Fontanelle - Cranial Fontanelle by A.Griguolo

Generality

The fountains are the characteristic soft and membranous spaces of the skull of newborns where they cross at least two different cranial sutures.

Destined to ossify between the 2nd and 18th months of life, the fountains are in all 6: the fontanelles of the cranial vault, known as posterior fontanelle and anterior fontanelle, and the two pairs of fontanelles of the base of the skull, whose name is fontanelle sphenoidals (or antero-lateral fontanelles) and mastoid fountains (or postero-lateral fountains).

The fountains give the newborn's skull a malleability that serves to facilitate the passage of the infant's head along the birth canal, and to allow the brain to develop and grow correctly during the first months of life.

Due to the presence of certain medical conditions, the fountains can change, resulting protruding, wider or narrower than normal, or deeper (or sunk).

Brief review of neurocranium, cranial vault and base of the skull

The neurocranium is one of the two large portions, in which the anatomists divide the human skull (the other portion is the so-called splancnocranio).

The neurocranium comprises 8 bones, which are: the frontal bone, the two parietal bones, the sphenoid bone, the ethmoid bone, the two temporal bones and the occipital bone.

Separated from each other by the fibrous joints known as cranial sutures, these bones are arranged so as to form the so-called cranial vault, in which the brain resides, and the so-called base of the skull, which houses the organ of hearing and serves as the support of the overlying cranial vault.

In order to better understand the subsequent description of the fontanelles, it is appropriate to specify the cranial vault and cranial base bone composition: the first results from the contribution of the upper region of the frontal bone, from the two parietal bones and from the upper region of the bone occipital; the second, instead, results from the lower regions of frontal bone, parietal bones and occipital bone and temporal, ethmoid and sphenoid bones.

What are Fontanelle?

The fontanelles, or cranial fontanelles, are the characteristic soft and membranous areas of the skull of newborns, located at the points of convergence of at least three bones of the neurocranium; according to another definition, they are also the characteristic soft and membranous areas of the skull of newborns, located at the intersection points (or points of intersection) of at least two different cranial sutures.

It is important to point out that with the expression "soft and membranous areas of the skull", the above definitions indicate that the fountains are not ossified spaces, but spaces covered with a membrane that is soft to the touch .

Deepening on cranial sutures

Cranial sutures are the joint lines present between the various bones of the neurocranium.

In newborns and up to a certain age, cranial sutures are structures with moderate flexibility ; this flexibility serves the neurocranium to adapt to the processes of enlargement and development of the brain, typical of the young age.

With aging the cranial sutures are the object of a completely physiological fusion process, which aims to make the cranial vault and the base of the skull more solid.

Accomplices some genetic alterations (such as those that cause Crouzon syndrome ), cranial sutures can be subject to premature fusion, a process that prevents the correct enlargement and development of the brain and that, in medicine, is called craniostenosis (or craniosynostosis ).

Anatomy

In the skull of a newborn, the fountains are in all 6:

The posterior fountain ;
The anterior fontanel ;
The two sphenoid fontanelles (or antero-lateral fontanelles );

The two sphenoid fontanelles (or antero-lateral fontanelles );
The two mastoid fountains (or postero-lateral fountains ).

As previously stated, fountains are characteristic spaces of the newborn's skull; this implies that, with growth, they disappear or, better, are the object of a physiological process such that, instead of the constituent soft membrane, bone tissue is formed ( process of ossification or closure of the fountains ).

Rear fountain

With a triangular shape, the posterior fontanel is a small fountain located at the point where the occipital bone and the two parietal bones converge; considering cranial sutures as a reference, it is the fontanel located at the point where the sagittal suture (cranial suture articulating the two parietal bones) and the lambdoid suture (cranial suture articulating the occipital bone to the parietal bones) intersect.

The posterior fontanel is the fontanelle that occupies the postero-superior portion of the neurocranium and belongs to the cranial vault.

From a dimensional point of view, the posterior fountain measures 0.5 centimeters, in subjects of white skin, and 0.7 centimeters, in subjects of black skin.

In healthy subjects, the posterior fontanelle disappears around the 2-3 month of life.

Front fountain

Morphologically similar to a diamond, the anterior fontanel is the fontanel placed at the point where the frontal bone and the two parietal bones converge; using the cranial sutures as a reference, it is the fontanelle with the site where the sagittal suture and the coronal suture cross (the cranial suture that articulates the frontal bone to the parietal bones).

The anterior fontanel is the fontanel that occupies the antero-superior portion of the neurocranium and belongs to the cranial vault.

In terms of size, in an infant with white skin on the first day of life, the anterior fontanelle can measure between 0.6 and 3.6 centimeters; on the other hand, in a black leather baby on the first day of life, it can measure between 1.4 and 4.7 centimeters.

In healthy subjects, the anterior fontanelle generally closes around the 18th month of life.

Did you know that ...

According to statistics, the front fountain is closed

In a meager 1% of children in the third month of life,
In 38% of children at the 12th month of life e
In 96% of children at the 24th month of life.

