Penn Neurology and Penn Neurosurgery are using intracranial monitoring and minimally invasive advanced epilepsy diagnostics to address the spectrum of epilepsy seizure types, and engaging in promising clinical studies of a new subcutaneous EEG device.
The Role of EEG Monitoring for Seizures
Researchers have made great strides since the first human electroencephalography (EEG) recording in 1924, including the use of intracranial EEG for more detailed recordings from the brain. But only within the last decade or so have neurologists and neurosurgeons in the United States shifted towards using minimally invasive intracranial EEG and long-term EEG monitoring techniques for epilepsy.
In patients with seizure disorders, including epilepsy, EEG often shows abnormal activity in some part of the brain. This data can help diagnose whether patients have seizures, what type of seizures they have and where in the brain seizures originate. In cases where epilepsy surgery is being considered, EEG can also be used to identify brain areas with critical functions, such as control of movement and language.
EEG has evolved in the last two decades to better represent the spectrum of seizure disorders.
“We offer everything from the basic routine EEG to advanced intracranial recordings, depending on what each patient needs,” says epileptologist Saurabh R. Sinha, MD, PhD, director of EEG laboratories at the Penn Epilepsy Center.
The full range of options includes:
- Standard EEG (overall scalp recordings)
- Extended scalp EEG (four to six-hour outpatient studies)
- Ambulatory EEG (portable, at-home recording system)
- Inpatient video-EEG monitoring (scalp or intracranial EEG recordings paired with high-resolution video)
- Intracranial monitoring (recordings from the brain’s surface or deep within the brain)
- Brain mapping (part of intracranial monitoring to identify eloquent brain)
Dr. Sinha and his colleagues turn to intracranial monitoring when other tests haven’t provided enough clarity. By placing electrodes directly into brain tissue, they can better pinpoint where seizure activity starts and determine treatment plans moving forward.
Experts in Stereotactic-EEG Diagnostics
Historically, intracranial monitoring for epilepsy meant a craniotomy to place subdural electrode grids and strips. In addition to the complexities of recovery from open surgery, craniotomy can be quite difficult for patients and provides limited access to deeper structures in the brain. To overcome these limitations, surgeons at Penn Medicine and elsewhere have increasingly turned to minimally invasive technologies and another approach to intracranial EEG, stereoelectroencephalography (or stereo-EEG).
This procedure places electrodes deep within targeted areas of the brain through keyhole openings in the skull. Stereo EEG is enhanced at Penn Medicine by the comprehensive Level 4 Epilepsy Center’s Robotic Stereotactic Assistance (ROSA) system.
The ROSA robot keeps Penn neurosurgeons on a precise trajectory as they insert each electrode in targeted areas of the brain. Using a noninvasive laser to make exact measurements, ROSA assists for a faster procedure, optimized electrode placement and reduced risk.
“The stereotactic approach is much better tolerated by patients, and you can get the same type of data — perhaps even better — as with grids and strips,” says Dr. Sinha. “I’ve seen 4-year-old kids playing with their toys the evening after they had electrodes put in.”
Patients fully recover from minimally invasive stereo-EEG in one to two weeks. Results from the testing inform plans for resective surgery, laser ablation, or a neuromodulatory device for epilepsy treatment. Brain mapping during intracranial monitoring also provides information necessary for surgery planning.
“Sometimes you need to know how close the area is that’s causing seizures to areas that might be critical for a patient's language function or movement,” says Dr. Sinha. This information helps the care team understand which treatment options are possible and what areas to avoid during resective surgery or laser ablation.
Following surgery, patients spend several days undergoing EEG monitoring in Penn’s state-of-the-art Epilepsy Monitoring Unit (EMU). Each room is equipped with a video EEG monitoring system, an automated ictal exam upon seizure onset, fall-resistant flooring, and integrated research equipment.
