Osteological anatomy of the skull

The skull is made up of two main parts: the neurocranium and the viscerocranium. The neurocranium bone encloses and protects the human brain.

The neurocranium is made up of the following bones: frontal, parietal, occipital, temporal, sphenoid, and ethmoid.

The viscerocranium consists of the facial bones and includes the following bones: mandible, maxilla, zygomatic, nasal septum, lacrimal, vomer, and palatine.

Sutures and cranial sutures:

The bones of the skull are connected by seams or sutures, which are the main sites of skull growth during infancy and each closes at its own due date. Fontanelles are also membranous spaces for growth in the skull. Sutures include: sagittal suture between the two parietal bones, coronal suture between the parietal and frontal bones, metopic suture in the middle of the frontal bone, lambdoid suture between the occipital and parietal bones, squamosal suture

Cranial bones: anterior cranial bone, posterior cranial bone, sphenoid bone, mastoid bone

Types of Newborn Skull Deformities

Plagiocephaly Deformity: In this type of deformity, an asymmetry or flattening is seen in the baby’s head. One side of the occipital bone or occipital bone is depressed or flattened, and consequently the forehead area on the same side becomes prominent, the frontal area on the opposite side becomes depressed, and the occipital area on the opposite side becomes prominent. These changes can be clearly seen from the top view of the head. In this deformity, the ear on the side where the occipital bone is depressed is moved forward compared to the ear on the opposite side. Also, the height of the head in the anterior-posterior view is greater on the side where the occipital bone is depressed than on the opposite side. In severe cases of plagiocephaly deformity, facial features including the eyes, eyebrows, nose, and chin also become asymmetrical.

Brachiocephalic deformity: In this type of deformity, the occipital bone is symmetrically depressed and flattened. The anterior-posterior dimension is significantly reduced compared to the mediolateral dimension. In the lateral view of the head, the occipital region appears flat, the upper part of the head (vertex) is pulled upward and the height of the head increases, and in this view, there is a large slope from the vertex to the forehead, and the head does not have a natural curvature.

Scaphocephaly: In this deformity, the parietal and temporal bones (lateral areas of the head) are flattened and the frontal and occipital areas are raised. The mediolateral dimension is significantly reduced compared to the anterior-posterior dimension.

Asymmetrical brachiocephalic deformity: In this deformity, in addition to flattening the symmetry of the occiput and a significant reduction in the anterior-posterior dimension of the head, an asymmetry similar to the positional plagiocephaly pattern is also created in the head.

Craniosynostosis malformations:

This type of neonatal skull deformity is caused by the premature closure of one or more sutures. The prevalence of craniosynostosis malformation is 3 to 5 per 10,000 live births. The most common suture to develop synostosis is the sagittal suture.

Helmet Use Objectives: To create symmetry and proportion of skull dimensions, to improve growth in desired directions in the skull, to direct growth from prominent areas of the skull to flattened areas of the skull

Types of helmets used in skull deformities:

Post-operative or post-op helmets: For craniosynostosis deformities after surgical correction of sutures

Objectives of using these helmets: To protect the surgical site, to correct remaining deformities in the head, to prevent secondary deformities. Post-operative helmets are often used after endoscopic surgeries and sometimes after cranial vault surgical procedures. Scanning and measuring of the infant’s head can be done three to four days after surgery, and delivery and fitting of the helmet on the infant’s head can be done 7 to 10 days after surgery.

Helmets for positional deformities

The duration of helmet use depends on various factors: the age of the baby at the time of treatment, the severity of the deformity, parental compliance, the type of cranial deformity, the way the orthosis is fitted, the presence or absence of cervical muscle imbalance

Diagnosis of neonatal skull deformities

Patient history: A patient history includes the following: date of birth, weight of the baby at birth, was the baby born prematurely or at full term? If premature, how many weeks early was he born? Type of delivery, complications during pregnancy and delivery, equipment and instruments used for delivery, time spent in the NICU, abnormal position of the fetus in the mother’s womb, the predominant position in which the baby is placed during the day, the baby’s usual sleeping position, was the head shape normal at birth or not?, was the head shape of the sibling or parents also deformed or normal? Does the baby have neck tightness and neck muscle imbalance?

Palpation of sutures and ossicles: By palpating the sutures and ossicles of the baby’s head, you can find out whether the sutures are open or closed. Protuberances can be felt at the sutures that have synostosis, which in this case leads to suspicion of the presence of craniosynostosis deformity.

مشاهده ی سر از نماهای مختلف: با

Prepare images of the upper, lateral, posterior, and anterior views of the infant’s head shape, considering the characteristics mentioned for each type of deformity.

