I agree with John, shoot for an MRI
of the brain, even if the doctor tries to foist a CT scan
on you. CT scan
is supposed to be good for heads and costs less, but the radiation is not helpful and too many CT scans can increase cancer risk, I believe.
It sounds like from your valve description that he got an echocardiogram in the past, but they will probably want to run another with a complete cardiovascular work-up, given his symptoms.