Cyclopia is a rare malformation due to the incomplete division of the prosencephalon (forebrain) into the left and right hemispheres during fetal development. The condition is also called cycloprocephaly or alobar holoprosencephaly. The division or cleavage of the forebrain may occur between 18 and 28 days of gestation. Thus, cyclopia could be detected during prenatal ultrasound.
Nearly 1.05 in 100,000 births (including stillbirths) are identified as infants with cyclopia (1). Proboscis (tube-like structure projecting from the forehead) above the eye and single median eye or partially divided eye in a single orbit is a characteristic clinical feature of this condition. Cyclopia is the severest facial dysmorphism or malformation of holoprosencephaly syndrome.
Read this post to know the causes, risk factors, clinical features, diagnosis, and prognosis of cyclopia in babies.
Causes Of Cyclopia In Babies
The exact cause of cyclopia is unknown. Mutations in various genes involved in the central nervous system (CNS) development may cause it (1). Sonic Hedgehog protein, a key signaling molecule involved in embryonic development, is often found to be mutated in some cases of cyclopia and other types of holoprosencephaly. However, many cases may not have an obvious cause.
Risk Factors For Cyclopia
Although the cause is unknown, possible risk factors for cyclopia and other types of holoprosencephaly are identified. The following fetal factors may increase the risk of cyclopia in babies (2).
- Patau syndrome or trisomy 13 is a chromosomal anomaly often associated with cyclopia. In this condition, extra genetic material on chromosome 13 disrupts normal organ development.
- Smith-Lemli-Opitz syndrome (SLOS) is characterized by slow growth before and after birth. It may cause multiple malformation syndromes, including facial malformations and microcephaly.
- Female gender of the baby.
The following maternal factors may also contribute to the development of cyclopia.
- Multiple pregnancies, especially with twins
- Gestational diabetes
- Previous unexplained pregnancy loss (miscarriages)
- Alcohol consumption
- TORCH infections and other trans-placental infections
- Nicotine exposure (cigarette smoking)
- Lithium exposure
- Anticonvulsant use during pregnancy
- Retinoic acid exposure during pregnancy
- Certain birth control pills to a lesser extent
- Exposure to cyclopamine, a toxin found in plants, such as corn lily, believed to cure morning sickness during pregnancy
Not all babies exposed to these factors develop cyclopia. Some may be born with other health issues or born perfectly healthy. However, it is always recommended to minimize risk by avoiding exposure to these factors.
Associated Features In Cyclopia
The following features are seen in babies born with cyclopia (1).
- Microcephaly (small head) due to an underdeveloped brain
- Absence of nose
- The single central eye is seen in true cyclopia (one-eyed baby)
- Synophthalmia is where two eyes are fused and forms a single eye in the middle of the forehead
- Proboscis (elongated appendage on the head) above the eye
- The underdeveloped mouth may appear as soft tissues with an opening
- Micrognathia is a very small lower jaw
Renal (kidney) dysplasia, polydactyly (extra fingers or toes), and omphalocele (protruding abdominal organs outside the abdominal wall) are common extracranial malformations seen in cyclopia.
Diagnosis Of Cyclopia
Cyclopia can be diagnosed during prenatal ultrasound. Prenatal scans at 11 and 13 weeks of gestation can enable early detection of cyclopia. The following features on ultrasound images indicate the condition.
- Lack of the third brain ventricle
- Severe facial deformities
- Absence or hypoplasia (underdeveloped) of certain parts of the brain, such as corpus callosum and fissures
- Changes in the arrangement of cerebral arteries
Chromosomal analysis is often done after birth since the information can be useful for parents’ genetic counseling.
Life Expectancy In The Case Of Cyclopia
Cyclopia is the most severe form of alobar holoprosencephaly. The prognosis is grave since it is not a condition compatible with life (3). Death may occur in the uterus or within a few hours after birth.
The maximum recorded lifespan of a baby with cyclopia is one day. Therefore, if cyclopia is present, doctors may suggest termination of pregnancy in the early weeks of gestation, depending on the country’s legislation.
Currently, there is no way to prevent or cure cyclopia. Avoiding risk factors may reduce the risk in some cases. You may seek support from family, friends, and professionals to know more about the condition while making decisions. Genetic counseling is often recommended in some countries where termination of pregnancy is allowed due to abnormalities. Do not hesitate to seek psychological help and support while coping with your loss.
2. Cyclopia; American Academy of Ophthalmology
3. Cyclopia; Radiopaedia