Selecting patients for epilepsy surgery: identifying a structural lesion.

Abstract

One of the most important components of presurgical evaluation of patients with epilepsy is structural imaging, predominantly using magnetic resonance imaging. This study is now part of the basic assessment of patients with epilepsy and is as important as the electroencephalogram. Epilepsy protocol magnetic resonance imaging studies must be part of the overall assessment of the patient. To understand the basis of the epileptic disorder, interpretation of these investigations relies on knowledge of the clinical details and features of the seizures, the functional abnormality in the brain as shown on the electroencephalogram, and structural assessment of the brain with a magnetic resonance imaging study optimized for epilepsy. This review considers the essential elements of this issue and gives a broad overview of what imaging options are available for the investigation of the patient with epilepsy from the perspective of the practicing epileptologist.

Full text

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From the American Epilepsy Society 2009 Annual Course
Selecting patients for epilepsy surgery: Identifying a structural lesion
Graeme D. Jackson⁎, Radwa A.B. Badawy
Brain Research Institute, Florey Neurosciences Institutes, Austin Repatriation Hospital, Heidelberg West, Victoria, Australia
Department of Neurology, Austin Health, Heidelberg West, Victoria, Australia
Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia
a b s t r a c ta r t i c l ei n f o
Article history:
Received 15 September 2010
Accepted 19 September 2010
Available online 9 December 2010
Keywords:
Epilepsy
Focus localization
Epilepsy surgery
Structural lesion
Magnetic resonance imaging
Functional magnetic resonance imaging
Tractography
One of the most important components of presurgical evaluation of patients with epilepsy is structural
imaging, predominantly using magnetic resonance imaging. This study is now part of the basic assessment of
patients with epilepsy and is as important as the electroencephalogram. Epilepsy protocol magnetic
resonance imaging studies must be part of the overall assessment of the patient. To understand the basis of
the epileptic disorder, interpretation of these investigations relies on knowledge of the clinical details and
features of the seizures, the functional abnormality in the brain as shown on the electroencephalogram, and
structural assessment of the brain with a magnetic resonance imaging study optimized for epilepsy. This
review considers the essential elements of this issue and gives a broad overview of what imaging options are
available for the investigation of the patient with epilepsy from the perspective of the practicing
epileptologist.
© 2010 Elsevier Inc. All rights reserved.
1. Introduction
The main goal of epilepsy surgery programs around the world is to
render the patient seizure free without major side effects. This
involves appropriate clinical assessment, accurate localization of the
origin of seizures, and detection of a focal abnormality of the brain.
It is important to acquire data that allow one to understand the
mechanism ofthe seizuresin each individualpatient andto generatea
likely hypothesis as to the origin of the epilepsy disorder. Options for
treatment arise from this understanding.
Outcome for seizures is reasonable (60–70%) for temporal lobe
epilepsy with hippocampal sclerosis (HS) and for extratemporal
circumscribed focal lesions [1]. When these lesions are not present,
and despite what appears to be precise focus localization on both
scalp and even invasive electroencephalography [1,2], long-term
outcome is poor (b50%) [3–5]. Therefore, after definition of the
clinical context and seizure semiology, finding these lesions is critical
to any thorough presurgical evaluation.
The most important tests for assessment of patients with epilepsy
are the electroencephalogram (EEG), which shows functional abnor-
mality, and structural magnetic resonance imaging (MRI), which
reveals anatomical abnormality.
Although this is well understood, the practical reality remains that
despite the high efficiency of most centers in providing good EEG
interpretation, MRI is still often fully outsourced to the radiology
service and usually includes only basic imaging. It can be argued that
good epileptology must include responsibility for good-quality and
advanced imaging optimized for the patient's particular epilepsy
problem.
Optimized MRI studies should fit into the overall assessment of the
patient. In this review, we explain the essential elements of this issue
and give a broad overview of what imaging options are available for
the investigation of the patient with epilepsy from the perspective of
the practicing epileptologist.
2. MRI epilepsy protocol
Acquiring appropriate epilepsy-focused magnetic resonance
(MR) images of high quality and diagnosing the important lesions
with high sensitivity and specificity are imperative to the definition
and understanding of structural brain abnormalities in patients with
epilepsy.
