fleiss kappa for multiple raters on categorical variables and intra-class correlation for agreement in pulsatility ratings were calculated.

RESULTS

After surgical decompression, the degree of tonsillar pulsatility appreciably decreased, confirmed by t test, both qualitatively (p values <0.001, <0.001, and 0.045 for three readers) and quantitatively (amount of decrease/p value for three readers 0.7 mm/<0.001, 0.7 mm/<0.001, and 0.5 mm/0.022). There was a better agreement among the readers in quantitative assessment of tonsillar pulsatility (kappa 0.753-0.834), compared to qualitative assessment of pulsatility (kappa 0.472-0.496) and qualitative assessment of flow (kappa 0.056 to 0.203). Posterior fossa decompression with duraplasty led to a larger decrease in tonsillar pulsatility, compared to posterior fossa decompression alone.

CONCLUSION

Tonsillar pulsatility in CM-1 is significantly reduced after surgical decompression. Quantitative assessment of tonsillar pulsatility was more reliable across readers than qualitative assessments of tonsillar pulsatility or CSF flow.

Upward Translation of Cerebellar Tonsils following Surgical Expansion of Supratentorial Cranial Vault: A Unified Biomechanical Explanation of Chiari Type I

Cerebellar tonsils moved significantly upward in 3 patients with Chiari type I who underwent supratentorial cranial vault expansion to alleviate intracranial pressure related to multisutural craniosynostosis. The Chiari type I deformities in these patients were the biomechanical consequence of posterior fossa-cerebellar disproportion caused by supratentorial craniocerebral disproportion secondary to multisutural craniosynostosis. The authors postulate that all cases of Chiari type I deformity share the sine qua non feature of posterior fossa-cerebellar disproportion.

Outcome methods used in clinical studies of Chiari malformation Type I: a systematic review

OBJECT

Chiari malformation Type I (CM-I) is a common and often debilitating neurological disease. Efforts to improve treatment of CM-I are impeded by inconsistent and limited methods of evaluating clinical outcomes. To understand current approaches and lay a foundation for future research, the authors conducted a systematic review of the methods used in original published research articles to evaluate clinical outcomes in patients treated for CM-I.

METHODS

The authors searched PubMed, Embase, the Cumulative Index to Nursing and Allied Health Literature, ClinicalTrials.gov , and Cochrane databases to identify publications between January 2003 and August 2013 that met the following criteria: 1) reported clinical outcomes in patients treated for CM-I; 2) were original research articles; 3) included at least 10 patients or, if a comparative study, at least 5 patients per group; and 4) were restricted to patients with CM-I.

RESULTS

Among the 74 papers meeting inclusion criteria, there was wide variation in the outcome methods used. However, all approaches were broadly grouped into 3 categories: 1) "gestalt" impression of overall symptomatic improvement (n=45 papers); 2) postoperative change in specific signs or symptoms (n=20); or 3) results of various standardized assessment scales (n=22). Among standardized scales, 11 general function measures were used, compared with 6 disease-specific tools. Only 3 papers used scales validated in patients with CM-I. To facilitate a uniform comparison of these heterogeneous approaches, the authors appraised articles in multiple domains defined a priori as integral to reporting clinical outcomes in CM-I. Notably, only 7 articles incorporated patient-response instruments when reporting outcome, and only 22 articles explicitly assessed quality of life.

CONCLUSIONS

The methods used to evaluate clinical outcomes in CM-I are inconsistent and frequently not comparable, complicating efforts to analyze results across studies. Development, validation, and incorporation of a small number of disease-specific patient-based instruments will improve the quality of research and care of CM-I patients.

External validation of the Chicago Chiari Outcome Scale

OBJECT

Historically, assessment of clinical outcomes following surgical management of Chiari malformation Type I (CM-I) has been challenging due to the lack of a validated instrument for widespread use. The Chicago Chiari Outcome Scale (CCOS) is a novel system intended to provide a less subjective evaluation of outcomes for patients with CM-I. The goal of this study was to externally validate the performance of the CCOS.

METHODS

Patients undergoing surgery for CM-I between 2001 and 2012 were reviewed (n = 292). Inclusion criteria for this study were as follows: 1) patients receiving primary posterior fossa decompression; 2) at least 5.5 months of postoperative clinical follow-up; and 3) patients ≤ 18 years of age at the time of surgery. Outcomes were evaluated using the CCOS, along with a "gestalt" impression of whether patients experienced significant improvement after surgery. A subgroup of 118 consecutive patients undergoing operations between 2008 and 2010 was selected for analysis of interrater reliability (n = 73 meeting inclusion/exclusion criteria). In this subgroup, gestalt and CCOS scores were independently determined by 2 reviewers, and interrater reliability was assessed using the intraclass correlation coefficient (ICC) and kappa (κ) statistic.

RESULTS

The median CCOS score was 14, and 67% of patients had improved gestalt scores after surgery. Overall, the CCOS was effective at identifying patients with improved outcome after surgery (area under curve = 0.951). The interrater reliability of the CCOS (ICC = 0.71) was high, although the reliability of the component scores ranged from poor to good (ICC 0.23-0.89). The functionality subscore demonstrated a low ICC and did not add to the predictive ability of the logistic regression model (likelihood ratio = 1.8, p = 0.18). When analyzing gestalt outcome, there was moderate agreement between raters (κ = 0.56).

CONCLUSIONS

In this external validation study, the CCOS was effective at identifying patients with improved outcomes and proved more reliable than the authors' gestalt impression of outcome. However, certain component subscores (functionality and nonpain symptoms) were found to be less reliable, and may benefit from further definition in score assignment. In particular, the functionality subscore does not add to the predictive ability of the CCOS, and may be unnecessary. Overall, the authors found the CCOS to be an improvement over the previously used assessment of outcome at their institution.