Longitudinal and cross-sectional analysis of
atrophy in pharmacoresistant temporal
lobe epilepsy
B.C. Bernhardt, BSc
K.J. Worsley, PhD
H. Kim, PhD
A.C. Evans, PhD
A. Bernasconi, MD
N. Bernasconi, MD,
PhD
Address correspondence and
reprint requests to Dr. Neda
Bernasconi, Montreal
Neurological Institute, 3801
University Street, Montreal,
Quebec, Canada H3A 2B4
neda@bic.mni.mcgill.ca
ABSTRACT
Background: Whether recurrent epileptic seizures induce brain damage is debated. Disease progression in epilepsy has been evaluated only in a few community-based studies involving patients
with seizures well controlled by medication. These studies concluded that epilepsy does not inevitably lead to global cerebral damage.
Objective: To track the progression of neocortical atrophy in pharmacoresistant temporal lobe
epilepsy (TLE) using longitudinal and cross-sectional designs.
Methods: Using a fully automated measure of cortical thickness on MRI, we studied a homogeneous sample of patients with pharmacoresistant TLE. In the longitudinal analysis (n ⫽ 18), fixedeffect models were used to quantify cortical atrophy over a mean interscan interval of 2.5 years
(range ⫽ 7 to 90 months). In the cross-sectional analysis (n ⫽ 121), we correlated epilepsy duration and thickness. To dissociate normal aging from pathologic progression, we compared aging
effects in TLE to healthy controls.
Results: The longitudinal analysis mapped progression in ipsilateral temporopolar and central and
contralateral orbitofrontal, insular, and angular regions. In patients with more than 14 years of
disease, atrophy progressed more rapidly in frontocentral and parietal regions that in those with
shorter duration. The cross-sectional study showed progressive atrophy in the mesial and superolateral frontal, and parietal cortices.
Conclusions: Our combined cross-sectional and longitudinal analysis in patients with pharmacoresistant temporal lobe epilepsy demonstrated progressive neocortical atrophy over a mean interval of 2.5 years that is distinct from normal aging, likely representing seizure-induced damage.
The cumulative character of atrophy underlies the importance of early surgical treatment in this
group of patients. Neurology® 2009;72:1747–1754
GLOSSARY
GM ⫽ gray matter; TLE ⫽ temporal lobe epilepsy; WM ⫽ white matter.
Supplemental data at
www.neurology.org
In temporal lobe epilepsy (TLE), a considerable body of MRI studies has established that
structural brain abnormalities extend beyond the hippocampus to involve other mesial and
limbic structures.1,2 Although the pathogenesis of such changes is not fully understood, experimental3 and human cognitive studies4 suggest that they may be related to recurrent seizures.5
MRI provides a unique tool to evaluate the effects of disease progression in vivo using
cross-sectional and longitudinal designs.6 Due to the difficulty in obtaining reliable estimates of
seizure counts, cross-sectional studies usually correlate morphometric measurements with duration of epilepsy. The drawback of this approach is the confounding effect of age, because it is
highly correlated to duration. On the other hand, correcting for age may fail to yield significant
results due to decreased effect size. However, cross-sectional studies generally offer the advan-
Editorial, page 1718
e-Pub ahead of print on February 25, 2009, at www.neurology.org.
From the Departments of Neurology (B.C.B., H.K., A.C.E., A.B., N.B.) and Mathematics and Statistics (K.J.W.), Montreal Neurological Institute
and Hospital, McGill University, Montreal, Quebec, Canada.
Supported by a grant from the Canadian Institutes of Health Research (CIHR). B.B. was supported by the German National Merit Foundation and
the German Academic Exchange Service.
Disclosure: The authors report no disclosures.
Copyright © 2009 by AAN Enterprises, Inc.
1747
Table 1
Demographic and clinical data in the cross-sectional sample
Group
Age, y
Male
Duration, y
SF
HA, n (%)
Surgery
Engel I
Controls (41)
33 ⫾ 12 (20–66)
19
NA
NA
NA
NA
NA
L TLE (54)
34 ⫾ 10 (16–54)
19
15 ⫾ 11 (0–42)
8 (1–150)
40 (74)
43
28
R TLE (49)
35 ⫾ 10 (18–55)
21
15 ⫾ 11 (0–49)
7 (1–330)
30 (61)
38
29
Age and duration of epilepsy are presented as mean ⫾ SD (range); SF is presented as median (range) seizure frequency per
month.
