My father age 76 is unable to walk properly. His steps are moving ahead automatically. Slowness in movement. Unable to climb up stairs. But can somehow walk down the stairs. Sense in his legs are good. But their is unbalance while he is walking. His handwriting seems to be distorted. Speech is ok but he often stammers these days. He is not diabetic and his CBC report is healthy. Takes blood pressure blood thinning, prostate gland medicine regularly. Post retirement he leads a sedentary lifestyle. His vision is good and their isn't any headache. What could have happened to him?