Neurosurgery

of an olfactory groove meningioma the head can be slightly hyperextended, and for a cerebello-pontine-angle lesion the patient may be placed in the lateral position. For large, deep, falcine tumors, the patient's head may be placed with the side of the tumor down and the direction of the sagittal sinus parallel to the operating room floor. In all of these examples, the brain falls away from the tumor and its attachment. In deep-seated tumors, brain retraction may be minimized by use of cerebrospinal fluid (CSF) drainage via either a ventricular drain (in patients with obstructive hydrocephalus) or a lumbar drain. Furthermore, many of the skull base approaches developed over the last two decades, which convert the deep basal menin-giomas to more superficial "convexity" lesions by reducing the working distance to the tumor, may reduce the need for brain retraction.

An optimal surgical approach also facilitates surgery by maximizing exposure of the tumor and surrounding structures, thereby minimizing risks of injury to the adjacent neurovascu-lar structures. For example, in surgery of large clinoidal or suprasellar meningiomas, complete removal of the anterior clinoid process (ACP) provides improved access and exposure of the regions surrounding the optic nerve, optic chiasm, ICA and sella. Additionally, by opening the optic sheath as an extension of the dural incision following anterior clinoidectomy, the optic nerve can be decompressed and visualized early, and mobilized safely during surgery, thereby reducing the risk of intraoperative injury to the nerve [29]. This maneuver also expands operative windows, particularly the optico-carotid triangle, facilitating access to tumors in the suprasellar and subchiasmatic regions.

In most situations, there exist a number of options in selecting the patient's position, surgical approach and exposure. The final selection must be based on what is best for the patient and the surgeon, based on the surgeon's knowledge, past experience and preference.

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