Congenital Craniofacial Clefts: Etiology and Treatment

Congenital craniofacial clefts are complex birth defects affecting the face and skull. These disfigurements vary widely in patterns and severity, involving deficiencies, excesses, or abnormal separations of tissue along linear regions. Understanding the etiology and treatment of congenital craniofacial clefts is crucial for both diagnosis and effective surgical intervention, impacting functional and aesthetic outcomes for affected individuals.

Unraveling Congenital Craniofacial Clefts: Causes and Classification

The true incidence of craniofacial clefts is rare, estimated at 1.4–4.9 per 100,000 live births. Most rare craniofacial clefts occur sporadically, meaning they arise without a clear genetic pattern in most cases. However, certain syndromes show a clear hereditary link, providing insights into their causes.

Etiologic Factors: What Causes Craniofacial Clefts?

Several factors contribute to the development of craniofacial clefts, broadly categorized into hereditary, environmental, and developmental failures.

Hereditary Factors:

• Treacher-Collins Syndrome: Caused by a dominant gene defect (TCOF-1). The malformation is consistent, though penetrance can vary. Animal models show TCOF-1 gene defects affect neural crest cell migration, leading to zygomatic abnormalities.
• Goldenhar Syndrome: Some familial cases suggest a hereditary role in this syndrome, which often involves craniofacial clefting.

Environmental Factors: Based on both animal and human clinical studies, several environmental factors have been linked to facial clefts:

• Radiation
• Infection
• Maternal metabolic imbalances
• Drugs and chemicals: While many have teratogenic potential, few are proven to cause craniofacial malformations in humans. Retinoic acid-containing medications are under investigation.

Developmental Failures:

• Amniotic Band Syndrome: Constriction limb deformities from amniotic bands have a statistically significant association with rare facial clefting.
• Critical Embryologic Phase: The most crucial phase of embryologic differentiation and development occurs early in pregnancy, often before a mother knows she is pregnant. Multiple factors acting on numerous pathways make it difficult to pinpoint a single cause for a particular cleft.

How are Craniofacial Clefts Classified? The Tessier System and Beyond

Classifying craniofacial malformations is essential for diagnosis, treatment planning, and morphogenetic understanding. Several systems have been developed, with the Tessier classification being the most widely accepted.

Early Classification Systems:

• American Association of Cleft Palate Rehabilitation (AACPR): Divided clefts into four categories based on pathological location:

1. Mandibular process clefts
2. Naso-ocular clefts
3. Oro-ocular clefts
4. Oroaural clefts

• Boo-Chai Modification: Refined the AACPR system based on surface anatomical landmarks, including skeletal components.
• Karfik Classification: An embryologic and morphologic system with five groups, including rhinencephalic malformations and anomalies of branchial arches.
• Van der Meulen Classification: Used the term “dysplasia” and labeled defects by the developmental area involved, believing malformations occur before or during facial process fusion.

The Tessier Classification: A Standard for Craniofacial Surgeons: Introduced in 1976, Tessier's numeric classification (0 to 14) is renowned for its completeness and clinical utility. It describes clefts along predictable embryologic lines, correlating soft-tissue features with underlying bony involvement. The orbit serves as a key landmark, dividing facial clefts (0-8) from cranial clefts (9-14).

Key aspects of the Tessier classification include:

• Predictable Patterns: Clefts follow well-defined zones of the face and orbit.
• Soft-tissue and Skeletal Correlation: Links clinical observations with skeletal deformities seen on 3D CT scans and confirmed during surgery.
• Variability: Soft-tissue and skeletal components are seldom affected to the same extent. Skeletal landmarks are generally more constant.
• Combinations: Specific combinations of numeric clefts are often observed (e.g., 0 and 14, 1 and 13, 2 and 12, etc.).
• Lateral vs. Medial: Clefts 5-9 are considered lateral, passing lateral to the infraorbital foramen. Tessier cleft number 7 is the most lateral.

Median Craniofacial Dysplasias: A Closer Look at Midline Defects

Median craniofacial clefts require special consideration due to their wide spectrum of variations. These are categorized based on tissue volume:

I. Median Craniofacial Hypoplasia (Tissue Deficiency): This involves missing or underdeveloped midline facial structures, often correlating with brain abnormalities.

