Yea... neurosurgery residencies generally only accept MD/PhDs who got their PhD in pure or applied mathematics.
Man has no way of cutting into the brain so neurosurgeons have to focus their mental math powers into a ephemeral blade of pure awesome that plunges into the brain and teleports out the tumor. Only PhDs in math or physics are known to be able to develop this arcane ability but physicists are often rejected because they are too tied to the realm of reality while mathematicians are off thinking in N-space.