Epileptogenesis is the process by which normal brain tissue is transformed into tissue capable of generating spontaneous recurrent seizures. It involves multiple mechanisms including genetic and acquired factors. The hippocampus is particularly susceptible to epileptogenesis due to its circuitry. Status epilepticus animal models are commonly used to study the process. Epileptogenesis occurs in acute, subacute, and chronic stages. Acute changes include increased expression of immediate early genes and post-translational modifications of proteins. Subacute changes involve neuronal death, alterations in neurotrophic factors and inflammation. Chronic changes include mossy fiber sprouting and neurotransmission alterations.

1. Epileptogenesis
&
Antiepileptogenesis
Supervised by:
Prof: Wafaa M. A Farghaly
Presented by
Ahmed Mamdouh

2. Definitions
 Ictogenesis: Is the propensity (susceptibility ) of the tissue to generate epileptic seizures.
 Seizure: is the transient occurrence of signs and/OR symptoms due to abnormal
excessive synchronous neuronal activity in the brain. A single seizure can occur in an
otherwise healthy individual; such individuals are generally not considered to have
epilepsy. However, having a seizure can increase the likelihood of future seizures, as
seizures themselves contribute to Epileptogenesis.
 Epilepsy: is a neurological disorder defined as a brain state that supports recurrent,
unprovoked seizures (spontaneous recurrent seizures) .

3.  Epileptogenesis is the process by which a brain network that was previously
normal, is functionally altered toward increased seizure susceptibility, thus
having an enhanced probability to generate spontaneous recurrent seizures
(SRSs) (Dudek and Staley 2012; Goldstein and Coulter 2013).
 Epileptogenesis: is simply defined as the process by which normal brain
tissue is transformed into tissue capable of generating spontaneous recurrent
seizures ( Loscher and Brandt 2010)

4.  Secondary Epileptogenesis: An area of normal
brain tissue is transformed into tissue capable of
generating SRSs because of the influence of
epileptogenic activity in a 1ry epileptogenic area,
which is separated from it by at least one synapse.
 Mirror focus: was shown to develop contralateral
and homotopic to the primary epileptogenic focus.

5. • Previously, Epileptogenesis was considered to be represented by the latent
period, which has been defined as the time between the precipitating brain insult
and the occurrence of the first unprovoked clinical seizure.
• Recently, Epileptogenesis is now considered to extend beyond the latent
period, which is still defined as the time from the precipitating injury and the first
clinical seizure. However, the observations that subconvulsive seizures may well
have occurred before the first clinical seizure and that seizure frequency and
severity progressively increase over time both indicate that the Epileptogenesis
can continue indefinitely (Williams et al 2009 &Kadam et al 2010).

6. Antiseizure treatment: (ASTs OR AEDs):
 Seizures can be controlled with medications (AEDs)or non medical therapy,
epilepsy surgery, vagal nerve stimulation, or ketogenic diet.
 However, approximately one third of all epilepsy patients are poorly
responsive or intractable to available therapies. Even in well controlled
most current treatments are primarily symptomatic therapies that suppress
seizures but don’t correct the underlying brain abnormalities causing

7. Antiepileptogenesis
 Antiepileptogenesis is a process that counteracts the effects of Epileptogenesis, including
prevention, cure and seizure modification.
 Prevention: Complete prevention aborts the development of epilepsy or Partial prevention
can delay the development of epilepsy or reduce its severity.
 Cure: The complete and permanent reversal of epilepsy, such that no seizures occur after
treatment withdrawal
 Comorbidity Modification: Treatment alleviates or reverses the symptomatic development
or progression of epilepsy-related comorbidities, such as anxiety, depression, somato-motor
impairment, or cognitive decline.

8. Antiepileptogenic Treatment
 Antiepileptogenic treatment can be given prior to or after epilepsy
onset.
 When an antiepileptogenic treatment is given prior to epilepsy
onset it prevents or delays the development of epilepsy.
 If seizures occur, they may be fewer in frequency, shorter, or of
milder severity.