SF ⫽ seizure frequency; HA ⫽ number of patients with hippocampal atrophy ipsilateral to the seizure focus (percentage of
patients in the group); Engel I ⫽ seizure-free, i.e. Class I postsurgical outcome in Engel’s classification; TLE ⫽ temporal lobe
epilepsy.
tage of large sample sizes. Longitudinal
designs based on relatively short interscan intervals remove potential aging confounds.
Moreover, as they control for intersubject
variability, statistical sensitivity to detect subtle changes increases. Importantly, they allow
the quantification of morphologic changes
over time, thus inferring causality.
In patients with pharmacoresistant TLE,
longer disease duration has been consistently associated with progressive atrophy of mesiotemporal lobe structures, including the hippocampus
and entorhinal cortex.7-9 Whether recurrent seizures in these patients induce neocortical damage remains unclear. Since patients with intractable
seizures rarely refuse surgical treatment, only
one previous longitudinal study has been preformed in this cohort.9 Thus, progressive neocortical damage has been evaluated only in a
few community-based studies involving patients with seizures well controlled by medication.10,11 These studies concluded that
epilepsy does not inevitably lead to global cerebral damage, which may develop insidiously
over a period longer than 3.5 years.
Analyzing cortical thickness on highresolution MRI offers a reliable, direct, and
biologically meaningful index to quantify
neocortical atrophy.12 Moreover, combining
thickness measurement13 with powerful
surface-based registration achieves optimal
preservation of local surface topology and anatomic correspondence between individuals.14
Using such techniques in TLE, we have previously shown widespread atrophy in the temporal and frontocentral cortices.15
Our purpose was to track progression of neocortical atrophy in intractable TLE on MRI using longitudinal and cross-sectional designs.
1748
Neurology 72
May 19, 2009
METHODS Subjects. We randomly selected from our database 121 patients referred to our hospital for the investigation of
medically intractable TLE and no mass lesion (malformations of
cortical development, tumor, or vascular malformations). Demographic and clinical data were obtained through interviews
with the patients and their relatives. TLE diagnosis and lateralization of the seizure focus were determined by a comprehensive
evaluation including detailed history, video-EEG telemetry, and
neuropsychological assessment in all patients. The hippocampus
was segmented manually on MRI according to our previously
described protocols.2 Based on a volumetric assessment that takes
into account absolute volume and interhemispheric asymmetry,
we classified patients into those with hippocampal atrophy and
those with normal hippocampal volume.
Eighteen patients refused to undergo surgery at the first evaluation by our epilepsy team. These patients, however, agreed to have
repeated MRI scans. Seven of them eventually followed our recommendation and were operated at subsequent hospitalizations.
For patients who underwent surgery, we determined surgical
outcome according to Engel’s modified classification scheme.16
Qualitative pathologic examination17 of the resected tissue revealed hippocampal sclerosis in 59 (65%) patients and temporal
cortex gliosis in 12 (13%). Due to subpial aspiration, specimens
were unsuitable for histopathology in 20 (22%) patients.
In total, 42 serial MR scans with at least 2 scans (range ⫽ 2
to 5) per subject were available. All images were acquired on the
same MR scanner. The interval between the first and last scan
was 31 ⫾ 21 months (range ⫽ 7 to 90). These scans were examined in the longitudinal analysis. We analyzed the remaining 103
patients together with the first scan of the longitudinal sample in
the cross-sectional analysis.
The control group for cross-sectional analysis consisted of 41
age- and sex-matched healthy individuals (19 men; age 20 – 66
years, mean 33 ⫾ 12 years). The Ethics Committee of the Montreal
Neurological Institute and Hospital approved the study and written
informed consent was obtained from all participants. Demographic
and clinical data of all subjects are shown in tables 1 and 2.
MRI acquisition and processing. MR images were acquired on a 1.5 T Gyroscan (Philips Medical Systems, Eindhoven, Netherlands) using a three-dimensional T1-fast field
echo sequence providing an isotropic voxel size of 1 mm3. Images underwent correction for intensity nonuniformity18 and
were linearly registered into a standardized stereotaxic space
based on the Talairach atlas.19
For cortical thickness measurements, registered images were
classified into gray matter (GM), white matter (WM), and CSF.
