Clinical Significance of Optic Nerve Enhancement on Magnetic Resonance Imaging in Enucleated Retinoblastoma Patients

The aim of this 8-year retrospective review was to determine the clinical significance of gadolinium-enhanced magnetic resonance imaging (MRI) findings in retinoblastoma patients after enucleation, particularly the presence of abnormal contrast enhancement of the transected optic nerve.

Retrospective chart review.

A review was done on 88 patients with retinoblastoma undergoing 90 enucleations between January 2008 and December 2015.

These patients underwent 233 MRI scans: 90 preoperative and 143 postoperative that were included for review.

The primary outcome measure assessed was abnormal MRI findings in the preoperative and postoperative MRI scans, specifically enhancement of the optic nerve and correlations between abnormal MRI findings and clinical outcomes for the 88 patients.

On the preoperative MRI, 4 optic nerves out of 90 scans showed positive enhancement. Fifty orbits had ≥1 postoperative MRI. Overall, 41 of 50 orbits (82%) of enucleated patients demonstrated postoperative contrast enhancement on MRI after enucleation, at a mean interval of 10 months after surgery. The percentage of MRI scans with optic nerve enhancement was 77% from 0 to 6 months after enucleation and 68% at >24 months after surgery. Postenucleation optic nerve enhancement did not correlate with preoperative optic nerve enhancement, chemotherapy administration, or the presence of optic nerve invasion on histopathology. No child required an orbital biopsy. None of the 88 patients were found to have subsequent orbital or metastatic disease at the last clinical follow-up visit (average, 29 months; range, 1-71).

Optic nerve contrast enhancement on follow-up MRI after enucleation for retinoblastoma seems to be a common, benign radiographic finding; none of the patients in this series developed extraocular tumor relapse. The presence of postenucleation enhancement on MRI did not correlate with preoperative chemotherapy or the presence of optic nerve invasion on histopathology. Based on our findings, intervention for isolated optic nerve enhancement on MRI is not indicated in the absence of other abnormal clinical or radiographic signs. A prospective trial with a validated radiographic grading system would be helpful to clarify the MRI features to differentiate orbital recurrence from benign postoperative enhancement.