A descriptive neuroimaging study of retinoblastoma in children: magnetic resonance imaging features

Introduction
Retinoblastoma (RB) is the most common intraocular malignancy of childhood. Magnetic resonance imaging (MRI) is essential for initial diagnosis, tumour extension, staging, and treatment planning of RB. Awareness of neuro­imaging findings and determining local extent are essential for early diagnosis and therapy guidance. The purpose of this study is to evaluate and to provide a detailed list of neuroimaging features of RB to improve the diagnostic work-up of children with RB.

Material and methods
Retrospective review was performed among children with confirmed RB diagnosis. MRI features were identified to evaluate: 1) growth pattern; 2) intraocular extension; 3) extraocular extension; 4) central nervous system disease; 5) conventional MRI characteristics of the RB lesions; and 6) DWI and ADC characteristics. These features were compared between unilateral and bilateral RB lesions.

Results
Twenty-four children (male/female: 18/6) were included in this study. The mean age at the time of diagnosis was 14.7 (11.4) months. In total, 34 RB lesions (bilateral = 18) were evaluated for the study. The most common features on MRI were: 1) endophytic RB lesion (50%); 2) subretinal haemorrhage (38%); 3) scleral involvement (3%); 4) leptomeningeal disease (12%); 5) contrast enhancement (97%); and 6) restricted diffusion (88%). The mean ADC value was 0.64 (0.15) × 10-3 mm2/s. Choroidal invasion (p = 0.05) and scleral involvement (p = 0.04) were significantly higher for bilateral RB lesions.

Conclusions
Contrast enhancement and restricted diffusion are the most common neuroimaging features of RB. Choroidal invasion and scleral involvement are more frequently seen in bilateral disease.