Fig. 1.

Schematic representation of a planned subtotal resection and gamma knife surgery (GKRS) planning of large vestibular schwannoma (VS). Upper part: illustrations of a the tumor in the coronal plane surrounded by the nerves that enter the internal auditory canal, and its relationship to the brainstem, b the internal decompression of the tumor guided by stimulation of the nerve, both from the external side of the capsule and through the residual capsule, c the progressive closure of the residual capsule and relief of brainstem compression, d the final size and shape of the residual tumor for GKRS. Lower part: e preoperative MRI, f intraoperative view, g immediate postoperative MRI (24 h after surgery), and h MRI at the time of GKRS with the dosimetry (prescription isodose volume colored in yellow, and the 4-Gy isodose line in green, while the cochlea is colored in magenta)