Identifying genetic causes of childhood epilepsy

Although it is believed that a large proportion of childhood-onset epilepsies are caused by genetic changes, it remains unknown precisely how many of these patients suffer from a genetic disorder and how often the treatment can be targeted to their specific genetic alteration. Now, researchers from the Danish Epilepsy Centre have shown a genetic cause for this condition among half of those studied, which should aid in the prescription of appropriate treatments as well as preclude the use of unnecessary diagnostic procedures.

Dr Allan Bayat and colleagues studied 290 children with a diagnosis of epilepsy or who presented with seizures accompanied by a high temperature that were either long, or in which consciousness was not regained between events (prolonged and clustering febrile seizures). After obtaining informed consent, the children underwent genetic testing.

“We found a genetic cause in half of those tested and also that half of those again could receive a tailored treatment,” Dr Bayat said. “We hope that drug companies and the scientific community will be able to produce new drugs or repurpose existing ones that may be being used to treat entirely unrelated conditions to improve precision treatment possibilities for those for whom this is currently not available.”

In recent years, the number of genes known to be associated with epilepsies has risen to over 500, and gene panel testing and exome sequencing are now routine in many countries. Such testing is most important in children whose seizures commence when they are under three years of age, or with a family history of seizures, brain malformations or cognitive comorbidities. The researchers’ results show that genetic testing is crucial in such patients in order for them to receive appropriate counselling and treatment.

An additional advantage of being able to identify a genetic cause is the avoidance of potentially harmful treatments. Genetic sequencing has shown that the majority of monogenic epilepsies, in which a single genetic change is involved, are caused by changes in ion channels — membrane proteins that are abundant in the central nervous system. While some genetic changes reduce the function of ion channels, others increase them. Most anti-epileptic drugs currently available target and block these ion channels — so their use in patients with symptoms caused by genetic changes that have already suppressed ion channel function would most likely do more harm than good.

The researchers intend to continue their work with further study of those individuals where they were unable to find a genetic explanation for their epilepsy. Dr Bayat said, “We will re-evaluate the dataset obtained from exome sequencing at regular intervals and perform additional genetic testing with a method that can detect genetic changes that may be missed by exome sequencing. And we hope to explore whether these patients have an accumulation of risk variants in genes or pathways associated with epilepsy when compared to those where a genetic cause has been uncovered, and to controls.

“Getting a genetic diagnosis is of great importance for the children and the families. It provides an explanation and certainty, and it enables a more targeted genetic counselling, including knowledge about the prognosis and recurrence risk. Furthermore, it allows the subject and families to enter gene-specific networks of families with the same genetic condition.”

Image credit: ©stock.adobe.com/au/mjowra

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