If your seizures are not controlled by medications (refractory epilepsy), the expert team at Penn State Epilepsy Center will evaluate you for epileptic surgery. Not all patients are surgical candidates, but surgery can offer the best hope for a cure if you have refractory epilepsy. You will undergo detailed testing, known as a pre-surgical evaluation, at Penn State Health Milton S. Hershey Medical Center to determine if surgery is the most effective treatment option for you.
To qualify for pre-surgical testing, both adult and pediatric patients must be refractory and:
- Have a partial rather than generalized epilepsy (your epilepsy comes from a single part of your brain, versus both sides or all over your brain).
- The epileptic region should be in a part of the brain that is unlikely to result in major neurological complications if removed.
Pre-surgical testing is done in two phases to determine if you will be a good fit for epileptic surgery. The Phase I evaluation focuses on non-invasive tests. Not all patients will require every test during Phase I. Your epileptologist will determine the necessary and appropriate tests to best fit your needs.
Phase I testing can include:
- Electroencephalography (EEG) – outpatient test used to diagnose epilepsy and to determine if epileptic seizures are partial or generalized.
- Inpatient video-EEG monitoring in adult and pediatric epilepsy monitoring units – this important non-invasive test is performed with electrodes attached to the scalp. Patients are admitted to the hospital for several days to record seizures with both video and EEG.
- 3-Tesla Magnetic Resonance Imaging (MRI) – this test can detect abnormalities that could be the cause of epilepsy.
- Positron emission tomography (PET) – PET scans look at the metabolic activity of the brain and allow physicians to determine if your brain is functioning normally. PET scans are typically done in an outpatient setting. Our team will also record an EEG during the PET to confirm that you aren’t have a seizure at the time of the scan.
- Single-photon emission computer tomography (SPECT) – this test is performed during seizures and can identify the region of the brain with blood flow increases, determining where the seizure originated.
- Neuropsychological evaluation, functional MRI – these tests are used to assess cognitive functions, especially language and memory function. The functional MRI also measures blood flow changes in areas of the brain during specific cognitive tasks.
- Intracarotid amobarbital/methohexital (Wada test) – this test is performed in select cases and injects medication into one carotid artery at a time. The medication can cause a one-to-five-minute paralysis of one half of the brain to allow for testing of the other half. This test is also used to predict post-operative deficits in language and memory function.
Results of the inpatient video-EGG monitoring are compared to additional Phase I test results. Your epileptologist will determine if all of the tests conclude that your seizures are in the same region of the brain as the origin of epileptic seizures. If all the tests pinpoint the same location, you could be a good surgical candidate. After Phase I evaluation, our epilepsy team meets to discuss potential surgical options in a multidisciplinary setting. The team might determine that more testing is necessary. This additional testing is called Phase II evaluation and is done on a patient-by-patient basis as needed.
Phase II evaluation is more invasive and higher-risk for patients, as it involves video-EEG monitoring with electrodes that are placed inside the skull. The surgical testing options can either implant electrodes on the surface of the brain or within the brain. Once the surgical placement of the electrodes is complete, you will be transferred to the epilepsy monitoring unit for video-EEG monitoring.
The electrode types and implantation options for Phase II testing varies but can include:
- Subdural electrodes – placed directly on the surface of the brain and records the EEG without the interference of skin, fatty tissue, muscle and bone.
- Depth electrodes – small wires with electrodes implanted directly in the brain to record deeper brain activity.
- Combination of subdural and depth electrodes – some patients will receive a combination of both subdural and depth electrodes.
- Stereoelectroencephalography (stereoEEG) – multiple depth electrodes are implanted in a specific pattern individualized to the patient to encompass the seizure focus.
- Functional mapping – typically occurs in the Epilepsy Monitoring Unit after a sufficient number of seizures has been recorded. The team maps out critically important areas of the brain by using brief, painless electrical stimulation through each electrode.