Exposure of the wide interior of the fourth ventricle without splitting the vermis: importance of cutting procedures for the tela choroidea.

In recent years, new procedures for fourth ventricular surgeries have been developed with good results. In particular, the trans-cerebellomedullary fissure approach, which exposes the fourth ventricle without splitting the inferior vermis, has proven successful. For optimum results, specialized techniques should be employed in order to effectively open the roof of the fourth ventricle and obtain a wide exposure of its interior. These techniques include the following steps: (1) placement of an incision over the teania extending from the foramen of Magendie to the ventricular entrance of the lateral recess; (2) lateral extension of the incision to the roof of the lateral recess to facilitate its exposure; (3) implementation of the same procedure on the contralateral side. Upon completion of these steps, the bilateral cerebellar tonsils can be easily retracted superolaterally; this eventually exposes a wide interior of the ventricle. In order to ensure successful surgeries, explicit and accurate descriptions of technique are vital. In this article, we employ detailed illustrations to precisely demonstrate the operative procedures and techniques for fourth ventricular surgeries.