Visual disturbance like blind spots, felling dizzy and numbness could be symptoms of migraine aura, even if they aren't followed with headache.
Rarely, aura may occur with no headache, known as a migraine equivalent.
It is good to know and talk with your physician about transient ischemic attack, known as a mini-stroke or predictor for further stroke.
It is a temporarily reduction of the blood supply to a specific area of the brain for less than 24 hours, causing stroke symptoms that usually resolve in a period of 20 minutes.
One of the reason for TIA is narrowed carotid artery, which in your case is negative.
You may ask your physician for a heart exam like ECG, to check the heart rhythm (atrial fibrilation is linked with TIA).
Other uncommon causes of TIA are blood clotting problems, tiny bleeds into the brain, blood disorders such as polycythaemia and sickle cell anaemia where the blood is very thick, spasm of a small artery in the brain.
