There are three main co-existing origins of epilepsy:
- Symptomatic epilepsies: these can be due to a brain injury, congenital malformation, encephalitis, consequences of trauma during birth, cranial trauma, cerebral vascular accident, tumour, infections of the central nervous system, progressive neurological illnesses, chromosomal abnormalities, cerebral malformations, etc.
- Cryptogenic epilepsies: when a cause is suspected but cannot be demonstrated via diagnostic methods, it is referred to as cryptogenic epilepsy. The number of cases of this type of epilepsy is constantly decreasing as exploratory techniques to determine causes are developed.
- Idiopathic epilepsies (without an identified cause): these often have a demonstrable genetic factor and mainly affect patients without brain injuries. That said, genetic predisposition does not mean that epilepsy is a hereditary illness. The transmission of epilepsy is highly complex and only affects a small number of cases. What’s more, the same anomaly can have different effects in different people. However, cases of epilepsy that are triggered by an illness, which itself is genetically transmitted, need to be considered differently.
A lower seizure threshold than normal
Every person has a seizure threshold (limit at which the individual could suffer an epileptic seizure) and therefore everyone has the potential to experience a seizure. People with epilepsy have the unusual characteristic of having a lower seizure threshold than normal.
Idiopathic epilepsies in adults are always generalised. These are essentially forms of epilepsy that started in infancy or adolescence, for which there is no cure but can be kept consistently under remission with treatment.
Symptomatic or cryptogenic epilepsies are usually focal. They represent close to 80% of cases of epilepsy in adults. Epilepsy can date back to early life, as a result brain damage that occurred during infancy; it can also be recent, requiring an assessment to investigate the residual or progressive cause.
Article drafted under the supervision of Dr Henri Rubinstein, a Paris-based specialist in neurological examination.
For further information: Epilepsy Foundation