How stereo-EEG and neurostimulation are helping in epilepsy treatment

A groundbreaking Mediclinic Constantiaberg epileptologist explains two new procedures in epilepsy treatment – stereo-EEG and neurostimulation. 

Becoming an epileptologist

Dr Aayesha Soni, the first female epileptologist in Sub-Saharan Africa, recently joined Mediclinic Constantiaberg. An epileptologist is a neurologist who specialises in diagnosing and treating epilepsy – the second most common neurological condition after stroke. Because South Africa currently has no fellowship programmes dedicated to this field, Dr Soni travelled abroad to pursue advanced training. She completed her clinical epilepsy and electroencephalography fellowship at Western University in Ontario, Canada, with a strong focus on epilepsy surgery.

Epilepsy is a chronic disease characterised by recurrent seizures that occur because of abnormal electrical signals produced by damaged brain cells. “When a patient has drug-resistant epilepsy – epilepsy that doesn’t respond to medication – extensive evidence-based medicine reveals that you can do surgeries for them,” she explains.

In cases of focal epilepsy, seizures start in a specific part of the brain. When that exact area, or “focus”, can be identified, surgeons may remove it, offering many patients the possibility of becoming completely seizure-free. “It’s about the workup,” says Dr Soni. This is an intensive series of tests that neurologists use to diagnose epilepsy, determine the type and severity of seizures and identify any underlying causes and where the seizures originate. “In the case of focal epilepsy, once the focus is found, resective surgery can be done to remove it in one of the least invasive brain surgeries.”

The evolution of stereo-EEG

Workup procedures for epilepsy surgery have advanced significantly over time. Previously, that meant performing a craniotomy to place a grid of electrodes on the surface of the brain, on top of the protective dura layer. The scalp was then closed, and recordings were taken over several days to locate the seizure focus. Afterwards, a second surgery was required to remove the electrode grid.

Stereo-EEG, which is performed with robotic guidance, avoids this open-skull approach. Instead, the neurosurgeon drills tiny, precise holes and places long, thin electrodes directly into the brain. Once the necessary data is collected, these electrodes are simply removed, so no second surgery is required.

“There is no other neurologist in South Africa who knows how to interpret stereo-EEG,” says Dr Soni. “I’m excited to offer this as an option to patients here.”

Regardless of the approach, the evaluation typically begins with a scalp EEG. “We place small electrodes on the head to see where the seizures are coming from,” says Dr Soni. “But if the activity is deep in the brain or not clear on the surface, we sometimes need to record directly from the brain.”

These electrodes are positioned based on information gathered from earlier non-invasive tests. Because the procedure is much less invasive, it carries fewer risks and patients are generally more comfortable, able to move around and stay close to their normal routine during monitoring. “If you can’t find the focus, you can also get a lot deeper into the brain with stereo-EEG than you can with the craniotomy, which only goes as far as the dura,” Dr Soni notes. “With stereo-EEG, doctors can view the whole epileptic network, pinpointing the origin, spread, and location of seizures. This is the most advanced method for intracranial monitoring and is currently the standard of care in workups for epilepsy surgery.” Dr Soni, together with neurosurgeons who are now training in this technique, hopes to soon offer it at Mediclinic Constantiaberg.

Understanding neurostimulation

After determining the source of the seizures, surgeons can perform resective surgery, removing a small portion of brain tissue from the area of the brain where seizures occur on the temporal lobe. This temporal lobe is located on both sides of the brain, behind the ears. It’s where sound, memory, and language is processed. In the first year after resective surgery the curative rate remains at up to 85-90% depending on where the epilepsy originates, Dr Soni explains. “Five years afterwards, that drops to about 70% but even in that case, it's still curative.”

Sometimes stereo-EEG shows that seizures are coming from more than one area of the brain. “In that situation, you can’t offer the patient resective surgery, because you can’t remove too many seizure foci without affecting their brain function,” explains Dr Soni. In these cases, neurostimulation can make a real difference. “While it doesn't offer seizure freedom, it reduces seizure frequency and severity, according to evidence-based medicine, and offers patients with drug-resistant epilepsy a higher quality of life potentially free of disabling seizures.”

Dr Soni is trained in two neurostimulation techniques: The first is vagal nerve stimulation (VNS), which works in a similar way to a heart pacemaker. “The VNS generator goes in the same place as a cardiac pacemaker, except it wraps around the vagus nerve in the neck,” she says. The device sends gentle electrical pulses to the brain to help control seizures, often reducing how often and how severely they happen.

This is a good option for people who can’t have surgery, Dr Soni says, for example, those with two seizure focal points or those with generalised epilepsy, where seizures start on both sides of the brain at once. While training in Canada, she was selected as one of only two epilepsy fellows to complete an additional mini-fellowship in North Carolina to learn how to program VNS devices – a service she plans to bring to Mediclinic Constantiaberg, and has already recommended for two of her patients.

The second option is deep brain stimulation (DBS), which the hospital already uses for movement disorders. “You can use it for epilepsy too, by inserting two electrodes into different parts of the brain to help regulate seizures,” says Dr Soni. “Within five years, 70% of people will still have a reduction in their seizures. While this does not offer recovery rates as high as resective surgery, it still provides a better quality of life, just as VNS does.”