Ethmocephaly
Encyclopedia
Ethmocephaly is a type of cephalic disorder
caused by holoprosencephaly
. Ethmocephaly is the least common facial anomaly. It consists of a proboscis separating narrow-set eyes with an absent nose and microphthalmia
(abnormal smallness of one or both eyes). Cebocephaly, another facial anomaly, is characterized by a small, flattened nose with a single nostril
situated below incomplete or underdeveloped closely set eyes.
The least severe in the spectrum of facial anomalies is the median cleft lip, also called premaxillary agenesis.
Although the causes of most cases of holoprosencephaly remain unknown, some may be due to dominant or chromosome
causes. Such chromosomal anomalies as trisomy 13 and trisomy 18 have been found in association with holoprosencephaly, or other neural tube defects
. Genetic counseling
and genetic testing
, such as amniocentesis
, is usually offered during a pregnancy if holoprosencephaly is detected. The recurrence risk depends on the underlying cause. If no cause is identified and the fetal chromosomes are normal, the chance to have another pregnancy affected with holoprosencephaly is about 6%.
There is no treatment for holoprosencephaly and the prognosis for individuals with the disorder is poor. Most of those who survive show no significant developmental gains. For children who survive, treatment is symptomatic. It is possible that improved management of diabetic pregnancies may help prevent holoprosencephaly, however there is no means of primary prevention.
Cephalic disorder
Cephalic disorders are congenital conditions that stem from damage to, or abnormal development of, the budding nervous system...
caused by holoprosencephaly
Holoprosencephaly
Holoprosencephaly is a cephalic disorder in which the prosencephalon fails to develop into two hemispheres. Normally, the forebrain is formed and the face begins to develop in the fifth and sixth weeks of human pregnancy...
. Ethmocephaly is the least common facial anomaly. It consists of a proboscis separating narrow-set eyes with an absent nose and microphthalmia
Microphthalmia
Microphthalmia also referred to as microphthalmos, nanophthalmia or nanophthalmos, is a developmental disorder of the eye that literally means small eye...
(abnormal smallness of one or both eyes). Cebocephaly, another facial anomaly, is characterized by a small, flattened nose with a single nostril
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
situated below incomplete or underdeveloped closely set eyes.
The least severe in the spectrum of facial anomalies is the median cleft lip, also called premaxillary agenesis.
Although the causes of most cases of holoprosencephaly remain unknown, some may be due to dominant or chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
causes. Such chromosomal anomalies as trisomy 13 and trisomy 18 have been found in association with holoprosencephaly, or other neural tube defects
Neural tube defects
Neural tube defects are one of the most common birth defects, occurring in approximately one in 1,000 live births in the United States. An NTD is an opening in the spinal cord or brain that occurs very early in human development. In the 2nd week of pregnancy called gastrulation, specialized cells...
. Genetic counseling
Genetic counseling
Genetic counseling or traveling is the process by which patients or relatives, at risk of an inherited disorder, are advised of the consequences and nature of the disorder, the probability of developing or transmitting it, and the options open to them in management and family planning...
and genetic testing
Genetic testing
Genetic testing is among the newest and most sophisticated of techniques used to test for genetic disorders which involves direct examination of the DNA molecule itself. Other genetic tests include biochemical tests for such gene products as enzymes and other proteins and for microscopic...
, such as amniocentesis
Amniocentesis
Amniocentesis is a medical procedure used in prenatal diagnosis of chromosomal abnormalities and fetal infections, in which a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amnion or amniotic sac surrounding a developing fetus, and the fetal DNA is examined for...
, is usually offered during a pregnancy if holoprosencephaly is detected. The recurrence risk depends on the underlying cause. If no cause is identified and the fetal chromosomes are normal, the chance to have another pregnancy affected with holoprosencephaly is about 6%.
There is no treatment for holoprosencephaly and the prognosis for individuals with the disorder is poor. Most of those who survive show no significant developmental gains. For children who survive, treatment is symptomatic. It is possible that improved management of diabetic pregnancies may help prevent holoprosencephaly, however there is no means of primary prevention.