Meningiomas of the cerebellar fossa

M ENINGIOMAS of the eerebellar fossa, although few in number, deserve special s tudy as a group. They show certain characteristic findings leading to an early diagnosis, which is particularly important for a cure. The cramped space in which they occur and their proximity to vital structures make removal hazardous, particularly since they are so vascular and so often attached to the large sinuses within the subtentorial space. Complete removal with far less hazard can therefore be accomplished before the tumor has at tained too great a size. Ten cases of meningiomas of the cerebellar fossa are presented here. These show a ratio of 1 to 5.8 in a total of 58 meningiomas and represent per cent of our intracranial tumor series. In Cushing's series, a there were ~3 cases in a total of ~95 meningiomas, a ratio of 1 to 13 and representing 1.04 per cent of his total. As he noted, the incidence is much less compared to the supratentorial meningiomas than the involved dural area would indicate, for by measuring a normal adult brain he found the subtentorial dural surface to be 166 sq. cm., and the total supratentorial dural surface including the falx to be 754 sq. cm., a ratio of 1 to 4.5. The site of a t tachment of these tumors in our series was found to be chiefly the tentorium and transverse and sigmoid sinuses. One of the tumors perforated the tentorium, and the ventriculograms of 1 other indicated a similar extension. The a t tachment of 3 situated in the angle could not be ascertained. In another in this position the a t tachment was to almost the entire anterior dural surface of the cerebellar fossa on one side with extension beyond the midline. In Cushing's series, similar a t tachments were found with specific mention of 11 tumors arising from the tentorium and the transverse and sigmoid sinuses. Of 7 tumors found in the angle an a t tachment was found of only 1 small one, and this was to the porus acusticus. Sufficient removal could not be accomplished in the others to ascertain the point of origin. I t appears from a study of the findings that the site of a t tachment determines to a large extent the symptomatology. For example, those tha t arose from the tentorium showed early 5th nerve changes while those situated in the angle showed symptoms characteristic of an acoustic neurinoma with early 8th nerve involvement. The most consistent and one of the earliest findings was pain in the back of the head and neck (Fig. 1). This was usually