Dizziness is commonly caused by neck problems.  The brain always keeps track of the head's position.  The inner ear gives information about whether the head is tilted, rotated, still, moving, etc...  The neck and eyes also give that same information to the brain.  If any of these sources of head position disagree, you get dizzy.  When problems develop in the upper neck, the information given to the brain coming from that area doesn't agree with the inner ear and eyes, so this causes dizziness, imbalance, vertigo, and/or sometimes nausea.  The treatment is simple, restore normal range of motion to the upper cervical spine.  This requires specialized treatment by a physical therapist trained in advanced mobilization techniques and ultrasound imaging biofeedback of the the deep neck flexors.   There is about an 80% success rate with proper treatment.