The PL in Group 1 (control group) is allowed to be increased to a higher setting when an SDE is detected. The patient thereby reaches study end, and the treating physician is free to decide how to manage the PL. The 9-month follow-up is still obtained. The PL in Group 2 is preset at the highest PL and eventually lowered 1 step at each follow-up visit when the modified mini mental state (3MS) or Gait score is not increased ≥ 15% provided that no SDE is visible on a new CT scan. The 15% is considered the minimum percentage to reliably determine improvement.