Skull Base Bone Lesions II: Benign and Malignant Tumors

Introduction

Most tumors affecting the skull base result from hematogenous spread of primary malignancies outside the skull base (hematogenous bone metastases) or from direct invasion or perineural spread of neoplasms arising from neighboring structures of the suprahyoid neck. As the skull base provides a frontier between the intracranial compartment and the extracranial head and neck, the first and most important issue in the differential diagnosis of a skull base lesion is to decide its site of origin: the bone elements of the skull base proper, the intracranial compartment, or the suprahyoid neck.

With the exception of metastases, bone tumors of the skull base are overall rare and can be a diagnostic dilemma. When facing a bone tumor in the skull base, the same rules used for the differential diagnosis of skeletal tumors elsewhere in the body should be applied, taking into account the specificities of this anatomic location regarding tumor extent and treatment planning. Although imaging features can be quite helpful in the differential diagnosis, they are not very familiar to radiologists who do not routinely deal with skull base lesions and only a scant specific literature is available on this subject. This chapter specifically focuses on primary and secondary skull base bone tumors. For the imaging technique, general rules for the differential diagnosis, and developmental and diffuse skull base lesions, please refer to the previous chapter ( Table 16.1 ).

Bone Tumors

Primary bone tumors encompass a variety of benign and malignant neoplasms. With the exception of osteomas and intraosseous hemangiomas in the benign category and metastases and multiple myeloma on the malignant side, other tumors are quite rare in the skull base. The imaging features of these primary and secondary bone tumors are similar to those of bone tumors arising in other sites of the skeleton, although the treatment and implications on patient’s management derive from the specificities of this particular location. The imaging features of these lesions in the skull base are reviewed.