*2.1.1. Hypertelorism*

**Definition:** Hypertelorism is an increased interocular distance.

**Embryology and pathogenesis:** At the first stage of the development of the human embryo, the eyes are to be found laterally, like in animals with panoramic vision. As the pregnancy evolves, the fetal eyes migrate toward the midline, thus generating the conditions for the stereoscopic vision to develop (**Figure 8**).

**Ultrasound diagnosis:** Interorbital diameter is larger than 95th. The accuracy of ultrasound

Congenital Abnormalities of the Fetal Face http://dx.doi.org/10.5772/intechopen.73072 97

**Investigations:** Detailed ultrasound examination for associated defects. Invasive testing for

**Follow up:** Standard follow-up in isolated cases. Any underlying syndrome antenatal care

**Isolated:** It is good, even if there might be esthetic implications in severe cases as well as impaired stereoscopic binocular vision. For these cases, there are several operative procedures such as canthoplasty, orbitoplasty, surgical positioning of the eyebrows, and rhinoplasty.

**Syndromic:** The prognosis of hypertelorism is usually poor, and it does have a risk of mental retardation. However, normal life span and normal intellect are to be expected in the case of

**Etiology**: Hypertelorism is almost always associated with other severe abnormalities, espe-

**Embryology and Pathogenesis:** Out of the mesenchymal mass there comes the craniofacial skeleton. This mass has two points of origin: the mesoderm and the neutral crest, the latter migrating to the region. The development of the median facial structures (forehead, nose, interorbital structures and upper lip) is closely linked to the forebrain differentiating process. It is possible that these two development steps are induced by the tissue, which lies between the prosencephalon and the stomodeum (the root of the primitive mouth), namely the prechordal mesenchyma. Thus, defects of the facial midline, for example, hypotelorism, are often linked to cerebral abnormalities, most often with holoprosencephaly. Hypotelorism can be found in association with trigonocephaly, microcephaly, Meckel syndrome and chromosome

**Ultrasound diagnosis:** It is based on the documentation of a reduced interocular distance. The interorbital diameter is lower than <5th and, together with the almost always present holoprosencephaly (**Figure 9**), is to be found among the midline migration defects; in this

**Associated abnormalities:** In half of the cases, we encounter chromosomal defects, especially

**Investigations:** A thorough ultrasound examination should be conducted, including neurosonography, in order to find associated defects as well as invasive testing for karyotyping

medial facial cleft syndrome [8]. The esthetic aspect should not be underestimated.

exam in the hypertelorism diagnosis has not been established.

should be adjusted, considering the additional risk of the condition.

**Delivery:** Standard obstetric care and delivery.

**Recurrence:** Isolated: no increased risk of recurrence.

**Definition:** Hypotelorism is a decreased interorbital distance.

cially with the sequence of holoprosencephalic abnormality.

case, the hypotelorism can be extreme, as in cyclopia [10].

trisomy 13, as well as genetic syndromes [9].

karyotyping and array.

*2.1.2. Hypotelorism*

aberrations [10, 11].

and array.

**Prevalence:** 1 in 20,000 births.

There are at least two theories as to why hypertelorism may appear. The first theory states that there are several mechanisms causing it: the forward migration of the first half of the eyes, a midline tumor, meningoencephalocele for instance, causing the second half, or skull bones with abnormal growth vectors. The second theory links a splanchnocranium, which presents an abnormal growth, to the undeveloped bones which derive from the first branchial arches [8].

**Pathology:** Three parameters are used to measure the fetuses' ocular spacing: interpupillary distance, canthal distance, and interorbital distance. Hypertelorism is bilateral most of the times, with little incidents of unilateral cases associated with plagiocephaly and proboscis lateralis. Also, this condition is either isolated or accompanied by other malformations or clinical syndromes such as the median cleft syndrome and craniosynostoses. In craniosynostoses, hypertelorism syndromes such as Apert, Crouzon, and Carpenter are usually present [9].

**Figure 8.** The facial structures development, represented schematically between the 5th and the 10th week of gestation. During the early stages, we can notice the primitive eyes on both sides of the cephalic pole. However, they move toward the median line as gestation goes on [7].

**Ultrasound diagnosis:** Interorbital diameter is larger than 95th. The accuracy of ultrasound exam in the hypertelorism diagnosis has not been established.

**Investigations:** Detailed ultrasound examination for associated defects. Invasive testing for karyotyping and array.

**Follow up:** Standard follow-up in isolated cases. Any underlying syndrome antenatal care should be adjusted, considering the additional risk of the condition.

**Delivery:** Standard obstetric care and delivery.

**Isolated:** It is good, even if there might be esthetic implications in severe cases as well as impaired stereoscopic binocular vision. For these cases, there are several operative procedures such as canthoplasty, orbitoplasty, surgical positioning of the eyebrows, and rhinoplasty.

**Syndromic:** The prognosis of hypertelorism is usually poor, and it does have a risk of mental retardation. However, normal life span and normal intellect are to be expected in the case of medial facial cleft syndrome [8]. The esthetic aspect should not be underestimated.

**Recurrence:** Isolated: no increased risk of recurrence.
