This is a complex question with no one-size-fits-all answer.
There are many different factors involved, such as:
- The type of seizures and how often they happen. For example, if someone has regular tonic-clonic seizures, say 2-3 per week, for a number of years then there is a likelihood this will affect their abilities such as thinking, learning and memory.
- Severe or prolonged seizures – If someone has a number of episodes of prolonged seizures (>30mins) this can also have a significant impact.
- Seizure control – how often the seizures are happening. The more often the seizures happen; the more likely there is an impact.
- Medications – people on high doses of medication or many types of antiepileptic medication are more likely to experience difficulties. Many of these effects can be reversed with changes in medication.
- Existing brain damage.
- Seizure related head injuries.
Gaining good seizure control even after years of poor seizure control can improve thinking and memory function.
All in all, poorly controlled epilepsy and repeated seizures of any type, affects the quality of life, and also may take a long-term toll on brain function. Prolonged seizures are clearly capable of causing injury to the brain.
Aiming for good seizure control is the best thing you can do to maintain and improve brain function.