Surgical Approaches to the Third Ventricle: An Update.

The third ventricle is located in the deepest part of the brain and is delimited by both telencephalic and diencephalic structures. Its location makes every surgical procedure inside or around it quite challenging, due to the distance from the surface to the fragility of the neurovascular structures that is necessary to dissect before entering its cavity and to the narrow surgical corridors through which it is necessary to work. Its geometric localization inside the cranial cavity and the anatomical relationship with the interhemispheric fissure offers nevertheless to the surgeon an impressive variety of surgical approaches, which allow to reach every millimeter of the third ventricle lumen. Mastering properly all these approaches requires an impressive anatomical knowledge, the best available technology, and most refined technical skills, making the surgery of the third ventricle a point of excellence in the evolution of each neurosurgeon. The development of neuronavigation and neuroendoscopy has been a revolution in neurosurgery in the last 20 years and offered special advantages for the surgery of the third ventricle. In fact, the narrow corridors of approach make the precision of the neuronavigation and the enlightenment and magnification of the neuroendoscopy especially useful to reach the third ventricle cavity and working inside or around it. This chapter reviews the history of the surgery of the third ventricle and offers an update of the variety of surgical corridors identified and of the technology now available to properly work through them and inside the third ventricle cavity.