Cyclopia (also
cyclocephaly or
synophthalmia) is a rare form of
holoprosencephalyHoloprosencephaly 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...
and is a
congenital disorderCongenital disorder involves defects in or damage to a developing fetus. It may be the result of genetic abnormalities, the intrauterine environment, errors of morphogenesis, or a chromosomal abnormality. The outcome of the disorder will further depend on complex interactions between the pre-natal...
(birth defect) characterized by the failure of the embryonic
prosencephalonIn the anatomy of the brain of vertebrates, the prosencephalon is the rostral-most portion of the brain. The prosencephalon, the mesencephalon , and rhombencephalon are the three primary portions of the brain during early development of the central nervous system...
to properly divide the
orbitsIn anatomy, the orbital bone is the cavity or socket of the skull in which the eye and its appendages are situated.It can also mean the skin which surrounds the eye of a bird....
of the eye into two cavities. Its incidence is 1 in 16,000 in born animals, and 1 in 250 in embryos.
Typically, the face is either missing or replaced with a non-functioning nose in the form of a
proboscisIn general, a proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate..-Etymology:...
.
Cyclopia (also
cyclocephaly or
synophthalmia) is a rare form of
holoprosencephalyHoloprosencephaly 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...
and is a
congenital disorderCongenital disorder involves defects in or damage to a developing fetus. It may be the result of genetic abnormalities, the intrauterine environment, errors of morphogenesis, or a chromosomal abnormality. The outcome of the disorder will further depend on complex interactions between the pre-natal...
(birth defect) characterized by the failure of the embryonic
prosencephalonIn the anatomy of the brain of vertebrates, the prosencephalon is the rostral-most portion of the brain. The prosencephalon, the mesencephalon , and rhombencephalon are the three primary portions of the brain during early development of the central nervous system...
to properly divide the
orbitsIn anatomy, the orbital bone is the cavity or socket of the skull in which the eye and its appendages are situated.It can also mean the skin which surrounds the eye of a bird....
of the eye into two cavities. Its incidence is 1 in 16,000 in born animals, and 1 in 250 in embryos.
Presentation
Typically, the face is either missing or replaced with a non-functioning nose in the form of a
proboscisIn general, a proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate..-Etymology:...
. Such a boscis generally appears above the central eye, or on the back, and is characteristic of a form of cyclopia called
rhinencephaly or
rhinocephaly.
Although cyclopia is very rare, several cyclopic human babies are preserved in medical museums (e.g. The Vrolik Museum, Amsterdam). There are also two known cases of children with
Down SyndromeDown syndrome , Down's syndrome , trisomy 21, or trisomy G is a chromosomal disorder caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British doctor who described the syndrome in 1866...
being born with one eye.
Some extreme cases of cyclopia have been documented in inbred farm animals (horses, sheep, pigs, and sometimes chickens). In such cases, the nose and mouth fail to form, or the nose grows from the roof of the mouth obstructing airflow, resulting in suffocation shortly after birth.
Causes
Genetic problems or toxins can cause problems in the embryonic forebrain-dividing process.
One highly teratogenic alkaloid toxin that can cause cyclopia is
cyclopamineCyclopamine is a naturally-occurring chemical that belongs to the group of steroidal jerveratrum alkaloids. It is a teratogen isolated from the corn lily that can lead to cyclopia ....
or 2-deoxyjervine, found in the plant
Veratrum californicumVeratrum californicum is a poisonous plant native to mountain meadows in southwestern North America and the Rocky Mountains...
(also known as
corn lily or
vetch weed). The mistake of ingesting
Veratrum californicum while pregnant is often due to the fact that
helleboreCommonly known as hellebores, members of the genus Helleborus comprise approximately 20 species of herbaceous perennial flowering plants in the family Ranunculaceae, within which it gave its name to the tribe of Helleboreae...
, a plant with which it is easily confused, is recommended as a natural treatment for
vomitingVomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Undesired vomiting may result from many causes, ranging from gastritis or poisoning to brain tumors, or elevated intracranial pressure...
,
crampFor the heraldic device, see cramp ; for the band, see The CrampsCramps are unpleasant, often painful sensations caused by contraction or over-shortening of muscles...
s, and poor circulation, three conditions that are quite common in
pregnantPregnancy is the carrying of one or more offspring, known as a fetus or embryo, inside the uterus of a female. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets. Human pregnancy is the most studied of all mammalian pregnancies. Obstetrics is the surgical field...
women. Cyclopia occurs in the womb when the protein is inhibited and causes the brain to stay a whole instead of having two distinct hemispheres, which also means one optic lobe and one olfactory lobe resulting in one eye.
Notable cases
An old description of a colt apparently suffering from cyclopia reads:
First, That it had no sign of any Nose in the usual place, nor had it any, in any other place of the Head, unless the double Bagg CC that grew out of the midst of the forehead, were some rudiment of it.
Next, That the two Eyes were united into one Double Eye which was placed just in the middle of the Brow.
On December 28, 2005, a kitten with cyclopia, "Cy", was born in the
RedmondThe City of Redmond Oregon, incorporated on July 6, 1910, is located on the eastern side of Oregon's Cascade Range and is considered the geographical heart of Central Oregon, within easy access to a multitude of recreational opportunities including mountain biking, fishing, hiking, camping, rock...
,
OregonOregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
,
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
and died about one day after birth.
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