231. The Role of Intraoperative MRI in Resection of Cerebellar Pilocytic Astrocytomas

Authors: Kimberly Hamilton, MD; Kimberly Hamilton, MD; David Bray, MD; Sona Desai; Andrew Reisner, MD; Joshua Chern, MD, PhD (Atlanta, GA)


Cerebellar pilocytic astrocytomas in the pediatric population are primarily a surgical disease.  Gross total resection (GTR) allows for an excellent prognosis without adjuvant therapies in many cases. The surgical techniques used to obtain these outcomes have advanced over the years as new technologies are developed, including the use of intra-operative MRI (iMRI).  We sought to evaluate if iMRI has had a profound impact on the outcome of patients, primarily regarding the rate of re-operation, the rate of GTR, and the rate of tumor recurrence.


A retrospective review of medical records was conducted for patients with cerebellar pilocytic astrocytoma at a single institution, spanning from 2007 to 2012.  Forty six patients were identified; 24 underwent surgery prior to installation of an iMRI, while 22 underwent surgical resection with utilization of the iMRI.   


There were no significant differences between the patient populations in age, tumor size, location or consistency.  GTR was obtained in 66% of patients without the iMRI, and 72% of patients with the iMRI (p=0.75, Fisher’s exact test).  Within 1 week, 2 of the 46 patients underwent repeat surgery due to residual disease, both from the group without iMRI.  In the iMRI group, 10 patients’ scans revealed residual tumor which was resected under the same anesthesia. Within 10 years, 4 additional patients underwent a second resection for recurrent disease, 2 from each group. 


The use of iMRI to guide surgical resection of cerebellar pilocytic astrocytomas had no significant impact on the rate of gross total resection (as defined by radiology report) or the rate of reoperation for recurrence over 10 years. This suggests that while iMRI use is not necessary for all such cases, it should be utilized for cases with particular anatomic or radiographic findings causing concern for unintentional subtotal resection.