CT scanning is essential, highly sensitive, and accurate for evaluating bony integrity, bone destruction, and calcifications or bone fragments within the lesion [3, 6]. CT should be reviewed in both soft and bone algorithm with multiplanar reconstruction (Fig. 45.3h, i). The classic appearance of the clivus chordomas at CT is that of a centrally located, well-circumscribed expansile soft-tissue mass with extensive lytic bone destruction [12] (Fig. 45.2b). The margin between the tumor and adjacent bone is not sclerotic. CT easily defines the exact nature and extent of the bone destruction caused by the tumor. CT is valuable in evaluating the integrity of cranio-vertebral junction and reliably demonstrates the lysis of the skull base foramina. The bulk of the tumor is usually hyperattenuating relative to the neighboring neural axis. Intratumoral calcifications appear irregular (Figs. 45.1c and 45.3h). Moderate to marked enhancement following administration of iodinated contrast material is seen in almost every case (Fig. 45.1d). Solitary or multiple low-attenuation areas are sometimes seen within the soft-tissue mass representing gelatinous material seen at gross examination (Fig. 45.2b). The bone changes and the extent of the resection after operation are precisely interpreted at CT [1].

Clivus chordomas have intermediate to low signal intensity and is easily recognized within the high signal intensity of the fat of the bone marrow of clivus on T1-weighted MR images (Figs. 45.1a, b, 45.3b and 45.4b). Small foci of hyperintensity can be visualized within the tumor on T1-weighted images which may represent a protein-rich content or intratumoral hemorrhage [1, 13] (Fig. 45.4b). Typically, intracranial chordoma has high signal intensity on T2-weighted images due to the high fluid content of cellular components (Figs. 45.2a and 45.4a). The intratumoral areas of calcification, hemorrhage, and a highly proteinaceous mucus pool usually demonstrate heterogeneous hypointensity at T2-weigted images (Fig. 45.3a, c). Low-signal-intensity irregular septations that separate high-signal-intensity lobules are commonly seen (Figs. 45.2a and 45.4a). MRI provides accurate evaluation of the involvement of the adjacent soft tissues, including vasculature, cranial nerve involvement, and changes in the brainstem related to tumor itself [1, 2, 6] (Figs. 45.3a and 45.4a). Fat saturation with T2-weighted images can be used to increase in delineation of the border of the tumor (Fig. 45.3a). Gradient echo T2* or susceptibility-weighted images (SWI) may show intratumoral calcification or hemorrhage better than conventional T1- and T2-weighted images (Fig. 45.3c). Furthermore, SWI can make a differentiation between calcification and hemorrhage with phase reconstruction algorithm.