We applied the Constrained Laplacian Anatomic Segmentation
using Proximity algorithm13 that iteratively warps a surface mesh
to fit the boundary between WM and GM in the classified im-
Table 2
Demographic and clinical data in the longitudinal sample
Group
Age, y
Male
Duration, y
SF
HA, n (%)
Surgery
Engel I
L TLE (8)
27 ⫾ 10 (17–46)
6
16 ⫾ 13 (1–39)
10 (2–30)
4 (50)
3
2
R TLE (10)
35 ⫾ 12 (17–48)
6
20 ⫾ 12 (7–43)
8 (80)
7
5
6 (4–330)
Age and duration of epilepsy are presented as mean ⫾ SD (range); SF is presented as median (range) seizure frequency per
month.
SF ⫽ seizure frequency; HA ⫽ number of patients with hippocampal atrophy ipsilateral to the seizure focus (percentage of
patients in the group); Engel I ⫽ seizure-free, i.e. Class I postsurgical outcome in Engel’s classification; TLE ⫽ temporal lobe
epilepsy.
age. It then expands the WM/GM boundary along a Laplacian
map to generate an outer surface along the GM/CSF boundary.
Surfaces were nonlinearly aligned to a surface template20 using a
2D registration procedure.14 We applied the inverse of the linear
registration matrix and measured cortical thickness in native
space as the distance between corresponding vertices of inner and
outer surface across 40,962 points in each hemisphere. Thickness data were blurred using a surface-based diffusion smoothing
kernel of 20 mm FWHM that preserves cortical topology.21
Statistical analysis. Analyses were conducted using the SurfStat (http://www.math.mcgill.ca/keith/surfstat/) toolbox for
Matlab.
Cross-sectional analysis. We correlated disease duration
and seizure frequency with mean hemispheric cortical thickness
and thickness at each vertex. As seizure frequency followed a
highly right-skewed distribution, it was log-transformed before
analysis. Hemispheres were pooled together according to side of
seizure focus to increase statistical power. To correct for potential effects of age, we correlated age with cortical thickness in
patients and controls separately. Linear models for mean hemispheric thickness and vertex-wise analysis contained a group and
age main effect term, and a group ⫻ age interaction effect term.
We assessed age-related differences in cortical thickness between
groups by testing the significance of the interaction term.
Longitudinal analysis. To examine the effects of the interscan interval, we fitted linear fixed-effects models containing time
from baseline scan and subject intercept as effects on mean hemispheric cortical thickness and thickness at each vertex. We tested for
a negative effect of time from baseline scan. Hemispheres were
pooled together according to side of seizure focus to increase statistical power.
To examine interactions between duration of epilepsy and
disease progression, we factorized duration of epilepsy with respect to its median (14 years) into short (i.e., ⬍14 years) and
long (i.e., ⱖ14 years). We then fitted a fixed-effects model as
above with the factorized duration as an additional term, and
tested on the interaction between time from baseline scan and
factorized duration.
Correction for multiple comparisons. In all vertex-wise
analyses, we used random-field theory for nonisotropic images to
detect significant clusters.22 This controlled the chance of ever
reporting a false positive to be below 0.05. Cortical significance
maps were also displayed at an uncorrected level of p ⬍ 0.005.
RESULTS Cross-sectional analysis. Effects of duration.
Duration of epilepsy was negatively correlated with
mean hemispheric cortical thickness ipsilateral (t ⫽
⫺2.0, p ⬍ 0.03) and contralateral (t ⫽ ⫺2.7, p ⬍
0.01) to the seizure focus (figure 1A). Vertex-wise
analysis (figure 1B) revealed cortical thinning in ipsi-
lateral mesiotemporal, orbitofrontal (p ⬍ 0.0001),
and parietal (p ⬍ 0.02) regions, as well as in a large
portion of the contralateral frontal lobe convexity (p
⬍ 0.0001), including the prefrontal, premotor, and
central areas.
Effects of seizure frequency. Seizure frequency was
negatively correlated with mean hemispheric cortical thickness ipsilateral to the seizure focus (t ⫽
⫺1.99, p ⬍ 0.05). Vertex-wise analysis (figure e-1
on the Neurology® Web site at www.neurology.
org) revealed cortical thinning in ipsilateral centroparietal regions (p ⬍ 0.001). Further trends (p
⬍ 0.005) were seen in ipsilateral posterior cingulate and frontal cortices bilaterally.
