Lissencephaly
ICD9 = |Lissencephaly, which literally means smooth brain, is a rare brain formation disorder characterized by the lack of normal convolutions (folds) in the brain. It is caused by defective neuronal migration, the process in which nerve cells move from their place of origin to their permanent location. It is a form of cephalic disorder.
The surface of a normal brain is formed by a complex series of folds and grooves. The folds are called gyri or convolutions, and the grooves are called sulci. In children with lissencephaly, the normal convolutions are absent or only partly formed, making the surface of the brain smooth. Terms such as 'agyria' (no gyri) or 'pachygyria' (broad gyri) are used to describe the appearance of the surface of the brain
Symptoms of the disorder may include unusual facial appearance, difficulty swallowing, failure to thrive, and severe psychomotor retardation. Anomalies of the hands, fingers, or toes, muscle spasms, and seizures may also occur.
Lissencephaly may be diagnosed at or soon after birth. Diagnosis may be confirmed by ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI).
Lissencephaly may be caused by intrauterine viral infections or viral infections in the fetus during the first trimester, insufficient blood supply to the baby's brain early in pregnancy, or a genetic disorder, such as the mutation of the gene coding for a glycoprotein reelin. There are a number of genetic causes of lissencephaly, but the two most well documented are - X-linked and chromosome 17-linked. Genetic counseling and genetic testing, such as amniocentesis, is usually offered during a pregnancy if lissencephaly is detected. The recurrence risk depends on the underlying cause.The spectrum of lissencephaly is only now becoming more defined as neuroimaging and genetics has provided more insights into migration disorders. There are around 20 different types of lissencephaly which make up the spectrum. Other causes which have not yet been identified are likely as well.
A consensus has been reached for a classification based on associated malformations and etiologies. On the basis of this classification, five major groups of lissencephalies can be recognized:
* Classic lissencephalies (previously known as type 1 lissencephalies), which include :
** lissencephaly due to LIS1 gene mutation, which subdivides into:
*** type 1 isolated lissencephaly and
*** Miller-Dieker syndrome
** lissencephaly due to doublecortin (DCX) gene mutation;
** lissencephaly, type 1, isolated, without a known genetic defects;
* Lissencephaly X-linked with agenesis of the corpus callosum (ARX gene);
* Lissencephaly with cerebellar hypoplasia, which itself is subdivided into 6 subtypes;
* Microlissencephaly;
* Cobblestone lissencephaly, which includes:
** Walker-Warburg syndrome;
** HARD(E) syndrome;
** Fukuyama syndrome;
** Muscle-Eye-Brain (MEB) disease.Treatment for those with lissencephaly is symptomatic and depends on the severity and locations of the brain malformations. Supportive care may be needed to help with comfort and nursing needs. Seizures may be controlled with medication and hydrocephalus may require shunting. If feeding becomes difficult, a gastrostomy tube may be considered.
The prognosis for children with lissencephaly varies depending on the degree of brain malformation. Many individuals show no significant development beyond a 3- to 5-month-old level. Some may have near-normal development and intelligence. Many will die before the age of 2, but with modern medications and care, children can live into their teens. Respiratory problems are the most common causes of death.* Lissencephaly immunodeficiency
* Lissencephaly syndrome type 1
* Lissencephaly syndrome type 2
* Lissencephaly, isolated Hong SE, Shugart YY, Huang DT, Shahwan SA, Grant PE, Hourihane JO, Martin ND, Walsh CA. (2000) Autosomal recessive lissencephaly with cerebellar hypoplasia is associated with human RELN mutations. Nat Genet. 26(1):93-6. PMID 10973257
Ross ME, Swanson K, Dobyns WB. (2001) Lissencephaly with cerebellar hypoplasia (LCH): a heterogeneous group of cortical malformations. Neuropediatrics. 32(5):256-63. PMID 11748497
* NIH
* Lissencephaly.org.uk
* Lissencephaly Launch Pad (support)
* Lissencephaly, generic term (pdf document) - concise and thorough classification of lissencephaly by prof. Alan Verloes.
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