Upper and Middle Clivus Meningiomas

Abstract

Under the heading of upper and middle clivus meningiomas we include those operated upon when the tumor is located exclusively or mainly in corre spondence of the upper and middle clivus. Only a few tumors fall into this group, and these represent the initial stage of tumors that with further growth would become petroclival, craniospinal, or incis-ural meningiomas. This view is supported by combined clinical and surgical observations showing that in many patients with petroclival, craniospinal, or incisural meningiomas the original symptoms were related to abducens paresis, often preceding by many years other symptoms and falsely diagnosed as strabism; moreover at surgery, in the same group of patients, many times the tumor attachment is found to be in proximity to the dural entrance or the intradural clival course of nerve VI, at the level of the middle-upper clivus. The reason why a counterpart does not exist in tumors originating from the lower clivus is the anatomical lack of a nervous structure which, like the abducens nerve, may be compressed by a still relatively small dural mass, resulting in a focal neurological deficit. The fact that these tumors are small at the time of surgery does not mean that their surgical removal is easier than that of larger meningiomas of this area (see “Surgical Considerations”).