Chihuahuas and "Molera" or "Open Fontanel"!

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The Chihuahua's molera(a.k.a. fontanel) is considered a breed characteristic and not a defect. Most Chihuahuas (80 percent to 90 percent) have a molera - a soft spot on the top of their head similar to a human baby's soft spot. But unlike babies, most Chihuahuas don't outgrow it. Although it usually shrinks as the dog matures and ends up between nickel- and dime-sized, Pepe's molera won't be a problem as long as you're gentle when petting or handling his head.

chihuahuas and Molera

The presence of a molera in a chihuahua DOES NOT make the dog any more or less susceptible to brain injury, seizures or hydrocephalus.

The molera should not usually be any larger than the size of your thumb print, and there should be no swelling, bulging or throbbing. Check carefully on the sides of the head for normal bone there as well; make sure there is no more then one molera, on the top of the head only, as more than a single molera is not normal.

In rare cases, the molera remains quite large and can be a sign of a serious problem called hydrocephalus (see the next section). But don't borrow trouble. Hydrocephalus has several other signs besides a larger-than-usual molera.


A dog with hydrocephalus (a.k.a. water on the brain) may have an unusually large head for his size caused by swelling. Other signs of this fatal condition are frequent falling, seizures, a lot of white showing in the eyes, an unsteady gait, and east-west eyes (the opposite of crossed eyes). A dog with hydrocephalus is in pain and won't live long, so euthanasia is the humane solution. (Euthanasia is the medical term for a humane, vet-assisted death.)