Fetal Skull Development

Develops from the mesoderm and the neural crest.

By end of the 4th week loosely woven tissue – embryonic connective tissue

Differentiation of cells within the skull is different. The flat bones ossifies from the membrane. Whist other bones form cartilage after which ossification takes place

Fetal Skull Development

Skull is divided into 2 parts: Neurocranium –protecting the

brain which is known as the vault. This is subdivided into:

1. Dermatocranium – parietal & frontal2. Chondrocranium –occipital,

temporal, sphenoid – base of the skull. Fusion of cartilage

Viscerocranium – forms the face – starts with the mandible at 6 weeks gestation

Fetal Skull

29 bones 8 form the cranium 14 form the face 7 form the base

The vault of the skull comprises Two frontal bones Two parietal bones One occipital bone Two temporal bones. 

Sutures Lambdoidal suture: separates the

occipital bone from the parietal bones

Sagital suture: lies between 2 parietal bones

Coronal suture: separates frontal bones from parietal bones

Frontal suture:runs between two halves of frontal bones

Anterior fontanelle /bregma: Found at junction of sagital coronal and frontal suture.

Broad, diamond shaped.

3-4 cm long and 1.5 – 2cm wide.

Closes at 18 months

Fontanelles. Posterior fontanelle or lambda:

located at junction of lambdoid and sagital sutures.

Triangular

Closes by 6 weeks of age

Diameters of fetal skull:

Biparietal diameter : this is 9.5 cm . this is the diameter between two parietal eminences.

Bitemporal diameter: this is 8.2 cm- diameter between the furthest points of the coronal suture at the temples.

Super sub parietal -8.5 cm. – it extends from a point placed below one parietal eminence to a point placed above the other parietal eminence. Of the opposite side.

Bi-mastoid diameter-7.5cm- it is the distance between the tips of the mastoid processes. The diameter is incompressible and it is impossible to reduce the length of the bimastoid diameter by obstetrical operation.

Suboccipitobregmatic: This is 9.5 cm, the diameter from below the occipital protuberance to the centre of the anterior fontanelle or bregma.

Suboccipitofrontal: This is 10 cm- the diameter from below the occipital protuberance to the center of the frontal suture

Occipitofrontal: This is 11.5 cm- the diameter from the occipito protuberance to the glabella.

Mentovertical: This is 13.5 cm- the diameter from the point of the chin to the highest point on the vertex

Submentovertical: This is 11.5 cm- the diameter from the point where the chin joins the neck to the highest point on the vertex.

Submentobregmatic: This is 9.5 cm-the diameter from the point where the chin joins the neck to the centre of the bregma.

MOULDING OF THE HEAD

Occurs with descent of the fetal head into the pelvis to reduce the head circumference

Frontal bones slip under parietal bones

Parietal bones override each other

Parietal bones slip under the occipital bone

MOULDING OF THE HEAD

DEGREE OF MOULDINGAssessed vaginally 0 suture lines are separate +1 suture lines meet +2 suture lines overlap but can be reduced by

gentle digital pressure +3 overlap irreducible

Caput succedaneum

Cephal hematoma

False cerebri and tentorium cerebelli

Fetal circulation

The fetal circulation differs mainly from the adult ones by the presence of 3 major vascular shunts. Ductus venosus: between umbilical vein and inferior venacava

Foramen ovale: Between the right and left atrium

Ductus arteriosus: Between the pulmonary artery and descending aorta.

1. The umbilical vein transports blood rich in oxygen and nutrients from the placenta to the fetal body. This vein travels along the anterior abdominal wall of the fetus to the liver, and then the umbilical vein divides into branches.

2. About half of the blood passes into the liver and the rest enters a shunting vessel called ductus venosus that bypasses the liver. The ductus venosus travels a short distance and joins the inferior venacava.

3. There the oxygenated blood from the placenta is mixed with deoxygenated blood from the lower parts of the fetal body. This blood continues through the venacava to the right atrium.

4. As the blood relatively high in oxygen enters the right atrium of the fetal heart, a large proportion of it is shunted directly into the left atrium through an opening in the atrial septum called the foramen ovale.

5. The more highly oxygenated blood that enters the left atrium through the foramen ovale is mixed with a small amount of deoxygenated blood returning from the pulmonary veins. This mixture moves into the left ventricle and is pumped into the aorta.

6. Some of this blood reaches the myocardium by means of coronary arteries. And some reaches the tissues of the brain through the carotid arteries.

