Congenital malformations - Edocr

102 PART III CRANIOFACIAL MALFORMATIONS
defects (most commonly hypoplastic or absent
thumbs and radial bones).
DIAGNOSIS AND EVALUATION
Identification of micrognathia in an infant requires
a careful examination for additional craniofacial
abnormalities and other congenital anomalies.
The presence or absence of other craniofacial
features and/or cleft palate can be helpful in
suggesting the most likely associated disorders
and directing further evaluation as illustrated in
Fig. 14-2. In cases of some suspected syndromes
(e.g., 22q11 deletion), confirmation by genetic
testing may be possible. However, diagnosis of
many disorders associated with micrognathia
can only be made on a clinical basis.
MANAGEMENT AND PROGNOSIS
Figure 14-1. Infant with micrognathia.
(Reprinted from Denny A and Christian A. New
techniques for airway correction in neonates
with severe Pierre Robin sequence. J Pediatr.
147:97–101. Copyright 2005, with permission
from Elsevier.)
(TCS) (mandibulofacial dysostosis) and Robin
sequence (see Chap. 13). Mandibular hypoplasia
is also frequently observed in infants with
chromosome abnormalities. TCS is a craniofacial
disorder characterized by hypoplasia of the zygomatic
bones and mandible, external ear abnormalities
(absent, small, malformed), coloboma of the
lower eyelid, absence of lower eyelashes, cleft
palate, and conductive hearing loss. TCS is inherited
in an autosomal dominant manner. More
than 90% of affected individuals have mutations
in the TCOF1 gene, which is the only gene currently
known to be associated with TCS. Approximately
60% of individuals have the disorder
as a result of a new (de novo) mutation in
this gene.
Nager syndrome is an autosomal recessive
disorder with craniofacial features similar to TCS
and, in addition, is also associated with limb
The degree of mandibular hypoplasia is quite
variable and, when severe can lead to significant
functional issues at birth. The majority of infants
born with micrognathia are either asymptomatic
or can be treated conservatively by prone positioning
with anticipation of catch-up mandibular
growth. 4 With severe mandibular hypoplasia,
obstruction at the hypopharynx occurs because
of the retroposition of the base of the tongue
into the posterior pharyngeal airway. This may
cause severe respiratory obstruction with frequent
hypoxic events and resultant poor feeding.
These infants may require more immediate
and aggressive intervention, including endotracheal
intubation.
Until recently, tracheostomy has traditionally
been the most common treatment option for infants
with severe upper airway obstruction. A new
advancement in the treatment of children with
congenital mandibular hypoplasia and significant
upper airway obstruction is mandibular distraction
osteogenesis. Distraction osteogenesis is
a surgical procedure which involves lengthening
of the jaw through new bone growth made
across a bony cut (osteotomy). The objective of
mandibular distraction osteogenesis is to advance
the tongue base anteriorly via its muscular
attachments to the distracted mandible, thus