Botox and immediately became lightheaded. Is that normal?

I had 2 small drops of Botox injected just below my nose to lift the tip today. Within a minute or two of that injection I felt "fuzzy or lightheaded". My practitioner didn't seemed surprised. It seemed like it was a common and brief side effect. I realize it's FDA approved safe but I've had juviderm in my lips and never experienced that. How does Botox effect the brain? Has anyone heard of any long term studies of how Botox affects the brain or know why I had that side effect?