OCCIPUT: CHARACTERISTICS, FUNCTIONS, MALFORMATIONS - ANATOMY AND PHYSIOLOGY - 2025

The occiput is the scientific term that describes an anatomical part of the head. This is located in the lower part of the skull, specifically in the lower area of ​​the back of the head. The term occiput comes from the combination of two Latin words (occĭput or occipitĭum).

It is also known as the external occipital protrusion, because in certain patients this area may be more bulky than in others. This is the case of patients born with Edward syndrome (trisomy 18) or with trisomy 9 syndrome.

Types of occiput (normal, flat and protruding). Source: (Centers for Disease Control and Prevention), (National Center for Birth Defects and Developmental Disabilities). Edited image.

Significant craniofacial malformations affecting the occiput are seen in both alterations. Microcephaly (small skull) with a protruding occiput is usually seen, in addition to other malformations that accompany these syndromes. In other cases of congenital malformations, the opposite may occur, with a flattened occiput being observed.

In neonatology, the measurement of the head circumference is an important piece of information as a general evaluation of the physical state of the newborn.

Head circumference (circumference) measurement is performed by passing a tape measure around the head, that is, the tape should be placed over the occiput towards the front of the head, specifically at the superciliary arch (above the eyebrows). Meanwhile, the length of the head is measured by placing the tape measure horizontally from the forehead to the occiput.

characteristics

In popular slang, the occiput is called a colodrillo. If you look up the word colodrillo in the dictionary, it means: "back of the head."

Anatomy

The bone in the occiput is called the occiput. This is a flat, unpaired bone. It joins the spinal column through the first cervical vertebra, called the atlas and with which it forms the atlanto-occipital joint.

This bone also has an occipital hole called the foramen magnum, which is where the spinal cord passes to reach the brain.

The occipital has four parts: basilar process, 2 lateral masses and the scale. The basilar process is attached by fibrocartilage to the temporal bones and the sphenoid. The 2 lateral masses are closely related to the first vertebra (atlas) and to the temporal bones. Whereas, the occipital scale has communication with the parietal bones. In the center is the external occipital protuberance.

In a normal individual the shape of the occiput is neither so bulky nor so flattened. When there are congenital malformations, the shape of the occiput can be altered (protruding or flattened occiput).

Source: Francois R. (2005). Treaty of Cranial Osteopathy. Temporomandibular joint. Analysis and orthodontic treatment. 2nd Edition. Editorial Panamericana. Madrid Spain. Available at: books.google.co.ve

Occiput and childbirth

Obstetricians are very interested in the position and size of the baby's head at the time of delivery. When the newborn comes from the head, the positions can be: occipital, face or front. Although it can also come from the shoulder or buttock, being less frequent.

The obstetrician must know if the perimeter of the head is capable of passing through the mother's pelvis. Although the baby's cranial bones can be adjusted to cross the birth canal, sometimes a very large head may warrant a C-section.

Under normal conditions, the baby's occiput rests on the mother's symphysis pubis and subsequently, in subsequent uterine contraction, the head extends out.

When the mother exerts too much force during delivery, the baby's head can temporarily deform. The use of forceps can also affect this.

Features

The occiput supports the rest of the bones of the skull and is what articulates with the vertebral column. Together with the rest of the bones of the skull, its function is to protect the brain.

In accidents with multiple injuries, the occiput may be affected. Trauma at this level can cause a fracture of the base of the skull, which is a fairly frequent and usually serious head injury.

This trauma not only leads to the fracture of the bones in the area, but also produces a significant intracranial hematoma, which can lead to death.

Congenital malformations affecting the shape of the occiput

- prominent occiput

In some congenital malformations, irregularities in the shape of the individual's head can be observed. In neonates born with tris syndrome 18 (Edwards syndrome) and trisomy 9, small skulls with protruding occiput are seen.

Other malformations may involve craniosynostosis, which suggests that the sutures between the bone plates have closed prematurely, limiting the growth of the skull in that area.

This results in a variety of malformations, which, depending on the size and shape of the head as a whole, receives a name.