Sfenoidal fountains

The sphenoid fontanel is the even and symmetrical fontanelle (that is, present, in the same position, both to the right and to the left of the skull) with seat between the sphenoid bone, the parietal bone, the temporal bone and the frontal bone; considering the cranial sutures as a reference, it is the fontanel located at the point where the squamous suture intersects (cranial suture that articulates the temporal bone to the ipsilateral parietal bone), the spheno-squamous suture (cranial suture that articulates the temporal bone to the 'sphenoid bone) and the spheno-frontal suture (cranial suture that articulates the sphenoid bone at the frontal bone).

In healthy subjects, sphenoid fontanels undergo ossification around the 6th month of life.

Mastoid fountains

The sphenoid fontanel is the even and symmetrical fontanelle situated between the temporal bone, the occipital bone and the parietal bone; using cranial sutures as a reference, it is the fontanel located between the lambdoid suture, the parieto-mastoid suture (cranial suture between the mastoid part of the temporal bone and the ipsilateral parietal bone) and the occipito-mastoid suture (cranial suture between the mastoid part of the temporal bone and the occipital bone).

In healthy subjects, mastoid fountains close between the 6th and 18th months of life.

Ossification of Fontanelle

In summary, the ossification process of the fountains takes place:

Around the II-III month of life, for the posterior fontanel;
Around the 18th month of life, due to the anterior fontanel;
Around the 6th month of life, due to the sphenoidal fountain;
Between the 6th and 18th months of life, the Mastoid fontanelle.

Did you know that ...

As a matter of size, the posterior and anterior fontanelles are considered the major fountains, while the sphenoid and mastoid fountains are the minor fountains.

Function

The fountains give the skull a malleability that is fundamental in two crucial moments in the life of any human being: at the moment of birth and in the first few months of life .

Drinking fountains and childbirth

At birth, the fontanelles provide the skull with the capacity for deformation which serves to facilitate the passage of the baby's head through the birth canal .

Without the fontanelles, the skull would be a more rigid structure and this would complicate not a little the crossing of a restricted duct like the aforementioned anatomical canal.

Drinking fountains and first months of life

In the first few months of life, the fountains provide the neurocranium of that adaptive capacity that is indispensable to it not to hinder the correct development and growth of the brain.

Without the fontanelles, the neurocranium of a child in the first months of life would be a structure incapable of allowing the encephalic organs (brain and cerebellum primarily) the correct space for growth.

To understand the function of the fountains, the reader thinks about what happens if he tries to inflate two balloons (both represent a human brain), one inside a mouldable container (equivalent to the neurocranium with fountains) and one inside a container rigid (equivalent to the neurocranium without fontanelles): in the first situation, there is freedom of inflation, in the sense that the mouldable container adapts to the balloon and its expansion; in the second situation, on the other hand, the balloon inflates until it has reached the walls of the rigid container.

diseases

In the presence and due to certain medical conditions, the fountains undergo alterations, which can cause their protrusion, early closure, unusual enlargement or excessive sinking .

When the Fontanelle pulsate should we worry?

Sometimes, for reasons not yet well understood (according to some experts, the heartbeat would play a role), the fountains pulsate .

This particular phenomenon should not cause concern in parents, as it is a phenomenon, so to speak, completely normal, verifiable in many healthy children and in perfect health.

Protruding fountains: the causes

The anomalous protrusion of the fontanelles is a consequence of the pathological increase in intracranial pressure, ie the pressure that the growing encephalon exerts on the internal walls of the cranial vault.

The medical conditions that determine the increase in intracranial pressure include:

Encephalitis . Generally due to infectious agents, it is inflammation of the brain.
Hydrocephalus . It is the excessive accumulation of cerebrospinal fluid inside the cerebral ventricles.

Hydrocephalus

Meningitis . Usually associated with an infection, it is the inflammation of the meninges.
The shaken baby syndrome (also known as abuse from head trauma ). It is the set of symptoms and signs that affect children under the age of life who are victims of violent shaking or head injuries.

Enlarged drinking fountains: the causes

The unusual enlargement and the slow closing of the fountains are two phenomena observable in the presence of:

Achondroplasia . It is a cartilage disease that causes disproportionate dwarfism.
Congenital hypothyroidism . It is the insufficient presence of thyroid hormones in the blood in place since birth.
Down syndrome . It is the known genetic disease due to the presence of three chromosomes 21;
Hydrocephalus ;
Rickets . It is a defect of bone mineralization, typical of young and very young age, which makes the bones yieldable and subject to easy deformation;
Imperfect osteogenesis . It is a genetic disease of the skeleton, which makes the person's bones affected weaker and subject to fracture;
Premature birth ;
Intrauterine growth restriction . Doctors talk about this condition when the fetus fails to reach its genetic growth potential.

Did you know that ...

The fear that the touch of the fountains will damage the brain is unjustified.

In addition to the membrane that forms the fontanelles, in fact, the underlying brain is protected from the skin, more externally, and from the three meninges, more internally.

Drinking fountains closed early: the causes

Early closure and excessive narrowness of fontanelles are two phenomena that can be observed in the presence of craniosynostosis.

There are different types of craniostenosis; among these types, the most widespread and worthy of a quote are: the aforementioned Crouzon syndrome, Apert syndrome and Pfeiffer syndrome .