What Could Cause Sudden Unconsciousness?

i am 43 year old male, i had a sudden fall ( without any warning )and was unconscious for few min. got admitted in apollo ranchi, and checked up CTscan , EEG, ECHO , ECG etc all possible test were done and all the result were negative. i had a past history of vertigo and recently developed ringing rt. ear and was on dose of vertin 24 mg twicw daily. after the above checkups i was teferred to ENT specialist now undergoing treatment under ENT can you help me by diagonising the desease particularly why there was a sudden fall without any warning , iam really worried about it, pl. help