• Holoprosencephalic Spectrum (Alobar Brain): Severe brain malformation with midline facial hypoplasia or agenesis.
• Cyclopia: Single eye in a single orbit, arrhinia (no nose) with a proboscis above the orbit, microcephaly.
• Ethmocephaly: Severe hypotelorism (closely spaced eyes), separate orbits, arrhinia with proboscis between orbits.
• Cebocephaly: Severe hypotelorism, rudimentary proboscis-like nose.
• Primary Palate Agenesis: Missing or hypoplastic premaxillary segment and midline structures.
• Median Cerebrofacial Hypoplasia (Lobar Brain): Midline facial hypoplasia with midline cerebral malformation but separate brain lobes.
• Median Facial Hypoplasia: Midline facial hypoplasia without gross cerebral involvement.
• Microforms of Median Facial Hypoplasia: Mild deficiencies, including Binder anomaly (maxillonasal dysplasia), central maxillary incisor anomalies, and absent upper lip frenulum.

II. Median Craniofacial Dysraphia (Normal Tissue Volume but Clefted): These Tessier 0 clefts involve normal tissue volume but an abnormal split or displacement of midline structures.

• True Median Cleft: An isolated cleft of the upper lip (0 cleft) or a split between median globular processes, often extending to the palate. May include orbital hypertelorism if it encroaches the interorbital region.
• Anterior Encephalocele: Central nervous system structures herniate through a cranial defect, communicating with cerebrospinal fluid. Divided into frontoethmoidal and basal groups.

III. Median Craniofacial Hyperplasia (Tissue Excess or Duplication): This spectrum ranges from thickened nasal septum to severe frontonasal dysplasia.

• Soft-tissue midline excess: Broad philtral columns, duplicated labial frenulum, bifid nose with broad columella.
• Skeletal excess: Diastema between central incisors, duplicate nasal spine, keel-shaped maxillary alveolus, thickened nasal septum, broad nasal bones, enlarged ethmoidal and sphenoidal sinuses contributing to hypertelorism.

Specific Tessier Craniofacial Clefts: Soft Tissue and Skeletal Features

Each Tessier cleft number denotes specific anatomical involvement, providing a detailed understanding for clinicians.

Facial Clefts (Numbers 0-8)

Number 0 Cleft (Median Craniofacial Dysraphia):

• Soft tissue: Isolated median cleft lip, absence or narrowing of columella, depressed nasal tip, dental abnormalities (absent, single, or hypoplastic central maxillary incisors).
• Skeletal: Separation between upper central canines, premaxilla absence, cleft palate, hypotelorism or cyclopia (with severe brain involvement), or hypertelorism (with encephalocele).

Number 1 Cleft (Paramedian Nasal):

• Soft tissue: Notching in the soft triangle of the nose, short broad columella, nasal tip and septum deviation, potential furrows on nasal dorsum, medial canthus malposition, telecanthus.
• Skeletal: Keel-shaped maxilla, anterior open bite, alveolar cleft (rarely, between central and lateral incisors), separation at piriform aperture lateral to nasal spine, extension through nasal bone/frontal process of maxilla, ethmoidal expansion causing hypertelorism.

Number 2 Cleft (Paramedian Naso-Orbital):

• Soft tissue: Deformity in the middle third of the alar rim, hypoplastic ala, flattened lateral nose, broad dorsum, medial canthus displacement (lacrimal duct usually not involved), medial brow distortion.
• Skeletal: Between lateral incisor and canine, extends into pyriform aperture lateral to septum and medial to maxillary sinus, distorted nasal bones, ethmoidal sinus involvement leading to orbital hypertelorism, asymmetry of sphenoid wings and anterior cranial base.

Number 3 Cleft (Oronaso-Ocular):

• Soft tissue: Deficiency between alar base and lower eyelid, superiorly displaced nasal ala, inferiorly displaced medial canthus, disrupted lacrimal system, medial lower eyelid colobomas. Eye malpositioned inferiorly and laterally; globe involvement rare but microphthalmia can occur.
• Skeletal: Between lateral incisor and canine, flat anterior maxillary arch, disrupts frontal process of maxilla, terminates in lacrimal groove. Direct communication of oral, nasal, and orbital cavities. Inferiorly displaced orbital floor and anterior cranial base.

