Seizure Devices Often Work Better Over Time

What was studied

This study was a systematic review and meta-analysis. That means the researchers gathered and combined results from published studies to look at how responder rates changed over time with neurostimulation in people with drug-resistant epilepsy.

They looked at four neurostimulation modalities in patients without prior resective surgery who received a single implanted device: open-loop vagus nerve stimulation (ol-VNS), closed-loop VNS (cl-VNS), deep brain stimulation (DBS), and responsive neurostimulation (RNS). The search covered studies published from 2014 to 2024, and 95 unique cohorts were included. The researchers mapped results into follow-up windows of about 3 months, 6 months, 12 to 18 months, and 21 months or longer after implantation.

What they found

Across all device types together, responder rates improved over time. A responder was defined as having at least a 50% reduction in seizures. The pooled responder rates were 39% at 3 months, 48% at 6 months, 58% at 12 to 18 months, and 63% at 21 months or longer.

There were numerical differences among devices, with closed-loop VNS, DBS, and RNS showing higher overall efficacy baselines than open-loop VNS. But when the researchers tested whether one device had a different pattern of change over time than another, they did not find statistical evidence of different temporal trajectories. In simple terms, all four types showed a similar pattern of gradual improvement over 1 to 2 years in the available data.

Limits of the evidence

This study combined many separate studies rather than randomly assigning people to different devices, so it cannot show from these data alone that one device is intrinsically better than another. Differences between devices may reflect patient selection or indication bias rather than the hardware itself.

The analysis used pooled study-level data rather than detailed data from each individual patient. The included studies may also have differed in patient characteristics and outcome reporting. The abstract does not provide detailed safety results, quality-of-life outcomes, or separate results for children versus adults. The idea that improvement may reflect delayed network remodeling is described as a hypothesis, and this study could not confirm a shared mechanism.

For families and caregivers

For families, the main message is that neurostimulation responder rates may improve over time rather than showing their full effect right away. If seizure improvement is modest early on, this review suggests that gains can continue to build over many months and up to 1 to 2 years.

It also suggests caution when comparing devices based only on simple percentages from different studies. The current evidence did not show clear differences in the time course of improvement across devices, and treatment choice still depends on the person’s epilepsy type, goals, and available options.

What to watch next

Future studies that directly compare devices in similar patients, and that report safety, quality-of-life outcomes, and separate results for children and adults, would help clarify differences between modalities.

Terms in this summary

drug-resistant epilepsy

Epilepsy that does not come under good control after trying appropriate seizure medicines.

neurostimulation

Treatment that uses an implanted device to send electrical signals to nerves or brain areas to help reduce seizures.

vagus nerve stimulation (VNS)

A device that sends electrical pulses to the vagus nerve to help reduce seizures.

deep brain stimulation (DBS)

A treatment that delivers electrical stimulation to specific deep areas of the brain.

responsive neurostimulation (RNS)

A device that monitors brain activity and gives stimulation when it detects patterns linked to seizures.

responder rate

The percentage of patients who had at least a 50% reduction in seizures.

meta-analysis

A study method that combines results from multiple studies to estimate overall patterns.