Anatomic Neuroimaging Characteristics of Posterior Fossa Type A Ependymoma Subgroups.

N.D Sabin,F.A Boop,E Anderson,A Gajjar,T Patni,Y Li,D.W Ellison,N Chambwe,S.N Hwang,T.E Merchant,P Klimo,R.G Tatevossian

doi:10.3174/ajnr.a7322

Abstract

Posterior fossa type A (PFA) ependymomas have 2 molecular subgroups (PFA-1 and PFA-2) and 9 subtypes. Gene expression profiling suggests that PFA-1 and PFA-2 tumors have distinct developmental origins at different rostrocaudal levels of the brainstem. We, therefore, tested the hypothesis that PFA-1 and PFA-2 ependymomas have different anatomic MR imaging characteristics at presentation. Two neuroradiologists reviewed the preoperative MR imaging examinations of 122 patients with PFA ependymomas and identified several anatomic characteristics, including extension through the fourth ventricular foramina and encasement of major arteries and tumor type (midfloor, roof, or lateral). Deoxyribonucleic acid methylation profiling assigned ependymomas to PFA-1 or PFA-2. Information on PFA subtype from an earlier study was also available for a subset of tumors. Associations between imaging variables and subgroup or subtype were evaluated. No anatomic imaging variable was significantly associated with the PFA subgroup, but 5 PFA-2c subtype ependymomas in the cohort had a more circumscribed appearance and showed less tendency to extend through the fourth ventricular foramina or encase blood vessels, compared with other PFA subtypes. PFA-1 and PFA-2 ependymomas did not have different anatomic MR imaging characteristics, and these results do not support the hypothesis that they have distinct anatomic origins. PFA-2c ependymomas appear to have a more anatomically circumscribed MR imaging appearance than the other PFA subtypes; however, this needs to be confirmed in a larger study.

Highlights

MethodsTwo neuroradiologists reviewed the preoperative MR imaging examinations of 122 patients with Posterior fossa type A (PFA) ependymomas and identified several anatomic characteristics, including extension through the fourth ventricular foramina and encasement of major arteries and tumor type (midfloor, roof, or lateral)
BACKGROUND AND PURPOSEPosterior fossa type A (PFA) ependymomas have 2 molecular subgroups (PFA-1 and PFA-2) and 9 subtypes
No anatomic imaging variable was significantly associated with the PFA subgroup, but 5 PFA-2c subtype ependymomas in the cohort had a more circumscribed appearance and showed less tendency to extend through the fourth ventricular foramina or encase blood vessels, compared with other PFA subtypes

Summary

Methods

Two neuroradiologists reviewed the preoperative MR imaging examinations of 122 patients with PFA ependymomas and identified several anatomic characteristics, including extension through the fourth ventricular foramina and encasement of major arteries and tumor type (midfloor, roof, or lateral). One hundred twenty-two patients with PF ependymoma treated at or who presented for consultation to the St. Jude Children’s Research Hospital between 1996 and 2017 with evaluable preoperative MR imaging examinations and tumor specimens available for DNA methylation profiling were identified. The preoperative examinations were performed at outside institutions and varied with respect to pulse sequences obtained and imaging technique Suitable studies were those that provided anatomic definition. Any tumor that extended beyond the margin of the fourth ventricle into one or both foramina of Luschka was characterized as involving those structures, and a tumor that appeared to extend around at least 50% of the circumference of the basilar and/or vertebral artery was classified as encasing those vessels

Results

Discussion

Conclusion