Syncope = a brief loss of consciousness and postural tone that resolves spontaneously with a return to baseline neurological function within seconds or a few minutes.

Presyncope = near LOC. Should be worked up the same as we know it portends a similar risk of downstream badness as syncope. presyncope is "I almost lost consciousness and then recovered" → more of acute thing. The final common pathway of syncope is the same regardless of the underlying cause. In general, 10 seconds of interrupted blood flow to the brain.