Creating a National Intracranial EEG Database
Most patients at Penn Medicine undergoing stereo-EEG monitoring are candidates for participation in the epilepsy team’s research efforts to create an extensive database. Carefully cataloging and collecting intracranial data from several epilepsy centers has been a major effort at Penn for well over a decade.
“Stereo-EEG is such a sophisticated process that even a busy center like Penn only does 30 to 40 procedures a year,” says Dr. Sinha. “To understand the whole picture, it’s really important to get data from other places and put it all together.”
The data helps inform research projects and proposals, including the study of EEG signal and the function of different areas in the brain. Dr. Sinha hopes the data will improve how care teams approach the diagnosis and treatment of epilepsy patients in the long term.
The Latest Research Advance: Subcutaneous Long-Term Home EEG Monitoring
To add to the methods of EEG monitoring for epilepsy, Penn Neurology is currently recruiting participants as one of two domestic locations for the first international trial to assess a new subcutaneous EEG device.
The 24/7 EEG™ SubQ solution, created by UNEEG medical A/S, offers continuous EEG monitoring at home and objective seizure counting for up to 15 months. Placed under the skin behind the ear using local anesthesia, the minimally invasive implant has one lead with three electrodes (two active and one reference). A small wearable recording device powers the implant, stores EEG data and shares it daily with providers.
“We often don’t have enough time to answer many of our questions, with ambulatory EEG limited to four days at most, and inpatient video-EEG monitoring limited to about a week,” says Michael Gelfand, MD, PhD, associate professor of clinical neurology and epileptologist at Penn Epilepsy Center. Among the unanswered questions are concerns about the nature of epilepsy seizures. Since neurologists don’t always know the patterns of a patient’s seizure cycle, for example, they may not conduct EEG monitoring at the optimal time to maximize findings. Additionally, inpatient monitoring can’t capture patients in their daily routine and home environment, which may influence seizure activity.
The UNEEG medical device eliminates these limitations. The study will evaluate the system’s safety and efficacy in detecting seizures in patients with temporal lobe epilepsy, as compared to the gold-standard video-EEG monitoring method.
“We’ve helped to develop the study and figure out the right questions to be asking to best understand the appropriate use of this device,” says Dr. Gelfand. “Although it’s not yet proven, I’m highly confident that the device will work for its fundamental indication.”
Currently, the UNEEG clinical trial only assesses the device over the temporal lobe. In the future, Dr. Gelfand expects it will be possible to place the device in multiple other locations, or on both sides of the brain simultaneously.
Who Can Benefit From Subcutaneous EEG?
The UNEEG medical device may help diagnose epilepsy in patients with seizures. According to the study’s eligibility criteria and Dr. Gelfand’s first-hand experience, the device could greatly benefit patients with:
- A clinical need for monitoring from an EMU
- An unknown seizure frequency
- Questions about whether events are seizures or not
- Seizures that may occur during sleep
- Symptoms that may or may not be associated with seizures
“For patients, a key question is, ‘Am I having seizures while I’m asleep that I don’t know about?’” notes Dr. Gelfand. “I think that’s a big need for a lot of patients, not just at Penn, but much more broadly in the future.”
The full study eligibility criteria is available at ClinicalTrials.gov (NTC04526418).
The Potential for a Broader Application
The Penn team believes that ultra-long-term EEG monitoring may help with additional aspects of epilepsy diagnosis and treatment, including:
- Confirming seizure freedom
- Helping with surgical treatment planning for drug-resistant epilepsy
- Identifying seizure foci
- Pinpointing the hemisphere(s) where seizures originate
- Tracking seizure occurrence over time
- Understanding the efficacy of seizure medication for an individual
“The UNEEG device may replace inpatient monitoring — a step into the future of recording what truly happens in a patient’s daily life, without needing to take patients off medication and introduce that risk,” predicts Dr. Gelfand. “It’s not a brain implant. It’s just a sub-scalp implant, and that’s a much lower impact.”
Additional Resources from the Penn Epilepsy Center