Effects of age. In controls, there were no negative
effects of aging on mean left and right hemispheric
cortical thickness (figure e-2A). In patients with
TLE, aging was associated with decreased cortical
thickness in the left (LTLE: t ⬍ ⫺4.48, p ⬍ 0.0001;
RTLE: t ⬍ ⫺4.08, p ⬍ 0.001) and right hemisphere
(LTLE: t ⬍ ⫺3.16, p ⬍ 0.002; RTLE: t ⬍ ⫺3.15,
p ⬍ 0.002). In the left hemisphere, the slope in both
TLE groups was steeper than in controls (LTLE: t ⬍
⫺1.95, p ⬍ 0.03; RTLE: t ⬍ ⫺1.89, p ⬍ 0.04).
Similar effects were seen in the right hemisphere, but
did not reach significance.
Vertex-wise analysis (figure e-2B) in controls
showed a cluster of negative age effects in left inferior frontal cortex (p ⬍ 0.0001). The effects of
aging were similar in both TLE groups. In LTLE,
clusters of negative age effects were located bilaterally in frontal and central (p ⬍ 0.0001), left posterior insular (p ⬍ 0.05), posterior mesiotemporal
(p ⬍ 0.05), and right prefrontal and cuneal (p ⬍
0.05) cortices. In RTLE, clusters of negative age
effects were found bilaterally in frontal and central
(p ⬍ 0.0001), parietal (p ⬍ 0.0001), temporooccipital (p ⬍ 0.04), and left prefrontal (p ⬍
0.005) cortices.
Vertex-wise analysis of differences in aging (figure
e-2C) revealed multiple areas in frontal and occipital
areas, with stronger effects in patients compared to controls. In LTLE, a cluster was found in left medial frontal
and central regions (p ⬍ 0.01). In RTLE, clusters of
Neurology 72
May 19, 2009
1749
Figure 1
Cross-sectional analysis
Effects of duration on (A) mean cortical thickness (black dots represent individual patients with temporal lobe epilepsy; the
solid black line describes the linear regression model) and (B) thickness at each vertex. Significances have been thresholded
at p ⬍ 0.005. Peak positions and resolution elements (i.e., resels) of significant clusters after random field theory correction
are shown (cluster threshold t ⬎3.2, cluster extent threshold 0.8 resels).
steeper aging effects were found in the left medial and
lateral frontal (p ⬍ 0.002), left occipital (p ⬍ 0.0001),
and right parietal (p ⬍ 0.0001) cortices.
Longitudinal analysis. Effects of interscan interval. We
found a progressive decrease in mean cortical thickness
in the hemisphere ipsilateral (⫺0.016 ⫾ 0.009 mm/
year; t ⫽ ⫺2.20, p ⬍ 0.02) and contralateral to the
focus (⫺0.022 ⫾ 0.009 mm/year; t ⫽ ⫺2.88,
p ⬍ 0.01) (figure 2A). Annual rates of cortical atrophy
(figure 2B) exceeded 0.05 mm/year in bilateral prefrontal, insular, frontocentral; ipsilateral entorhinal; and
contralateral temporal and posterior cingulate regions.
Vertex-wise analysis (figure 2C) revealed progressive cortical atrophy in contralateral insular
and posterior cingulate (p ⬍ 0.05) regions. Moreover, additional areas of atrophy were found in
bilateral frontal (orbitofrontal and superior frontal), parietal, and temporal (ipsilateral temporopolar and contralateral lateral temporal) areas (p ⬍
0.005, uncorrected).
Interaction between epilepsy duration and disease progression.
1750
We found a faster progression of atrophy in
Neurology 72
May 19, 2009
patients with long duration of epilepsy (ⱖ14 years)
compared to those with shorter duration (⬍14 years)
in the hemisphere ipsilateral (t ⫽ 2.12, p ⬍ 0.03)
and contralateral (t ⫽ 1.84, p ⬍ 0.05) to the focus
(figure 3). Vertex-wise analysis showed that in patients with longer disease, cortical atrophy progressed
faster in bilateral frontocentral (ipsilateral: p ⬍
0.002; contralateral: p ⬍ 0.04) and ipsilateral parietal
(p ⬍ 0.01) regions.
