I have lightheadedness and nausea. Will MRA test help?

Hello doctor,

Extreme lightheadedness (not vertigo), sometimes a feeling of nausea, and feeling like I am going to black out any second. These symptoms hit me in very intense 20 to 30 seconds waves and then go away. I get these episodes about 7 to 10 times a day and they completely stop me in my tracks when they happen because I feel like I am seconds away from blacking out. These episodes come completely random and are not provoked by postural changes or anything else specific. All my blood work including vitamin levels and hormone levels have been normal. Cardiac: I have had numerous electrocardiogram (EKGs), two D-Dimer tests, an echocardiogram, a carotid doppler, and a 30 day event monitor. All was normal. Neurologic: Basic in-room neurological exam by the neurologist, head computed tomography (CT) no contrast, magnetic resonance imaging (MRI) focused on brain and inner ears no contrast and an electroencephalogram (EEG). All normal. ear, nose, throat (ENT): Basic exam of ears and sinuses with a scope, videonystagmography (VNG) vestibular testing. All normal. When I get these episodes, my blood pressure and oxygen levels are normal. I am not dehydrated, not diabetic, not anemic, and electrolytes are normal along with all other blood work. Kindly suggest what has to be done.

Thank you doctor,

I really appreciate the reply. I forgot to include that I actually have had the tilt table test as well and they did not see anything abnormal. Is there anything else at all you can think of that could be causing these symptoms? I have told my, neurologist, that I wanted an magnetic resonance angiography (MRA) to test for things like vertebrobasilar insufficiency but my neurologist said that my symptoms do not match that and is not needed I guess. Kindly give your inputs.