Index
In this condition, the distance between the corners of the inner eye and the distance between the pupils is greater than normal.
Hypertelorism is an abnormally increased distance between two organs or parts of the body, generally refers to a greater distance between the orbits (eyes) or orbital hypertelorism.
Hypertelorism should not be confused with telecanthus, in which the distance between the inner corners of the eye increases, but that of the outer corners of the eye remains unchanged. Therefore, the distance between the pupils is normal.
Symptoms
Hypertelorism is a symptom in a variety of syndromes, including Edwards syndrome (trisomy 18), 1q21.1 duplication syndrome, basal cell nevus syndrome, DiGeorge syndrome, and Loeys-Dietz syndrome. Hypertelorism can also be seen in:
- Apert syndrome .
- Craniofrontonasal dysplasia.
- Noonan syndrome.
- Neurofibromatosis.
- LEOPARD syndrome.
- Crouzon syndrome.
- Wolf-Hirschhorn syndrome.
- Andersen-Tawil syndrome.
- Sindrome de Waardenburg.
- Cat cry syndrome .
Along with piebaldism, prominent inner third of the eyebrows, different colored irises, spondyloepiphyseal dysplasia, disorders of mucopolysaccharide metabolism (Morquio syndrome and Hurler syndrome), deafness and also in hypothyroidism .
Some links have been found between hypertelorism and attention deficit / hyperactivity disorder.
Causes
Hypertelorism is probably established in an embryonic stage of approximately 28mm when a defective development of the nasal capsule leads to the freezing of the future fronto-naso-orbito-ethmoidal complex, thus preventing the movement of the orbit towards the midline.
Another reason could be poor lateral-medial movement of the orbit. Mann feels that early ossification of the lesser wings of the sphenoids leads to arrest of the orbits in the fetal position.
If the frontonasal prominence remains in its embryonic position, the optic plascocci cannot move toward the midline, resulting in hypertelorism.
Because hypertelorism is an anatomical condition associated with a heterogeneous group of congenital disorders, it is believed that the underlying mechanism of hypertelorism is also heterogeneous.
Theories include too early ossification of the lower wings of the sphenoid, an increase in the space between the orbit, due to the increase in the width of the ethmoid sinuses, field defects during development.
A nasal capsule that does not form, leading to a failure in medial orbital migration and also an alteration in the formation of the cranial base, which can be seen in syndromes such as Apert and Crouzon.
Treatment
Surgery to correct hypertelorism is usually done between the ages of 5 and 8. This addresses psychosocial issues in the child’s early school years. One would like to operate as soon as possible to avoid teasing from peers and the emotional aftermath of hypertelorism.
Another recommended reason for performing this surgery at the age <5 years or older is that the surgery should be delayed until the teeth have sufficiently erupted in the maxilla, thus preventing damage, since the osteotomy lines during surgical procedures traverse the inferior orbital border.
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 childhood can inhibit the growth of the middle part of the face.
Additionally, bone material may not be very good at supporting osteotomies along with fixation, predisposing to relapse of the deformity.
Therefore, most craniofacial centers would delay correction of hypertelorism to approximately 5-7 years of age. The results of surgery performed in adults are more reliable, stable and the operation is much easier than in a child.
However, waiting until adulthood can lead to many psychological and body image problems. For the treatment of hypertelorism there are two main operative options: box osteotomy and facial bipartition (also known as median fasciotomy).
Box osteotomy
The surgery can be performed as a “box osteotomy” that allows translational movement along the horizontal or vertical axes depending on the needs of the hyperteloric deformity . This involves bone cuts across the infraorbital border.
This treatment for orbital hypertelorism was first performed by Paul Tessier . The surgery begins with several osteotomies that separate the entire bony part of the orbit of the skull and the surrounding facial bones. One of the osteotomies consists of extracting the bone between the orbits. The orbits are mobilized and carried towards each other.
The procedure is best performed by a combined intracranial and extracranial approach. Access to the orbital roof and cribriform region is obtained after performing a frontal craniotomy, and the frontal lobes have been gently retracted. The birronal incision offers a good view of the medial and lateral orbital walls.
However, the addition of subciliary incisions is recommended for better access to the infraorbital rim and the floor of the orbit. All soft tissue is separated from the orbital roof, lateral wall, medial wall, and floor.
The cuts are made in the orbital roof, being about 2cm from the supraorbital margin, and the cut is stopped before the cribrifying region to protect the olfactory nerves.