Magnetic resonance image acquisition and interpretation need to
be focused on the problem of epilepsy, which involves close
interaction between the epileptologist, the radiologist, who must
understand the clinical needs, and the radiographer, who provides
high-quality epilepsy-focused images. All members of this team need
to understand some of the technical issues related to acquiring
optimum MR studies, such as dealing with partial volume, which can
blur the edges of a structure such as the hippocampus, as well as
having good spatial resolution, good signal-to-noise ratio, good con-
trast, and short imaging time (For a review of the physical principles
of imaging, see Jackson et al. [6].)
Epilepsy & Behavior 20 (2011) 182–189
⁎ Corresponding author. Brain Research Institute, Florey Neurosciences Institutes,
Austin Repatriation Hospital, Heidelberg West, Victoria 3081, Australia.
E-mail address: g.jackson@brain.org.au (G.D. Jackson).
1525-5050/$ – see front matter © 2010 Elsevier Inc. All rights reserved.
doi:10.1016/j.yebeh.2010.09.019
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2.1. Optimized imaging axis
Because the diagnosis of abnormalities in the mesial temporal
region is fundamental to the assessment of any patient with epilepsy,
all imaging should be performed in the plane of the hippocampal axis.
This means that the cross-sectional size of the hippocampus must be
assessed in images obtained in the coronal axis that transects the
hippocampus at right angles. This is because the hippocampus is
shaped like a seahorse, curving around the mesencephalon with a
superior rostrocaudal angulation of approximately 30° to 35°. Using
this angulation largely avoids partial volume effects, in particular in
the posterior sections of the body and tail of the hippocampus. Axial
images or reconstructions should also follow the long axis of the
hippocampus, thus avoiding similar problems.
2.2. Epilepsy protocol
A typical clinical scanning protocol for a patient with refractory
epilepsy may include T1-weighted imaging, T2-weighted imaging,
fluid-attenuated inversion–recovery (FLAIR) imaging, and three-
dimensional volume acquisition sequences. This protocol is the basis
of the initial screening study used to obtain structural information
with good morphology and signal data. This is usually sufficient to
detect all obvious lesions and evaluate HS and suggestive areas of
gyral abnormality. Further assessment using special studies, for
example, volumes, T2 relaxometry, further analysis of images, MR
spectroscopy, diffusion-weighted imaging, diffusion tensor imaging,
quantitative methods, and reconstructions, can be done to detect
subtle structural changes not easily seen on visual inspection.
Intensive investigation using functional studies, for example, lan-
guage and memory and functional MRI (fMRI), would be the final step
in assessment of surgical options and outcome.
2.3. T1-weighted images
T1-weighted imaging (short repetition time [TR] and echo time
[TE]) is commonly used to initially define the brain anatomy; thus
cerebrospinal fluid (CSF) is black, gray matter is gray, and white
matter is bright. Different sequences give different types of T1-
weighted images. Sequences giving an inversion-prepared, gradient-
echo, echoplanar image are fast, give good brain coverage, and often
allow reasonably thin slices to avoid “partial volume” effects. On the
other hand, a true inversion–recovery image gives better gray–white
matter contrast, improved contrast for gliosis, and also better
delineation of the internal features or architecture of the hippocam-
pus. These images take longer and have thicker slices and often
incomplete brain coverage, but they can be extremely helpful in
difficult cases.
2.4. T2-weighted images
T2-weighted images (long TR, long TE) usually show the CSF as
white and the gray matter of higher signal (brighter) than the white
matter. These images typically show pathology as areas of increased
signal and are used to assess whether the tissue is abnormal. As with
T1-weighted images, there are many choices of sequence that one can
use. Fast spin echo is a sequence that allows high-resolution images
with good contrast in a short time.
2.5. Fluid-attenuated inversion–recovery images
On FLAIR images, the CSF appears dark, which helps to identify
lesionswithlongT2relaxationtimes.Pathologystilllookshighinsignal
(bright). It is often much easier to see the pathology in these images,
largely because there is no concern that the signal change can be
attributed to partial voluming of the CSF and also because it is visually
easier to identify. FLAIR images are not good for looking at morphology
and may produce some artifactual signal increases in some areas. In the
case of epilepsy, the issue of most concern relates to subtle signal
changes in the mesial temporal regions on coronal images, in which
these artifacts need to be interpreted with an experienced eye.
