219. The Relationship Between Chiari 1.5 Malformation and Sleep-Disordered Breathing on Polysomnography

Authors: Nicholas Sader, MD; Aaron Hockley; Valerie Kirk; Adeleye Adetayo; Walter Hader; Jay Riva-Cambrin (Calgary, Canada)


The Chiari 1.5 malformation is a recently defined subgroup of Chiari malformation whereby the descent of the tonsils into the foramen magnum is accompanied by descent of the brainstem. However, no published data exists answering if operative decompression of Chiari 1.5 pediatric patients improve sleep-disordered breathing (SDB) and whether there are radiologic factors that predict improvement?


We performed a retrospective cohort study of consecutive pediatric patients presenting with a Chiari 1.5 malformation and SDB at the Alberta Children’s Hospital. SDB was characterized by nocturnal polysomnography (PSG) before and after surgical decompression. We compared the apnea-hypopnea index (AHI), obstructive apnea index (OAI), and central apnea index (CAI). We assessed radiographic factors for an association with SDB and response to surgery.    


Seven patients met the inclusion criteria. One patient had two surgical decompressions with pre-operative and post-operative PSGs (n=8). The median age was nine years old (4,13) with five males and two females. Before surgical decompression, 75% underwent a tonsillectomy/adenoidectomy. The majority (87.5%) experienced snoring and witnessed apnea pre-operatively. The median tonsillar and obex descent was 21.3mm and 11.2mm, respectively. The median pB-C2 and clival axis angle were 5.4 (4.5, 6.8) and 144° (139°, 167°). There was a statistically significant change from pre-operative to post-operative AHI [19.7, 5.1] (p=0.015) and OHI [4.5, 1.0] (p=0.01). There was no significant change in CAI pre-operatively and post-operatively [0.9, 0.3] (p=0.12). No radiologic factors were statistically significant in predicting pre-op AHI and change in AHI.


This is the first reported series of pediatric Chiari 1.5 patients with SDB who demonstrated a marked improvement in their polysomnography after decompression. Sleep apnea has been shown to have a significant impact on memory and learning in children, highlighting the urgency to recognize Chiari 1.5 as a more severe form of the Chiari type 1 malformation.