This study combines both crosssectional and longitudinal designs to assess the impact of disease progression on the neocortex in
intractable TLE. In the cross-sectional study, we
took advantage of a large sample of patients with a
wide range of epilepsy durations and compared aging
effects to healthy controls, dissociating pathologic
progression from normal aging. In the longitudinal analysis, we used fixed-effect models to
precisely quantify cortical change over time. Importantly, we applied conservative corrections for
multiple comparisons using random field theory,
DISCUSSION
Figure 2
Longitudinal analysis
Effect of interscan interval on (A) changes in mean hemispheric cortical thickness (gray lines connect the MR scans, indicated as black dots; the mixed-effects model is plotted as a solid black line); (B) vertex-wise mean annual rate of cortical
thinning (in mm/year) in blue; (C) regions of vertex-wise progressive thinning (p ⬍ 0.005) in blue. Peak positions and resolution elements (i.e., resels) of significant clusters after random field theory correction are shown (cluster threshold t ⬎3.5,
cluster extent threshold 0.8 resels).
which ensures with 95% confidence that no reported result is a type 1 error despite the large
number of tests performed.22
The purpose of our cross-sectional analysis was to
study the overall effect of duration of epilepsy on
neocortical thickness. We found progressive atrophy
in ipsilateral orbitofrontal, mesiotemporal, and postcentral, as well as in contralateral prefrontal areas. In
a previous cross-sectional study using cortical thickness, progressive atrophy was found in somatomotor
and parahippocampal regions.23 Aging effects, however, were not dissociated from those related to disease duration. As disease duration is highly correlated
with age, statistically controlling for aging severely
reduces the sensitivity to detect significant effects.
In our study, we opted to separate these effects by
statistically comparing aging in patients to that in
healthy controls. Similarly to previously reported data,24
in controls we found neocortical atrophy related to aging in the inferior and middle frontal cortices. Aging
effects in patients, while somewhat similar in topography to those of duration of epilepsy, were considerably
more extensive and involved virtually the entire frontal
lobe. However, after comparison to controls, differences
became limited to smaller portions of the mesial frontal
and superior frontal lobe convexity, as well as the parietal cortex. This analysis therefore confirms that progressive atrophy in TLE is distinct from aging.
Using relatively short follow-up periods in a longitudinal design allows controlling for aging effects.
Since a subject is compared to his or her own baseline, such design provides a true measure of change
over time required to infer causality between seizures
and atrophy. However, adequately powered longitudinal analyses are difficult to perform as they entail
the combination of several factors, such as repeated
Neurology 72
May 19, 2009
1751
Figure 3
Longitudinal analysis
Interaction between duration of epilepsy and disease progression. Superior view showing areas undergoing faster
progression of atrophy (p ⬍ 0.005) in patients with longer
disease duration (ⱖ14 years). Peak positions and resolution
elements (i.e., resels) of clusters after random field theory
correction are shown (cluster threshold t ⬎3.5, cluster extent threshold 0.8 resels).
scans performed on the same hardware, reliable and
sensitive image postprocessing, and availability of a
relatively large group of patients.
In our study, we specifically aimed to assess cortical changes in a homogeneous cohort of patients with
pharmacoresistant TLE. We localized progressive
thinning in ipsilateral temporopolar and central, as
well as contralateral orbitofrontal, insular, and angular regions, over a mean interscan period of 2.5 years.