2.6. High-resolution three-dimensional volume images
High-resolution three-dimensional (3D) volume images provide a
useful degree of T1-weighted contrast betweengray and white matter
and help greatly in the identification of subtle abnormalities, such as
those associated with malformations of cortical development. The 3D
data are made up of contiguous slices and allow characterization of
the spatial extent of anatomic structures. Common 3D acquisition
sequences include magnetization-prepared rapid acquisition gradient
echo (MPRAGE) and 3D fast spoiled GRASS (3D-SPGR) imaging,
where GRASS stands for gradient recalled echo acquisition at steady
state. These sequences use a combination of short TR and TE to
improve the time efficiency of the acquisition.
2.7. Quantification of volumes and T2 relaxometry in epilepsy
High-resolution T1-weighted 3D volume sequences can be used
quantitatively to measure the volume of any particular region of
interest. In the case of epilepsy this is usually the hippocampus [7].
Volumetric assessment can be done manually or with half- or fully
automated software, and increasingly advanced methods of anatomic
analysis are being developed and implemented. T2 relaxometry is the
quantitative determination of the T2 relaxation time. To achieve this,
several T2-weighted images are acquired at different echo times, and
in each voxel the resultant values are fit with an exponential decay
curve to estimate the T2 decay rate of the imaged tissue. In contrast to
elaborate volumetric assessment, the T2 relaxometry is a quick
technique with small variance and can be implemented in large-scale
studies.In addition,longitudinal studiesare possible,andthismakesit
possible to assess the progression of volumetric changesand may help
determine the effects of the primary disease from the secondary
effects of seizures.
2.8. Diffusion-weighted imaging
A diffusion-weighted signal reflects the molecular motion of water
in the extra- and intracellular environments. The extentof this motion
depends on the microscopic environment and, therefore, is tissue
dependent. In tissues with a linear arrangement of myelinated fibers,
such as white matter tracts, the molecular motion is restricted to the
axis along the white matter tracts. This is known as anisotropic
diffusion. In other tissue components, such as CSF, molecular motion is
not restricted in any direction, and this is known as isotropic diffusion.
Diffusion-weighted MR techniques are frequently used to assess early
signs of cerebralischemia. Diffusion changes similar to those observed
in ischemia may also be present in tumors or infection. Diffusion
imaging requires postprocessing, which allows the measurement of
summary parameters such as diffusivity and fractional anisotropy [8].
It is also possible to visualize the path of the white matter tracts using
tractography techniques [9].
2.9. Advanced analysis techniques
There are a number of methods for analysis of images. Voxel-based
methods such as voxel-based morphometry (VBM), voxel-based
relaxometry (VBR), and voxel-based diffusivity (VBD) can use
statistical methods to demonstrate the areas of the brain that differ
from control values. This approach is particularly powerful when
examining the effects between groups (such as patients with
temporal lobe epilepsy [TLE] and controls) [10].
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3. Findings on magnetic resonance imaging
The basic epilepsy protocol study is usually sufficient to detect HS,
malformations of cortical development, and other obvious lesions
(Table 1). If no abnormality is found, then advanced methods of
imaging and analysis need to be considered as quantitative analysis
can reveal more subtle abnormalities.
3.1. Hippocampal sclerosis
Hippocampal sclerosis is the most common cause of mesial TLE
[11] and is therefore one of the commonest lesions seen in patients
presenting with refractory focal epilepsy [12]. As described earlier,
imaging of the hippocampus and temporal lobe structures depends on
image orientation and image sequences optimized to display the
anatomy and signal abnormality of HS and temporal pathology [13].
The features of HS are altered signal in a small hippocampus and loss
of the normal internal architecture (Figs. 1 and 2) [13].
3.2. Abnormal signal in the hippocampus
Increased signal from the hippocampal body can easily be detected
by experienced observers using optimized T2-weighted sequences
(orientation and sequence) including CSF nulled sequences such as
the FLAIR sequence. The high signal is localized to the hippocampal
gray matter and usually can be seen in the middle of the structure if
the corresponding T1-weighted image is used to define the anatomic
boundaries (Fig. 1). Abnormal T2 signal is a reliable finding for HS;
however, the presence of normal dilation of the hippocampal fissure
can sometimes be incorrectly diagnosed as a high signal from the
hippocampus, though it is rarely mistaken for HS. It is also important
to remember that the mesial temporal region is an area where signal
change from flow artifacts in the adjacent major intracranial vessels
can generate doubt. This is why good knowledge of the mesial
temporal anatomy is of utmost importance.
A heavily T1-weighted sequence can be used if the hippocampus
looks normal or equivocal on other sequences in the context of a
diagnosis of TLE. If atrophic, the hippocampus more often demon-
strates decreased signal with a dark appearance in this sequence.
