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  • Review Article
  • Published:

Imaging in the surgical treatment of epilepsy

Nature Reviews Neurology volume 6, pages 537–550 (2010)Cite this article

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Abstract

Medically refractory focal epilepsy is potentially curable by surgery. This Review considers the application of recent advances in structural and functional brain imaging to increase the number of patients with epilepsy who are treated surgically, and to reduce the risk of complications arising from such intervention. Current optimal MRI of brain structure can identify previously undetectable lesions, with voxel-based and quantitative analyses further increasing the diagnostic yield. If MRI proves unremarkable, PET (with 18F-fluorodeoxyglucose) and single-photon emission CT of ictal–interictal cerebral blood flow might identify the brain region that contains the epileptic focus. Magnetoencephalography plus simultaneous EEG and functional MRI can map the location of interictal epileptic discharges, thereby facilitating placement of intracranial recording electrodes to define the site of seizure onset. Functional MRI can also lateralize language and localize primary motor, somatosensory and language areas, and shows promise for predicting the effects of temporal lobe resection on memory. Tractography can visualize the main cerebral white matter tracts, thereby predicting and reducing surgery risk. Currently, displays of the optic radiation and pyramidal tracts are the most relevant for epilepsy surgery. Reliable integration of structural and functional data into surgical image-guidance systems is being pursued, and promises safer neurosurgery for epilepsy in the future.

Key Points

  • Currently available optimal structural MRI can reveal previously covert epileptic lesions, with quantitative and voxel-based analyses of MRI data increasing the diagnostic yield of such imaging

  • PET, single-photon emission CT (SPECT), EEG with simultaneous functional MRI (EEG–fMRI), and magnetoencephalography (MEG) should be considered if MRI is unremarkable or discordant with clinical and EEG data

  • PET, SPECT, EEG–fMRI and MEG can inform the strategy for placement of intracranial EEG electrodes

  • In clinical practice, fMRI is now used to lateralize language function and localize primary motor and sensory cortices

  • Electrical stimulation mapping is recommended for resections close to eloquent cortex to estimate and minimize the risk of causing new deficits

  • Tractography visualizes the main white matter tracts, and is used in surgical planning so as to minimize the risk of causing damage to these tracts

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Figure 1: Coronal fluid-attenuated inversion recovery MRI sequence acquired at 3T.
Figure 2: High-resolution T2-weighted coronal MRI scan.
Figure 3: Coronal 18F-FDG PET scan.
Figure 4: Combined EEG–fMRI and simultaneous ESI.
Figure 5: MEG of an interictal epileptic discharge.
Figure 6: Language mapping.
Figure 7: Prediction of verbal and visual memory decline after anterior temporal lobe resection using memory fMRI.
Figure 8: Visualization of the optic radiation.

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Acknowledgements

I am grateful to the Wellcome Trust (Program Grants 067,176 and 083,148), Wolfson Trust, Medical Research Council (G0301067), European Union (201,380) and the National Society for Epilepsy for their support. This work was undertaken at University College London Hospital and University College London, UK, which both receive a proportion of their funding from the UK Government Department of Health's National Institute of Health Research Biomedical Research Centers funding scheme. I am indebted to J. de Tisi for assistance with the bibliography and for formatting this paper, and to my colleagues at the National Society for Epilepsy's MRI Unit for their enthusiastic collaboration.

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  1. Department of Clinical and Experimental Epilepsy, National Society for Epilepsy, University College London Institute of Neurology, Queen Square, WC1N 3BG, London, UK

    John S. Duncan

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Duncan, J. Imaging in the surgical treatment of epilepsy. Nat Rev Neurol 6, 537–550 (2010). https://doi.org/10.1038/nrneurol.2010.131

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