Hypertelorism is an abnormally increased distance between two organs or bodily parts, usually referring to an increased distance between the orbits (orbital hypertelorism). In this condition the distance between the inner eye corners as well as the distance between the pupils is greater than normal. Hypertelorism should not be confused with (bony)telecanthus, in which the distance between the inner eye corners is increased but that of the outer eye corners remains unchanged. Therefore the distance between the pupils is normal.

Hypertelorism can be seen a variety of syndromes, including 1q21.1 duplication syndrome

1q21.1 duplication syndrome

1q21.1 duplication syndrome or 1q21.1 microduplication is a rare aberration of chromosome 1. , the international rare chromosome disorder group, has 38 genetically confirmed registered cases of this duplication worldwide ....

, Basal Cell Nevus syndrome, DiGeorge syndrome

DiGeorge syndrome

22q11.2 deletion syndrome, which has several presentations including DiGeorge syndrome , DiGeorge anomaly, velo-cardio-facial syndrome, Shprintzen syndrome, conotruncal anomaly face syndrome, Strong syndrome, congenital thymic aplasia, and thymic hypoplasia is a syndrome caused by the deletion of a...

 and Loeys-Dietz syndrome

Loeys-Dietz syndrome

Loeys-Dietz syndrome is a recently-discovered autosomal dominant genetic syndrome which has many features similar to Marfan syndrome, but which is caused by mutations in the genes encoding transforming growth factor beta receptor 1 or 2 .It was identified and characterized by American physician...

.
Hypertelorism can also be seen in Apert syndrome

Apert syndrome

Apert syndrome is a form of acrocephalosyndactyly, a congenital disorder characterized by malformations of the skull, face, hands and feet. It is classified as a branchial arch syndrome, affecting the first branchial arch, the precursor of the maxilla and mandible...

, craniofrontonasal dysplasia, Noonan syndrome

Noonan syndrome

Noonan Syndrome is a relatively common autosomal dominant congenital disorder considered to be a type of dwarfism, that affects both males and females equally. It used to be referred to as the male version of Turner's syndrome ; however, the genetic causes of Noonan syndrome and Turner syndrome...

, Neurofibromatosis, LEOPARD syndrome

Leopard syndrome

LEOPARD syndrome - is part of a group called Ras/MAPK pathway syndromes - is a rare autosomal dominant, multisystem disease caused by a...

, Crouzon syndrome

Crouzon syndrome

Crouzon syndrome is a genetic disorder known as a branchial arch syndrome. Specifically, this syndrome affects the first branchial arch, which is the precursor of the maxilla and mandible...

, Wolf-Hirschhorn syndrome

Wolf-Hirschhorn syndrome

Wolf–Hirschhorn syndrome , also known as chromosome deletion 4p syndrome, Pitt-Rogers-Danks syndrome or Pitt syndrome, was first described in 1961 by Americans Herbert L...

, Andersen–Tawil syndrome, Waardenburg syndrome

Waardenburg syndrome

Waardenburg syndrome Waardenburg syndrome Waardenburg syndrome (also Waardenburg­ Shah Syndrome, Waardenburg-Klein syndrome, Mende's syndrome II, Van der Hoeve-Halbertsma-Waardenburg syndrome, Ptosis-Epicanthus syndrome, Van der Hoeve-Halbertsma-Gualdi syndrome, Waardenburg type Pierpont,[5] Van...

 and Cri du chat

Cri du chat

Cri du chat syndrome, also known as chromosome 5p deletion syndrome, 5p minus syndrome or Lejeune’s syndrome, is a rare genetic disorder due to a missing part of chromosome 5. Its name is a French term referring to the characteristic cat-like cry of affected children. It was first described by...

 syndrome, along with Piebaldism, prominent inner third of the eyebrows, irises of different color, spondyloepiphyseal dysplasia, mucopolysaccharide metabolism disorders (Morquio syndrome

Morquio syndrome

Morquio's syndrome is an autosomal recessive mucopolysaccharide storage disease , usually inherited. It is a rare type of birth defect with serious consequences...

, Hurler's syndrome), deafness and also in hypothyroidism.

Embryology

Because of the fact that hypertelorism is an anatomic condition associated with a heterogeneous group of congenital disorders, it is believed that the pathalogical etiology of hypertelorism is also heterogeneous. Theories include too early ossification of the lower wings of the sphenoid

Sphenoid bone

The sphenoid bone is an unpaired bone situated at the base of the skull in front of the temporal bone and basilar part of the occipital bone.The sphenoid bone is one of the seven bones that articulate to form the orbit...

