In true hypertelorism there is lateralization of the entire orbit. In interorbital hypertelorism, the lateral orbital walls are in a normal position while there is an increased interorbital distance. Hence, movement of the medial walls only is required. Conditions commonly associated with interorbital hypertelorism include:
Encephaloceles are the most common and can be classified as nasofrontal (located between nasal and frontal bones), nasoethmoidal (located between nasal bones and nasal cartilages), naso-orbital (located trough the medial orbital wall), and combined (coexisting nasoethmoidal and naso-orbital).
To illustrate the principles of a MOCUT procedure, the management of a midline encephalocele follows.
If the encephalocele courses laterally into the orbit, slight variations in the osteotomies and the use of bone grafts to repair the defect may be required.
Management of tumors vascular malformations etc. may be slightly different. However the principles remain the same.
Planning of surgery
The interorbital distance is measured with a caliper for reference.
Parallel osteotomies are planned so as to remove enough interorbital bone so that when the orbits are translocated medially the interorbital distance is normalized to 25 – 30 mm in the adult, and the tilt of the orbit is corrected. In the younger child this distance may be less, and is based on age and gender matched norms.
Normal interorbital distance (mm)
A coronal incision is use to expose the naso-orbital-ethmoid region. The encephalocele is then dissected free from the overlaying soft tissue. A frontal craniotomy is then planned and performed.
Beginning 1 cm above the orbital roof a limited frontal craniotomy is outlined.
Bur holes are first placed in the middle of the frontal bone and laterally just above the orbit. An epidural dissection between these points is made.
The neurosurgeon then completes the osteotomies using a craniotome.
After the bone flap is removed, the dura is freed from the anterior fossa in an epidural plane.
The dura is protected using neurosurgical cottonoids.
The encephalocele is freed from the orbit, nose, or ethmoid region, resected and the dura repaired.
Sometimes it is necessary to first remove the bone between the orbits to get access to the encephalocele.
Malleable retractors are used intracranially to retract and protect the dura and intraorbitally to protect the orbital contents during the osteotomies.
Lateral cuts are then made with a saw from the burr hole placed above the orbit, down to the orbital rim.
Medial orbital wall osteotomy
An osteotome is inserted from intracranially and the medial orbital wall is osteotomized posterior to the canthus down to the medial floor.
Two parallel osteotomies are then made from the anterior cranium down the side of each nasal bone to the bone cartilage junction.
A saw is then used to make an osteotomy through the infraorbital rim, connecting the inferior part of the medial orbital wall osteotomy and the pyriform aperture. The osteotomy must be made lateral to the lacrimal bone.
An osteotome is then inserted intracranially just in front of or partially through the cribriform plate and an osteotomy is made through the cranial base and septum.
Preservation of some of the cribriform plate may help preserve some sense of smell. For severe deformities this may not be possible.
Some surgeons may prefer to remove the medial nasal bone and complete the medial orbital osteotomes before the removal of the encephalocele.
The interorbital bone is then removed if it has not previously been removed and stripped of mucosa. It may be used as a source for bone grafts.
4. Mobilization and fixation
Mobilization and fixation of orbits
The two medial orbital halves should now be completely mobile and able to be translocated medially. Any interference with bone spicules, ethmoid sinus tissue, or redundant mucosa, may need to be removed with a rongeur or scissors. There may be interference at the pyriform level as well, requiring bony removal.
Positioning of the segments and fixation
The lateral orbital segments are medialized and affixed with sutures, wires, or plates and screws. (Resorbable in children).
The gaps created laterally in the supraorbital bar are now bone grafted and affixed.
If the medial canthus has not been detached it will be moved with the bone segment. If it has been detached a transnasal canthopexy will need be performed. This may be performed with wire and metallic plates as in posttraumatic reconstruction, with a bone anchor, or with stout transnasal sutures and bone grafts. Lateral canthal resuspension may also be performed.
Replacement of frontal bone flap
The frontal bone flap is then replaced, held in place with resorbable, sutures and wires, or screws and plates.
Repair of encephalocele defect
A bone graft is often placed in the midline to repair the residual defect from the encephalocele (inset).
