External validity of the chiari severity index and outcomes among pediatric chiari I patients treated with intra- or extra-Dural decompression.
INTRODUCTION
Chiari malformation type-1 (CM-1) may be treated by intradural (ID) or extradural (ED) posterior fossa decompression, although the optimal approach is debated. The Chiari Severity Index (CSI) is a pre-operative metric to predict patient-defined improvement after CM-1 surgery. In this study, we evaluate the results of ID versus ED decompression and assess the external validity of the CSI.


METHODS
We performed a retrospective cohort study of pediatric CM-1 patients undergoing decompression at a single academic children's hospital. Characteristics of headache, syrinx, and myelopathy were collected to derive CSI grade. The primary outcome measure was pre-operative symptom resolution. The proportion of patients with favorable outcome was tabulated for each of the three CSI grades and compared to previously published results.


RESULTS
From 2004 to 2014, 189 patients underwent ID (48%) or ED (52%) decompression at the Children's Hospital of Philadelphia (CHOP). Follow-up ranged from 1 to 75 months. Rates of symptom resolution (58-64%) and reoperation (8%) were similar regardless of surgical approach. Although proportions of favorable outcomes differed between the CHOP and Washington University (WU) cohorts, the difference was not related to CSI grade (p = 0.63). Furthermore, there was no difference in the proportion of favorable outcomes between the two cohorts regardless of ID (p = 0.26) or ED approach (p = 0.11).


CONCLUSIONS
Equivalent rates of symptom resolution and reoperation following ID and ED decompression support the ED approach as a first-line surgical option for pediatric CM-1 patients. In addition, our findings provide preliminary evidence supporting the generalizability of the CSI and its use in future comparative trials.
['Pisapia|Jared M|JM|', 'Merkow|Maxwell B|MB|', 'Brewington|Danielle|D|', 'Henn|Rosemary E|RE|', 'Sutton|Leslie N|LN|', 'Storm|Phillip B|PB|', 'Heuer|Gregory G|GG|']
D000293:Adolescent D001139:Arnold-Chiari Malformation D002648:Child D015331:Cohort Studies D019299:Decompression, Surgical D004388:Dura Mater D005260:Female D006801:Humans D008279:Magnetic Resonance Imaging D008297:Male D011788:Quality of Life D015203:Reproducibility of Results D012720:Severity of Illness Index D016896:Treatment Outcome
Chiari Chiari severity index Outcome Intradural Extradural Posterior fossa decompression Syrinx