Brain Disorder. Dandy-walker syndrome is a neurological condition that occurs when part of the brain (the cerebellum) does not properly develop. This part of the brain helps to control movements as well as reflexes and perhaps some reflexive emotional responses as well. It can exist in mild to severe forms. For more info see http://www. Ninds. Nih. Gov/disorders/dandywalker/dandywalker. Htm.