Stereoelectroencephalography (SEEG) to Help
Treat Refractory Epilepsy Doug Coppa
Refractory Epilepsy
Epilepsy that cannot be controlled or treated by medication, also known as intractable or drug resistant epilepsy.
Affects about a third of epilepsy patients (20-40%)
Some disagreement on the precise definition of refractory epilepsy, difficult to diagnose
Treatment of Refractory Epilepsy
Inactivation or complete disconnection of Epileptogenic Zone (EZ) ◦ Epileptogenic Zone is defined as the “area of cortex x that is necessary and sufficient for initiating seizures and whose removal (or disconnection) is necessary for complete abolition of seizures” (Lüders et al. 1993)
◦ Can be inactivated by precise lesions in the brain or removed surgically
Detecting the Epileptogenic Zone
Brain Imaging ◦ Functional Magnetic resonance imaging (fMRI) ◦ Different forms of electroencephalography, both noninvasive and invasive (EEG) Focus on stereoelectroencephalography
EEG ◦ Measures electrical activity of the brain Ionic currents in neurons produce voltage fluctuations
Stereoelectroencephalography (SEEG)
EEG through electrodes implanted in/on brain tissue (invasive) ◦ Subdural Grid Electrodes
Square or rectangular grid used to cover large surface area of brain
SEEG continued Stereotactic Depth Electrodes
◦ Thin wires with electrodes, implanted deep into cerebral tissue
Implantation of Depth Electrodes
Multiple Brain Images produced to create mapping of brain
Stereotactic Planning software used to evaluate placement of depth electrodes
Implantation of Depth Electrodes Continued
Surgeons use robots to assist with lining up guiding screws for electrodes
SEEG Monitoring
Patients monitored for 3-15 days to allow for seizures to occur, doctors pinpoint epileptogenic zone
Advantages of SEEG depth electrodes
Minimally invasive compared to subdural electrodes
Low complication rates (1-5%)
Allows for monitoring of deep brain structures to determine EZ
Seizure-free rate after SEEG-guided resections was 62% after 12 months
Disadvantages
High cost for procedure
Complications are serious ◦ Can result in loss of motor function or death
Somewhat new method
Discussion
Can become more accurate and have less complications in future
Depth electrodes can pave way for brain-machine interfaces ◦ Electric signals in brain can be interpreted and used to operate computers
◦ Only 2 dimensional movement as of now, could become more advanced in the future
Sources Lüders HO, Engel J, Munari C. General Principles. In : Engel Jr. J, ed. Surgical
Treatment of the Epilepsies, Second Edition Ed. New York : Raven Press, 1993 : 137-53.
Vadera S, et al. Stereoelectroencephalography for continuous two-dimensional cursor control in a brain-machine interface http://thejns.org/doi/full/10.3171/2013.3.FOCUS1373
Cardinale F, et al. Stereoelectroencephalography: Surgical Methodology, Safety, and Stereotactic Application Accuracy in 500 Procedures https://academic.oup.com/neurosurgery/article/72/3/353/2236040/StereoelectroencephalographySurgical-Methodology
Gonzales-Martinez J, et al. Stereotactic placement of depth electrodes in medically intractable epilepsy http://thejns.org/doi/full/10.3171/2013.11.JNS13635
Turning to SEEG for Pediatric Patients with Refractory Epilepsy https://consultqd.clevelandclinic.org/2015/03/turning-to-seeg-for-pediatric-patients-with-refractory-epilepsy/
https://www.researchgate.net/figure/259111389_fig6_Intracranial-EEG-recording-recording-A-Localization-of-SEEG-electrodes-shown-on
Pre -surgery Intracranial Monitoring: Stereo-EEG Versus Subdural Electrodes https://www.epilepsy.com/learn/professionals/diagnosis-treatment/surgery/presurgical-evaluation/pre-surgery-intracranial