Home Dentistry Articles Crouzon syndrome
Crouzon Syndrome is a type of genetic disorder
known as a branchial arch syndrome. Specifically, this syndrome
affects the first branchial (or pharyngeal) arch, which is the
precursor of the maxilla and mandible. Since the branchial arches
are important developmental features in a growing embryo, disturbances
in its development create lasting and widespread effects.
Ocatve Crouzon, a French physician, first
described this disorder while also noting the affected patients
were a mother and her daughter. Thus, a genetic basis was implied.
First known as Craniofacial Dysostosis, the disorder was characterized
by a number of clinical features, which to this date has no
known single, initiating defect to account for all of its characteristics.
Breaking down the name, "craniofacial"
refers to the skull and face, and "dysostosis" refers
to synostosis (a union between adjacent bones or parts of a
Known now as Crouzon Syndrome, the disease
can be described by the rudimentary meanings of its former name.
What occurs in the disease is that an infant's skull and facial
bones, while in development, fuse early or are unable to expand.
Thus, normal bone growth cannot occur. Fusion of different sutures
lead to different patterns of growth of the skull. Examples
include: trigonocephaly (fusion of the metopic suture), brachycephaly
(fusion of the metopic suture), dolichocephaly (fusion of the
sagittal suture), plagiocephaly (fusion of coronal and lambdoidal
sutures), oxycephaly (fusion of most sutures).
As stated previously, there is evidence for
a genetic basis to this disorder, but there is also no known
series of events leading to all the manifestations present.
Instead, it is more accurate to view the symptoms arising independently
from one another.
As in many syndromes, aberrations in chromosomes
seem to be responsible in some cases, and in particular there
is support that this disorder may propagate in an Autosomal
Dominant mode. Evidence shown is that males and females are
affected equally and affected offspring tend to have an affected
parent. Furthermore, some researchers point to the long arm
of chromosome 10 as a possible location for a genetic abnormality.
On the other hand, 20-40% of people with this
disorder have no family history of this disorder, meaning that
there is little likelihood of a familial inheritance in those
cases. Thus, it is believed that a cause may be a fresh mutation,
or, alternatively, an environmental disruption of the developing
embryo which results in the same physical characteristics as
the genetically-derived disorder. In other words, though genetic
anomalies may be leading to a disruption of embryogenesis, facts
suggest an important role of environmental factors.
As a result of the changes to the developing
embryo, the symptoms are very pronounced features, especially
in the facial areas. Low-set ears is a typical characteristic,
as in all of the disorders which are called branchial arch syndromes.
The reason for this abnormality is that ears in fetal life are
much lower than those on an adult. During normal development,
the ears "travel" upward on the head but, in these
cases, do not follow this normal pattern of development since
these syndromes have the greatest effects on the head.
The most notable characteristic of Crouzon
Syndrome is cranial synostosis, as described above, but it usually
presents as brachycephaly which results in the appearance of
a short and broad head. Exophthalmos (bulging eyes due to shallow
eye sockets after early fusion of surrounding bones), hypertelorism
(greater than normal distance between the eyes), and psittichorhina
(beak-like nose) are also symptoms. Additionally, a common occurrence
is external strabismus, which can be thought of as opposite
from the eye position found in Down Syndrome. Lastly, hypoplastic
maxilla (insufficient growth of the midface) results in relative
Mandibular prognathism (chin appears to protrude despite normal
growth of mandible) and gives the effect of the patient having
a concave face.
Diagnosis of Crouzon Syndrome usually can
occur at birth by assessing the signs and symptoms of the baby.
Further analysis, including radiographs, magnetic resonance
imaging (MRI) scans, and genetic testing, can be used to confirm
Who is Affected
Incidence of most diseases depends on time
and place, but Crouzon Syndrome is estimated currently to occur
1 out of every 25,000 people in the general population. Naturally,
there is a greater frequency in families with a history of the
disorder, but that does not mean that everyone in the family
is afflicted (as referred to above).
Surgery is typically used to prevent the closure
of sutures of the skull from damaging the brain's development.
Without surgery, blindness and mental retardation is a typical
outcome. To treat the cosmetic troubles, a combination of orthodontic
and orthognathic surgery can be used to relieve some of the
For dentists, this disorder is very important
to understand since most of the physical abnormalities are presented
in the head, and particularly the oral cavity. Common features
are a narrow/high-arched palate, posterior lingual crossbite,
hypodontia (missing some teeth), and increased spacing between