Below are past findings from the Epilepsy Family Study.
- In the close relatives (parents, brothers, sisters, and children) of people with generalized epilepsy, the risk of epilepsy is about four times as high as in the general population, whereas in the close relatives of people with localization-related (partial or focal) epilepsy, the risk is about two times as high as in the general population.
- Genetic risk does not play a significant role in causing epilepsy in people with serious brain injuries that occurred after birth (e.g., head injuries, brain tumors, strokes, etc.)
- The effect of genetic factors on the risk of epilepsy decreases as people get older. After age 35, there is no definite effect of genetic factors on epilepsy.
- In most families, the pattern of risk does not fit any simple genetic model (dominant, recessive, etc.), so it is difficult to predict which family members will develop epilepsy.
- When more than one person in a family has epilepsy, there is an increased chance that different family members will have the same type of epilepsy (either generalized epilepsy where seizures begin on both sides of the brain at once, or partial epilepsy where seizures begin in part of the brain). This suggests that some genes have specific effects – that is, they raise risk for only one of these two types of epilepsy without raising risk for the other. However, some genes are known to raise the risk for more than one type of epilepsy, and in families with these genetic causes, different family members can have different epilepsy types.
- A form of epilepsy that we have named "autosomal dominant partial epilepsy with auditory features," is sometimes caused by a change in a gene on chromosome 10 called LGI1. People with this form of epilepsy frequently report changes in their hearing either before their grand mal seizures or as a separate seizure type. These symptoms include hearing sounds such as buzzing, ringing, or humming, or more rarely, hearing more complex sounds such as music, or having seizures precipitated by sounds.
- About half of the families with this form of epilepsy have a mutation in the LGI1 gene. In the other half of families, the cause has not yet been identified, so auditory symptoms sometimes occur in people who do not have this genetic form of epilepsy. Also, some of those who inherit a mutation in the LGI1 gene never develop epilepsy at all.