Aicardi syndrome

Aicardi syndrome is an uncommon malformation syndrome characterized by absence of a key structure in the brain called the corpus callosum, the presence of retinal abnormalities, and seizures in the form of infantile spasms. Aicardi syndrome is inherited as an X-linked dominant trait that is lethal in males.

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History

This disorder was first recognized as a distinct syndrome in 1965 by Jean Aicardi, a French neurologist. A review article by Dr. Aicardi (Aicardi J, Aicardi syndrome: old and new findings, Int Pediatr. 1998;14(1):5-8) describes the syndrome. Aicardi syndrome should not be confused with Aicardi-Goutières syndrome, a distinct disorder.

Epidemiology

Around 500 cases of Aicardi syndrome have been reported worldwide. Except that the syndrome is fairly uncommon, its precise frequency in the population is unknown.

Genetics

Almost all reported cases of Aicardi syndrome have been in females. The few males that have been identified with Aicardi syndrome have proved to have 47 chromosomes including an XXY sex chromosome complement, a condition called Klinefelter syndrome.

Aicardi syndrome appears to be lethal in normal males who have only one X chromosome (and a Y chromosome). In other words, Aicardi syndrome appears to be inherited in an X-linked dominant pattern due to a mutant gene on the X chromosome that is lethal in XY males.

All cases of Aicardi syndrome are thought to be due to new mutations. No person with Aicardi syndrome is known to have transmited the X-linked gene responsible for the syndrome to the next generation.

Features

Children are most commonly identified with Aicardi syndrome between the ages of three and five months. A significant number of these girls are products of normal births and seem to be developing normally until around the age of three months, when they begin to have infantile spasms. The onset of infantile spasms at this age is due to closure of the final neural synapses in the brain, a stage of normal brain development.

Diagnosis

Aicardi syndrome is characterized by the following triad of features:

1. Partial or complete absence of the corpus callosum in the brain (agenesis of the corpus callosum);
2. Eye abnormalities known as "lacunae" of the retina that are quite specific to this disorder; and
3. The development in infancy of seizures that are called infantile spasms.

Other types of defects of the brain such as microcephaly, porencephalic cysts and enlarged cerebral ventricles due to hydrocephalus are also more common in Aicardi syndrome.

Treatment

Treatment of Aicardi syndrome primarily involves management of seizures and early/continuing intervention programs for developmental delays.

Additional complications sometimes seen with Aicardi syndrome include porencephalic cysts and hydrocephalus, and gastro-intestinal problems. Treatment for prencephalic 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 gastro-intestinal issues.

Prognosis

The prognosis varies widely from case to case. However, all individuals reported with Aicardi syndrome to date have experienced developmental delay of a significant degree, typically resulting in moderate to profound mental retardation. The age range of the individuals reported with Aicardi syndrome is from birth to the mid 40’s.

References

GeneReviews: Aicardi Syndrome
Phenotype and Management of Aicardi Syndrome: New Findings from a Survey of 69 Children
Neurology India: Aicardi syndrome: A report of five Indian cases
Aicardi Syndrome: Old and New Findings

Current Research

• UCSF Brain Development Research Program
  
• Baylor Department of Molecular and Human Genetics