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Aicardi syndrome is also known as agenesis of the corpus callosum with chorioretinitis abnormality, agenesis of the corpus callosum with infantile spasms and ocular anomalies, callosal agenesis, and ocular abnormalities, chorioretinal anomalies with ACC, corpus callosum, agenesis of chorioretinal abnormality is an extremely rare genetic disorder. People with Aicardi syndrome have absent or underdeveloped tissue connecting the left and right halves of the brain (agenesis or dysgenesis of the corpus callosum). Almost all people with Aicardi syndrome are females. Individuals with Aicardi syndrome have agenesis of the corpus callosum, chorioretinal lacunae, and seizures. Agenesis of the corpus callosum means that the structure that connects the right half of the brain with the left half of the brain (corpus callosum) does not develop normally. Chorioretinal lacunae are small holes in the retina (back part of the eye). These are only visible to a doctor using a device to look into the back of the eye. It is very unusual (maybe impossible) to have Aicardi syndrome without having chorioretinal lacunae. The seizures can be of different types. Infants with Aicardi syndrome usually have a type of seizure known as “infantile spasms”. These are single jerks of the whole body. They may happen many times a day. Infants are usually awake during infantile spasms. These look different from the more common type of seizures known as “generalized tonic-clonic” seizures. Generalized tonic-clonic seizures are rhythmic jerking of arms and legs. People often blackout during this type of seizure. Children with Aicardi syndrome usually grow out of infantile spasms and then have generalized tonic-clonic or other types of seizures. Other parts of the brain also do not develop normally. These brain malformations cause frequent seizures and intellectual disability.
Causes
Aicardi syndrome is likely caused by a new mutation in a gene located on the X chromosome. The gene that causes Aicardi syndrome is not known. A report describing changes in the genes TEAD1 and OCEL1 in two girls with Aicardi was not confirmed in a large cohort of other girls with Aicardi syndrome. Thus these genes do not seem to be the cause of Aicardi syndrome. This condition is presumed to be lethal in males.
The parents of a female with Aicardi syndrome are typically unaffected. Transmission of Aicardi syndrome from an affected mother to her child has not been reported. Other family members are also not usually at increased risk.
The cause of Aicardi syndrome is unknown. Because it occurs almost exclusively in females, researchers believe that it is probably the result of a mutation in a gene on the X chromosome. People normally have 46 chromosomes in each cell. Two of the 46 chromosomes, known as X and Y, are called sex chromosomes because they help determine whether a person will develop male or female sex characteristics. Genes on these chromosomes are also involved in other functions in the body. Females typically have two X chromosomes (46, XX), and males have one X chromosome and one Y chromosome (46, XY).
Early in embryonic development in females, one of the two X chromosomes is permanently inactivated in somatic cells (cells other than egg and sperm cells). X-inactivation ensures that females, like males, have only one active copy of the X chromosome in each body cell. Usually, X-inactivation occurs randomly so that each X chromosome is active in about half the body’s cells. Sometimes X-inactivation is not random, and one X chromosome is active in more than half of the cells. When X-inactivation does not occur randomly, it is called skewed X-inactivation.
Skewed X-inactivation sometimes occurs when there is a severe gene mutation in one of the X chromosomes in each cell. Because the cells where this chromosome is active will not be able to survive as well, X-inactivation will appear to be skewed. Skewed X-inactivation has been identified in girls with Aicardi syndrome, further supporting the idea that the disorder is caused by a mutation in a gene on the X chromosome. However, this gene has not been identified, and it is unknown how the genetic change that causes Aicardi syndrome results in the various signs and symptoms of this disorder.
Diagnosis
It is usual to have an MRI of the brain. This study makes pictures of the brain to look for a small or missing corpus callosum and other problems with the formation of the brain. Individuals with Aicardi syndrome should have a test to look at the brain waves (EEG) to diagnose and treat seizures. An ophthalmologist should look into the eyes at the retina. In Aicardi syndrome, this almost always reveals small cream-colored cavities (lacunae) within the retina.
- Partial or complete absence of the corpus callosum in the brain (agenesis of the corpus callosum);
- Eye abnormalities are known as “lacunae” of the retina that are quite specific to this disorder; optic nerve coloboma; and
- The development in the infancy of seizures that are called infantile spasms.
Other types of defects of the brain such as microcephaly, polymicrogyria, porencephalic cysts, and enlarged cerebral ventricles due to hydrocephalus are also common in Aicardi syndrome
Tests that confirm the diagnosis after a child is born include:
- MRI of the brain to check for abnormalities in the corpus callosum or other brain structures.
- EEG to assess brainwaves and confirm an epilepsy diagnosis, including which type.
- An eye exam from a pediatric ophthalmologist to check for coloboma and choroidal lacunae.
Treatment
Medications may be used to suppress the seizures caused by Aicardi syndrome. The seizures are often hard to treat. The doctor may need to try a number of medicines to see which medication works best. Studies have shown that there is no one medicine that works for everyone with Aicardi syndrome.
Treatment of Aicardi syndrome primarily involves the management of seizures and early/continuing intervention programs for developmental delays. Additional comorbidities and complications were sometimes seen with Aicardi syndrome including porencephalic cysts and hydrocephalus, and gastrointestinal problems. Treatment for porencephalic cysts and/or hydrocephalus is often via a shunt or endoscopic fenestration of the cysts, though some require no treatment. Placement of a feeding tube, fundoplication, and surgeries to correct hernias or other gastrointestinal structural problems are sometimes used to treat gastrointestinal issues
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