Update:
He went back last Saturday, plane tickets round trip is $1200. Did whatever scan on his brain needed for only US$400 (that would have cost $4000 here in the US), and the result is that nothing is wrong. No tumor, no stroke, no broken vane, no clogged vessel, no nothing.
The next step of the checkup is any potential nerves problem. We will see...
Thanks for all the support guys.