Bilateral hippocampal T2 signal abnormalities may be present,
which may create difficulties. In addition, artifact in the mesial
temporal region requires careful and experienced interpretation. For
example, high FLAIR signal in the hippocampus can be artifactual and
does not necessarily reflect increased T2 signal, which is the hallmark
of HS [14]. These and other problems are usually resolved by using
clearly defined criteria for the diagnosis of HS in optimized images or
by using more advanced methods of analysis or quantitation.
Table 1
Common MRI findings in patients with epilepsy.
Type of findingComment
Hippocampal sclerosis
Malformations of cortical
development
Other lesions
Dedicated epilepsy protocol is a must.
Signal-to-noise ratio and spatial resolution must be
optimal.
Basic MRI is appropriate and will demonstrate tumors
and vascular lesions.
Advanced methods of imaging and analysis might be
considered for further investigation; quantitative
analysis can reveal subtle abnormalities.
Nothing
Fig. 1. Coronal T1 (left) and coronal T2 (right) images showing small right hippocampus with high signal on T2, consistent with right hippocampal sclerosis.
Fig. 2. Coronal FLAIR image showing diffuse increase in signal in left hippocampus. An
additional small cystic nodule is present within this background high FLAIR signal.
These features are compatible with either a low-grade glioma or dysplastic/gliotic
nodule within the left hippocampus.
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3.3. Loss of definition of internal microarchitecture of the hippocampus
Normal internal morphological structure of the hippocampus is
produced by the alveus, the molecular cell layer of the dentate gyrus,
and the pyramidal cell layer of the cornu ammonis, and can be seen on
optimized coronal MR images. In HS, the loss of this normal internal
structure is a consequence of neuronal cell loss and replacement of
normal anatomic layers with gliotic tissue. Even in severe cases, the
alveus can sometimes give the appearance of structure in the
hippocampus, so experience in identification of the appearance of
the normal layers is important (Fig. 1).
3.4. Hippocampal dysplasia
Sometimes HS can exist without significant atrophy. Usually, high
signal in a large hippocampus reflects hippocampal dysplasia, and this
is why asymmetry between hippocampi should not be accepted as HS
on the side that may be interpreted as being small, and careful
assessment of the signal in that hippocampus is essential (Fig. 2) [7].
3.5. Anterior temporal lobe changes: The temporal pole
Hippocampal sclerosis is often associated with changes in the
anterior temporal lobe (Fig. 3). This includes hemisphere atrophy, and
white matter changes in the anterior temporal lobe. When HS is
present there also can be increased signal in the anterior temporal
pole whitematter. In somecases, thegray mattermay also showsome
change in signal; however, these changes are different than, and can
be distinguished from, focal cortical dysplasia.
3.6. Dual pathology
Dual pathology is present in at least half of all cases of HS. It is
nearly always ipsilateral. This can take one of two forms. In the first
case, there is a lesion, clearly unrelated to the HS (Fig. 4), and it is
usually on the same side as the HS. In the second, the MRI shows
changes in other parts of the brain that might be related to a common
injury that caused both the HS and changes such as unilateral atrophy
and anterior temporal lobe changes.
3.7. Malformations of cortical development
Malformations of cortical development (MCD) comprise a number
of pathological entities that result from derangements of normal
cortical development as a result of either abnormal neuronal prolif-
eration, migration, or organization [15]. These malformations usually
manifest during childhood with relatively dramatic refractory epi-
lepsy. Corticaldysplasia has been classified into what is nowknown as
Taylor-type dysplasia, characterized by the presence of balloon cells
with the abnormality often extendingfrom the ventricleto the cortex;
focal cortical dysplasia (FCD), which is a disorder of cortical organi-
zation and does not contain such cell types [16–18]; and hamartomas
of the temporal lobe, which are defined as abnormal proliferation of
neurons, meningeal cells, glial cells, or any combination of these cell
types without evidence of neoplastic changes [19,20].
Abnormal MRI signal changes can be seen in many patients with
focal dysplasia (Fig. 5a); however, they are often subtle, and
sometimes may not be very easy to appreciate on MRI, even with
ideal imaging, and the abnormality appears to be predominantly in
the white matter and may sometimes have a transmantle element
(arrow in Fig. 5b). Tuberous sclerosis has imaging features that are
similar to those of Taylor-type dysplasia (Fig. 6). Periventricular
nodular heterotopia is another important finding that can be easily
Fig. 3. Coronal T2 image showing left hippocampal sclerosis with additional left
temporal pole atrophy.
