I had the same problem from time to time before my surgery.

Lightheadedness while even just sitting, and sometimes problems getting words out without stumbling over them.

They thought once I had had a stroke, but of coarse when tests were ran and they didn't see that........that was when I was told I needed a Shrink.

Of coarse, this was before TOS was diagnosed.

Feel better soon! I know that's a bad feeling!