I am Dr. Arun and will be helping you today.
I am sorry that your question was unanswered for long.
Following investigations need to be pursued or repeated in your case for persisting dizziness and brief passing out;
1) MRI with gadolinium contrast
2) Magnetic resonance angiography (MRA)
3) Tilt table test
4) Carotid sinus massage
5) Electroencephalography (EEG)
6) Stress cardiac test
7) Total creatine kinase (CK) and heart enzymes; done immediately after the fainting episode and would tell about the abnormal brain or heart activity which caused the fainting.
8) Following also may be done after the fainting episode; blood electrolytes and blood glucose.
These should be able to zero down the cause and accordingly treatment would be initiated.
Please feel free for your follow up questions.
I would be happy to assist you further, if you need any more information.
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