Doctor Stewart, Otorhinolaryngologist-in-chief at New York Presbyterian Hospital, explains just what the rare condition known as tongue tie is.

Doctor Stewart: Frenum is one of the attachments of the tongue, which is normal, and when it's too short or too thick and doesn't allow mobility, that's the problem. Tongue tie has to do with this little fold of tissue that is one of the attachments of the tongue to the floor of the mouth. And in some patients, that's actually shortened or elongated in a way so that it does not enable the tongue to have front and back and side to side mobility. So the tongue is basically tethered by a short Frenum of the tongue to the floor of the mouth. Sometimes tongue tie problems can be related to cleft lip, cleft pallet and other sort of mid-line oral cavity abnormalities, but many times, it's completely isolated. It's present at anywhere from, you know, 1 in 500 to maybe as many as 1 in 150 or so or at 1 and 100 births, depending on the population or the study that you look at. So it's not vanishingly rare, it's not super common either.