Meningioma

MENINGIOMA (meningioma), a tumor of the cerebral meninges; usually, this refers to endothelioma (see), although Cushing, based on the fact that the origin of brain membrane tumors from endothelium is completely unproven, proposed the name "meningioma" for them. Meningiomas develop from accumulations of cells belonging to the arachnoid membrane; they consist of cells with elongated nuclei, arranged either in strands or nests of bulbous structure and surrounded by a more or less developed stroma. Usually, these tumors are dense, sometimes with a nodular surface, reaching a large size (up to an orange and larger). The most characteristic feature of them is that they do not infiltrate the brain, but, slowly increasing in growth, gradually push away and compress the brain tissue [see separate plate (articles 743-744), Fig. 3]. Sometimes, especially when they develop at the base of the brain, they form a huge bed in place of the displaced brain tissue. Meningiomas are among frequent tumors. According to Cushing's statistics (1922), among 751 cases of brain tumors, meningiomas occurred 85 times, i.e., in 11.3%. On pathoanatomical material, they are encountered even more frequently. Thus, according to the statistics of Bostroem and Spatz, meningiomas are found in 40% of all brain tumors. Meningiomas are benign, grow slowly, and can reach very significant sizes, far from always causing deficit symptoms. Symptoms of increased intracranial pressure may also be absent for a long time, especially when tumors develop in the anterior cranial fossa, because due to slow growth, the brain gradually adapts to new conditions. On an X-ray image, meningiomas sometimes cast a shadow due to the deposition of lime in them (psammomas). In any tumor with a calcified shadow, one should therefore think of the possibility of a meningioma. In view of the fact that meningiomas present very favorable conditions for surgery, their diagnosis, especially early diagnosis, is of enormous practical importance. Diagnosis is facilitated by the fact that meningiomas develop in fairly specific locations: 1) spinal meningiomas, originating from the site of passage of spinal nerves, where, as is known, the arachnoid membrane is in contact with the dura; 2) meningiomas of the sites of passage of cranial nerves, most frequently in the region of the acoustic nerve (not to be confused with acoustic neuromas!); 3) meningiomas of the sella turcica; 4) meningiomas of the olfactory groove; 5) meningiomas of the sphenoid bone edge; 6) meningiomas of the Sylvian fissure; 7) meningiomas of the cerebral convexity; 8) parasagittal meningiomas; 9) meningiomas of the falx cerebri; 10) meningiomas of the transverse sinus. The prognosis depends on localization. Regarding surgical treatment, see Brain surgery. With very large tumors, it is best to remove them by electrolytic means.

M. Krol