What Is Aicardi Syndrome?

Aicardi syndrome is a rare genetic disorder characterized by a partial or complete absence of the corpus callosum, a key brain structure. This syndrome also causes abnormalities in the retina of the eyes and seizures.  

Researchers think Aicardi syndrome is caused by an X chromosome gene mutation. Symptoms of this condition may appear as early as 4 months of age.

Aicardi syndrome is named after Jean Aicardi, a French neurologist who first described the condition in 1965. Keep reading to learn more about Aicardi syndrome, its prevalence, symptoms, causes, and treatment options.

Prevalence 

Aicardi syndrome is very rare, affecting one out of 105,000 to 167,000 newborns in the United States. Researchers believe there are about 4,000 cases worldwide.

This condition primarily affects newborn females. Aicardi syndrome can also affect newborn males who have an extra X chromosome.

Aicardi Syndrome Symptoms

Infantile seizures (a seizure disorder in babies) are the earliest signs of Aicardi syndrome. These are involuntary spasms that involve single jerks of the entire body. These seizures appear before 3 months of age and can occur up to several times a day.

According to a 2015 study in the journal Pediatric Neurology, these seizures can improve with age. In this study, researchers sought to identify Aicardi syndrome in Norway by examining patients and reviewing their medical records.

Six females between the ages of 7 and 27 were diagnosed with the condition, and only one of the six had not experienced epileptic seizures. The others had also experienced infantile spasms. All had signs of hypsarrhythmia (abnormal, chaotic brain waves), the most common electroencephalography (EEG) pattern of infantile spasms.

Two of the females had suppression bursts—abnormal spikes and waves with alternating periods of flatness shown on EEGs. Three had periods of suppression. Four out of the five females who had a seizure disorder showed improvement with time.

Additional symptoms of Aicardi syndrome include:

• Intellectual disability
• Delays in motor development, physical growth, bone and muscle strength, movement, and touch
• Microcephaly (an abnormally small head)
• Microphthalmia (abnormally developed or small eyes)
• Muscle weakness
• Abnormal rib or spine development (scoliosis)
• Small hands and hand malformations
• Vision impairment, including blindness, resulting from what is called central chorioretinal lacunae (lesions in the pigmented layer of the eye's retina)
• Gastrointestinal symptoms, including constipation, diarrhea, and gastroesophageal reflux disease (GERD)
• Feeding problems
• Unusual facial features, including a short area between the upper lip and nose, a flat nose with an upturned lip, large ears, and thin eyebrows

Aicardi syndrome was once considered to require the three components of failed development of the corpus callosum, abnormal retinas in the eye, and seizures. However, newer research shows that not all female children who have Aicardi syndrome experience all three features of the classic triad.

Causes

Researchers now believe that a mutation in a specific gene or multiple genes can lead to Aicardi syndrome. However, they have not yet identified an exact gene that causes the condition. Most researchers believe that the responsible gene is on the X chromosome because the syndrome frequently affects girls and females have two X chromosomes.

Because males have only one X chromosome (and one Y)—and therefore only one copy of the abnormal gene—the mutated gene usually proves fatal early in fetal development. This means a male embryo or fetus with the flawed gene does not make it to birth.

Males with Aicardi syndrome who do survive are also born with Klinefelter syndrome, in which they have two X chromosomes (one is abnormal) and one Y chromosome.

Females with Aicardi syndrome usually have one abnormal X chromosome and one normal one. The second, normal one helps the female fetus to survive and triggers the condition to develop and progress after the baby is born.

While Aicardi syndrome is genetic, scientists do not believe it is passed down from parent to child. This is because there is no evidence that adult females with the condition have passed it on to their children and there are no case reports of the syndrome running in families.

The only exception is identical twins, according to a 2018 report in the American Journal of Medical Genetics. This lack of evidence towards an inheritance pattern has led researchers to believe that the gene mutation is spontaneous and is triggered after conception.

Diagnosis

The only way to diagnose Aicardi syndrome is by reviewing symptoms. Additional tests are needed since each child might present with different symptoms.

