Hello! My name is Dr. Aida and I am glad to attend you on Healthcaremagic! The fact that there is increased size of ventricles, could be a sing of shunt dysfunction. That is why, it is necessary to compare your previous CT scan finding with the last one. The dizziness could also be related to other causes : an inner ear disorder, chronic degeneration of the cervical spine, etc.. For this reason, it is necessary consulting with a neurologist for a physical exam and discuss on the above issues. Best wishes!