« We must learn to live together as brothers or perish together as fools.» (Martin Luther King Jr. (1929-1968)) Martin Luther King was aware that cohesion is the foundation of success. The news give us an excellent illustration: the virtual epileptic patient (VEP).
This project is held in collaboration with Aix-Marseille University, The INSERM, the CNRS, and the epileptology department and clinical neurophysiology department of Marseille. Viktor Jirsa initiated this cooperation. It relies on the international project « The virtual brain». The aim of this project was to create a virtual brain to better understand the neural networks.
Starting from this idea, researchers used all the data from an epileptic patient to virtualize his own brain with all its peculiarities.
So before that, let’s start by understanding what epilepsy is, so as to be able to understand the advantage of the virtual epileptic patient.
An epileptic seizure is the result of a neuronal hypersynchronization which means there is an excessive synchronisation of neurons as a shorted wire. We can classify epilepsy into two categories : generalized epilepsy and focal or partial epilepsy. Generalized epilepsy is when the phenomenon takes place in the whole brain. In the case of focal epilepsies, the shock takes place in a specific zone thus called « epileptogenic zone ». Jirsa defines the epileptogenic zone by « the area in the brain responsible for the origin and early organization of epileptic activity. ». Furthermore, the « propagation zone » consists of areas that are recruited during the seizure evolution, but are by themselves not epileptogenic.
Some medications can cure epilepsy. However, thirty percent of the patients fail to respond to treatment. To solve partial epilepsies, patients can pass into surgery where surgeons remove the epileptogenic zone. These operations can leave more or less significant effects on the behavior or cognition. Today, each patient who candidates for surgery pass through a very invasive step: a stereotactic electroencephalogram (SEEG). This step consists of nine electrodes implanted directly into the brain. Then the surgeon can locate the source.
The VEP project is intended for patients with focal epilepsy so the aim is to avoid the SEEG. Jirsa uses every patient data to virtualize each patient’s brain peculiarity. Jirsa uses only non-invasive techniques to collect data.
This computer program taking into consideration the epileptogenicity of the brain areas. For example, right or left hipocampus and right or left hypothalamus are epileptogenic zones. On the other side, left thalamus, left temporal pole are propagation zones.
When the patient’s brain is virtualized, Jirsa apply a mathematical model called « the epileptor ». It’s a network node model. Concretely, it a succession of equations as a computer programming. This model allows several tests on the virtual epileptic patient. The epileptor contains variables for the fast discharges and the slow energetic processes.
To define the epileptogenic zone, the computer uses a spatial map of epileptogenicity. The epileptor can refer to the map of epileptogenicity and trigger seizures.
With this new technique, the surgeon can:
- simulate a seizure : the computer can calculate the magnitude of the propagation zone from an epileptogenic area
- Find the most appropriate surgical procedure for the patient’s situation: the computer can compare a large number of surgical options and determine the best.
- Anticipate the operation sequelae: he can simulate the operation. The surgeon can know in advance what cognitive functions are affected by the operation.
This is an important advance in the field of epilepsy because the operation can cure epilepsy and with this technology, operations will be more accurate with less sequelae. Moreover, the patient does not need to go through an invasive step before surgery.
The VEP is one of the first work about the implementation of the human virtual brain project. However, the aim is bigger because researchers want to use this technology to explore other pathologies. For example it could be interesting to apply this type of models to understand the degeneration of neurons in the brain of an Alzheimer’s patient.
Bibliography
Jirsa, V. K., Proix, T., Perdikis, D., Woodman, M. M., Wang, H., Gonzalez-Martinez, J., … & Bartolomei, F. (2017). The virtual epileptic patient: individualized whole-brain models of epilepsy spread. Neuroimage, 145, 377-388.
Un cerveau virtuel pour décrypter l’épilepsie. (2016). Repéré le 21 novembre 2017 à http://ins.univ-amu.fr/fr/a-virtual-brain-helps-decrypt-epilepsy/.
PIAU Clémentine, RECALDE Laura, BASTARD Camille