9. Epileptogenesis
GENETIC
FACTORS
ACQUIRED
PROCESSES

10. Genetic mechanism
Over 40 genes associated with human epilepsy have been identified so far and at least 133
single gene mutations in mice have been linked to an epileptic phenotype.
 Gene defects affecting neuronal excitability through Ion channel defects: Autosomal
Dominant Nocturnal Frontal Lobe Epilepsy
 Genes encoding development defects lead to neuronal migrational disorders:
Lissencephaly
 Genes encoding cerebral energy metabolism defects lead to mitochondrial disorders
Myoclonic Epilepsy with Ragged Red Fibers (MERRF).
 Genetic defects lead to neurodegenerative disorders: Progressive myoclonic epilepsy

11. 2-Acquired mechanism:
 traumatic brain injury (TBI): is reported to cause subsequent chronic epilepsy in 2 –25% of patients, While
the risk is highest in the months directly after TBI, it remains elevated for more than 5 years in patients with
moderate to severe injury and for more than 15 years in patients with penetrating missile wounds to the
brain.
 Stroke: is reported to cause subsequent chronic epilepsy within the next 5 years in 2 – 4% of cases, and the
risk of seizures is increased in patients with subarachnoid and intracerebral haemorrhage.
 cerebral vein and dural sinus thrombosis: is reported to cause subsequent chronic epilepsy in about 10% of
patients.
 nervous system (CNS) infections: is reported to cause subsequent chronic epilepsy in about 7% of patients
within 20 years with a 4-fold higher risk after viral encephalitis compared to bacterial meningitis.
 Symptomatic Status Epilepticus: The 10-year risk of developing epilepsy after acute symptomatic SE has been
reported to be 41% and thus 3.3 fold higher than after a single epileptic seizure with comparable aetiology ,
giving evidence for the major impact of SE itself on Epileptogenesis.

12. Mechanism of Epileptogenesis
Epileptogenesis has been demonstrated in a number of brain
regions, but most studies using experimental animal models
have focused on the hippocampus, because of the region’s
well characterized network architecture and afferent and
efferent pathways.

13. Anatomy of the hippocampus

14. Anatomy of the hippocampus
 The primary neurons of the cornu ammonis are the pyramidal cells
 Dentate gyrus are granule cells, axons of granule cells called mossy
fibers” while
 Dentate hilus cells are called mossy cells.

15. Anatomy of the hippocampus
 The hippocampal circuitry consists of a Trisynaptic excitatory pathway – from the
entorhinal cortex to the dentate granule cells, which project to the CA3 pyramidal
neurons via mossy fibers, and from there to the CA1 region through Schaffer
collaterals. There are local circuits in each region with excitatory and inhibitory
interneurons.

16. Hippocampal circuitry
The hippocampal circuitry consists of a Trisynaptic excitatory pathway:


17. Hippocampal circuitry
 The CA3 region is most prone to epileptiform activity, partly because
of excitatory connections with neighboring cells. On the other hand, it
is difficult to induce seizures in granule cells, in part due to the lack
of excitatory connections with neighboring granule cells and the
presence of strong polysynaptic inhibitory synapses on granule cells.
 Normally, dentate granule cells limit seizure propagation through the
hippocampal network. However, structural reorganization with
alteration of the synaptic circuitry may transform the granule cells into
an epileptogenic population and promote seizure initiation and/or
propagation.

18. Pathophysiological concepts of Epileptogenesis:
 Transient loss of inhibition and increased excitation are
currently assumed to represent the pathophysiological basis
for Epileptogenesis.
 GABAergic inhibition in the dentate gyrus (dg) has repeatedly
been shown to be markedly impaired shortly after SE and to
be fully restored and sometimes even hyper compensated
within 4 – 8 weeks after se.
 Initial GABAergic disinhibition may be due to:
 Loss of specific GABAergic interneurons and
 Reduced number and sensitivity of postsynaptic GABAA
receptors.

19. Pathophysiological concepts of Epileptogenesis
 However, loss of inhibition does not sufficiently explain the development of
chronic epilepsy, as spontaneous seizures occur several weeks later, when
inhibition has recovered. Therefore, two major steps have been assumed to
participate in the process of Epileptogenesis
1-Disinhibition of the DG results in a loss of the filter function of this structure,
allowing physiological stimuli to affect highly vulnerable downstream structures
of the hippocampus proper
2- Excitatory transmission in the hippocampus proper is enhanced, resulting in
the generation of spontaneous epileptic seizures.