Any residual defects in the cranium are now filled with bone shavings prior to closure of all wounds.
The redundant skin overlaying the nasal region may now be resected and closed.
5. Aftercare following transcranial and Le Fort III procedures in infants and children
Most surgeons favors placement of a bulb suction drain under the scalp for 3-5 days. Resorbable skin sutures are often used.
A circumferential head dressing is utilized for 48 hours. The neurosurgeon may request placement of a lumbar drain if significant dural tears have occurred during surgery. Patients should spend at least 1-2 days in an intensive care unit for neurological monitoring.
Keeping the patient’s head in an upright position postoperatively may significantly improve periorbital edema and pain. Some surgeons use injectable corticosteroids during surgery to reduce periorbital swelling.
To prevent orbital emphysema, nose-blowing should be avoided for at least 10 days.
The following perioperative medications are controversial. There is little evidence to make strong recommendations for postoperative care.
Avoidance of aspirin or nonsteroidal antiinflammatory drugs (NSAIDs) for 7 days.
Analgesia as necessary.
Antibiotics (many surgeons use perioperative antibiotics. There is no clear advantage of any one antibiotic, and the recommended duration of treatment is debatable.).
Nasal decongestant may be helpful for symptomatic improvement in some patients.
Steroids may help with postoperative edema. Some surgeons have noted increased complications with perioperative steroids.
Ophthalmic ointment should follow local and approved hospital protocol. This is not generally required in case of periorbital edema. Some surgeons prefer it. Some ointments have been found to cause significant conjunctival irritation.
Regular perioral and oral wound care has to include disinfectant mouth rinse, lip care if intraoral incision has been used.
Postoperative examination by an ophthalmologist may be requested, although sever periorbital edema may prevent useful assessment. The following signs and symptoms are usually evaluated:
Postoperative imaging has to be performed within the first days after surgery to verify accuracy of surgery. 3-D imaging (CT, cone beam) is recommended.
Remove sutures from skin after approximately 7-10 days if nonresorbable sutures have been used. Apply ice packs for the first 12 postoperative hours as able although infants and young children do not tolerate this well (may be effective in a short term to minimize edema). Avoid sun exposure and tanning to skin incisions for several months.
Soft diet can be taken as tolerated until there has been adequate healing of any maxillary vestibular incision. In children and infants age appropriate diets are then prescribed. Patients in MMF will remain on a liquid diet until such time the MMF is released.
Clinical follow-up depends on the complexity of the surgery, and whether the patient has any postoperative problems. Most patients are discharged at postoperative day 3-5 and seen again in 2-3 weeks.
In patients undergoing monoblock or Le Fort III distraction, distraction typically begins at day five at 1 mm/day and is assessed weekly with plane radiographs and clinical examination until the desired position is reached. After advancement a period of consolidation of 1-3 months is recommended before the retractors are removed.
In patients undergoing conventional advancement with intermaxillary fixation, MMF is kept in place for 4-6 weeks. Routine oral hygiene is prescribed. Patients with arch bars and/or intraoral incisions and/or wounds must be instructed in appropriate oral hygiene procedures. The presence of the arch bars or elastics makes this a more difficult procedure. A soft toothbrush (dipped in warm water to make it softer) should be used to clean the surfaces of the teeth and arch bars. Elastics are removed for oral hygiene procedures. Chlorhexidine oral rinses should be prescribed and used at least 3 times a day to help sanitize the mouth. For larger debris, a 1:1 mixture of hydrogen peroxide/chlorhexidine can be used. The bubbling action of the hydrogen peroxide helps remove debris. A Waterpik® is a very useful tool to help remove debris from the wires. If a Waterpik is used, care should be taken not to direct the jet stream directly over intraoral incisions as this may lead to wound dehiscence.
The patient needs to be examined and reassessed regularly and often. Additionally, ophthalmological, ENT, and neurological/neurosurgical examination may be necessary. If any clinical signs for meningitis or mental disturbances develop, professional help has to be sought. Due to the young age of many patients, routing CT-scans are performed only if clinically indicated to avoid excessive radiation exposure.