Strongest effects were seen in prefrontal and frontal
regions, with rates of atrophy in the order of 0.1 mm/
year. As drug-responding patients with TLE are generally not referred to our tertiary center, we could not
include a sizeable sample of these patients for comparison. A previous semiquantitative longitudinal
MRI study over a median interval of 3.5 years10 failed
to detect significant progression of cortical atrophy
in patients with relatively benign, pharmacologically
controlled forms of epilepsy. Although elevated proportions of patients with TLE had progressive subtle
diffuse atrophy compared to healthy controls,11 the
authors concluded that these changes resulted mainly
from an initial precipitating insult and aging, and not
from the disease. There are a number of differences
between these studies and our work. First, we have
assessed progressive changes in a homogeneous group
of patients with intractable TLE, while previous
data10,11 were based on groups of community-based
patients with various types of pharmacologically controlled epilepsy. From a methodologic point of view,
our approach is more sensitive and more reproducible since it does not require any operator intervention.11 Indeed, in contrast to a rater-based
1752
Neurology 72
May 19, 2009
measurement of change,10 automatically assessing
cortical thickness is an unbiased and more direct
measurement of atrophy. The algorithm used has
been validated against phantom data, and crossvalidated against other MRI surface extraction surface software, showing superior reproducibility.25
Importantly, by avoiding surface self-intersection, it
provides the most accurate geometry of the reconstructed surface, thus a topologically sound representation of the cortical mantle.25 In our analysis, the use
of a nonlinear 2D surface registration14 in addition to
the linear volumetric registration ascertains optimal
correspondence of thickness measurements from homologous regions across subjects, thus increasing the
sensitivity to detect significant changes. Moreover, in
contrast to volumetry, measuring thickness across
thousands of points allows precise mapping of the
topography of GM atrophy.
The pattern of progressive atrophy encompasses
both group differences of frontocentral cortical thinning and alterations of limbic network organization
in orbitofrontal and posterior cingulate and angular
gyri that we recently reported in TLE.15 Seizures have
been shown to increase markers of excitability, such
as glutamate.26 Furthermore, TLE has been associated with disruptions in cortical GABA-A-ergic circuits, potentially contributing to the genesis or
maintenance of seizure activity.27 Excessive metabolic activation resulting from a disrupted balance in
these systems may in turn promote epileptogenicity
and excitotoxicity, possibly through cellular reorganization.3 This may result in neuronal death and
plasticity in both seizure-generating regions, and in
neocortical circuits affected by seizure spread.28
Thus, it is plausible that changes observed in the current study may be related to the combined effects of
neuronal disconnection and seizure-related damage.
However, the putative effects of genetic factors and
antiepileptic drugs on atrophy progression cannot be
ruled out. The genetic makeup of an individual is
thought to influence susceptibility to precipitating
events, development of plasticity in neuronal networks, and pharmacoresistance.29,30 On the other
hand, we could not control for the effects of drugs
since our patients had been on multiple and varying
antiepileptic medication for several years. Effects of
drugs on the neocortex are largely unknown. While
some studies suggest that phenytoin31 induces cerebellar
atrophy and valproic acid32 pseudoatrophy of the brain,
others have shown that these drugs may have neuroprotective effects and promote neurogenesis.33,34
A recent randomized controlled trial35 demonstrated that 58% of surgically treated patients were
seizure free at 1 year, compared with 8% of medically
treated patients. The resulting practice guideline rec-
ommends that patients with partial seizures and
failed first-line antiepileptic medications should be
referred to an epilepsy surgery center, and that those
who meet the criteria for temporal lobe resection
should be offered surgery.36 Referral for evaluation,
however, tends to occur many years after medications
have failed, despite the fact that further medication
trials are ineffective once intractability sets in.35 During this time, patients are at increased risk of mortality37 and disability.
Neocortical atrophy in our patients with epilepsy
for longer than 14 years progressed more rapidly
than in those with shorter disease duration. Arguably, our results in pharmacoresistant patients may
not directly apply to those amenable with optimized
medical treatment. However, recent observations
from prospective studies in community-based centers
indicate that up to 35% of children with TLE may
develop intractability.38 Therefore, in light of functional data in humans showing progressive cognitive
decline4 and evidence demonstrating that recurrent
epileptic discharges provoke an extension of the epileptogenic network,39 our findings support the view
that early surgery should be offered to patients with
pharmacoresistant TLE.40
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
AUTHOR CONTRIBUTIONS
Statistical analysis was conducted by B. Bernhardt (Department of Neurology) and K. Worsley (Department of Mathematics).
17.
ACKNOWLEDGMENT
The authors thank the individuals who participated in this study.
18.
Received August 20, 2008. Accepted in final form December 15, 2008.
REFERENCES
1. Salmenpera T, Kalviainen R, Partanen K, Mervaala E,
Pitkanen A. MRI volumetry of the hippocampus, amygdala, entorhinal cortex, and perirhinal cortex after status
epilepticus. Epilepsy Res 2000;40:155–170.