Number 4 Cleft (Oro-Ocular, Medial Maxillary):

• Soft tissue: Begins lateral to Cupid's bow, medial to oral commissure, passes lateral to nasal ala (which is intact but displaced superiorly), extends into lower eyelid lateral to inferior punctum. Medial canthus and nasolacrimal system are normal.
• Skeletal: Between lateral incisor and canine, through maxilla between infraorbital foramen and piriform aperture. Oral, maxillary sinus, and orbital cavities communicate. Terminated at medial aspect of inferior orbital rim.

Number 5 Cleft (Oculofacial Cleft II, Lateral Maxillary):

• Soft tissue: Begins medial to oral commissure, courses along cheek lateral to nasal ala, terminates in lateral half of lower eyelid. Globe typically normal; microphthalmia may occur.
• Skeletal: Alveolar cleft between premolars, lateral to infraorbital foramen, terminates in lateral aspect of orbital rim and floor. Maxillary sinus may be hypoplastic. Prolapse of orbital contents through lateral orbital floor defect.

Number 6 Cleft (Zygomaticomaxillary):

• Soft tissue: Vertical furrow from oral commissure to lateral lower eyelid due to hypoplastic soft tissue. Inferiorly displaced lateral palpebral fissure and canthus, antimongoloid slant, lateral lower eyelid colobomas.
• Skeletal: Along zygomatic-maxillary suture, hypoplastic zygoma with intact arch. No alveolar cleft, but short posterior maxilla. Choanal atresia common. Enters orbit at lateral third of orbital rim and floor, connects to inferior orbital fissure.

Number 7 Cleft (Temporozygomatic, Craniofacial Microsomia):

• Soft tissue: Most common craniofacial cleft. Varies from broad oral commissure to complete fissure extending to microtic ear. Ipsilateral tongue, soft palate, muscles of mastication underdeveloped. Parotid gland/duct absence, facial nerve weakness, external ear deformities.
• Skeletal: Through pterygomaxillary junction, centered in zygomaticotemporal suture. Hypoplastic posterior maxilla and mandibular ramus, canted occlusal plane. Hypoplastic/asymmetric coronoid process and condyle. Malformed, hypoplastic, displaced zygomatic body, disrupted zygomatic arch. Asymmetric cranial base, abnormally positioned glenoid fossa.

Number 8 Cleft (Frontozygomatic):

• Soft tissue: From lateral canthus to temporal region. Dermatocele in lateral commissure coloboma, occasional hair markers. Associated with Treacher-Collins syndrome (6, 7, 8 combination) and Goldenhar syndrome.
• Skeletal: At frontozygomatic suture. Notch in this region (Goldenhar). In Treacher-Collins, zygoma may be hypoplastic/absent, lateral orbital wall missing.

Cranial Clefts (Numbers 9-14)

Number 9 Cleft (Upper Lateral Orbit):

• Soft tissue: Rarest. Abnormalities of lateral third of upper eyelid and eyebrow. Distorted lateral canthus, microphthalmia in severe forms. Anteriorly displaced temporal hairline, temporal hair projection. Cranial nerve VII palsy common.
• Skeletal: Superolateral aspect of orbit. Distortion of upper greater wing of sphenoid, squamosal portion of temporal bone, parietal bones. Hypoplasia of greater wing of sphenoid results in posterolateral rotation of lateral orbital wall.

Number 10 Cleft (Upper Central Orbit):

• Soft tissue: Begins at middle third of upper eyelid and eyebrow. Lateral eyebrow may angulate temporally. Elongated palpebral fissure, amblyopic eye displaced inferolaterally, ablepharia (absent upper eyelid) in severe forms. Colobomas and ocular anomalies.
• Skeletal: Middle of supraorbital rim, lateral to superior orbital foramen. Often encephalocele. Deformed orbit with lateroinferior rotation, orbital hypertelorism in severe cases.

Number 11 Cleft (Upper Medial Orbit):

• Soft tissue: Involvement of medial third of upper eyelid with coloboma. Disruption of upper eyebrow extending to frontal hairline. Tongue-like projection at medial third of frontal hairline.
• Skeletal: Cleft in medial third of supraorbital rim (lateral to ethmoid bone). If through ethmoid air cells, extensive pneumatization and orbital hypertelorism.

