I am a mommy of premmie twins as well, and one of them had a grade three brain bleed that led to hyrdocephalus. He had a vp shunt placed at 12 weeks. I won't go through all the gory details but he's had a couple revisions (mostly due to infection) but has come through remarkably well. During the shunt failure, we noticed that he was not meeting milestones like his twin, and even had some setbacks. We were told that we could not compare them- which is true. When he starting losing what he learned though, I knew there was a problem. I had a lot of trouble getting a dr. to revise it, and when I finally found a dr. who would, he was so far behind and so sick it was getting dire. After the surgery his whole personality changed. Cheerful, playful, and trying to keep up with his sister. He still wouldn't walk though. We took him to the opthamologist who felt his nystagmis (a slight shaking of the eyes from the increased pressure on the optical nerve in the brain) was giving him vertigo and keeping him from walking. There was a new study that said if they corrected the eye muscle (like they would do for a lazy eye) before age two, they was a marked reduction with the nystagmis. A week after the surgery, he walked. He was 26 months- 23 months by his adjusted age.
I only mention it due the severity of the brain bleed to keep and "eye" on the eyes. Increased eye shaking also means increased pressure on the nerve, and can be an indication of a shunt problem. If you don't have one already, find an opthamologist who can keep an eye on it for you. He can look at the nerve with a light and possibly save a trip to the hospital or ct scan.