Chiari and Dementia

My son 38 has spina bifida, hydrocephylous and chiari malformation. In 2003 he had another shunt put in, at that time they shaved some of the vertabre off to allow for the brain to have more room. We noticed he was having memory issues, this was new. Chalked it up to surgery. I went back to the Neurologist once a year and complained his memory was getting worse !! Finally this last January they did surgery but found the shunt was working. For a few days after surgery my son had talked about best friends, who he had forgotten before, then the memory disappeared again. It was determined the tube that drains was getting backed up causing pressure. So now he is scheduled for surgery, to have the shunt tube draped over the liver in hopes there will be space to drain without any backup. Because of all the memory loss they thought he may have dementia, we are waiting for the next surgery to be done to determine if there is a chance he has dementia also. We saw the Dr. yesterday and they did testing for dementia, he thinks he does but is not familiar with chiari malformation and has referred us to Calgary Foothills. Has anyone come across dementia as also an issue ? Thanks so much for your input !!!