Hemicraniectomy: external decompressive surgery technique. I. Fronto-temporo-parietal hemicraniectomy: (a) schematic drawing of the hemicraniectomy defect, (b) incision, (c) craniectomy borders (to the skull base), (d) tense dura mater with swollen brain underneath. II. Dura mater is removed for duraplasty: (a) preparation, (b) dura stretched on aluminium foil. III. Dura incisions: (a) schematic drawing of incisions, (b) preparation. IV. Insertion of the dura (duraplasty). V. Bone flap is stored at -80°C. Cranioplasty is performed after 6 to 12 weeks.