A typical scan of a human’s brain will reveal many complicated wrinkles, folds, and grooves. This is one way the body packs a large amount of brain tissue in a relatively small space. The brain typically starts to fold during fetal development. But some babies experience a condition known as lissencephaly. In babies with this condition, the brain does not fold properly. Instead, the brain remains smooth. This condition can affect a baby’s neural function, and the symptoms can be severe.
Lissencephaly is extremely rare. It occurs in 11.7 per one million births in the United States, according to The Cortical Foundation.
Lissencephaly is considered to be primarily a genetic condition. Scientists have identified malformations in five genes as contributors to lissencephaly. They are LIS1, 14-3-3ε, DCX, RELN, and ARX. Mutations in these genes can cause varying levels of lissencephaly.
Lissencephaly typically develops when a fetus is 12 to 14 weeks old. During this time, nerve cells begin to move to other areas of the brain as it develops. For fetuses with lissencephaly, the nerve cells do not move. This affects brain development.
The condition can occur alone, but it is also associated with genetic conditions such as Miller-Dieker syndrome and Walker-Warburg syndrome.
Babies born with lissencephaly may have an abnormally small head, a condition known as microlissencephaly. But not all babies with lissencephaly have this appearance. Other symptoms include:
- difficulty feeding
- failure to thrive
- intellectual impairment
- malformed fingers, toes, or hands
- muscle spasms
- psychomotor retardation
- trouble swallowing
If one or both parents have a family history of lissencephaly, imaging scans can be performed on a fetus as early as week 20. However, weeks 25 to 30 are more common for an ultrasound to be performed. At this time, the brain should be developing folds.
If a baby experiences symptoms related to brain development, a physician may recommend an imaging scan after birth to examine the brain. This includes ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI) scans. If lissencephaly is the cause, a physician will typically grade the degree to which the brain is affected.
Brain smoothness is called agyria, and brain thickening is called pachgyria. A grade 1 diagnosis means that a child has generalized agyria or that most of the brain is affected (The Cortical Foundation, 2012). This occurrence is very rare and results in the most severe symptoms and delays.
Most affected children have grade 3 lissencephaly. This condition results in thickening on the front and sides of the brain and some agyria throughout the brain.
Lissencephaly cannot be reversed. Treatments aim to support and comfort affected children. For example, children who have difficulty feeding and swallowing may require a gastrostomy tube. This is a tube that is inserted directly into a child’s stomach. If a child experiences hydrocephalus, or an excessive accumulation of cerebrospinal fluid, a surgical procedure that shunts fluid away from the brain may be necessary.
If a child experiences seizures as a result of lissencephaly, he or she may require medications to control seizures.
The outlook for a child with lissencephaly depends on the condition’s severity. For example, severe cases may result in the child failing to develop mentally beyond a three- to-five month old function. Children with severe lissencephaly have a life expectancy of about 10 years, according to The National Institute of Neurological Disorders. Common causes of death include aspiration (choking on) food or fluids, respiratory disease, or seizures.
Children with mild lissencephaly can experience near-normal development and brain function.