Today we thought it was quite interesting discovering more about a Chihuahua's "molera," a unique trait of this pint-sized pet. While once it was considered a mark of purity in the breed, and at some point, even a defect, today a better understanding of this "soft spot" reveals that it's simply a characteristic of the breed, perhaps just as unique as the spots on a Dalmatian or the ridge on a Rhodesian ridgeback. However, unlike spots or ridges, the molera is not seen on all Chihuahuas, and if it's present, it's often destined to shrink and possibly disappear within a certain time frame. OK, for those folks who have never heard about a molera and are dying to know, what is a molera in the first place? Read on to learn more.
What on Earth is a Molera?
In its simplest definition, the molera is a "hole" in the Chihuahua's head. When Chihuahuas are still in the womb, the bones in their heads are not fused together as they should be, so when they're born, they have this "hole" on the top of their heads between the ears which is called "molera."
The molera isn't unique to Chihuahuas. Human babies have something similar too, but in human babies these soft spots on a baby's head are known as "fontanelle."
The American Kennel Club mentions the molera in the Chihuahua's breed standard when referring to the Chihuahuas's head. According to the Chihuahua breed's standard the head should have: "A well rounded "apple dome" skull, with or without molera."
What's Its Purpose?
Why do some Chihuahua puppies have a soft spot on their head? Not all Chihuahuas have them, but many toy breeds are born with a palpable open fontanelle. The molera is there for an important purpose: it helps the puppy pass through mother dog's birth canal safely.
In small breeds, the mother dog's birth canal is very narrow, yet, those puppy heads are quite big. The gap in the head therefore allows the puppy's head to pass through without too much pressure being applied on the skull and brain.
The molera therefore allows the pup's bony plates of the skull to flex upping the chances for an uneventful birth. However, due to their conformation, it's not unusual for Chihuahua mothers to require a C-section.
At the puppy grows, the bony plates of the skull gradually grow around the brain, becoming less soft and eventually ossifying. When do puppy soft spots close? Once the puppy is born, the molera should gradually close on its own generally by the age of 9 to 12 weeks.
In certain breeds like the Chihuahua or miniature dachshund though, it may remain permanently open without any particular consequences, explains veterinarian William D. Fortney. However, it's best to avoid pushing on the area as there is no protection for the brain, adds veterinarian Dr. Tammy. If the open fontanelle is large, some owners have found it helpful to protect these vulnerable spots with helmets.
Not as Bad as Thought
It was once thought that a domed head and the presence of a soft spot was associated with a medical condition known as "hydrocephalus," where cerebrospinal fluid accumulates in the brain making it swell and triggering neurological signs.
However, according to a study conducted by Greene and Braund in 1989, "Many clinically normal toy breeds and brachycephalic (short faced) breeds also may have open fontanelle without associated hydrocephalus. There did not appear to be any relationship between the presence or size of the fontanelle and the concomitant presence of hydrocephalus."
The Canine Inherited Disorders Database web site seems to agree, according to the website, “an open fontanel is not diagnostic per se of hydrocephalus, as it may occur in a normal healthy dog. "
- Chihuahua Club of America: Molera Statement
- Chihuahua Club of America: Understanding Differences Between a Molera and Hydrocephalus