Brain embolism usually begins suddenly and develops rapidly, often reaching a peak in a very short time. This can cause patients to quickly become comatose or experience weakness in limbs on one side of the body, with some presenting with complete paralysis or speech impairments. These symptoms occur because a major blood vessel in the brain is blocked abruptly, leading to ischemia and tissue necrosis in the supplied area. Common sources of the emboli include plaques in the cervical arteries, where soft plaques can dislodge and form emboli that block cerebral vessels with the bloodstream. Alternatively, patients with atrial fibrillation may suffer from embolism when thrombi attached to the inner walls of the heart dislodge and block cerebral vessels through circulation. Brain embolism is generally a severe condition with a rapid onset.