The evaluation: how we find where seizures start.
Before anyone recommends surgery, we need to know your seizure types, where the seizures begin, and what that part of the brain does. The evaluation happens in phases. Your neurologist and the epilepsy surgery team decide which tests you need. Not every patient needs every test.
Phase 1: noninvasive testing.
Phase 1 is an admission to the epilepsy monitoring unit (EMU) for video EEG, combined with several tests that do not require surgery. The goal is to gather as much information as possible from outside the head.
Video EEG in the epilepsy monitoring unit. An EEG records the electrical activity of the brain through electrodes glued to the scalp. EEG technicians and neurologists watch the recording in real time for spikes, sharp waves, and rhythmic patterns that point to seizure activity. In the EMU we pair the EEG with continuous video, so we can match what your body does during a seizure with what the brain recording shows at the same moment. Staying for several days rather than a single outpatient session makes it much more likely that we capture your typical seizures, which is what surgical planning depends on.
MRI. Magnetic resonance imaging produces detailed pictures of the brain and is the main tool for finding a structural abnormality, such as scarring or a malformation, that may be producing seizures. MRI does not use radiation. You must hold still during the scan to get clear images. Some metal implants, such as certain pacemakers, cochlear implants, or metal fragments, can make MRI unsafe, so tell the team about anything metal in your body.
PET. A positron emission tomography scan measures how the brain uses energy. A small amount of radioactive tracer is injected into a vein and taken up by brain cells according to their activity. The region where seizures start often shows abnormal energy use, and this shows up on the PET images. PET helps us localize the seizure focus when the MRI is normal or ambiguous.
MEG. Magnetoencephalography detects the tiny magnetic fields produced by brain activity. You lie quietly in a shielded room while a helmet of sensors records the signals. Software then maps where the abnormal activity comes from, and the map is overlaid on your MRI. MEG is useful for pinpointing the seizure focus and for planning surgery around important brain regions.
Functional MRI. Functional MRI shows which parts of your brain handle language, movement, and sensation. You perform simple tasks, such as reading words or tapping your fingers, while the scanner records brain activity. This tells us how close the seizure focus is to regions we need to protect, and whether surgery can be done safely.
Neuropsychological testing. A neuropsychologist assesses memory, attention, language, planning and problem solving, visual and spatial skills, and general intellectual functioning through a series of structured tests. The results show how epilepsy is affecting your thinking and daily life, and they tell us how well the brain regions near the seizure focus are working. This helps predict how you might do after surgery. Testing is repeated after surgery to compare with your baseline.
Phase 2: stereo EEG.
When Phase 1 narrows the search but does not settle it, we may recommend stereoelectroencephalography, or sEEG. This is a surgical procedure in which thin, flexible electrodes are placed directly into the brain through small holes in the skull. Each electrode has multiple recording contacts along its length, so a single electrode samples a whole trajectory through the brain. The electrodes record seizures from inside the brain, which is far more precise than scalp EEG.
sEEG tells us whether the seizure focus can be removed or disconnected safely, and whether doing so is likely to stop the seizures. Compared with older intracranial recording methods that required opening the skull, sEEG uses small incisions, has a lower infection risk, and is well tolerated. While the electrodes are in place, we also keep scalp EEG electrodes on to provide the widest possible coverage.
The main risks are bleeding, at about 0.17 percent per electrode, and infection, at about 4 percent. Your surgeon will review these with you in detail.
Common questions about sEEG.
How much hair is removed? Only small patches are shaved where each electrode enters, to keep the site sterile and give the surgeon a clear field. The number of shaved spots matches the number of electrodes. The rest of your hair usually covers them during the monitoring period.
How many electrodes will be placed? It depends on what Phase 1 showed and varies widely from patient to patient. Most patients have between 8 and 22 electrodes.
How long will I be in the hospital? Seven to ten days is typical, but it depends on how many seizures you have. We can continue monitoring for up to three weeks if needed.
Will it hurt? Most patients tolerate sEEG well. Some have temporary jaw pain after the procedure, and mild headache is common. The care team treats any discomfort.
What happens when monitoring is done? Once we have the information we need, the electrodes are removed at the bedside. You are observed for six hours and go home later that day or the next morning, depending on the timing.
The multidisciplinary conference.
Every patient who completes an evaluation is discussed at our epilepsy surgery conference. Epileptologists, neurosurgeons, radiologists, neuropsychologists, physician assistants, and nurses review all of your results together. The purpose is to make sure nothing is missed and to reach a recommendation as a group. The outcome is a personalized plan, which may be a specific operation, further testing, or a nonsurgical treatment. Your neurologist or surgeon will then go over the recommendation with you.