Data deluge: A patient waves a wand over her head to download data recorded by the Neuropace device before and after stimulation.
While the results of the trial may seem modest, the neurosurgeons who ran the clinical studies emphasize that the patients in the trial had severe epilepsy. “These patients tended to have frequent seizures, at least three per 28-day period, and many had three times that many,” says Gregory Bergey, a neurologist and director of the Johns Hopkins Epilepsy Center at Johns Hopkins University in Baltimore, who led one part of the Neuropace trial.Most of the patients had suffered from epilepsy for 20 years or more and were taking an average of three drugs to control their seizures. A third had already tried vagus nerve stimulation, and a third had already had epilepsy surgery.
“Itsounds incredibly invasive, but these patients have a form of the disease that is so terrible that they are almost willing to try anything we can do to stop there seizures,” says Kenneth Vives, a neurosurgeon at Yale who also ran part of the clinical trial. “We would have been happier to see a better effect, but these patients had tried everything. So these gains are quite significant.”
According to the study, both the procedure and device appear relatively safe. A few patients suffered infections or bleeding, but at rates lower than for comparable procedures. And those who were treated with the device didn’t show any differences in signs of depression or memory impairment compared to those given the sham treatment. While invasive, one of the benefits of the device is that it doesn’t carry the side effects of many epilepsy medications, such as sleepiness or double-vision, says Bergey.
A drawback is that the device is fairly complex to use. After surgery, patients go through an optimization period, during which doctors program it to recognize a typical pattern that precedes the seizure and deliver a particular pattern of electrical activity. Patients wave a wand over the device to download data recorded before and after stimulation, so that physicians can monitor how well these parameters are working and adjust them accordingly. “There is a steep learning curve,” says Vives. “But as we gained experience, it was not so difficult.”
Because the device is so new, researchers believe that its effectiveness will improve as they learn more about what works best in individual patients. For example, since starting the trial, researchers have learned that the most effective pattern of stimulation is predicted in part by the spot in the brain where the seizure originates. Most patients in the study have seizures originating in the hippocampus, though some had abnormal activity originating in parts of the cortex, or in both areas. “We learned that people with hippocampal origins tend to respond better to high-frequency stimulus,” said Morrell, while those whose seizures originate in the neocortex respond better to somewhat lower frequencies.
Neurosurgeons are also excited about the device’s potential to help them better understand epilepsy. “We have, in some cases, four to five years of continuous activity,” says Bergey, recorded as people go about their everyday lives.
“There are all sorts of interesting phenomena we can start to look at and understand,” adds Vives. For example, researchers can determine if the patterns indicating the onset of a seizure change over time, or if there are certain factors that predict the outcome of a seizure. “These are questions we could never answer before,” says Vives.