Hemifacial Microsomia - Tratment algorithm

Treatment for Hemifacial microsomia depends on the classification of the deformity, the severity of the deformity, the age of the patient, and the wishes of the patient and their family.

While most surgeons working in this field carry out treatment during growth based on the complexity and individual features of the deformity, some surgeons still prefer to delay all treatment until maturity.

Pruzansky I

It is rarely necessary to consider any surgery for the Pruzansky I mandible in childhood. From the age of about 16 years, some patients would benefit from a genioplasty or conventional orthognathic surgery.

Treatment of the deformity is generally going to be deferred to maturity. Surgery is likely to consist of either:

• No surgery
• Genioplasty
• Conventional orthognathic surgery

Pruzansky IIa and IIb

Depending on the severity of the deformity and the wishes of the family, Pruzansky IIa and sometimes IIb cases can be considered for distraction osteogenesis to lengthen the mandibular ramus from the age of about 3 or 4 years. Any young child who receives such lengthening during growth is likely to need further intervention over time. This is because the operated side of the mandible does not usually grow as much as the normal side and the deformity tends to re-establish. Parents should always be warned about this possibility.

Some cases of IIb would benefit from positioning of the condyle and glenoid fossa into a more lateral position before lengthening of the ramus can be considered.

There are cases of Pruzansky IIa and IIb in which the zygomatic arch or part of it is missing. Consideration should be given to whether reconstruction of the arch with a rib graft would be beneficial.

Treated Pruzansky II cases with a persistent deformity or de novo cases presenting after the age of 12 may be candidates for bimaxillary distraction osteogenesis provided that the occlusion can be managed by orthodontics.

All HFM cases may require management of residual skeletal deformity from the age of 16 years onwards. This is generally carried out using orthognathic surgery and usually requires bimaxillary rotational osteotomies. Sometimes onlay bone grafting is also necessary.

Some cases will have such severe deficiency of the soft tissues that correction of the bony deformity alone is not adequate to correct the facial contours.

There are a number of options to address this problem:

• Lateral augmentation of the mandibular angle by DO or osteotomy
• Augmentation of the lateral mandible with onlay bone grafting
• Augmentation of the facial contours with dermis fat grafts and/or fat injections
• Augmentation of the facial contours with soft tissue vascularized flaps

Pruzansky III

Pruzansky III cases present with not only severe hypoplasia of the ramus condyle unit, but with missing bony structures. The principle of treatment is to construct the missing structures especially the zygomatic arch and glenoid fossa as well as the mandibular condyle, ramus, and body. This is generally achieved with a combination of rib and costo-chondral grafts. The procedure can be performed as early as 2-3 years of age. The Pruzansky III case is thus converted to a Pruzansky II and can then be treated as described above.

Costo-chondral grafting used to lengthen the ramus is rarely effective. For this reason it is generally better to lengthen by distraction osteogenesis, at least 6 months after costochondral grafting.

In some cases the costo-chondral graft produces sufficient improvement in appearance and also grows so that further intervention is not needed.

Preauricular ear tags are common and often bilateral. Parents often want these removed as early as possible because they are unsightly. This can be done any time.

Well-formed ears require no treatment although sometimes they are not in a good position. It can be extremely difficult to move them.

Sometimes the ear is abnormally formed but most of the tissues are present. Those cases can be managed by correcting the deformity rather than by constructive surgery.

The options for treatment of severe microtia or anotia are:

• Do nothing (unless the child or parents request intervention)
• Autogenous construction with skin and cartilage by one of the recognized techniques (eg. Brent, Tagata etz…) around age 8 when the ear is normally fully grown
• A bone anchored ear prosthesis attached to titanium craniofacial implants placed in the temporal bone, which can be considered from 3 years of age

In general management of the facial soft tissues are carried out late after completion of the skeletal constructions.

Exceptions to this rule are:

• Correction of macrostomia should be carried out during the first year of life as it is analogous to a cleft lip. The same principle would apply to a complete lateral facial cleft. It is as important to carry out a definitive muscle repair and to break the scar up with z-plasties.
• Soft tissue augmentation is sometimes carried out early as part of a composite vascularized free tissue transfer in severe Pruzansky III cases.
• Also in Pruzansky III cases when the soft tissues are extremely thin and most of the underlying soft tissue structures are missing eg. the parotid gland, the masticatory muscles etc, skeletal construction can make the face look very gaunt. Early soft tissue augmentation may then be required and could involve either a de-epithelialized free flap, a perforator free flap, dermis fat grafts and/or fat injections. The same techniques apply to later soft tissue augmentation if indicated.

Orbital dystopia can occur. If mild, no intervention is advisable. If severe, the principles of correction are the same as for hypertelorism and vertical dystopia that is a craniofacial procedure which may include a four wall box osteotomy. This is normally carried out after the age of around 13 year when the teeth in the midface have erupted and are out of the way. Correction would involve a major intracranial procedure to move the orbit and eye upwards. The dystopia has to be severe to justify such a procedure and this should be done relatively late because of the presence of teeth in the maxilla which may be damaged during surgery.

Facial nerve palsy is common in HFM. However it is rarely severe enough to obtain significant benefits from nerve reanimation. Sling procedures can be carried out as well as free flaps such as pectoralis minor.

When the facial nerve is affected, the condition needs to be quite severe and affecting the second and/or third branches of the nerve for surgery to be considered. Various procedures for facial reanimation can be considered although palsy affecting the first branch of the facial nerve is usually managed by the insertion of a gold weight into the upper eyelid to facilitate lid closure.