7. The rest of the blood entering the right atrium, as well as the large proportion of the deoxygenated blood entering from the superior venacava, passes into the right ventricle and out through the pulmonary artery

8. Enough blood reaches the lung tissue to sustain them. Most of the blood in the pulmonary artery bypasses the lungs by entering the ductus arteriosus, which connects the pulmonary artery to the descending portion of the aorta arch

9. Some of the blood carried by the descending aorta leads to various parts in the lower regions of the body.

10.The rest of the blood passes into the umbilical arteries which branch from internal iliac arteries and lead to the placenta.

REVIEW OF LITERATURE

Noninvasive Assessment of the Early Transitional Circulation in Healthy Term Infants.

Author: Popat H, Kluckow M.

Source Department of Neonatology, Royal

North Shore Hospital and University of Sydney, Sydney, N.S.W., Australia.

Abstract Background: The early neonatal

circulatory transition usually occurs smoothly but occasionally it is incomplete or reverts to the fetal state of high pulmonary vascular resistance, resulting in significant neonatal morbidity.

Objective: To define the normal values for echocardiographic parameters during the early transitional circulation in term infants.

Methods: Two-dimensional, M-mode, pulsed

and color flow Doppler echocardiography

was used to assess healthy term infants in

the first 4 h of life. Left and right ventricular

outputs (LVO and RVO) and myocardial

performance indices (MPI), left ventricular

fractional shortening, end-systolic diameter

and end-diastolic diameter, ductal size,

shunt and peak velocities, tricuspid

regurgitation and left pulmonary artery

diastolic velocities were documented.

Results: A total of 21 normal term infants were

assessed with median gestation of 39 weeks, birth

weight of 3,470 g and postnatal age of 3 h and 22

min. The median echocardiographic values were

LVO 193 ml/kg/min, RVO 216 ml/kg/min, left MPI

0.41, right MPI 0.63, and fractional shortening 29%.

The ductus was patent in all 21 infants with a

median size of 2.3 mm; ductal flow was bidirectional

in 86% with median peak left-to-right velocity of

1.07 m/s. The median left pulmonary artery diastolic

velocity was 0.31 m/s and physiological tricuspid

regurgitation was present in all infants.

Conclusion: This study defines normal

values for echocardiographic

measurements in healthy term infants

during the first 4 h after birth. These

normative data may be useful in early

identification of infants with abnormal

circulatory transition, allowing more

rapid determination of cardiovascular

dysfunction.

2. journal of reproductive medicine. 1976 Jun;16(6):321-4.

Intrauterine spontaneous depression of fetal skull: a case report and review of literature.

Author: Guha-Ray DK.

Abstract

Intrauterine depression of fetal skull,

with or without fracture, unassociated

with any known trauma during

pregnancy or delivery, is extremely

rare in Western countries though not

so rare in Africa among African women.

Usually fetal skull depression is caused

by forceps or digital pressure of the

obstetrician during manual rotation.

Forty such cases are reported in the

literature-nine in Western countries and

the remaining 31 over a period of three

years at Harare Hospital Maternity

Centre, Salisbury, Rhodesia, Africa.

There, an incidence of one in 4,000

deliveries was observed among the

African women but none in 6,000

deliveries of European women during the

same period at a nearby hospital.

The presentation of this paper is made

in view of the rarity of intrauterine

spontaneous fetal skull depression in

Western countries and the not so

infrequent occurrence in African and

possibly other developing countries

and because of the persistent

controversy about the treatment of

this condition.

3.child’s nervous system:ChNS: Official journal of the international society for pediatric neuro surgery . 1996 Feb;12(2):117-20.

Craniocerebral birth trauma caused by vacuum extraction: a case of growing skull fracture as a perinatal complication.

AUTHOR: Papaefthymiou G, Oberbauer R, Pendl G.

Source Universitäts-Klinik für Neurochirurgie,

Karl-Franzens-Universität Graz, Austria.

Abstract

A case of growing skull fracture

following birth trauma and caused by

vacuum extraction is reported in order

to emphasize the incidence of this

peculiar head injury at the beginning

of extrauterine life and to point out its

relation to possible neuropsychological

disturbances that may appear later in

childhood.

Delivery by vacuum extraction increases the

incidence of perinatal injuries and

consequently the incidence of neurological

deficits in children. Neurosurgical repair is

advocated as the appropriate treatment, with

the aim not only of cosmetically correcting

the lesion's typical subgaleal protuberance

with cranioplasty, but also of performing a

water-tight closure of the dura, enabling the

cerebral cortex to "fill in" the intracerebral

lesion

The surgical technique and gross pathology of

the lesion are described together with

radiological findings before and after surgery.

Reports by other authors are reviewed in an

attempt to identify the conditioning factors and

pathological features of this traumatic injury to

skull and brain in neonates and infants. The

literature on cranial fractures associated with

intracerebral lesions at this age shows a

significant difference in recovery and outcome

from that after similar lesions in older children.

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