Additional testing might include:

• An EEG to evaluate the electrical activity of the brain and detect seizures
• Eye exams to assess vision, abnormal eye movement, eye changes, and strabismus
• Magnetic resonance imaging (MRI) or computed tomography (CT) scans to assess any abnormalities of the brain’s structure, including the underdevelopment or absence of the corpus callosum

Treatment

No treatment will cure Aicardi syndrome. The only symptom that can be controlled is seizures. Doctors can prescribe antiseizure drugs to help control seizures and spasms. Your child’s doctor may need to prescribe different drugs before finding one that works best. 

Your child’s doctor can recommend programs to help the child learn to cope with intellectual disabilities and developmental delays that are identified with Aicardi syndrome.

Your child will need to see a neurologist for the rest of their life to help manage their long-term care. Doctors from other specialties might need to be consulted based on the symptoms experienced.

Additional specialists that might be involved in your child’s care might include:

• Neurosurgeons: Doctors specializing in surgery on the brain and nervous system)
• Ophthalmologists: Doctors specializing in the eye
• Orthopedists: Doctors specializing in disorders of the muscles and bones
• Gastroenterologists: Doctors who specialize in treating problems with the digestive system
• Physical therapists: Licensed practitioners who evaluate and treat problems with movement and physical abilities
• Occupational therapists: Licensed practitioners who evaluate and recommend solutions for limitations in daily living
• Speech therapists: Licensed practitioners who evaluate and treat problems with speech, hearing, and swallowing
  

Summary

Aicardi syndrome is a rare genetic condition that causes the corpus callosum of the brain to fail to develop. Symptoms include infantile seizures. It is caused by a mutation on the X chromosome that is believed to happen after conception.

It primarily affects females since the mutation is usually fatal for males before birth. There is no cure, but antiseizure medication and therapy can help with symptoms.

A Word From Verywell

The outlook for a child with Aicardi syndrome will depend on the severity of symptoms and if other conditions are present. Your child might need to be dependent on others their entire lifetime or they may have a mild intellectual disability and few development delays. Talk to your medical team about your child's particular outlook and needs.

Being a parent of a child with a rare disorder can be difficult and isolating. Support groups can be a good place to voice your concerns and talk to others with similar challenges. The Aicardi Syndrome Foundation is a helpful place to start for parents of children with Aicardi syndrome. 

Frequently Asked Questions

What is the survival rate of Aicardi syndrome?

Survival rates for Aicardi syndrome have been improving, with one 2016 report in the journal Eye showing an estimated survival rate of 62% at 27 years of age.

The Genetics and Rare Diseases Information Center estimates the average lifespan of girls with Aicardi syndrome is between 8 and 18 years of age. Women with mild symptoms of the condition have lived into their 30s and 40s.  

Life expectancy is often dependent upon the severity and frequency of seizures. Females with very severe cases of Aicardi syndrome usually do not survive past infancy.

What happens when you have an underdeveloped corpus callosum?

People with Aicardi syndrome have absent or underdeveloped tissues to connect the left and right halves of the brain. This is called agenesis of the corpus callosum (ACC). The corpus callosum is part of the brain where nerve fibers connect the cerebral hemispheres (the two sides of the brain).

According to the National Institute of Neurological Disorders and Stroke, children with an absent or underdeveloped corpus callosum can have delays reaching milestones, including walking, talking, and reading.

They may also have poor motor coordination and social interaction challenges that get worse as they become older. There might be speech and language delays and some cognitive impairment, but many people with ACC have normal intelligence.

Can tests identify Aicardi syndrome before birth?

A gene for Aicardi syndrome has not been identified, so genetic testing before birth or before conception isn’t possible. However, it might be possible to identify agenesis of the corpus callosum using prenatal ultrasound with color Doppler or transfontanellar ultrasound (cranial/head ultrasound) with an ophthalmological examination.

Why are girls more likely to develop Aicardi syndrome? 

While research is not yet conclusive, researchers believe Aicardi syndrome results from genetic mutations to the X chromosome that occur while the embryo is developing. Females usually have two X chromosomes, while males usually have only one.

The research shows that when the mutations occur in only one X chromosome, the female embryos survive because the second X chromosome is healthy. Male embryos usually don’t survive because they have only one X chromosome.