The eagle sign: a new preoperative MRI-based tool for predicting topographic correlation between craniopharyngioma and hypothalamus

Accurate prediction of topographical correlation between craniopharyngiomas (CPs) and hypothalamus is important for treatment. This study sought to develop a predicting tool based on preoperative-MRI through radiological–surgical–pathological–outcome analysis. Third ventricle floor (TVF), mammillary bodies and cerebral peduncle were evaluated through preoperative-MRI. An eagle-head-like sign named “eagle sign” was observed. Normal TVF on sagittal-MRI was defined as the baseline. Variants of the sign were analyzed by comparing with the baseline and corresponding correlations of CPs with hypothalamus were verified using intraoperative records, histopathology and outcome evaluation. A total of 146 CPs patients, who undergone endoscopic endonasal procedure were divided into four groups based on the variants of “eagle sign”. Group A: 24 patients with the upward sign; group B: 81 with the downward sign; group C: 21 with the anterior TVF upward sign and group D: 20 with the unidentifiable sign. Surgical–pathological analysis showed significant correlations between 95.8% CPs in group A and 95.2% in group C with tumor topography and tumor adherence to the hypothalamus. These CPs had their origins beneath the hypothalamus. In contrast, groups B and D, with hypothalamic origin, showed hypothalamic infiltration by tumor in 97.5% and 95% of cases in groups B and D, respectively. Outcomes of groups A and C were relatively better than groups B and D. Predictive sensitivity and specificity of “eagle sign” were more than 90%. “Eagle sign” is an accurate tool for predicting topographic correlations between CPs and hypothalamus with high sensitivity and specificity.