Fig. 4. Left: Axial T2 image showing a cystic lesion in the left parietal lobe surrounded by a rim of hemosiderin consistent with cavernous hemangioma. Right: Coronal FLAIR image in
the same patient showing left hippocampal sclerosis.
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missed(Fig. 7).Whennodularheterotopiaare present,focalresections
usually do not lead to a good outcome, regardless of how localized the
cortical EEG activity is. Dysplasia in the mesial temporal region can
also cause seizures indistinguishable from those in mesial TLE from
HS. In some cases these lesions can be subtle, and sometimes they are
associated with ipsilateral HS. Bilateral perisylvian polymicrogyria can
be easily missed if the thickened gray matter is not appreciated. These
lesions are often better appreciated in the parasagittal images, and
these need to be reviewed in all cases in which no other lesion is
identified (Fig. 8).
Careful assessment of the sulci and gyri is required, as a number of
lesions thatare highlysignificant for epilepsyare foundat the “bottom
of the sulcus.” In some cases there is a fine tract from the ventricle to
the sulcus. These lesions are often the hardest to see on MRI, but small
resections (Fig. 9) can render the patient seizure free. There are also a
range of abnormalities that give rise to diffuse pathology in the
hemisphere. These are usually readily identified. Curvilinear surfaces
can be of great help in visualizing abnormalities of gyral pattern and
understanding the anatomic location of an abnormality that may be
hard to appreciate in standard imaging planes. The curvilinear surface
maintains information about the gray and white matter and can be
more useful than a simple surface-reconstructed image. A number of
nonstandard investigations can be requested that might help in par-
ticularcasessuchasMRIsurfacecoilstudies,voxel-basedmorphometry,
and voxel-based relaxometry. Hypothalamic hamartomas (Fig. 10) are
best appreciated on sagittal MR images. Large lesions usually protrude
well down into the interpeduncular and prepontine cisterns, whereas
smaller lesions in the third ventricle can be easily missed on a cursory
examination of MR images [19,20].
3.8. Other lesions
3.8.1. Tumors
Astrocytic tumors constitute about 20% of lesions detected in
patients with epilepsy and often involve the parahippocampal gyrus
and the amygdala. Although anaplastic tumors or glioblastomas are
the most frequent astrocytic tumors; they usually present as a
primary tumor problem and are rarely seen in patients with
intractable epilepsy. In those patients, fibrillary astrocytomas are
most common. MRI typically demonstrates homogeneous masses,
with calcifications present in up to 20% of cases. The location is
variable, with cortical lesions extending into the white matter and
poorly demarcated. Pilocystic astrocytomas are more frequent in
children. On MRI these lesions are sharply demarcated and often
Fig. 5. Coronal T2 images from two separate patients showing (a) focal right frontal cortical dysplasia and (b) transmantle left frontal dysplasia with a clear tract (tail) going down
into the ventricle.
Fig. 6. Axial T2 image showing right frontal tuberous sclerosis.
Fig. 7. Coronal T2 image showing right periventricular nodular hetertopia (arrow). Note
overlying gyrus showing dysplastic features.
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lobular. Contrast enhancement is typically present as a result of prom-
inent vascularity. Edema is rare, and calcifications are not seen.
Xanthoastrocytomas usually occur in the first decade of life and have a
good prognosis. Cystic components are common in this tumor, which
usually occurs in the temporal or parietal region [21].
Oligodendrogliomas are histologically characterized by the pres-
ence of compact groups of large, rounded cells with empty cytoplasm,
often also with mixed glial components. These tumors are less
frequent than astrocytomas and uncommon in patients referred for
intractable epilepsy, but, when present, they are located within the
temporal lobe and tend to involve the amygdala and the uncus and
parahippocampal gyrus, with sparing of the middle and inferior
temporal convolutions. The underlying white matter often shows
tumor infiltration.
Mixed glial lesions are a common tumor type in epilepsy (about 5%
of foreign tissue lesions). Calcifications are often present. Seizures
begin typically in childhood. These tumors are seen predominantly in
young patients (b14 years). Gangliogliomas tend to spare the lateral
temporal neocortex and involve primarily the mesial structures.