The medial wall cut is posterior to the lacrimal ridge to protect the nasolacrimal duct and lacrimal sac. The lateral cut can divide the sagittal orbital wall or simply go through the greater wing of the sphenoid.
The cut in the infraorbital region is below the infraorbital nerve that exits the infraorbital foramen and extends to the floor of the orbit. The desired bone resection to be performed is marked on the back of the nose and removes excess nasal bone, nasal septum, and enlarged ethmoid sinuses.
After removing the excess central tissue that is causing hypertelorism, the bony orbits can be moved medially to this space and held in place with plates and screws or with wires.
Medially orbital displacement causes bony gaps in the lateral orbital wall that must be filled with bone graft, and split cranial bone graft is a good option. Since all the walls of the orbit move as a single unit, the orbital volume remains unchanged.
Tessier advocated maintaining a supraorbital bar to stabilize and guide the mobilized orbits. The orbital cage osteotomy procedure is generally chosen as long as dental occlusion is normal.
Because this often creates excessive skin between the orbits, excision of the skin in the midline is often necessary. This brings the eyebrows and corners of the eyes closer together and provides a more pleasing appearance.
Facial splitting
The standard procedure (box osteotomy) was modified by Jacques van der Meulen and resulted in the development of facial bipartition (or median faciotomy). Facial bipartition first involves dividing the frontal bone from the supraorbital border.
The orbits and midface are then freed from the skull base with a monobloc osteotomy. Next, a triangular piece of bone is removed from the midline of the midface.
The base of this triangular segment is located above the orbit and the apex is located between the upper incisor teeth. After removing this segment, it is possible to rotate the two halves of the midface towards each other, resulting in the reduction of the distance between the orbits.
It also results in the leveling of the V-shaped jaw and thus its widening. Because hypertelorism is often associated with syndromes such as Apert, hypertelorism is often seen in combination with midface dysplasia.
If this is the case, facial bipartition can be combined with distraction osteogenesis. The goal of midface distraction osteogenesis is to normalize the relationship between the orbital rim and the eye and also to normalize the position of the zygomas, nose, and maxilla relative to the mandible.
Soft tissue reconstruction
To create an acceptable esthetic result in the correction of orbital hypertelorism, it is also important to consider soft tissue reconstruction. In this context, correction of nasal deformities is one of the most difficult procedures.
Bone and cartilage grafts may be necessary to create a nasal frame and local rotation with, for example, front wings, or advancement flaps may be used to cover the nose.
Cantopexia
The medial canthus needs to be identified and anchored. These can be repaired using transnasal cables. This technique can be very frustrating at times. The author has devised a technique in which a two-hole titanium plate is used for this purpose.
The plate is attached to the thick nasal bone, and the lower hole is held at the level of the lacrimal crest. The ipsilateral edge is securely fixed this hole with steel wires.
Fronto-galeal fin
Removal of the ethmoid and nasal septum exposes the extradural space to the nasal cavity and can be a source of ascending infection. A vascularized flap such as the fronto-galeal flap as described by Jackson et al. It is interposed between the two cavities to prevent infection.
Dorsal nasal augmentation
Most of these patients will need a back augmentation, and this is best accomplished using a split skull graft as a cantilever.
Management of excessive skin
In many patients, there is excess skin present on the back. Excess skin is mainly removed at the time of definitive surgery.
In selected patients, excess skin and soft tissue could be removed very early around 9 months for better social acceptance without major orbital osteotomies.
Complications of hypertelorism
As with most types of surgery, the main complications in both hypertelorism treatments include excessive bleeding, risk of infection, and cerebrospinal fluid leaks and dural fistulas .
Infections and leaks can be prevented by administering perioperative antibiotics and identifying and closing any dural tears. The risk of major bleeding can be prevented by meticulous technique, and blood loss is compensated by transfusions.
Blood loss can also be reduced with hypotensive anesthesia. In rare cases, significant eye damage, including blindness, is seen. Visual disturbances can occur due to eye muscle imbalance after orbital mobilization.
Ptosis and diplopia can also occur postoperatively, but this is usually self-correcting. A rather difficult problem to correct postoperatively is canthal drift, which can best be managed by carefully preserving the canthal tendon junctions as much as possible.
Despite the breadth of these procedures, mortality is rarely seen in surgical correction of hypertelorism.
