Neuroanatomy Atlas in Clinical Context

68 CHAPTER 4 / MENINGES, CISTERNS, VENTRICLES, AND RELATED HEMORRHAGES—MENINGIOMA

A

B

D

E

C

Internal cerebral vein

Edema

Choroid plexus in atrium

Vein of Galen

Tentorium cerebelli

Tentorium cerebelli

meningiomas are seen in about 15% of cases, and parasagittal meningi omas are found in about 21% of patients. The tentorial meningioma ( C , sagittal; D , coronal) is located on the midline, close to the rostral edge of the tentorium, and on its inferior surface. The tumor significantly impinges on the cerebellum ( C , D ) but does not involve the occipital lobes. This patient has motor deficits of the cerebellar type due to the involvement of the cerebellum. Due to its location, this tumor presents a greater surgical challenge than does the convexity meningioma and may contribute to eventual occlusion of the cerebral aqueduct. Tentorial meningiomas are seen in 3%–4% of cases. The meningioma en plaque ( E , arrows) can also be classified as a convexity meningioma or sphenoidal meningioma, due to its location. Based on its location, a meningioma in this configuration may go unde tected for a considerable time or be an incidental finding.

4-8 Examples of a right-sided convexity meningioma ( A , B ), a meningioma of the tentorium cerebelli ( C , D ), and a meningi oma en plaque ( E ). Meningiomas are slow - growing , noninfiltrating, usu ally benign , extra-axial tumors that are curable assuming they can be completely removed (91+%, 5-year survival). They may present with headache or seizure , but many are asymptomatic and some are discov ered as an incidental finding (~30+%). The convexity meningioma ( A , sagittal; B , coronal) is located in the medial aspect of the superior fron tal gyrus rostral to the paracentral gyri. It is slightly off the midline; meningiomas that are directly adjacent to the midline and involve the superior sagittal sinus are called parasagittal meningiomas . Note its attachment to the dura ( A, arrow ); this attachment, seen in many menin giomas, is commonly called the dural tail . The slightly darker gray area immediately adjacent to this tumor likely represents edema. Convexity

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