2. Bernasconi N, Bernasconi A, Caramanos Z, Antel SB, Andermann F, Arnold DL. Mesial temporal damage in temporal lobe epilepsy: a volumetric MRI study of the
hippocampus, amygdala and parahippocampal region.
Brain 2003;126:462–469.
3. Sanabria ER, da Silva AV, Spreafico R, Cavalheiro EA.
Damage, reorganization, and abnormal neocortical hyperexcitability in the pilocarpine model of temporal lobe epilepsy. Epilepsia 2002;43 suppl 5:96–106.
4. Helmstaedter C, Kurthen M, Lux S, Reuber M, Elger CE.
Chronic epilepsy and cognition: a longitudinal study in
temporal lobe epilepsy. Ann Neurol 2003;54:425–432.
5. Sutula TP, Hagen J, Pitkanen A. Do epileptic seizures
damage the brain? Curr Opin Neurol 2003;16:189–195.
6. Briellmann RS, Berkovic SF, Syngeniotis A, King MA,
Jackson GD. Seizure-associated hippocampal volume loss:
a longitudinal magnetic resonance study of temporal lobe
epilepsy. Ann Neurol 2002;51:641–644.
19.
20.
21.
22.
23.
24.
25.
Bernasconi N, Natsume J, Bernasconi A. Progression in
temporal lobe epilepsy: differential atrophy in mesial temporal structures. Neurology 2005;65:223–228.
Theodore WH, Bhatia S, Hatta J, et al. Hippocampal atrophy, epilepsy duration, and febrile seizures in patients with
partial seizures. Neurology 1999;52:132–136.
Fuerst D, Shah J, Shah A, Watson C. Hippocampal sclerosis is a progressive disorder: a longitudinal volumetric MRI
study. Ann Neurol 2003;53:413–416.
Liu RS, Lemieux L, Bell GS, et al. Progressive neocortical
damage in epilepsy. Ann Neurol 2003;53:312–324.
Liu RS, Lemieux L, Bell GS, et al. Cerebral damage in
epilepsy: a population-based longitudinal quantitative
MRI study. Epilepsia 2005;46:1482–1494.
MacDonald D, Kabani N, Avis D, Evans AC. Automated
3-D extraction of inner and outer surfaces of cerebral cortex from MRI. Neuroimage 2000;12:340–356.
Kim JS, Singh V, Lee JK, et al. Automated 3-D extraction
and evaluation of the inner and outer cortical surfaces using a Laplacian map and partial volume effect classification. Neuroimage 2005;27:210–221.
Robbins S, Evans AC, Collins DL, Whitesides S. Tuning
and comparing spatial normalization methods. Med Image
Anal 2004;8:311–323.
Bernhardt BC, Worsley KJ, Besson P, et al. Mapping limbic network organization in temporal lobe epilepsy using
morphometric correlations: insights on the relation between mesiotemporal connectivity and cortical atrophy.
Neuroimage 2008;42:515–524.
Engel J, Jr., Van Ness PC, Rasmussen T, Ojemann LM.
Outcome with respect to epileptic seizures. In: Engel J, Jr.,
ed. Surgical Treatment of the Epilepsies, 2nd ed. New
York: Raven; 1993:609–621.
Meencke HJ, Veith G. Hippocampal sclerosis in epilepsy.
In: Lüders H, ed. Epilepsy Surgery. New York: Raven;
1991:705–715.
Sled JG, Zijdenbos AP, Evans AC. A nonparametric
method for automatic correction of intensity nonuniformity in MRI data. IEEE Trans Med Imaging 1998;
17:87–97.
Collins DL, Neelin P, Peters TM, Evans AC. Automatic
3D intersubject registration of MR volumetric data in
standardized Talairach space. J Comput Assist Tomogr
1994;18:192–205.
Lyttelton O, Boucher M, Robbins S, Evans A. An unbiased iterative group registration template for cortical surface analysis. Neuroimage 2007;34:1535–1544.
Lerch JP, Evans AC. Cortical thickness analysis examined
through power analysis and a population simulation. Neuroimage 2005;24:163–173.
Worsley KJ, Andermann M, Koulis T, MacDonald D,
Evans AC. Detecting changes in nonisotropic images.
Hum Brain Mapp 1999;8:98–101.
