Atypical Facial Clefts



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Atypical Facial Clefts



  • Incidence uncertain ~ 1-5:100,000 live births. Varies with definitions and awareness.

  • Range 10 – 34 per 1000 “common” clefts (Recall cleft lip ~ 1/1000 live Caucasian births)

  • Heterogeneous group aetiologically and pathogenetically

  • Limited influence of genetics (exception is Treacher Collins syndrome if considered as atypical cleft)

  • may occur unilaterally or bilaterally, and multiple Tessier clefts may be seen in a single patient.

  • Tissues around the cleft margins are hypopolastic


Aetiology

  1. Radiation

    1. Large doses of radiation have been associated with microcephaly.

  2. Infections

    1. The children of mothers with influenza, toxoplasmosis, rubella, or cytomegalovirus infections exhibit increased frequencies of facial clefts.

  3. Maternal disease.

    1. Mothers of children with cleft lips and palates have been noted to exhibit a higher-than-normal incidence of phenylketonuria, and the FAVS spectrum has been observed with unusual frequency among infants with diabetic mothers.

  4. Drugs

    1. Vitamin deficiencies are associated with increased incidences of cleft lips and palates, which may be reduced with vitamin supplementation diets for the mothers.

    2. Vitamin A, its derivatives, and related compounds such as isotretinoin have been implicated in the development of facial clefting and hemifacial microsomia.

    3. anticonvulsants

    4. Maternal smoking has been demonstrated to be associated with craniosynostosis



Morphogenesis


  • grooves between these facial prominences usually disappear by day 46 or 47 of gestation, as the processes meet their equivalents from the contralateral side and fuse in the midline.

  • Any persisting groove between meeting or adjoining processes results in a congenital facial cleft.

  • Two main theories:

  1. Fusion theory (Dursy (1869) and His (1892))

    1. Clefts form due to failure of fusion of normally merging facial processes.

  2. mesodermal penetration theory (Veau, Pohlmann)

    1. Contends that free ends of processes do not exist but that the fetal face consists of a continuous bilaminar ectodermal membrane with processes marking epithelial seams.

    2. Into this bilaminar structure migrates mesenchyme to smooth out the seams followed by merger of facial processes.

    3. Clefting is due to failure of mesenchymal migration.

Other theories to explain rarer clefts

  1. Neural crest migration (Johnston & Weston)

    1. propose that the primary defect is in neural crest cell migration.

    2. Incomplete/insufficient migration or abnormal differentiation of neural crest cells.

    3. Observations based on non-mammalian vertebrate embryos.

  2. Failure of differentiation (Vermiej-Keers et al;)

    1. Propose that neural crest cells do not migrate but exist as developmental rests

    2. Facial clefts develop due to failure of differentiation of neurectoderm and mesenchyme

    3. shown not to be the case as cell labeling clearly shows migration

  3. Deficiencies of the anterior neural plate

    1. early in development when the brain and facial form are intimately connected leads to a series of malformations termed holoprosencephaly. The result is failure of separation of cerebral hemispheres and associated facial dysmorphisms.

  4. Arrest of frontonasal process

    1. Occurs in low embryonic position with failure of forward growth of the nasal septum results in orbital hypertelorism



Classification

Committee on Nomenclature and Classification of Craniofacial Anomalies of the American Cleft Palate Association

Type

I Clefts (Tessier classification)

II Synostoses

III Atrophy/hypoplasia

IV Neoplasia/hyperplasia

V Unclassified

Median Facial Anomalies

1. Tissue-Deficient Median Cerebrofacial Dysmorphogenesis

Holoprosencephaly


  • Failure of cleavage of prosencephalon (primitive forebrain) sagittally into cerebral hemispheres, axially into telencephalon and diencephalon or coronally into olfactory and optic bulbs.

