Endoscopic reverse third ventriculostomy via the cisterna magna: anatomical study and proposal of a novel procedure.

Basilar artery injury has been known as a potential lethal complication of endoscopic third ventriculostomy. In order to avoid this complication, endoscopic reverse third ventriculostomy via a trans-cisterna-magna route was studied. A cadaveric study was performed for navigation of a flexible endoscope through the cisterna magna. Three fresh, unfixed cadavers were used for this endoscopic navigation. In the prone position, a small vertical paramedian skin incision is made at the mid-portion of the posterior neck. An 11-mm threaded plastic tube is inserted towards the posterior arch of the atlas. After a partial hemilaminectomy of the atlas, a flexible endoscope is introduced into the cisterna magna and is navigated cephalad along the vertebrobasilar artery to the inferior aspect of the floor of the third ventricle. Through the working channel of a fiberscope, third ventriculostomy is performed in a reverse direction. Additional detailed anatomy was studied in fixed cadaveric head specimens with a rigid rod-lens endoscope for anatomic orientation. A novel technique of a trans-cisterna-magna reverse third ventriculostomy was studied in cadaveric specimens. This technique may avoid basilar artery injury which occurs occasionally during conventional third ventriculostomy.