Читать книгу Anterior Skull Base Tumors - Группа авторов - Страница 81

ONB can be regarded as the prototype of a neoplasm arising from the skull base itself. In most cases, the site of origin of the neoplasm is the cribriform plate or the adjacent superior turbinate and the superior half of the nasal septum. From this restricted area, the neoplasm permeates the ASB floor, extends intracranially, and also grows in the nasoethmoidal cavity. The result of these two vectors is an “hourglass” pattern: a solid intracranial and intranasal mass with a “waist” at the ASB floor (Fig. 15). In the checklist, it is important not to overlook the findings contraindicating TES. These include: a large invasion of the frontal sinus, a massive extension to the cerebral parenchyma, spread of the tumor above the orbits, or erosion of the anterior facial skeleton [41]. Among the ONB imaging findings described, intratumoral necrosis and significant postcontrast enhancement should be considered [42]. The presence of a peritumoral cyst and meningeal dural tail have also been reported [43, 44]. Nevertheless, MRI and CT signal/density patterns are non-specific [42]. Careful evaluation of RLPN and cervical lymph nodes is recommended, since nodal metastases can be observed in up to 25% of patients [42]. PET-CT has been reported to modify staging in a relevant fraction of patients, particularly during follow-up [45].

Fig. 14. Squamous cell carcinoma. Axial planes: CT (bone window, a, d) and MRI (postcontrast VIBE, b; TSE T2, c). a The neoplasm (T) arises from the maxillary sinus. The walls are thickened (long standing inflammation?) with focal erosion of the anterior and posterior walls (black arrows). b MRI shows the tumor extent beyond both sinus walls (white arrows). The neoplasm invades the nasal fossa and the choana. c, d In the coronal plane, MRI clearly separates the solid neoplastic projection into the olfactory fissure from the blocked mucus within the posterior ethmoid cells (pec). A marked bone sclerosis (black arrows) surrounds the infraorbital nerve groove (ion), at the same time erosion of the maxillary sinus wall is present (curved white arrow). mpl, medial pterygoid plate.