  • 1 in 16,000 live births, 1 in 200 spontaneous abortions

  • etiologically heterogeneous entity – there are teratogenic causes, maternal diabetes being the most significant, giving a 200-fold increased risk

  • Facial morphology represents a hypoplastic Tessier no. 14 cleft in association with a tissue deficiency or a tissue excess

  • Graded in severity :

  1. Alobar HPE, the most severe, in which there is a single ventricle and no separation of the cerebral hemispheres

  2. Semilobar HPE, in which the left and right frontal and parietal lobes are fused and the interhemispheric fissure is only present posteriorly

  3. Lobar HPE, the mildest, in which most of the right and left cerebral hemispheres and lateral ventricles are separated but the most rostral aspect of the telencephalon, the frontal lobes, are fused, especially ventrally

  • Degree of facial disorganisation usually reflects an equally severe anomaly of the brain.

Subtype of HPE

Facial Findings

Alobar HPE

  • Cyclopia: single eye or partially divided eye in single orbit with a proboscis above the eye

  • Cyclopia without proboscis

  • Ethmocephaly: extreme ocular hypotelorism but separate orbits with proboscis between the eyes

  • Cebocephaly: ocular hypotelorism with single-nostril nose

  • Premaxillary agenesis with median cleft lip, ocular hypotelorism, flat nose

  • Bilateral cleft lip

  • Ocular hypotelorism only

  • Anophthalmia or microophthalmia

  • Relatively normal facial appearance

Semilobar
HPE

  • Bilateral cleft lip with median process representing the philtrum-premaxilla anlage

  • Flat nasal bridge

  • Absent nasal septum

  • Flat nasal tip

  • Midline cleft (lip and/or palate)

  • Ocular hypotelorism

  • Flat nose

  • Anophthalmia/microophthalmia

  • Relatively normal facial appearance

Lobar HPE

  • Bilateral cleft lip with median process

  • Ocular hypotelorism

  • Flat nose

  • Relatively normal facial appearance

MIHF

  • Relatively normal facial appearance

Modified from DeMyer et al 1963


I Cyclopia.

II Ethmocephaly.

III Cebocephaly.

IV Hypoteleorbitism with median cleft lip.



V Hypoteleorbitism with bilateral cleft lip.


  • Types I to III usually have an alobar brain and rarely survive twelve months and are not candidates for reconstruction.

  • Types IV and V may be candidates for reconstruction depending on their brain morphology.

  • Since there are a spectrum of midfacial hypoplasia and false median clefts with relatively normal brain morphology, types IV and V may be further classified based on prognostic and functional criteria. Here, type IV represents alobar or semilobar holoprosencephaly, type V lobar holoprosencephaly and type VI is added to include the facial dysmorphic features with normal brain development. Here, types V and Vi may be candidates for reconstruction.


2. Tissue Excess and Near-Normal Median Cerebrofacial Dysmorphogenesis

Median cleft face syndrome (Frontonasal dysplasia)

  • most likely occurs during the early induction of the forebrain, resulting in anomalies involving frontonasal process, midfacial structures as well as the primordium of the eyes.

Features

  1. Orbital hypertelorism

  2. V-shaped frontal hairline

  3. broad flat nose, lack of nasal tip

  4. Bifid cranium

  5. Median cleft of upper lip

  6. Median cleft of premaxilla

  7. Median cleft of the palate

  8. Primary telecanthus

  • Spectrum of dysmorphic features ranging from subtle notch in upper lip to severe hyperteleorbitism.

  • Little predictive value between degree of facial dysmorphism and brain development although the likelihood of mental impairment increases with severe hyperteleorbitism.

(left) frontonasal malformation in a 4-year-old girl. Note the symmetrical second-degree interorbital hypertelorism, prominent widow's peak, and broad bifid nasal tip. She had resection of a nasal dermoid that extended intracranially.( center) frontonasal malformation (minor) with bipartate nasal tip and second-degree interorbital hypertelorism.( right) frontonasal malformation (major) in a 3-month-old girl. Note the symmetrical third-degree orbital hypertelorism, disjoined nares, median cleft lip/palate, and basal encephalocele.




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