Adcoms rarely take applicants' claims of specific specialties seriously. People change, they get introduced into other specialties and suddenly realize that they love them. They get married and have children, which force them to choose more family-friendly fields... The adcoms have seen it all. True, neurosurg is filled with MD/PhDs, I know a few personally. However, applying to neurosurg residency as an MD/PhD after your 3rd year rotations and 4th year neurosurg electives is one thing, insisting you want to do neurosurg on your medschool secondaries and interviews is another.