In most of these cases, a larger or smaller skull than normal is seen, with a prominent occiput. Among the malformations that result in an outstanding occiput are:

Scaphocephaly

It occurs due to a sagittal synostosis, that is, a premature closure of the sagittal suture that runs from the fontanel to the nape occurs. This produces a long and narrow head. There may be bumps at the frontal or occipital level. This abnormality is quite common and does not improve spontaneously.

Dolichocephaly

In this case the head is long and narrow. It occurs in low-weight premature babies. It is a postural malformation due to the immaturity of the cervical muscle. It is very similar to scaphocephaly, but they differ in that there is no premature closure of the sagittal suture and therefore it is corrected spontaneously.

Occipital encephalocele with intact sac

When during pregnancy the neural tube does not fold and does not close to form the brain, then it comes out taking advantage of any opening in the skull. This malformation causes the formation of a sac-like protrusion that contains the brain.

The bulge can occur anywhere, however the most common is on the posterior and lower face of the head at the occiput level.

Macrocephaly

A common malformation in certain neonates is an exaggerated increase in head circumference, that is, the size of the head. It is usually caused by an increase in intracranial pressure.

In some syndromes, the patient may present with macrocephaly along with a prominent occiput, among other abnormalities. A clear example is given in individuals with acrocallosal syndrome.

Hydrocephalus

In this case there is an increase in the size of the head due to an accumulation of cerebrospinal fluid. The most frequent cause is obstructive. Some congenital syndromes present with hydrocephalus and a prominent occiput, such is the case of Dandy-Walker disease.

- Flat occiput

There are other malformations at the level of the head that present with a completely flat occiput. For example, acrocephaly, turricephaly, brachycephaly, among others.

Acrocephaly

It is a deformation characterized by a cone-shaped skull, that is, the skull has an exaggerated height, with a flat occiput. This deformity is caused by the early closure of the cranial sutures.

Turricephaly

It is a deformation that is characterized by a tower-shaped skull (skull with great height and flat occiput). This deformity is caused by early closure of the coronal and lambdoid sutures.

Brachycephaly

It is caused by a bicoronal synostosis, that is, the premature closure of the coronal sutures on both sides of the head. Which results in a short, broad head. The occiput is flattened.

Positional plagiocephaly

Also called flattened head syndrome, it usually occurs in premature babies who spend long periods of time lying in one position. This causes a flattening of the head, since the skull of premature babies is still very soft.

The types of plagiocephaly can be occipital (flattened occiput), frontal (flattened forehead) or mixed.

It can also occur before birth due to pressure of the head from the womb against the mother's pelvis or from torticollis.

In the latter case, the baby has difficulty moving his head and this causes him to remain in a single position, usually on his back, causing flat head syndrome (flat or partial occiput).

Synostotic plagiocephaly

It occurs due to the early closure of the cranial sutures. If the affected suture is the coronal one, it is called anterior or coronal plagiocephaly. And if the affected suture is the lambdoid, it is called lambdoid craniosynostosis.

Gómez-López-Hernández syndrome

This syndrome is also called cerebellum-trigeminal-dermal dysplasia. It is characterized by presenting rhombocephalic synapses, alopecia, and trigeminal anesthesia.

Galvez et al. Analyzed a clinical case whose brain MRI revealed severe hydrocephalus, turricephalic shape of the skull, fusion of cerebellar hemispheres, flat occiput, and absence of anterior and posterior vermis.

Apert syndrome

Also called acrocephalo-syndactyly. It is a hereditary congenital syndrome. It is characterized by the fusion of certain bones in the skull, in the hands and in the feet. This results in significant craniofacial malformations, as well as the hands and feet.

In relation to skull malformations, they are characterized by acrocephaly, a decrease in the anteroposterior diameter of the skull, exophthalmus (protruding eyes), a prominent forehead with occiput and a flattened face.

References

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8. Centers for Disease Control and Prevention. CDC's National Center for Birth Defects and Developmental Disabilities. Birth defects. 2016.Available at: cdc.gov.
9. "Occiput." Wikipedia, The Free Encyclopedia. 10 Oct 2018, 01:42 UTC. wikipedia.org
10. François R. (2005). Treaty of Cranial Osteopathy. Temporomandibular joint. Analysis and orthodontic treatment. 2 ^gives Edition. Editorial Panamericana. Madrid Spain. Available at: books.google.co.ve