Craniofacial Microsomia

Craniofacial microsomia represents 2nd most common congenital anomalies after cleft lip and palate. It is seen as 1 in 3500 live births. Males are more affected than females (M:F = 63:39).

Etiology

Teratogens: Retinoic acid exposure is frequently associated with CFM.
Stapedial artery haemorrhage.
Genetic: CFM is also known to be transmitted as genetically as autosomal dominant and autosomal recessive trait both. Chromosome 10 deletion has been known to cause CFM. However even after genetic transmission as AD, the incidence is low possibly due to
- maternal gene resistance
- genomic imprinting
- mosaicism

Face develops from first and second branchial arches. Several theories have been put to explain the development of face. Older ones by Dursy and His ( Failure of fusion), Stark ( Theory of mesodermal migration and penetration). latest being the neuromeric theory by Michael H Carstens. The timeline and sequence of of facial prominence coming together is given somewhere else.

Structures involved with CFM

Ear.
Mandible.
Maxilla and rest of facial skeleton (zygoma, temporal bone, orbit, frontal bone.)
Soft tissues.
Facial Nerve.

There is Domino effect during development of face as explained by Pruzansky. Mal development is one area of face leads to involvement of other structures of the facial skeleton.

Mandible on the affected on the same side as the the rest of the structures. Condyle is hypoplastic or absent. Ramus is either hypoplastic or absent. The body curves upwards and joins the hypoplastic ramus. Chin is deviated to the same side.

Mandible on the normal side has increased gonial angle, increased horizontal dimensions and represents compensatory growth.

The posterior wall of glenoid fossa is partially formed by the tympanic portion of the temporal bone which also provides bony portion of EAC in normal developed ear. In CFM this posterior wall is deficient and cannot be identified. Ramus is hinged on a flat surface in such cases.

Occlusion cantt is deviated upwards on the affected side. Ramus and condyle are short as previously said.

Floor of the maxillary sinus and nose are higher on the affected side. Base of the skull may also be elevated. The styloid process is smaller. Mastoid process is flattened with reduced or absent pnematization. Zygoma is underdeveloped and malar eminence is flattened.

Soft tissue bulk is also reduced on the affected side as compared to the affected side. Lateral pterygoid is weakened on the affected side hence it shifts the mandible to the normal side. Hence on testing lateral pterigoid one finds inability to shift the jaw to the unaffected side or deviate the chin to affected side on forceful protrusion.

Facial nerve (Marginal mandibular being most commonly involved) involvement seen in many cases. Fourth, 5th, 6th cranial nerves may also be involved in CFM. Parotid hypoplasia is sometimes seen with patients having facial nerve involvement.

One of the contrasting feature of CFM from TMJ ankylosis is ability to open the mouth. In TMJ ankylosis the ability to open the mouth is greatly reduced.

Soft tissue, skeletal framework, ear and facial nerve involvement

Diagnostic criteria for Craniofacial microsomia (Cousley)

Ipsilateral Mandible and Ear defects
Asymmetrical mandibular or ear defects in association with either
- positive family history of CFM ortwo or more indirectly associated anomalies. (anomalies not related either in terms of development, field or function to CFM).

Differential Diagnosis

TMJ ankylosis
Rombergs disease (click here)
Hemifacial Atrophy(Click here)
Condylar hyperplasia
Treacher collins syndrome.

Diagnosis is helped by clinical evaluation along with CT scans of facial skeleton. Nerve conduction studies may be needed in cases where cranial nerves are involved.

Classification systems

Pruzansky grading system
Modified Pruzansky system
Meurman system of auricle defects
Munro and Lauritzen Classification
SAT classification
OMENS Classification
OMENS plus classification

Pruzansky system:

Pruzansky subdivides the ear and the mandible deformities.

Mandible

I a small ramus with identifiable anatomy
II a functioning TMJ but with an abnormal shape and glenoid fossa (IIa and IIb as modified by Kaban)
- IIa the glenoid fossa is in an acceptable functional position
- IIb the TMJ is abnormally placed and cannot be incorporated in the surgical construction
III an absent ramus and nonexistent glenoid fossa

This system has two weaknesses.

• It is possible to have a Pruzansky II with a functioning TMJ but with or without a zygomatic arch and glenoid fossa.
• It is possible to have a Pruzansky III with no condyle and no functioning TMJ with or without a zygomatic arch and a glenoid fossa.

Modified pruzansky Classification (Kaban, Padwa, Mulliken)

I Small mandible.
IIa Short mandibular ramus of abnormal shape; glenoid fossa in satisfactory position.
IIb TMJ abnormally placed inferiorly, medially and anteriorly.
III Absent TMJ.

Meurman Classification of ear defects

E₁ ear (mild hypoplasia and cupping with all structures present).
E₂ ear (absence of the external auditory canal with variable hypoplasia of the concha)
E₃ ear (malpositioned lobule with absent auricle).

OMENS classification

O- orbit defects (O0-O3)
M- mandible defects ( M0-M3)
E- Ear defects (E0-E3)
N- Nerve defects (N0-N3)
S- Soft tissue defects (S0-S3)

OMENS plus is an extension of existing OMENS classification. it includes extracranial manifestations.

SAT classification was put forward by David et al. It includes skeletal (S1-S5), auricle (A0-A3) and soft tissue (T1-T3) categories for classification.

Munro and lauritzen is a 5 part classification used for classification for CFM. OMENS is most frequently used classification system now a days.

Management

There are two school of thoughts regarding pathogenesis of the CFM. The first school of thought believes it to be a progressive disorder where early intervention should be done to minimize the deformity. The second school of thought believes the disease is non progressive with age and the intervention can be delayed till CFM becomes stable. In second case the intervention will be minimal.

As the disease has several components a plethora of procedures are sometimes required in a single patient. Minimal deformity patients may get away with a simple fat grafting.

Tracheostomy if sleep apnea in infant.
Early Distraction osteogenesis if sleep apnea.
Distraction osteogenesis at any age before skeletal maturity achieved. (click here)
le fort Osteotomy if skeletal maturity achieved.
Fat grafting for soft tissue defects.
free flaps for soft tissue defect.
FFMT/ Static sling procedures for facial weakness.
Dental procedures for occlusion.
Ear reconstruction (click here)