Distinguish between the two types of positional deformity and craniosynostosis based on appearance: In positional plagiocephaly, the forehead is prominent on the side where the back of the head is depressed, and the forehead is depressed on the opposite side where the occipital region is prominent. From the anteroposterior view, the head height on the side where the back of the head is depressed increases compared to the opposite side. From the anterior view, the eye socket appears wider on the side where the forehead is prominent. In this type of deformity, the ear on the side where the occipital region is depressed is displaced anteriorly. In this type of deformity, the ears do not move up and down in the frontal plane.

In the plagiocephaly deformity of the craniosynostosis type, the forehead is sunken on the side where the occiput is depressed and the forehead is raised on the side where the occipital region is raised. From the anterior-posterior view, the head height on the side where the occipital region is depressed is greater than on the opposite side. Also, in this type of deformity, the ear is closer to the depressed occipital region. And in the posterior-anterior view, the ear is displaced in the frontal plane, so that the ear on the side of the depressed occiput is displaced downward.

Imaging methods for definitive and differential diagnosis of positional deformities and craniosynostosis: Simple radiography, the use of ultrasound as a rapid and less complicated method, and it is also possible to use it to diagnose the deformity before the baby is born, CT scan with 3D reconstruction.

Explanations regarding measurements (head measurements and calculation of head asymmetry and disproportion indices):

Note: Dear colleague, if possible, measure the main measurements including the maximum head width, head length and circumference two to three times to minimize the error during measurement. Also, specify the measurement that you are most confident about so that in case of discrepancy in the measurements, the design can be done based on it.

Head Landmarks:

Glabella (g): A point midway between the eyebrows

Euryon (eu): The outermost point of the head on either side in frontal view

Opisthocranion (op): The most posterior point of the head in lateral view

Vertex: The uppermost point of the head in lateral view

(zy) frontozygomatic suture: A palpable, bony prominence on the outside of the eye

Tragus point: A cartilaginous point in front of the ear

Measurement method:
Head length: From the glabella point to the most posterior point on the back of the head in lateral view
Head circumference: The tape measure should pass just above the eyebrow line and above the ear and the maximum head circumference should be taken. The tape measure should not be tilted during measurement and should be completely parallel to the ground.
Length from the outer corner of the eye to the front of the ear: Measure from the outer bony prominence of the eye to the most anterior point of the ear (which is cartilaginous).
Ear dimensions:
Vertical dimension of the ear from the highest point of the earlobe to the lowest point of the ear.
Horizontal dimension from the most posterior point of the earlobe to the most anterior point of the ear (tragus point).
Facial width: Distance between the two bony prominences of the outer corner of the eye on the left and right sides.
Maximum head width: From the outermost points of the head on both sides from the front view
Head width above the ear: Place the caliper jaws exactly on the upper edge of the earlobe and measure the width above the ear.
Head height: One caliper jaw is placed at the highest point of the head and the other jaw is under the patient’s chin. (If you measure height in a different way, please mention it.)
Anterior ear to ear: Measure from the front of the left and right ear with the tape measure just above the eyebrow line.
Posterior ear to ear: Measure from the back of the earlobe.
Upper ear to ear: Measure from the top of the ear.
Neck roll width: Place the two caliper jaws in the submastoid or under the ear and measure the width of the suboccipital or neck roll (this measurement is necessary to create a grip in the helmet.)
Diagonal head diameters: If there is any asymmetry in the baby’s head, be sure to send the diagonal diameter measurements.

Place one jaw of the caliper at the outer corner of the eyebrow or the outer prominence of the eye and the other jaw of the caliper at the opposite point that has the most depression or prominence (in the occipital region) so as to measure the minimum or maximum diameter of the head in this area

Calculation of head asymmetry and disproportion indices:

Cranial vault asymmetry index or CVAI: To determine the severity of plagiocephaly deformity and head asymmetry

Calculation formula: (larger diagonal diameter – smaller diagonal diameter) / larger diagonal diameter

Cephalic index or CI: To determine the severity of brachiocephaly deformity or the degree of flattening of the back of the head

Calculation formula: Maximum head width / maximum head length

Helmet prescription based on the severity of blagiocephaly deformity:

Deformity grade Clinical findings CVAI treatment
1 Normal The head is symmetrical and normal No treatment required <3.5
2 Mild Minimal asymmetry in one dimension Posterior head without secondary changes, requires positioning of the infant 3.5-6.25
3 Moderate involvement of two areas of the head (two dimensions of the head) Moderate to severe flattening of one posterior dimension of the head Minimal ear displacement and forehead involvement Positioning of the infant Use of a helmet (based on the age of the infant and patient history) 6.25-8.75
4 Severe involvement of two to three dimensions of the head Severe flattening of the posterior dimension of the head Moderate ear displacement Anterior involvement including significant asymmetry of the face and eyes Needs to use a helmet 8.75-11
5 Very severe involvement of three to four dimensions of the head Severe flattening of the posterior dimension of the head Severe ear displacement Anterior involvement including asymmetry in the facial features