Dysembryoplastic neuroepithelial tumors (DNETs) are a common
tumor type in patients with intractable epilepsy [22] (Fig. 11). These
tumors are usually located in the temporal region or, less commonly,
the frontal region. Cysts are uncommon. DNETs involve both gray and
white matter. Imaging findings are quite characteristic and, although
not pathognomonic of this condition, should strongly suggest the
underlying abnormality.
Metastatic spread of tumor to the brain is common and constitutes
approximately 20% of brain neoplasms. Seizures are the presenting
symptom in about 30% of patients with cerebral metastasis. Metas-
tases have fairly stereotyped localization (gray–white matter junc-
tion) and often have peripheral edema.
3.8.2. Vascular malformations
These lesions are not commonly (1–2%) encountered in patients
with intractable epilepsy referred to epilepsy surgery [23]. These
abnormalities are less frequent in the temporal lobes than in other
regions and can be divided into arteriovenous malformations,
cavernous angiomas, capillary telangiectasia, and venous angiomas.
Capillary telangiectasias and venous angiomas are rarely associated
with chronic seizure disorders Cavernous angiomas constitute a dis-
tinct vascular malformation. In the majority of patients with intrac-
table seizures, cavernous angiomas constitute the most common
vascular abnormality, particularly with multiple lesions. The MRI
features of cavernous angiomas are fairly characteristic (Fig. 4, right).
The lesions have a central core with mixed signals indicating blood
byproducts of different stages. Within the core, methemoglobin
Fig. 8. Coronal T1 image showing bilateral perisylvian polomicrogyria.
Fig. 9. Sagittal FLAIR image showing bottom of sulcus dysplasia with a tail into the
ventricle.
Fig. 10. Axial FLAIR image showing small to medium-sized hypothalamic hamartomas
from the mammilary bodies to the third ventricle, attached mainly to the left side.
Fig. 11. Coronal FLAIR image showing enlargement of the right amygdala with in-
creased FLAIR signal. The features are consistent with a dysembryoplastic neuroep-
ithelial tumor.
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appears as high signals often intermixed with lower signals. Typically,
a complete rim of hypointensity surrounds the central core. This rim is
usually hypointense on both long and short echoes, with marked
hypointensity in the longer echo. These lesions are void of mass effect
or surrounding edema, and they should be easily recognized. Venous
angiomas are probably the most common vascular malformation, but
they are rarely the cause of chronic epilepsy.
3.8.3. Posttraumatic lesions and stroke
Reorganization of damaged tissue after injury of any kind can lead
to epilepsy, and the presence of blood products in particular is highly
epileptogenic [24,25]. The imaging of these disorders is usually
straightforward and does not require an epilepsy protocol per se. Of
note, contusions commonly affect the temporal lobes, and the brain
injury is often bilateral and multilobar, even if the abnormalities seem
very focal on MRI.
4. Other imaging techniques
Functional MRI and EEG–fMRI can reveal remarkable aspects of
brain function. Functional MRI is a good technique for localizing
different body representations in the primary motor [26–31] and
somatosensory [32–34] cortex. Language fMRI using blood oxygen
level-dependent (BOLD) is a robust technique for the lateralization of
language, and this is in common use in epilepsy centers [26,35–40].
EEG–fMRI studies can be used to identify positive (activation) and
negative (deactivation) changes in BOLD contrast related to interictal
epileptiform discharges [41–44]. This can be used to provide further
localizing information for seizure foci [45,46]. Diffusion imaging and
tractography can also reveal important aspects of the microarchitec-
ture of the brain that are important in understanding the networks of
the brain that may be altered in epilepsy [8,9].
5. Conclusion
To understand the basis of the epileptic disorder, clear definition
of the epileptic events (clinical and EEG, functional neuroimaging),
the structural abnormalities in the brain, and the clinical context in
which seizures occur need to be taken into account. Unless high-
qualityinformationisobtainedinallthreeofthesedomains,thebasis
of the epilepsy in any individual has not been fully assessed. Many
levels of information can be acquired using MRI in patients with
refractory epilepsy. To make use of all the options available for the
investigation of the patient with epilepsy from the perspective of the
practicing epileptologist, a well-structured and continuous interac-
tion between the epileptologist and radiologist is necessary. This will
lead to acquisition of appropriate epilepsy-focused MR images of
high quality and diagnosis of the important lesions with high sensi-
tivity and specificity.
Ethical approval
We confirm that we have read the Journal's position on issues
involved in ethical publication and affirm that this report is consistent
with those guidelines.
Conflict of interest statement
None of the authors has any conflict of interest to disclose.
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