Some congenital abnormalities (present at birth) are not inherited. For example, the abnormalities in the limbs of the children whose mothers had taken the drug thalidomide during pregnancy are congenital and will not be passed on to their children, as the thalidomide affected the developing cells in the limbs without, (although there continues to be some debate), causing any mutations in the baby’s own ovaries or testes. Other congenital abnormalities may have an inherited basis.
One congenital abnormality relevant to epilepsy is a maldevelopment of blood vessels known as an angioma. The abnormal vessels may be either arterial, venous, or capillary. Sometimes a clot or thrombus forms in one or more of the abnormal vessels, exacerbating the situation. One type of capillary angioma of the brain is associated with a similar malformation of blood vessels in the skin of the upper part of the face—the Sturge-Weber syndrome. Children with this particular combination of angiomatous abnormalities have a high probability of developing seizures.
More common than angiomas as a cause of epilepsy are disorders oi migration of nerve cells during fetal development, so some end up in the wrong place, the wrong layer of the brain, or with the wrong connections. They are congenital abnormalities, but unlike a harelip, for example, externally invisible. The causes of such disorders are not known, but some probably have a genetic basis. This sort of abnormal brain development may cause seizures and fits in the first few weeks or months of life, including infantile spasms (West’s syndrome).
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