For people living with epilepsy, there’s always a looming fear that an epileptic seizure is around the corner. A new international study, however, suggests that it may be possible to predict the onset of such seizures days in advance.

To come to this conclusion, scientists analyzed data from a brain implant called NeuroPace. The device, which was approved for clinical trials in 2013, is meant to help prevent seizures by delivering imperceptible pulses of electrical stimulation to certain parts of the brain upon detecting abnormal brain activity.

18 patients have had a brain implant for years, giving the researchers long-term data about the relationship between seizures and brain activity. From this, the researchers were able to develop predictive algorithms that forecast seizures.

As NewAtlas reports, these algorithms were then tested on long-term data gathered from the more than 150 people who participated in the decade-long clinical trials testing the brain implant system. According to Vikram Rao, the co-senior author of the new study, the data shows that it was possible to effectively forecast high seizure risk three days ahead in nearly 40 percent of subjects and one day ahead in 66 percent of subjects.

This doesn’t mean they can predict when one will take place, but they can predict when it’s most likely to occur. You could think of it more like a weather forecast that helps guide a person with epilepsy in their decisions over future activities.

Although more work will have to be done to get the system ready for further clinical use, the scientists believe they are a big step closer to being able to forecast seizures days in advance.