Can this be used as a reference to somebody with microcephaly resulting from Zika? Or is microcephaly more extreme than just having a small head within some normal range?
It’s not a name for any disorder, if you ask about it. I believe it just means the same as English ‘small head’, a head that is small, by any measure used by the speaker. One could use it to describe microcephaly’s symptoms as well as to describe person with a somewhat-small-but-healthy head. Or maybe metaphorically to describe a not so clever person (as opposed to a genius with metaphorically giant head).