Epilepsy Surgery May Not Be Advised in Dravet With SCN1A Mutations, Study Finds

Epilepsy Surgery May Not Be Advised in Dravet With SCN1A Mutations, Study Finds
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Epilepsy surgery may be ineffective, and even detrimental, in people with Dravet syndrome caused by mutations in the SCN1A gene, a small multicenter study suggests.

While patients with other SCN1A-associated epilepsies benefited from this type of surgery, Dravet patients did not, even in the presence of a single brain lesion likely to cause seizures.

These results support previous findings indicating that epilepsy surgery may not be advised for this patient population.

Published in the journal Developmental Medicine & Child Neurology, the study is titled “Focal epilepsy in SCN1A‐mutation carrying patients: is there a role for epilepsy surgery?

Mutations in the SCN1A gene are the most common genetic cause of genetic epilepsy with febrile seizures plus (GEFS+), a wide spectrum of seizure conditions ranging from mild febrile seizures — a convulsion in a child caused by a spike in body temperature — to the most severe Dravet syndrome.

SCN1A mutations result in the production of a non-functional sodium channel called NaV1.1., which is essential for transmitting electric signals throughout the brain.

GEFS+ patients, including those with Dravet syndrome, can have focal seizures — those starting at a single area or side of the brain — and local brain lesions, as detected by magnetic resonance imaging (MRI) scans.

When focal seizures start at a single non-critical brain region that shows MRI-detected abnormalities, its surgical removal may prevent further seizures. That procedure is known as resective epilepsy surgery.

However, it remains under debate whether people with SCN1A mutations and co-occurrence of focal seizures and a single brain lesion benefit from resective epilepsy surgery. Notably, previous reports have suggested that such Dravet patients may not be helped by this type of surgery.

Now, a team of European researchers have reported on cases involving eight individuals (four males and four females) with disease-causing SCN1A mutations who underwent resective epilepsy surgery in five epilepsy surgery centers.

The patients’ mean age was 13.9 years (range, 3–26) and seizure onset occurred at a mean of 8.25 months. Each underwent a full presurgical evaluation, including an electroencephalogram, or EEG, and an MRI scan. An EEG is a technique used to analyze the brain’s electrical activity and to study seizures and their origin.

Two boys and one girl had Dravet syndrome. Both boys showed seizures originating from several brain areas and localized lesions in the outer layer of the brain (focal cortical dysplasia). The girl had focal seizures involving the right temporal lobe and a lesion in the right hippocampus, a brain region located in an inner section of the temporal lobe.

In addition, three females and one male had temporal lobe epilepsy, the most common form of partial epilepsy. These patients had focal seizures starting in one of the temporal lobes, as well as MRI-detected lesions in the corresponding-side hippocampus. A 26-year-old man showed focal seizures involving the occipital lobe, but no MRI-detected lesion.

Epilepsy surgery was used to remove the brain areas involved in seizure onset and/or showing MRI-detected lesions.

The results showed that the surgery failed to reduce seizure frequency in the Dravet patients. In contrast, those with epilepsies other than Dravet syndrome became free of local seizures after undergoing the surgery.

Notably, the girl with Dravet syndrome also stopped having focal seizures, but she continued experiencing and developed other types of generalized seizures, dying from sudden unexpected death in epilepsy four years after surgery.

“Patients with Dravet syndrome had unfavourable outcomes, whilst patients with focal epilepsy, proven to arise from a single structural lesion, had good results,” the researchers wrote.

These findings, which are consistent with previous reports in Dravet syndrome, suggest that patients with this mutation “are not epilepsy surgery candidates, even in the presence of a single structural lesion,” the researchers concluded.

Clinicians should consider continuing anti-seizure therapy in patients undergoing epilepsy surgery, since it may help prevent generalized seizures, the team said.

Marta Figueiredo holds a BSc in Biology and a MSc in Evolutionary and Developmental Biology from the University of Lisbon, Portugal. She is currently finishing her PhD in Biomedical Sciences at the University of Lisbon, where she focused her research on the role of several signalling pathways in thymus and parathyroid glands embryonic development.
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Ana holds a PhD in Immunology from the University of Lisbon and worked as a postdoctoral researcher at Instituto de Medicina Molecular (iMM) in Lisbon, Portugal. She graduated with a BSc in Genetics from the University of Newcastle and received a Masters in Biomolecular Archaeology from the University of Manchester, England. After leaving the lab to pursue a career in Science Communication, she served as the Director of Science Communication at iMM.

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Marta Figueiredo holds a BSc in Biology and a MSc in Evolutionary and Developmental Biology from the University of Lisbon, Portugal. She is currently finishing her PhD in Biomedical Sciences at the University of Lisbon, where she focused her research on the role of several signalling pathways in thymus and parathyroid glands embryonic development.
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