Neuroanatomy Atlas in Clinical Context

MENINGIOMA 69

B

A

Internal cerebral vein

B

Vein of Galen

G

S

Tentorium cerebelli

D

C

Internal cerebral vein

G

Vein of Galen

S

Tentorium cerebelli

4-9 Examples of meningiomas that are located on the midline. The sellar meningioma ( A , sagittal; B , coronal, also called tubercu lum sellae meningioma ), arises from the sella turcica and, due to its position, may impinge on optic structures and/or cause deficits indica tive of involvement of the hypothalamus. Note that, although the tumor has reached significant size, major structures in the central region of the hemisphere, such as large veins and the corpus callosum (G, genu; B, body; S, splenium), are in their normal positions. Tumors are seen in this area in about 12%–13% of cases and may require special surgical approaches. The large meningioma in C and D was diagnosed as a falcine men ingioma , a tumor that arises from the falx cerebri . Such tumors may arise at any point along the course of the falx cerebri, are frequently bilateral, and may impinge on the medial aspects of both hemispheres. In this location a falcine meningioma may result in unilateral or bilat eral somatomotor and/or somatosensory deficits localized to the lower extremities. Note that the central portions of the hemisphere have been pushed caudally as seen by the foreshortened internal cerebral vein and the change in shape and position of the corpus callosum (G, genu; S, splenium). At the same time, olfactory groove meningiomas are also

seen in this location and have a similar appearance. These arise from the area of the cribriform plate and enlarge upward to impinge on the frontal lobes. Falcine meningiomas constitute about 8% and olfactory groove meningiomas about 10% of all tumors of this type. Meningiomas located in the immediate vicinity of the superior sagit tal sinus ( SSS ) are called parasagittal ; these may be attached to the lat eral wall, invade the lateral recess or SSS in various patterns, or invade and totally occlude the SSS. The general appearance of these examples, and those in Figure 4-8 (facing page), illustrates that these lesions, in many cases, grow so slowly that a significant portion of the brain can be displaced with out untoward effects. The presenting deficits may be persistent head ache and seizure . The sulci and midline may not be effaced and brain structures may not be displaced from their normal position. However, meningiomas that may block the egress of cerebrospinal fluid will likely result in signs and/or symptoms characteristic of increased intracranial pressure ( headache , vertigo , visual disturbances , seizure ) or in deficits that reflect the point of the blockage of CSF egress. Depending on their size and location meningiomas may also present with focal symptoms and/or signs.

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