The skull base is simply the bottom of the skull, a platform supporting the brain. Numerous perforations and channels carry the various communication and supply lines from the brain out and down to the rest of the body. The anatomy is complex and until recently surgery of this area was undertaken only with great trepidation. Now with precision imaging acting as a map, the modern skull base surgeon reaches into places previously considered unapproachable. Definition of the precise relationship of a tumor to blood vessels and nerves allows preoperative determination of possible morbidity from a procedure.<sup>6 Curtin H.D., Som P.M., Braun I.F., Nadel L. Skull base  St. Louis: Mosby-Year Book (1996).  1233-1399

Cliquez ici pour aller à la section Références</sup> Because the boundaries of a lesion can be confidently determined, precise forms of targeted radiation treatment allow physicians to treat the margin of a tumor, avoiding vital structures millimeters away.

A radiologist seeking to image patients with skull base problems must know the intricate anatomy and must develop an approach to differentiating the various pathologies that can occur in this area. Furthermore, if the radiologist deals with surgeons who venture into this complex region, then more exact knowledge of the landmarks crucial to decision making must be developed. Which structures must be sacrificed to remove a lesion? Which is the safest pathway to achieve a biopsy? Which landmarks, if involved, will force the surgeon to choose another approach or will make a procedure much more hazardous? Which will make the surgeon back away?

Some aspects of the skull base are covered in other contributions to this issue. Discussion of some of the deeper reaches of the temporal bone and sinonasal tract is found in this article. This article then covers the sphenoid bone, the petrous apex, and briefly the anterior skull base.

The anatomy is beyond the scope of this effort and is readily available in many texts. This is not to belittle the importance of the anatomy. As stated, the anatomy is crucial. Those not extremely familiar with the anatomy should read this article with an anatomy book close at hand.

In sections describing pathology, the differential diagnosis hinges first on determination of the position of the apparent origin of a lesion. Although the number of possible lesions that occur in the skull base is very large, determination of the position of apparent origin of a mass or a pathology narrows the list to a few likely possibilities. The actual imaging findings on CT or MR imaging are then used to narrow the list even further. One should always think of the structures normally found in a certain location because these are the most likely contributors that define the cell type of the particular lesion. In the skull base there is always bone and dura. The radiologist should also consider whether or not air cells are present. Are there nerves? Is there a synchondrosis filled with cartilage? Is this the embryonic pathway of the Rathke's craniopharyngeal canal or of the notochord?