In our experience, the lesions that affect the skull base, and the clivus in particular, may be easily overlooked and can be difficult to differentiate given their cellular and embryologic diversity. This is further confounded by overlapping findings, benign variants, and pseudolesions. As a result of its diverse histologic makeup, primary clival lesions that emanate from the skull base can be derived from residual notochord (eg, chordoma, ecchordosis physaliphora), cartilaginous tissue (eg, chondrosarcoma, enchondroma), or hematopoietic cells (eg, plasmacytoma, lymphoma). Other real or pseudolesions can complicate the differential diagnosis and include arrested pneumatization, marrow variants, arachnoid granulations, meningocele, fibrous dysplasia, and Paget disease. Due to its central location in the skull base, secondary tumors that infiltrate the clivus can originate from a cephalad origin (eg, invasive pituitary macroadenoma, meningioma, craniopharyngioma) or a caudal origin (eg, nasopharyngeal carcinoma, rhabdomyosarcoma). Osseous metastases are also frequently a consideration. The aim of this review article is to elucidate the embryologic origins of these clival findings as well as their anatomic predispositions to better delineate between malignant tumors and benign lesions. We hope to achieve this through the exposition of cases from our local institution cross-referenced with information gleaned from reference articles. Learning Objective: Understand predictable embryologic changes and anatomic predispositions to accurately characterize clival lesions and pseudolesions.
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