Topographic Diagnosis of Craniopharyngiomas: The Accuracy of MRI Findings Observed on Conventional T1 and T2 Images

MR imaging predictors of CP topography. This growing decision tree shows the variables selected in a multivariate model to define the CP topography. The appearance of the pituitary stalk on preoperative MR imaging was chosen in the first step. The occupation of the chiasmatic cistern (Ch Cistern), the position of the hypothalamus regarding the tumor (Hypoth-CP level), the MBA, the tumor shape (CP shape), and the chiasm distortion (Chiasm) were selected in the following steps. Note that the probability for the not strictly intraventricular category (3V-Not Strict) significantly increased when the PS was either amputated or infiltrated, the Hypoth-CP level was not in the lower third of the tumor, the Ch cistern was occupied by tumor, and the Chiasm was compressed forward (nodes 2, 6, 10, 16). In contrast, the probability of the strictly intraventricular category (3V-Strict) significantly increased when the Ch cistern was free of tumor (node 3). The probability of the pseudointraventricular topography (Pseudo) significantly increased when the PS cistern was not visible, the Ch cistern was occupied by tumor, the MBA was obtuse (>90°), and the tumor had a multilobulated or pearlike shape (nodes 1, 4, 7, 12). Among the cases with an MBA of <90° (node 8), the position of the hypothalamus above the upper third of the tumor indicated the sellar-suprasellar category (Sellar-SS), whereas its position around the middle portion of the tumor suggested a secondary intraventricular topography (Secondary, nodes 13, 14). Correct prediction of CP topography with this multivariate model, including 6 categoric variables studied on preoperative MR imaging, reached 83.8%.

Multivariate model of CP topography for CPs: A 2D plot showing the multiple correspondence analysis between CP topographic categories (black circles) and the appearance of the pituitary stalk, the hypothalamus level in relation to the tumor (HYP), and the occupation of the chiasmatic cistern (CHc) (gray triangles). Dimension 1 separates the intraventricular topographies (strictly and not strictly) from the remaining variables, whereas dimension 2 mostly separates the strictly intraventricular CPs (3V-Strict) from the not strictly ones (3V-Not-Strict). Note that the position of the secondary intraventricular category (Secondary), the most difficult to define preoperatively, is in the trajectory between the 3V-Not-Strict and the sellar-suprasellar (SS) or pseudointraventricular (Pseudo-3V) categories, owing to the radiologic signs that these lesions share with the other topographies. A visible PS, a lower position of the hypothalamus, and a free chiasmatic cistern typically characterize the 3V-Strict group. In contrast, the 3V-Not-Strict category is defined by amputation or infiltration of the stalk, a position of the hypothalamus around the middle-third of the tumor, and a partial occupation of the chiasmatic cistern. Lack of visualization of the pituitary stalk was a sign common to the remaining 3 categories. However, the hypothalamus is typically observed at the upper third of the tumor in the sellar-SS and Pseudo-3V groups, whereas it is around the middle third in the Secondary-3V category. The variance of CP topography explained only by these 3 radiologic variables was 76.3%.