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Aicardi syndrome

Background

Aicardi syndrome is a very rare neurological condition that occurs because of a congenital (present at birth) abnormality during brain development. It only occurs in girls as it is lethal to male babies and thought they are lost as a miscarriage. The exact cause is unknown; it is probably due to a gene defect on the X chromosome. Aicardi syndrome is characterised by underdevelopment or absence of the development the corpus callosum, (the structure that links the two halves of the brain together), infantile spasms and an abnormality to the structure and appearance of the retina of the eyes. In addition, other structures within the brain can also be abnormal. This can result in a variety of types of brain cyst and/or abnormal structure within areas of grey or white matter of the brain (polymicrigyria/heterotopias).

Credits

Medical text written February 2000 by Dr KRE Pohl. Last updated December 2011 by Dr KRE Pohl, Consultant Paediatric Neurologist, Evelina Children's Hospital, Guy's and St Thomas' NHS Foundation Trust, London, UK. 

What are the symptoms?

Learning disability is common and varies from moderate to severe. Most affected will have no expressive language and remain totally dependent on adults for their self-care. Self-injurious behaviours and aggression towards people and objects has been reported.

Associated epilepsy usually occurs by two months of age and remains difficult to control. Investigation with electroencephalogram (EEG), a recording of the brain's electrical activity, may reveal a pattern characteristic of these spasms called hypsarrhythmia. This form of epilepsy is sometimes referred to as West syndrome. The majority of individuals with Aicardi syndrome are severely affected with persisting epilepsy. Disturbed sleep (possibly due to fitting) and waking in the night are also common problems.

The abnormalities at the back of the eye, evident only on internal examination with an ophthalmoscope, are to the structure of the choroid and retina. They appear as distinctive multiple, round 'footprint shaped' yellow-white lesions (marks). The level of vision depends upon the extent of these retinal lesions and the severity of any associated learning disability.

Aicardi syndrome is associated with a host of other variable symptoms. These can include abnormalities of the bony structure of the spine, spinal curvature (see entry Scoliosis) and cleft lip and palate. Life expectancy can be severely limited. There are some children with a milder structural brain abnormality who, although suffering visual impairment and learning difficulties, may have some understanding of language, some independent mobility and be responsive to their environment.

How is it diagnosed?

Diagnosis may not be made until the affected girl develops seizures and investigations such as a magnetic resonance imaging (MRI) scan to assess the corpus callosum and a special eye examination are carried out.

How is it treated?

There is no cure for Aicardi syndrome. Treatment is only supportive aiming to alleviate the symptoms experienced by an individual. Choice of antiepileptic medication can be difficult as seizures are often resistant to it. Depending on the type of seizures present, drugs which may be effective include vigabatrin (Sabril) or a course of corticosteroids.

Inheritance patterns and prenatal diagnosis

Inheritance patterns
The condition is transmitted in an X-linked dominant manner with lethality (death during development of the baby) in males. Reoccurrence within a family appears to be extremely uncommon.

Prenatal diagnosis
Although structural brain abnormalities may sometimes be evident on prenatal ultrasound scan, this is not the case in the majority of cases of Aicardi syndrome. There is no prenatal diagnosis available.

Is there support?

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