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                                                       UNDERSTANDING THE MOLERA

Historically, the Chihuahua developed in Mexico and the United States has displayed a “soft spot” on the top of the head. In the Chihuahua this spot, or fontanel, is known as a MOLERA; and is the same as that found in human babies. In the past, this molera was accepted as a mark of purity in the breed, and it is still mentioned in most Chihuahua breed standards all over the world. It is important to note that while many Chihuahua puppies are born without the molera, there are probably just as many born with one and its presence is nothing to become alarmed over. As shown in the illustration below, the molera in a Chihuahua will occur on the top of the head and may vary in shape and size. The hole itself tends to be either round or diamond-shaped, and may have clear, smooth edges or slightly uneven ones


Unfortunately, some veterinarians are not familiar with the Chihuahua have tried to link the mere presence of a molera with the condition known as hydrocephalus. This has caused many new puppy owners serious concern and undue worry. The truth is that a domed apple head with a molera present does not predispose the Chihuahua to this condition. Along with the observations of devoted breeders over the years, there is adequate medical evidence to support this statement.

  • In “Diseases of the Brain” 1989, Green & Braund stated that many clinically normal toy breeds may have open fontanels without associated hydrocephalus.

  • Drs. Walker and Rivers, Veterinarians at the University of Minnesota concluded that there did not appear to be any relationship between the presence or size of a fontanel and the condition of hydrocephalus.

  • Dr. Alexander de Lahunta of Cornell University in New York, one of the top neurologists in this country, stated that it would be wrong to conclude that any opening is abnormal

While it would be impossible to list all the medical documentation here on this page, these few included here are perfectly clear; the presence of a molera does not mean the Chihuahua has a medical problem. The Chihuahua is a little dog! They belong in the house, at their owner’s side, receiving all the love they deserve to receive. With or without a molera, the healthy Chihuahua that is loved and given proper veterinary care will live well into its teens as an irresistible member of the family 




                                       Understanding the basics of a molera

Does the molera close up?

In a lot of cases, the molera will naturally close itself as the pup gets older and the bones fuse together. This can take up to 18 months in some cases – and some Chihuahuas born with moleras will always have a small gap or soft spot that never closes.


Do moleras cause any problems?

The molera within the Chihuahua breed is not seen as a flaw, and rarely causes problems for tthe breed as long as their owners are aware of it.


However, the presence of a molera , does mean that there is a weaker, unprotected area on the dog’s skull that is particularly fragile and at risk for injury or damage if the dog hits their head or otherwise hurts themselves. For this reason, it is wise to work out whether or not your own pup has a molera and check over time if it is closing. In the meantime, it is important to be careful to keep your Chihuahua safe from bumps and accidents (without wrapping them in cotton wool!) and ensure that if they do take a tumble or hit their heads, they are checked out by the vet immediately.


Owning a dog with a molera doesn’t have to mean that the way that you care for or manage your dog should be highly overcautious, but you should keep it in mind and be careful to keep your dog safe – and avoid knocking them accidentally if they get underfoot!

Historically, a connection was made between the presence of a molera and a predisposition to a condition called hydrocephalus, or fluid on the brain. However, more modern research has proven that the presence of a molera is not immediately connected to the development of hydrocephalus.


What is hydrocephalus?

In dogs with hydrocephalus, cerebrospinal fluid accumulates in excessive amounts within the skull itself, enlarging the brain’s ventricles and leading to a build up of pressure in the skull as the brain presses into the skull due to this excess fluid.

Because hereditary hydrocephalus is present from birth it often becomes evident in younger dogs, but this is not always the case. Both males and females are equally at risk of inheriting hereditary hydrocephalus.


Can hydrocephalus in Chihuahuas be treated or cured?

In order to make a formal diagnosis of hydrocephalus in the Chihuahua, your vet will need to conduct a number of tests and examinations on your dog. These might include ultrasound examination of your dog’s brain and potentially, more technical diagnostic imaging tools like an MRI scan, CT scan, or electroencephalogram. A diagnosis of hydrocephalus CAN NOT be made by a visual examination.



To treat hydrocephalus, your vet may consider a variety of approaches. Easing the pressure in the dog’s skull and brain might be achieved with the use of diuretics, or a surgically placed drainage shunt in acute cases. Medications may be used to reduce inflammation and reduce the incidence rate of seizures, but dogs with hydrocephalus that presents with symptoms need close monitoring and special care for life.


Hydrocephalus can also result in brain damage over time, which cannot be reversed or cured and that may affect your dog’s development, socialization and ability to learn new skills; however, if the pressure in the dog’s skull can be reduced before brain damage occurs, this can be prevented.


In some cases, hydrocephalus cannot be treated or managed effectively, and may have an acute impact on the dog’s life and health, as well as of course potentially causing brain damage. This means that in some cases, euthanasia is the kindest option

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