Research: Patient Info Sheets

print this page | close window

Polymicrogyria

You’ve been told that your child has a condition called polymicrogyria. Most people have never heard of this and have no idea what it means for their child or for their family. This brochure gives you some general information about polymicrogyria. Our knowledge of polymicrogyria is expanding all the time but currently we still have many, many unanswered questions.

What is polymicrogyria?

Polymicrogyria is a medical term that refers to a particular abnormality in the way that the surface of the brain developed during pregnancy. The first, most important thing to understand is that there are many different forms of polymicrogyria and many potential causes, so two patients with polymicrogyria do not necessarily have the same condition or the same prognosis. Your child’s doctor will attempt to find out what particular kind of polymicrogyria your child has and what might have caused it, since these are important to understanding your child’s future and planning his or her treatment.

Normally, the surface of the brain is composed of many different folds. Polymicrogyria means that in at least one region of the brain, there are too many folds and they are smaller than normal. Polymicrogyria can occur focally (i.e., in just one area of the brain) or it can occur in a more generalized way (i.e., all over the brain). In addition, it can occur by itself or it can occur in association with other abnormalities of brain formation. How your child may be affected by polymicrogyria depends on many things, including where exactly the polymicrogyria is occurring, how extensive it is, and whether or not other problems are associated with it.

How is polymicrogyria diagnosed?

The folding pattern on the surface of the brain requires a radiological test (one that takes pictures of the brain) in order for doctors to be able to see it. For this reason, polymicrogyria cannot simply be diagnosed by physical examination, blood tests, or EEGs. MRI (magnetic resonance imaging) is the best way to diagnose polymicrogyria. Sometimes, CAT (computed axial tomography) scans can suggest the presence of polymicrogyria, but MRI gives much better views of the folding pattern of the brain surface.

What causes polymicrogyria?

Polymicrogyria can arise from multiple different causes. Sometimes problems during pregnancy, such as infections or episodes in which there was a lack of oxygen to the fetus, can lead to polymicrogyria. Sometimes, polymicrogyria is due to a genetic problem (i.e., an abnormality in the genes, or DNA). Genetic problems include both those that run in families and those that have appeared for the first time in the child who is affected. Sometimes, we cannot find a specific cause for polymicrogyria in a particular child.

How will polymicrogyria affect my child?

As discussed above, how significantly your child may be affected by polymicrogyria depends on where it occurs in the brain, how extensive it is, and whether it is associated with other brain malformations as well. In some cases, polymicrogyria is present in only a very small portion of the brain on one side – in these situations, patients may only have very mild problems, or no problems at all. At the other extreme, polymicrogyria is sometimes present across the entire brain on both sides. In these cases, patients can have severe mental retardation, cerebral palsy, and seizures. Therefore, to get the best information on how your own child will do, it is important to discuss with your doctor the specific characteristics of his or her polymicrogyria.

What are some of the bilateral syndromes of polymicrogyria?

Bilateral syndromes of polymicrogyria are those that affect both sides of the brain, usually in a symmetric manner. Many of these syndromes are either known to have a genetic cause or are suspected to be genetic in origin. Three of these disorders are summarized below.

Bilateral perisylvian polymicrogyria (also called congenital bilateral perisylvian syndrome) affects the regions around the Sylvian fissures on both sides of the brain. Patients with this form typically have problems with motor control of the mouth, such as speaking or swallowing difficulties. Sometimes mental retardation, cerebral palsy, and seizures can also be present. This disorder appears to be inherited, although it may be passed down in different ways in different families.

Bilateral frontoparietal polymicrogyria affects the frontal and parietal lobes of the brain on both sides to a greater extent than other regions of the brain. Patients often have mental retardation, cerebral palsy, crossed eyes, and seizures that are difficult to control. This disorder appears to be inherited in an autosomal recessive manner, meaning that in most cases both parents are carriers of the abnormal gene but do not have any brain problems themselves. If both parents are carriers, then each of their children has a 25% chance of having this disorder.

Bilateral parasagittal parietooccipital polymicrogyria affects the parietal and occipital lobes at the back of the brain. Patients typically have seizures and occasionally have mental retardation as well. So far this disorder has only been seen in patients without affected family members and it is not clear if it has a definite genetic cause.

Is my child appropriate for your research studies?

Our laboratory and others around the world are studying the forms of polymicrogyria that have genetic causes. If your child’s polymicrogyria is bilateral (affects both sides of the brain) or if there is some other reason to suspect that your child’s condition has a genetic cause, he or she may be appropriate for our research. We are trying to identify the genes that may be responsible for some of these forms. Identification of these genes will tell researchers the types of proteins that are important in brain development. Researchers can then study these proteins to learn how they function and this knowledge, eventually, may lead to better treatment for individuals with polymicrogyria in the future.


If you are interested in this study, please contact our research coordinator by e-mail at walshlab@bidmc.harvard.edu or by phone at (617) 667-8035.