Number 12 Cleft (Paramedian Frontal):

• Soft tissue: Medial to medial canthus, colobomas extending to root of eyebrow. Lateral displacement of medial canthus, aplasia of medial end of eyebrow. Short downward projection of paramedian frontal hairline.
• Skeletal: Through flattened frontal process of maxilla, increasing transverse dimension of ethmoid air cells, producing orbital hypertelorism and telecanthus. Frontal and sphenoid sinuses pneumatized and enlarged. Cribriform plate normal in width.

Number 13 Cleft (Paramedian Frontal, Nasal Dome):

• Soft tissue: Paramedian frontal encephalocele between nasal bone and frontal process of maxilla. Soft-tissue cleft medial to intact eyelids/eyebrows. Medial end of eyebrow displaced inferiorly. V-shaped frontal hair projection.
• Skeletal: Paramedian bony cleft traversing frontal bone, along olfactory groove. Widening of olfactory groove, cribriform plate, ethmoid sinus, resulting in hypertelorism. Paramedian frontal encephalocele can cause cribriform plate displacement inferiorly, leading to orbital dystopia.

Number 14 Cleft (Midline Forehead and Cranium):

• Soft tissue: Midline forehead and cranium. Agenesis or overabundance of tissue. Orbital hypotelorism with agenesis (e.g., holoprosencephalic disorders: cyclopia, ethmocephaly, cebocephaly). Hypertelorism with midline masses like frontonasal encephalocele.
• Skeletal: Frontal encephalocele herniates through medial frontal defect. Flattened caudal frontal bone. No frontal sinus pneumatization, extensively pneumatized sphenoid sinus. Bifid crista galli and perpendicular plate of ethmoid. Increased distance between olfactory grooves, low cribriform plate.

Number 30 Cleft (Median Lower Jaw):

• Soft tissue: Median cleft of lower lip and mandible. Vermillion notch to involvement of entire lower lip and chin. Bifid anterior tongue attached to split mandible. Atrophic neck strap muscles.
• Skeletal: Cleft between central incisors extending into mandibular symphysis. Thought to be caused by failure of fusion of the first branchial arch. Associated neck anomalies (absent hyoid, incomplete thyroid cartilages).

Treatment Approaches for Craniofacial Clefts: Surgical Management and Timing

Treatment plans for craniofacial clefts are highly individualized due to their variety and severity. However, guiding principles help determine the optimal timing and stages for corrective surgery.

General Treatment Principles:

• Early Intervention: Necessary for functional problems (e.g., ocular exposure, airway issues) or severe malformations.
• Delayed Surgery: For mild malformations.
• Infancy (3-12 months): Correction of soft-tissue clefts and midline cranial defects (like encephaloceles).
• Older Children (6-9 years): Midface and orbital reconstruction with bone grafting or facial bipartition.
• Skeletal Maturity (14+ years): Orthognathic and final soft-tissue corrective procedures.

Surgical Techniques by Cleft Group:

1. Midline and Paramedian Clefts (e.g., 0-14, 1-13, 2-12):

• Diagnosis: Proper classification into hypoplasia, dysraphia, or hyperplasia guides treatment.
• Upper Lip: Align white roll and vermillion, restore muscular continuity. Microforms may be corrected intraorally without cutaneous scar. Rotation-advancement repair for lateral clefts.
• Nose: Primary rhinoplasty in early childhood to unify bifid cartilages after excising fibrofatty tissue. Cartilage or composite skin-cartilage grafts for paramedian defects. Alar retraction corrected with local rotation or Z-plasty flaps. Secondary nasal reconstruction (septoplasty, cranial bone grafts). Correction of duplicated nasal septum reserved until nasal growth completion.
• Orbital Dystopia: Orbital box osteotomy or facial bipartition (more versatile, especially in mixed dentition). Facial bipartition involves bilateral monobloc osteotomies and anterior encephalocele reduction. Vertical adjustment of bipartition segments for vertical dystopia. Misaligned occlusal plane is usually temporary and correctable.

2. Oro-naso-ocular Clefts (e.g., 3-11, 4-10, 5-9):

• Soft Tissue: Original correction involved Z-plasty flaps to lengthen the distance between medial canthus and alar base. Modern approaches respect aesthetic units, placing scars along aesthetic lines.
• Repair: Complete cleft dissection. Small orbital floor bone graft to separate orbit from maxillary sinus. Banner flap from median nasal sidewall rotated into subciliary incision. Transnasal medial canthopexy.
• Encephaloceles: Large encephaloceles from cranial defects may require staged correction in infancy.
• Lateral Lip Clefts (4 & 5): Excision of intervening tissue between philtral column and lateral cleft.

