Microsurgical anatomy of sphenoidsal segment of cistern in lateral fossa of cerebrum

Objective: To study the microanatomical characteristics and surgical significance of sphenoidal segment of cistern in lateral fossa of cerebrum (Sylvian cistern). Methods: The anatomical characteristics of sphenoidal segment of Sylvian cistern were observed on 28 sides of cadaveric human head specimens under an operating microscope. Results: Sphenoidal segment of Sylvian cistern was posterior inferior to sphenoidal ridge.It was between front lobe and temporal lobe.Its roof wall was the pia mater lining the lowr surface of posterior orbital gyrus.Its wall was the pia mater lining the superior surface of temporal lobe.The posterior pole was the folding line of pia mater lining the inferior wall and superior wall.The medial end was the most space.There were separating membranes between Sylivian cistern and carotid cistern in 57.1% of the specimens.The veins in the cistern varied greatly.Most of superficial middle cerebral veins run in anteriorsuperior part of the cistern.Deep middle cerebral veins run along the posterior inferior aspect of Ml segment of middle cerebral artery or across the compartment of the cistem.The smallest number of fibrous trabeculae in the cistern was more than 10 strips; the greatest number ranged from 30 to 50 strips that arranged in a crisscross pattern.Superior and inferior walls were adhered by short and compact fibrous pieces of membranes anterior to middle 1/3 segment of M1 in 35.7% of Sylvian cisterns. Conclusions: When anterior wall of Sylvian cistern is being cut in pterion approach, it is not easy to injury M1.A quarter of the veins in sphenoidal segment of Sylvian cistern are wrapped up in arachnoid sheath and should not be taken as arachnoid to break.This kind of vein can be identfied by the appearace of well stacked tube like sheath. In separation of superior and inferior walls, the adherence of small area should be sharply sectioned in tangent line.The separating membrane between Sylivain cistern and carotid cistern is not a trustworthy mark of the medial end of Sylvian cistern.