Insufficient blood flow to the cerebellum and mid brain. The vertebral arteries feed into the basilar artery. They supply blood to the cerebellum and mid brain. Decreased blood flow in this area causes balance problems, room spinning, double vision and difficulty speaking. These blood vessels can be blocked from atherosclerosis, an arterial dissection, or an embolus (a blood clot from the heart that breaks loose and lodges in the vertebral or basilar artery). Atrial fibrillation is the most cause of emboli travelling from the heart to an artery.