3. Lateral Craniofacial Clefts (e.g., 6, 7, 8; Treacher-Collins, Craniofacial Microsomia):

• Oral Commissure (Cleft 7): Macrostomia correction at early age due to feeding, saliva control, and speech issues. Oral commissure corrected for symmetry (below medial canthal vertical line). Orbicularis oris muscle reoriented and interlaced at neo-commissure. Cleft closed in straight line, medial aspect with small Z-plasty along nasolabial fold.
• Lower Lip (Cleft 30): Vertical excision with bilateral extensions (not crossing labiomental fold), layered closure.
• Mandibular Reconstruction (Clefts 6, 7, 8): Costochondral grafts for severe deformities. Distraction osteogenesis for moderate deformities in mid-childhood (6-8 years).
• Maxillary Deformities: Mild occlusal cant correction can wait until adulthood with Le Fort I osteotomy.
• Periorbital Region: Urgent intervention for globe exposure (corneal ulceration risk). Early reconstructive procedures for globe protection must allow enough eye opening to prevent deprivation amblyopia.
• Eyelid: "Lid switch" transposition flaps for skin/muscle deficiencies. Palatal grafts for lower lid conjunctival lining.
• Orbit: Cranial bone grafting to restore orbital continuity and correct dystopia. Transnasal wiring for accurate medial canthus repositioning. Lateral canthopexies for symmetry.
• Lacrimal Apparatus: Silastic stents or formal dacryocystorhinostomy for canalicular system disruption.

Outcomes and Potential Complications of Craniofacial Cleft Treatment

Proper timing and technique in staged corrective procedures are crucial to minimize perioperative complications and long-term sequelae. Untreated functional issues like globe exposure can lead to corneal ulceration and blindness. Speech problems may also develop if not addressed.

Complications can arise from the challenging nature of these procedures, affecting both soft and hard tissues. Continuous advancements in surgical techniques aim to improve functional and aesthetic outcomes for individuals with craniofacial clefts.

Frequently Asked Questions about Craniofacial Clefts

What is the main difference between congenital craniofacial clefts and common cleft lip and palate?

Congenital craniofacial clefts are rarer and more complex malformations of the face and cranium, involving a wider range of tissue deficiencies, excesses, or abnormal separations. Common cleft lip and palate specifically involve the lip and/or roof of the mouth, while craniofacial clefts can affect many other facial and cranial structures along various embryologic lines, often with greater severity.

How does the neural crest cell migration relate to craniofacial cleft formation?

Neural crest cells are specialized embryonic cells crucial for forming many craniofacial structures, including bones, cartilage, muscles, and connective tissues of the face and head. Any defect in the quantity or quality of their migration can result in craniofacial malformations. If neuroectoderm migration and penetration fail, the epithelium can break down to form a facial cleft, with severity proportional to the failure of penetration.

What is the Tessier classification, and why is it important?

The Tessier classification is a comprehensive numeric system (0 to 14) for categorizing rare craniofacial clefts based on their anatomical location and involvement of both soft tissue and underlying bone. It's crucial because it provides a standardized, reproducible system for clinicians, correlating clinical observations with surgical anatomy and embryological development, which aids in diagnosis, treatment planning, and understanding the malformations.

At what age are surgical corrections typically performed for craniofacial clefts?

Surgical timing depends on the severity and functional impact of the cleft. Functional problems like ocular exposure or airway issues warrant early intervention (infancy, 3-12 months). Soft-tissue clefts and midline cranial defects (encephaloceles) are also often corrected in infancy. More extensive midface and orbital reconstructions, often involving bone grafting, are usually performed in older children (6-9 years), while final orthognathic and soft-tissue corrective procedures are typically delayed until skeletal maturity (14 years or older).

What are some examples of hereditary syndromes associated with craniofacial clefts?

Hereditary syndromes associated with craniofacial clefts include Treacher-Collins syndrome, caused by a dominant gene defect (TCOF-1), and some familial cases of Goldenhar syndrome. These syndromes demonstrate a clear genetic component in the causation of certain craniofacial clefting patterns, although most rare craniofacial clefts occur sporadically.