Temporal lobe epilepsy (TLE) has a genetic component, but for most people it’s not inherited in a simple, predictable way. A small percentage of cases follow a clear family inheritance pattern tied to a single gene. The majority involve a complex mix of genetic susceptibility and other factors like brain injuries, infections, or structural abnormalities. Whether genetics plays a major or minor role depends heavily on which type of TLE you’re looking at.
Two Types With Different Genetic Stories
Temporal lobe epilepsy is broadly divided into two subtypes, and they have distinct genetic profiles. Lateral temporal lobe epilepsy originates from the outer surface of the temporal lobe and is more likely to run in families through a single gene. Mesial temporal lobe epilepsy, the more common form, originates deeper in the brain near the hippocampus and typically has a more complex genetic picture involving many genes with small effects.
The lateral form has a well-recognized inherited version called autosomal dominant lateral temporal lobe epilepsy (ADLTE). This means a single copy of a mutated gene, inherited from one parent, can cause the condition. Seizures in this form often include unusual sensory symptoms, particularly auditory features like hearing buzzing, ringing, or distorted sounds before or during a seizure.
Mesial TLE, especially when accompanied by hippocampal sclerosis (scarring in the hippocampus), is harder to pin on any one gene. Large genome-wide studies have identified several genetic variants that increase susceptibility, but each one raises risk only modestly. The overall heritability from common genetic variants in focal epilepsies, the category TLE falls into, is estimated at about 16%. That’s meaningful but far lower than the 40% seen in generalized epilepsies, which affect the whole brain at once.
Genes Linked to Familial Forms
Two genes account for most genetically confirmed cases of the inherited lateral form. The first discovered was LGI1, found in roughly 30% of families with ADLTE in a large Italian study spanning 14 years. The second is RELN, which encodes a protein called reelin that helps organize brain structures during embryonic development and continues to influence how brain cells connect and communicate throughout life. RELN mutations were found in about 17.5% of ADLTE families in that same study. Notably, over half of families with the clinical pattern of ADLTE had no identifiable mutation in either gene, suggesting other genes remain to be discovered.
The seizure patterns caused by LGI1 and RELN mutations are clinically indistinguishable, so genetic testing is the only way to tell them apart. Both genes appear to disrupt how neurons communicate in the temporal lobe, but through slightly different biological pathways.
A third gene, DEPDC5, is linked to a broader condition called familial focal epilepsy with variable foci, where different family members can have seizures originating from different brain regions. When DEPDC5 mutations cause temporal lobe seizures, the mesial form is most common. These seizures often include feelings of déjà vu, sudden fear, or nausea. Some affected individuals also have a history of febrile seizures in childhood, and hippocampal sclerosis is frequently seen on brain imaging.
Inheriting a Gene Doesn’t Guarantee Seizures
One of the most important findings in epilepsy genetics is that penetrance, the probability that someone carrying a disease-causing gene variant actually develops epilepsy, is surprisingly low. A 2025 analysis of over 400,000 people found that carriers of variants classified as disease-causing for autosomal dominant epilepsy had only a 4% to 10% chance of developing the condition. That means the vast majority of people who carry these variants never have a seizure.
This low penetrance likely explains why TLE can seem to skip generations in a family, or why one sibling with a mutation develops epilepsy while another doesn’t. Other genetic variants, environmental exposures, and brain development all influence whether a mutation actually leads to seizures. It also means that finding a known epilepsy gene in your DNA is not a diagnosis on its own.
Common Genetic Variants in Non-Familial TLE
Most people with temporal lobe epilepsy don’t have a single causative gene. Instead, their risk is shaped by dozens or hundreds of common genetic variants, each contributing a small amount. Genome-wide association studies are beginning to identify some of these. One recent study of mesial TLE with hippocampal sclerosis found a variant near the TMEM14A gene that was more than twice as common in affected individuals compared to controls. This variant appears to cause abnormal processing of the TMEM14A gene specifically in hippocampal tissue, potentially disrupting the normal regulation of cell death in that region.
Other candidate variants have been identified near genes involved in calcium signaling in neurons and in cellular transport, though none individually explain a large share of risk. This polygenic architecture, where many small-effect genes combine, is a pattern seen across most common neurological conditions. It makes genetic risk harder to measure for any single person but confirms that biology plays a real role even in cases with no obvious family history.
What Genetic Testing Can and Can’t Tell You
Genetic testing in epilepsy has become more accessible, and national guidelines now recommend that all people with epilepsy be offered genetic evaluation regardless of age. The strongest predictors of actually finding a causative gene are early seizure onset (particularly in infancy), the presence of developmental delays or intellectual disability, and brain malformations visible on imaging.
In a pediatric study of 259 children with epilepsy, focal epilepsies, the category that includes TLE, had a diagnostic yield of 56.5% from genetic sequencing. That’s higher than the 18.8% yield for generalized epilepsies, which was a somewhat surprising finding. However, this study included children with a range of focal epilepsies and severities, and the yield drops significantly for adults whose seizures began later in life.
Genetic testing is also increasingly used during presurgical evaluation for people whose TLE doesn’t respond to medication. Identifying a genetic cause can change surgical planning, since some genetic epilepsies respond differently to surgery than those caused by a visible lesion. In some cases, a genetic finding opens the door to more targeted treatment approaches.
Risk to Family Members
If you have temporal lobe epilepsy and are wondering about risk to your children or siblings, the answer depends on which type you have. For the rare autosomal dominant forms linked to LGI1, RELN, or DEPDC5, each child of an affected parent has a 50% chance of inheriting the mutation. But because penetrance is low, inheriting the mutation translates to a much smaller actual chance of developing seizures, likely under 10%.
For the more common, non-familial forms of TLE, first-degree relatives do have a modestly elevated risk of epilepsy compared to the general population, but the absolute risk remains small. Having a parent or sibling with TLE does not mean you will develop it. The genetic contribution in these cases is spread across many variants, and most relatives will not carry enough of them to cross a clinical threshold, especially without additional triggers like a head injury or brain infection.