Correlation of MRI Findings in Optic Pathway Glioma with the Presence of Neurofibromatosis

Abstract

Background: Optic nerve glioma (also known as optic pathway glioma) is the  most common primary neoplasm of the optic nerve. The tumor can arise anywhere along the optic pathway from behind the globe to the occipital cortex. Optic pathway gliomas (OPGs) are associated with high rate of visual morbidity and mortality. Studies have shown no specific clinical histologic or neuro imaging features to differentiate aggressive from non-aggressive OPGs. Purpose: The biological behaviour of optic pathway glioma is unpredictable and it is not clear if specific anatomical patterns may be of use in prognosis of the OPGs. The prognosis is reportedly better in OPGs associated with neurofibromatosis (NF). The purpose of the study was to compare the MRI findings between patients with NF, with those without NF and to determine prognostic imaging signs if any. Material and Methods - MRI studies of 41 patients with OPG (21 with NF and 20 without NF)  were reviewed at presentation and at follow up. Statistical bivariate analysis was used to compare the size and extension of tumor between patients with and those without NF.  Results: Orbital component of the optic nerve was most commonly involved in patients with NF (65%) with optic chiasma being the most common site of involvement (90%) in the non NF group. Extension beyond the optic pathway at diagnosis was more frequent in the non-NF group. In patients with NF, the morphological appearance of the optic nerve was preserved with the tumor being of limited size as compared to the patients in the non-NF group. Statistically significant correlation between MRI features and growth pattern of glioma was absent. Conclusion: As per our study we found that more than half the NF patient’s tumor size  remained stable in contrast to less than 5% of the non-NF group. Although no statistical correlation was found between MRI imaging and the biological behaviour of the tumor, we can infer that NF OPG is a separate entity from non-NF OPG with different prognostic features requiring a customised approach as per the type.