A 45-year-old woman with right-sided hearing loss underwent a brain MRI that showed a right CPA mass [Figure 2a]. The patient underwent surgery with subtotal removal of the lesion through a right translabyrinthine approach. A residue was left in place because tenaciously attached to the facial nerve and the brainstem. Histopathological diagnosis was schwannoma. Postoperatively, she developed cerebellar symptoms and right vocal cord paresis that gradually resolved. Nine months after surgery, an MRI showed a millimeter increase in the residue and the appearance of a cyst in the tumor. Surgery was not considered because of the risk of a permanent injury of the facial nerve. The patient was sent for GKR in a single fraction (PTV 3.14 cc, 13 Gy isodose 50%). We did not add any margins (PTV was equal to GTV). The procedure was frame-based (Gamma Knife Perfexion) [Figure 2b]. Ten months later a persistent headache appeared without other neurological symptoms. High dose corticosteroid therapy was administered for 1 month without clinical improvement. A brain MRI revealed an important increase in the size of the residual tumor with large PTBE in cerebellum and brainstem with fourth ventricle compression and hydrocephalus [Figure 2c]; this potentially life-threatening condition led us to prompt surgery. A macroscopically radical removal of the tumor with facial nerve sacrifice was performed. Of note, no evident signs of brainstem or cerebellar swelling were found during surgery. Histopathological analysis reconfirmed the presence of a schwannoma. Three months after surgery, brain MRI showed the complete reabsorption of PTBE in cerebellum and brainstem [Figure 2d]. At 2 year follow-up the MRI showed no tumor recurrence.