By: Natalie L. Boehm, MBA, RBLP-T and Dr. Sharon Raju, BDS, MHA, LSSGB, PMEC
What is a Stereo EEG?
According to Cleveland Clinic, a stereoelectroencephalography, also known as a SEEG or Stereo EEG, is a minimally invasive surgical procedure that is used to precisely find the areas of the brain where seizures originate. Stereo EEGs are used to pinpoint the area that seizure activity is taking place and can find more information than an EEG.
History of Stereo EEG
Stereo EEG was created by Jean Talairach, a French neurosurgeon and Jean Bancaud, a French neurologist and neurophysiologist. In the article, The history of invasive EEG evaluation in epilepsy patients, Talairach was working with stereotactic procedures. He worked to improve the implantation technique, defined a system of reference lines and structures that allowed an individualized and optimized approach for investigations of deep brain structures and their anatomical localization (Reif et. al., 2016). Years later, Talairach met Bancaud, a neurologist and neurophysiologist interested in EEG. Together, the two advanced stereotactic techniques in epilepsy patients (Reif et. al., 2016). Through learning about the depth electrodes had to be placed and where, gave Talairach and Bancaud access to examining seizure patterns. It allowed longer recording and allowed neurologists and neurosurgeons to have a resource in finding specifically where a seizure was taking place in order to decide if surgery was a solution to controlling seizure activity.
Who is eligible to have a Stereo EEG?
According to Cleveland Clinic, if you have been diagnosed with focal epilepsy and experience complex partial seizures that do not respond to medication treatment, are a potential candidate for surgery, and other tests (EEG, MRI) cannot locate the location of seizure activity, you are a candidate for a Stereo EEG.
What are the benefits?
Stereo EEGs give the neurologist and neurosurgeon the chance to pinpoint where seizure activity is coming from. Patients with refractory epilepsy, also known as drug-resistant epilepsy (when two or more anticonvulsant medications fail to control seizure activity) can have a Stereo EEG done to locate where their seizures are located in the brain. Once the location is found, doctors can do further testing to make sure there will be no risk in removing the part of the brain.
How to prepare for a Stereo EEG
Before the procedure, your doctor will review your medical history and may order some tests before scheduling the procedure. It is important to answer all questions and comply with what the doctor needs before having the procedure.
How a Stereo EEG is performed
A Stereo EEG takes one to two hours to perform. Patients are put under general anesthesia. Once asleep, the surgeon drills several very small access holes, around 2.3 millimeters in diameter into the skull (Mayo Clinic, 2018). Around ten to fifteen electrodes are placed in the brain, where physicians suspect seizure activity is taking place (University of Pittsburgh, 2022). The purpose of the test is to map out where seizure activity is taking place and locate important functioning areas such as speech.
Once the procedure is completed, a CT scan is performed, and the patient is taken back to the Epilepsy Monitoring Unit for observation (University of Pittsburgh, 2022). Patients can be kept for days while the team gathers the necessary information. Patients will be slowly taken off their anticonvulsant medication to gather seizure activity. Once the mapping is completed and any seizures activity is collected, the patient is taken back to surgery to have the electrodes removed. Patients are kept overnight for observation and are allowed to go home the next day.
What to expect after
The neurologist and EMU team will consult with the patient to let them know the test results and if they are a candidate for surgery. A few weeks after testing, if a patient is eligible for surgery, the surgical team will contact the patient to plan surgery. According to the University of Pittsburgh, options for surgery are craniotomy for removal of the seizure focus, laser ablation of the seizure focus, and neuromodulation including RNS, DBS, and VNS (University of Pittsburgh, 2022).
Risks
Like all procedures, SEEG’s have risks, even though the statistics are very low. According to the article, Stereoelectroencephalography: Indication and Efficacy, the pooled prevalence (statistical measuring technique) was low. Major complications of SEEG were intracerebral hemorrhages (pooled prevalence 1.0%) and infections (pooled prevalence 0.8%) (Ilda and Otsubo, 2017). Permanent neurological deficits accounted 0.6% and mortality rates are 0.5% (1 in 200 patients) primarily due to intracerebral hematoma due to electrode placement (Ilda and Otsubo, 2017).
Conclusion
According to Cleveland Clinic, a stereoelectroencephalography, also known as a SEEG or Stereo EEG, is a minimally invasive surgical procedure that is used to precisely find the areas of the brain where seizures originate. Stereo EEGs are used to pinpoint the area that seizure activity is taking place and can find more information than an EEG.
Individuals who are battling focal epilepsy and are experiencing complex partial seizures are candidates for a Stereo EEG. Once the area where seizure activity is discovered, doctors can decide if surgery is an option.
Stereo EEGs are low risk to have. According to the University of Pittsburgh, options for surgery are craniotomy for removal of the seizure focus, laser ablation of the seizure focus, and neuromodulation including RNS, DBS, and VNS (University of Pittsburgh, 2022).
Resources:
Cleveland Clinic (2020). Stereoelectroencephalography (SEEG). Cleveland Clinic. Retrieved from: https://my.clevelandclinic.org/health/diagnostics/17457-seeg-test
Ilda, K., & Otsubo, H. (2017). Stereoelectroencephalography: Indication and Efficacy. Neurologia medico-chirurgica, 57(8), 375-385. https://doi.org/10.2176/nmc.ra.2017-0008
Mayo Clinic (2018). Minimally invasive options for medically refractory epilepsy. Mayo Clinic. Retrieved from: https://www.mayoclinic.org/medical-professionals/neurology-neurosurgery/news/minimally-invasive-options-for-medically-refractory-epilepsy/mac-20430455
Reif, P.S., Strzelczyk, A., and Rosenow, F. (2016). The history of invasive EEG evaluation in epilepsy patients. Seizure, 41, 191-195. https://doi.org/10.1016/j.seizure.2016.04.006 University of Pittsburgh Neurological Surgery (2022). Stereoelectroencephalography (SEEG). University of Pittsburgh School of Medicine. Retrieved from: https://www.neurosurgery.pitt.edu/centers/epilepsy/seeg
