118. Imaging Predictors Of Surgery In Chiari I Malformation

Award: Top Poster

Authors: Elizabeth Naylor Kuhn, MD; Travis Atchley, MD; Tofey Leon, MD; Nicholas Laskay, MD; Anastasia Arynchyna, MPH; Burkely Smith, MD; James Johnston, MD; Jeffrey Blount, MD; Curtis Rozzelle, MD; Brandon Rocque, MD, MS (Birmingham, AL)


In Chiari I malformation (CM1), a variety of imaging findings have been purported to be important. However, results have been inconclusive, inconsistent, or not replicated in independent studies.

The purpose of this study is to report imaging characteristics for a large cohort of patients with CM1 and identify predictors of needing surgical decompression.


Patients were identified using ICD-9 codes for CM1 from 1998 – 2016. After review of the medical records, patients were excluded if they: did not have a diagnosis of CM1, were not evaluated by a neurosurgeon, or did not have available preoperative magnetic resonance (MR) imaging. Retrospective chart review was performed to collect demographic and clinical data. Imaging parameters were measured according to the CM1 Common Data Elements.


A total of 731 patients were included for analysis with mean follow-up duration of 25.5 months. Mean age at presentation was 8.5 years. Mean tonsil position was 11.4mm below the foramen magnum and 62.8% of patients had pegged tonsil shape. Two hundred patients (27.4%) underwent surgery for life-dominating tussive headache, lower cranial nerve dysfunction, other focal neurologic deficit, and/or syrinx. Surgical treatment was associated with age at initial visit (OR 1.04, 95% CI: 1.01-1.08, p=0.01), lowest tonsillar position (OR 1.15, 95% CI: 1.11-1.18, p<0.0001), syrinx length (OR 1.15, 95% CI: 1.08-1.23, p<0.0001), syrinx diameter (OR 1.44, 95% CI: 1.24-1.66, p<0.0001), basion dens interval (OR 0.90, 95% CI: 0.83-0.98, p=0.009), supraocciput length (OR 1.02, 95% CI: 0.99-1.05, p=0.03), and basilar invagination (OR 0.89, 95% CI: 0.83-0.96, p=0.002).


Comprehensive imaging characteristics for a large cohort of patients with CM1 are reported, along with clinical and imaging features associated with undergoing surgical decompression.