Aicardi syndrome is a rare neurologic disorder first described by the French neurologist, Dr. Jean Aicardi, in 1965. It occurs almost exclusively in females (46,XX), however, it can also occur in males with Klinfelter Syndrome (47,XXY). A handful of reports in the literature exist of Aicardi syndrome in a normal male. Some of these reports have been disputed, and it is possible that these cases are caused by mosaic mutations of the Aicardi syndrome gene(s).
What Causes Aicardi Syndrome
The genetic basis or mutation which causes Aicardi syndrome has not been identified despite the efforts of several laboratories worldwide and genetic sequencing of affected children and their parents. Because Aicardi syndrome occurs only in a single member of a family, and virtually all cases are female, the genetic mutation is thought to be a dominant de novo (i.e., spontaneous) mutation in an X-linked gene with lethality in normal (46,XY) males. There are at least 6 sets of twins that are discordant for Aicardi syndrome, and one known set of monozygotic twins and one pair of non-twin sisters that are both affected. Aicardi syndrome in the non-twin sisters is likely due to chance since there have been no other reports of Aicardi syndrome in two siblings.
Features of Aicardi Syndrome
Aicardi syndrome is classically defined in over 90% of cases by three cardinal features:
- Agenesis (absence of or failed development of a body part) of the corpus callosum
- Chorioretinal lacunae (punched out lesions in the pigmented layer of the retina)
- Infantile spasms (a seizure disorder of infancy and early childhood)
In 1999, the diagnostic spectrum of Aicardi syndrome was broadened to include patients with present, but usually abnormal, corpus callosum or absence of infantile spasms or lacunae, if other typical brain abnormalities are present. Specifically, the revised criteria were expanded to include two classic features plus at least two other major or supporting features. Retinal lacunae and seizures are present in all, or almost all, of the cases. Major and supporting features include:
- Cortical (one of the two types of osseous tissue that form bones) malformations; mostly polymicrogyria (abnormal development of the brain before birth)
- Periventricular heterotopia (nerve cells [neurons] do not migrate properly during the early development)
- Subcortical heterotopia (abnormal brain development that is present from birth)
- Cysts around third cerebral ventricle and/or choroid plexus
- Papillomas of choroid plexuses (a rare, benign [noncancerous] tumor)
- Optic disc/nerve coloboma (developmental defect of the eye)
- Vertebral and costal (the ribs or the upper sides of the body) abnormalities
- Microphthalmia or other eye abnormalities
- “Split-brain” EEG
- Gross cerebral hemispheric asymmetry.
Involvement of other organ systems besides the brain and eyes are also common but the signs and symptoms are not part of the diagnostic criteria and are not present in all cases. These include:
- Vascular malformations or vascular malignancy
- Microcephaly (when a person’s head is significantly smaller than normal for their age & sex)
- Hypotonia (decreased muscle tone)
- Spasticity (stiff or rigid muscles)
- Hypertonia (abnormal increase in muscle tension and a reduced ability of a muscle to stretch)
- Scoliosis (abnormal curving of the spine)
- Prominent premaxilla (bilateral cleft lip and palate)
- Gastroesophageal reflux
- Feeding problems
- Small or malformed hands
- Precocious or delayed puberty
- Global developmental disabilities
It is generally accepted that the number and severity of features present in a child with Aicardi syndrome is associated with the individual prognosis.