Epilepsy is a relatively common brain disease, and may lead to frequent seizures (bursts of electrical activity in the brain leading to a range of malfunctions. In very severe cases an epileptic focus has to be removed surgically.
When this is at the medio-temporal location, there is a risk of cutting accidentally the optic radiation, a fiber bundle of the visual system (also called Meier’s loop, green in the picture), connecting the thalamus (red dots) to the visual cortex.
This could partially blind the patient, by blacking out the upper left or right visual field. This is a severe condition, preventing e.g. driving a car. The optic radiation however is located in different patients at quite different depths.
They asked us for help in designing a personalized surgical planning tool for surgical resection of the epileptic focus in severe cases. This had a large risk of damaging the optic fibers between the thalamus and V1. This sometimes partially made the patient blind. With our brain connectivity tools we were able to visualize the optic radiation, with the surgical path, and succeeded in enabling it as a vision sparing operation.
We have been asked by Kempenhaeghe, Academic Center for Epileptology in Heeze, the Netherlands, to assist: tractography from Diffusion Tensor Imaging can assist the neurosurgeon to plan a safe operation beforehand. Kempenhaeghe, 10 km from TU/e, is the largest epilepsy center in the Netherlands. They have excellent facilities, such as a dedicated 3T MRI.
We developed an excellent collaboration with prof. Paul Boon and dr. Pauly Ossenblok.
Dr. Ossenblock
Prof.Boon
First, the location of the visual primary cortex (V1) is mapped with functional MRI. Then the fibers are tracked from the manually delineated lateral geniculate nucleus (LGN, in the thalamus) to V1.
We developed a dedicated workstation to accurately measure surgical distances in 3D, e.g. from the medio-temporal horn to the tip op Meijer's loop.
The fiber fields are de-noised, and visualized into the 3T MRI for surgical planning.
Three different bundles are visualized: The blue bundle depicts the lower visual field, the purple depicts the foveal field, and the yellow the upper visual field. Movies by (MSc student) Stephan Meesters.
As can be seen in the picture below, the resected area at the right has not damaged the optic radiation, leaving all vision intact.
At Kempenhaeghe, thanks to this effective visualization and surgical planning no patient has been visually impaired anymore due to this operation.
vIST/e, the world's most sophisticated GPU-based brain connectivity visualization package, written by Anna Vilanova and her team at the Biomedical Image Analysis Group at Eindhoven University of Technology, the Netherlands (chair: prof. Bart M. ter Haar Romeny).
Kempenhaeghe Epilepsy Institute, Heeze, the Netherlands.DTI data: 3 Tesla MRI scan, diffusion tensor imaging with 32 directions.
C. Tax, R. Duits, B. ter Haar Romeny, A. Vilanova and P. Ossenblok, "Tractography of the optic radiation for vision sparing epilepsy surgery," 2012 IEEE International Conference on Information and Automation, 2012, pp. 441-445, Doi: 10.1109/ICInfA.2012.6246846. Tax, Chantal MW, Remco Duits, Anna Vilanova, Bart M. ter Haar Romeny, Paul Hofman, Louis Wagner, Alexander Leemans, and Pauly Ossenblok. "Evaluating contextual processing in diffusion MRI: application to optic radiation reconstruction for epilepsy surgery." PloS one 9, no. 7 (2014): e101524. URL. Meesters, Stephan, Pauly Ossenblok, Louis Wagner, Olaf Schijns, Paul Boon, Luc Florack, Anna Vilanova, and Remco Duits. "Stability metrics for optic radiation tractography: towards damage prediction after resective surgery." Journal of Neuroscience Methods 288 (2017): 34-44. URL.
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