J Clin Neurol.  2008 Mar;4(1):1-16. 10.3988/jcn.2008.4.1.1.

Role of Neuroimaging in the Presurgical Evaluation of Epilepsy

• Wehner T
• Luders H

• KMID: 2287679
• DOI: http://doi.org/10.3988/jcn.2008.4.1.1

Abstract

A significant minority of patients with focal epilepsy are candidates for resective epilepsy surgery. Structural and functional neuroimaging plays an important role in the presurgical evaluation of theses patients. The most frequent etiologies of pharmacoresistant epilepsy in the adult population are mesial temporal sclerosis, malformations of cortical development, cavernous angiomas, and low-grade neoplasms. High-resolution multiplanar magnetic resonance imaging (MRI) with sequences providing T1 and T2 contrast is the initial imaging study of choice to detect these epileptogenic lesions. The epilepsy MRI protocol can be individually tailored when considering the patient's clinical and electrophysiological data. Metabolic imaging techniques such as positron emission tomography (PET) and single photon emission tomography (SPECT) visualize metabolic alterations of the brain in the ictal and interictal states. These techniques may have localizing value in patients with a normal MRI scan. Functional MRI is helpful in non-invasively identifying areas of eloquent cortex.

Keyword

Epilepsy; Surgery; MRI; PET; SPECT

MeSH Terms

Adult
Brain
Epilepsies, Partial
Epilepsy
Functional Neuroimaging
Hemangioma, Cavernous
Humans
Magnetic Resonance Imaging
Malformations of Cortical Development
Neuroimaging
Positron-Emission Tomography
Sclerosis
Tomography, Emission-Computed, Single-Photon

Figure

• 

  Figure 1 Left hippocampal sclerosis. The hippocampal formation is significantly smaller on the left (arrow) compared to the right on coronal T1 (A). Coronal FLAIR demonstrates subtle hyperintensity within the hippocampus on the left (arrow, B).

• 

  Figure 2 Malformation of cortical development in the right occipital lobe. Coronal T1 (A) shows abnormally configured cortex. Note the mass effect on the occipital horn of the lateral ventricle. On coronal T2, the heterotopic cortex is more clearly appreciated (B).

• 

  Figure 3 Cavernous angioma in the right frontal lobe. Coronal T1 shows an area of mixed signal intensity involving the orbitofrontal cortex (arrow, A). Axial gradient echo reveals a corresponding area of low signal intensity (arrow, B).

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  Figure 4 Dysembryoplastic neuroepithelial tumor (DNET) in the left mesial temporal lobe. Coronal T1 shows a mass with relatively homogenous hypointense signal (arrow, A). Coronal T2 reveals a more extensive area of hyperintense signal (B).

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  Figure 5 Ganglioglioma in the right mesial temporal lobe. Coronal T1 reveals mixed signal intensity in the right hippocampal formation (arrow, A) and a cystic-appearing structure of hypointense signal extending into the right temporal white matter. Axial FLAIR demonstrates more widespread hyperintensity in the right mesial temporal structures (arrows, B).

• 

  Figure 6 Convergent multimodal imaging in a patient with intractable left frontal lobe epilepsy. SISCOM demonstrated a cluster of hyperperfusion in the left superior frontal gyrus, consistent with the patient's ictal EEG. A subtle linear hyperintensity extending from the periventricular area to the left superior frontal sulcus is seen on the corresponding coronal FLAIR MRI slice. 18-FDG PET shows mildly reduced metabolism in the overlying cortex. Invasive video EEG using a combination of grid and depth electrodes revealed ictal onset from this area. Histopathology after prefrontal lobectomy showed focal cortical dysplasia.

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