Lissencephaly Definition:
Lissencephaly, which literally means "smooth brain," is a rare, gene-linked brain malformation characterized by the absence of normal convolutions (folds) in the cerebral cortex and an abnormally small head (microcephaly). It is caused during embryonic development by defective neuronal migration, the process in which nerve cells move from their place of origin to their permanent location. Symptoms of the disorder may include unusual facial appearance, difficulty swallowing, failure to thrive, muscle spasms, seizures, and severe psychomotor retardation. Hands, fingers, or toes may be deformed. Lissencephaly may be associated with other diseases including isolated Lissencephaly sequence, Miller-Dieker syndrome, and Walker-Warburg syndrome.
Other definitions:
Lissencephaly is a set of rare brain disorders and you will probably find that very few people have heard of it. Lissencephaly is used as an 'umbrella' term to describe a range of disorders where the whole or parts of the surface of the brain appear smooth.
The cause of lissencephaly:
We know that in Lissencephaly the brain develops normally in early pregnancy but then fails to progress normally after the third to fourth month. There are several causes and these can be identified in many children.
The different types of Lissencephaly generally have different causes. These fall into four main categories:
- An inherited genetic condition that may come from either one or both parents;
- A new genetic mutation (i.e not inherited) that occurs in a gene that is critical for the correct development of the brain;
- An infection from a virus during pregnancy;
- An interruption of the blood supply to the foetus during pregnancy.
There have been a lot of advances recently in testing for some specific genetic problems, known to be the cause of some types of Lissencephaly, so these tests may he recommended in your family. Your paediatrician will be happy to discuss this with you and if necessary refer you to a Neurologist or Geneticist for further advice.
Lissencephaly treatment?
The severe malformations of the brain in Lissencephaly most likely will not respond to treatment. Normal supportive care may be needed to help with comfort and nursing needs. Seizures may be controlled with medication. Progressive hydrocephalus (an excessive accumulation of cerebrospinal fluid in the brain) may require shunting. If feeding becomes difficult, a gastrostomy tube may be considered.
Other general information:
All children with Lissencephaly suffer from mental retardation, the degree of which can vary considerably and is very dependant on the type of lissencephaly, the degree of malformation (i.e. whether the whole brain is affected or just a part of it) and also whether the child suffers from seizures.
Seizures or fits occur in a large percentage of children. These may often be controlled by the use of anticonvulsant drugs or in some cases by a special diet, the 'Ketogenic diet'.
Feeding can be a problem. Many children may have to use a Gastronomy (or G-tube) to feed if they are unable to swallow correctly. Related to feeding problems is aspiration (the swallowing of food or other matter into the lungs). This can be the source of infection which can cause pneumonia or other chest problems which can be life threatening. Reflux (stomach contents coming back up through into the throat) can also be the cause of great discomfort. Reflux can be treated with drugs or with surgery - the Nissen fundoplication.
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