Lin JJ, Salamon N, Lee AD, et al. Reduced neocortical
thickness and complexity mapped in mesial temporal lobe
epilepsy with hippocampal sclerosis. Cereb Cortex 2007;
17:2007–2018.
Salat DH, Buckner RL, Snyder AZ, et al. Thinning of the
cerebral cortex in aging. Cereb Cortex 2004;14:721–730.
Lee JK, Lee JM, Kim JS, Kim IY, Evans AC, Kim SI. A
novel quantitative cross-validation of different cortical surface reconstruction algorithms using MRI phantom. Neuroimage 2006;31:572–584.
Neurology 72
May 19, 2009
1753
26.
Zilles K, Qu MS, Kohling R, Speckmann EJ. Ionotropic
glutamate and GABA receptors in human epileptic neocortical tissue: quantitative in vitro receptor autoradiography.
Neuroscience 1999;94:1051–1061.
27. Ragozzino D, Palma E, Di Angelantonio S, et al. Rundown of
GABA type A receptors is a dysfunction associated with human drug-resistant mesial temporal lobe epilepsy. Proc Natl
Acad Sci USA 2005;102:15219–15223.
28. Loup F, Picard F, Andre VM, et al. Altered expression of
alpha3-containing GABAA receptors in the neocortex of
patients with focal epilepsy. Brain 2006;129:3277–3289.
29. Dube CM, Brewster AL, Richichi C, Zha Q, Baram TZ.
Fever, febrile seizures and epilepsy. Trends Neurosci 2007;
30:490–496.
30. Sutula TP. Mechanisms of epilepsy progression: current
theories and perspectives from neuroplasticity in adulthood and development. Epilepsy Res 2004;60:161–171.
31. McLain LW, Jr., Martin JT, Allen JH. Cerebellar degeneration due to chronic phenytoin therapy. Ann Neurol
1980;7:18–23.
32. Papazian O, Canizales E, Alfonso I, Archila R, Duchowny M,
Aicardi J. Reversible dementia and apparent brain atrophy
during valproate therapy. Ann Neurol 1995;38:687–691.
33. Hao Y, Creson T, Zhang L, et al. Mood stabilizer valproate
promotes ERK pathway-dependent cortical neuronal
growth and neurogenesis. J Neurosci 2004;24:6590–6599.
34.
Magarinos AM, McEwen BS, Flugge G, Fuchs E. Chronic
psychosocial stress causes apical dendritic atrophy of hippocampal CA3 pyramidal neurons in subordinate tree
shrews. J Neurosci 1996;16:3534–3540.
35. Wiebe S, Blume WT, Girvin JP, Eliasziw M. A randomized, controlled trial of surgery for temporal lobe epilepsy.
N Engl J Med 2001;345:311–318.
36. Engel J, Jr., Wiebe S, French J, et al. Practice parameter:
temporal lobe and localized neocortical resections for epilepsy: report of the Quality Standards Subcommittee of
the American Academy of Neurology, in association with
the American Epilepsy Society and the American Association of Neurological Surgeons. Neurology 2003;60:538–
547.
37. Sperling MR, Feldman H, Kinman J, Liporace JD,
O’Connor MJ. Seizure control and mortality in epilepsy.
Ann Neurol 1999;46:45–50.
38. Berg AT, Vickrey BG, Testa FM, et al. How long does it
take for epilepsy to become intractable? A prospective investigation. Ann Neurol 2006;60:73–79.
39. Bartolomei F, Chauvel P, Wendling F. Epileptogenicity of
brain structures in human temporal lobe epilepsy: a quantified study from intracerebral EEG. Brain 2008;131:
1818–1830.
40. Langfitt JT, Wiebe S. Early surgical treatment for epilepsy.
Curr Opin Neurol 2008;21:179–183.
Earn Practice Management CME with AAN Audio
Conferences
The Academy is helping members take some of the confusion out of coding with a four-part series.
The 2009 Coding Audio Conferences will review proper coding in common circumstances, helping
participants to code with greater precision. Upon completion, physician participants will receive 1
CME credit per call, up to 4 CME credits total. Non-neurologists (e.g., practice managers) will
receive a certificate of completion redeemable for credits. Special pricing is available when you
register for more than one call and several people can listen in from one office—making these
sessions particularly cost effective as well as educational.
For details on savings and to register, visit www.aan.com/codingcme.
1754
Neurology 72
May 19, 2009