Figure 1: Intraoperative photographs showing the surgical steps of the microsurgical arachnoidolysis in the procedure in case 1. (a) Dural opening revealed the adhesive arachnoid membrane around the spinal cord. (b) Higher magnifi cation of the boxed area in a revealed the thickened arachnoid tissue on the dorsolateral side of the spinal cord. (c) The dentate ligament at all exposed levels was resected. (d) and (e) A ventral dissection was started from both sides with avoidance of excessive manipulation of the spinal cord. (f) The pulsative movement of the spinal cord was visualized at the fi nal step.