, an increased space between the orbita, due to increasing width of the ethmoid sinuses, field defects during the development, a nasal capsule that fails to form, leading to a failure in normal medial orbital migration and also a disturbance in the formation of the cranial base, which can be seen in syndromes like Apert and Crouzon.

Timing of surgical correction

The surgery to correct hypertelorism is usually done between 5 and 8 years of age. This addresses to the psychosocial aspects in the child's early school years. Another reason for correction age 5 or older is that the surgery should be delayed until the tooth buds have grown out low enough into the maxilla, thus preventing damage to them. Also, before age 5 the craniofacial bones are thin and fragile, which can make surgical correction difficult. In addition, it is possible that orbital surgery during infancy may inhibit midface growth.

Therapy

For the treatment of hypertelorism there are 2 main operative options: The box osteotomy and the facial bipartition ( also referred to as median fasciotomy).

Box osteotomy

This treatment of orbital hypertelorism was first performed by Paul Tessier

Paul Tessier

Paul Tessier was a French surgeon. He was considered the father of modern craniofacial surgery.-Biography:...

. The surgery starts off by various osteotomies that separate the entire bony part of the orbit from the skull and surrounding facial bones. One of the osteotomies consists of removing the bone between the orbits. The orbits are then mobilized and brought towards each other. Due to the fact that this often creates excessive skin between the orbits a midline excision of skin is frequently necessary. This approximates the eyebrows and eye corners and provides a more pleasing look.

Facial bipartition

The standard procedure (box osteotomy) was modified by Jacques van der Meulen and resulted in the development of the facial bipartition(or median faciotomy) .
Facial bipartition first involves splitting the frontal bone from the supraorbital rim. Then the orbits and the midface are releaseddrom the skull-base using monoblock osteotomy. Then a triangular shaped piece of bone is removed from the midline of the midface. The base of this triangular segment lies above the orbita and the apex lies between the upper incisor teeth. After removing this segment it is possible to rotate the two halves of the midface towards each other, thus resulting in reduction of the distance between the orbits. It also results in leveling out the V-shaped maxilla and therefore widening of it.
Due to the fact that hypertelorism is often associated with syndromes like Apert, hypertelorism is often seen in combination with midface dysplasia

Dysplasia

Dysplasia , is a term used in pathology to refer to an abnormality of development. This generally consists of an expansion of immature cells, with a corresponding decrease in the number and location of mature cells. Dysplasia is often indicative of an early neoplastic process...

. If this is the case, facial bipartition can be combined with distraction osteogenesis. The aim of distraction osteogenesis

Distraction osteogenesis

Distraction osteogenesis, also called callus distraction, callotasis and osteodistraction is a surgical process used to reconstruct skeletal deformities and lengthen the long bones of the body...

 of the midface is to normalize the relationship between orbital rim to eye and also normalize the position of zygomas

Zygoma

The term zygoma generally refers to the zygomatic bone, a bone of the human skull commonly referred to as the cheekbone or malar bone, but it may also refer to:...

, nose and maxilla in relation to the mandible.

Soft tissue reconstruction

To create an acceptable aesthetic result in the correction of orbital hypertelorism, it is also important to take soft-tissue reconstruction in consideration. In this context, correction of the nasal deformities is one of the more difficult procedures. Bone and cartilage grafts may be necessary to create a nasal frame and local rotation with for example forehead flaps, or advancement flaps can be used to cover the nose.

Complications

As with almost every kind of surgery, the main complications in both treatments of hypertelorism include excessive bleeding, risk of infection and CSF

Cerebrospinal fluid

Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...

 leaks and dural fistulas. Infections and leaks can be prevented by giving perioperative antibiotics and identifying and closing of any dural tears. The risk of significant bleeding can be prevented by meticulous technique and blood loss is compensated by transfusions. Blood loss can also be reduced by giving hypotensive anesthesia. Rarely major eye injuries, including blindness, are seen. Visual disturbances can occur due to the eye muscle imbalance after orbital mobilization. Ptosis

Ptosis (eyelid)

Ptosis is a drooping of the upper or lower eyelid. The drooping may be worse after being awake longer, when the individual's muscles are tired. This condition is sometimes called "lazy eye", but that term normally refers to amblyopia...

 and diplopia

Diplopia

Diplopia, commonly known as double vision, is the simultaneous perception of two images of a single object that may be displaced horizontally, vertically, or diagonally in relation to each other...

can also occur postoperatively, but this usually self-corrects. A quite difficult problem to correct postoperatively is canthal drift, which can be managed best by carefully preserving the canthal tendon attachments as much as possible. Despite the extensiveness in these procedures, mortality is rarely seen in operative correction of hypertelorism.