A deviated septum happens when the nasal passages in the nose are not the same size. This can be apparent when a child is born or can be caused by some kind of physical trauma to the nose. The smaller nasal passage may be mildly affected and not be an issue at all. However, the person may have a problem breathing though the nasal passage. At this point , the deviated septum needs to be treated symptomatically or by having septum repaired surgically.