20. Pathophysiological concepts of Epileptogenesis
 Aberrant sprouting of mossy fibers allows new excitatory
connections to be established with granule cell dendrites in the
DG inner molecular layer. This results in an expansion in the
number of recurrent excitatory synapses between granule cells.

21. Experimental Models to study Epileptogenesis:
Neurobiological processes underlying Epileptogenesis after brain injuries have been studied extensively in
experimental animal models of Status epilepticus , and to some extent in models of brain trauma and
ischemic stroke.
A. Experimental models of Status epilepticus can be induced in rats by: systemic or local administration
of chemoconvulsants such as kainic acid or pilocarpine or by continuous or intermittent electrical
stimulation of the amygdala, the ventral hippocampus or the perforant path.
B. A new animal model of posttraumatic epileptogenesis has recently been reported following severe,
non-penetrating lateral fluid-percussion brain injury in rats.
C. Experimental focal ischaemia induced by cortical photothrombosis or permanent occlusion of the
middle cerebral artery.
D. Kindling Model: Repeated subconvulsive stimuli resulting in electrical after discharges. Eventually
leads to stimulation-induced clinical seizure. In some cases leads to spontaneous seizures (epilepsy).

22.  The initial insult is usually accompanied by acute seizure activity and is
followed by a period (latent or silent) without overt seizure activity, this
latent period can extend for months to years and corresponding to
Epileptogenesis cascade.
 Subsequently, a final stage is reached, which is characterized by the
emergence of spontaneous seizures, an increase in seizure frequency,
and in some cases refractoriness to antiepileptic drugs.

23. Collectively, experimental data from animal models indicate several major
stages in the Epileptogenesis Cascade:
1-Early acute changes that occur within minutes to days following the initial
insult.
2-The subacute period of hours to weeks following the triggering insult.
3-Chronic changes that occur over weeks to months.

28. Acute changes in Epileptogenesis
A-Induction of immediate early genes
• IEGs are transcriptionally activated in response to neuronal activity,
and have been implicated in normal synaptic plasticity and
synaptogenesis.
• A number of IEGs, including Fos, Jun, Egr1, Egr4, Homer1, Nurr77,
and Arc, have been identified as being transcriptionally activated
or upregulated in animal models of epilepsy.
• An increase in the expression of IEGs has been previously
described in neocortical and hippocampal tissue in patients with
epilepsy.

29. The molecular cascades associated with IEG induction are
initiated by:
1-Repeated intense synaptic activation, which leads to depolarization and
opening of NMDAR channels.
2-Subsequent calcium influx can lead to the activation of kinase cascades,
which ultimately results in the phosphorylation of transcription factors such as
cyclic AMP response element binding protein (CREB).
3- Transcription factor alter gene expression through DNA methylation or
Histone Acetylation (Epigenetic effect).
4-The upregulated IEGs can modulate secondary response genes , which in
turn modulate synaptic function.

30. B) Post-translational changes of existing proteins and
alteration of ion channel activity:
 The calcium influx following a seizure has the potential to activate a variety of
signaling cascades, such signaling could affect mechanisms that are
hypothesized to increase synaptic efficiency.
 Calcium activates phosphatases and kinases that alter ion channel and
neurotransmitter receptor function.
• Phosphatases like Calcineurin which is by Activation can lead to:
 GABAAR Endocytosis (by Dephosphorylation), decreased inhibitory
postsynaptic potential frequency and reduced network inhibition.
 Rapid Dephosphorylation of Kv2.1 channels “voltage-gated k+ channel
regulating excitability and Ca2+ influx during periods of repetitive high
frequency firing and action potential repolarization ”, which leads to their
subsequent internalization and prolongation of neuronal depolarization.

31. • Kinases: Protein kinase C, A and calcium-calmodulin-dependent
protein kinase activity increase within minutes after seizures, leading
to an increase in phosphorylation of ser831 on GluR1 and ser880 on
GluR2.
 The phosphorylation changes on GluR1 have been described to
increase channel conductance and open-channel probability.

32. Mechanism targeted Potential therapeutic options
Acute changes
Immediate early genes Chromatin acetylation modifiers or histone
deacetylation inhibitors (for example, valproate,
suberoylanilide hydroxamic acid)
NMDAR NMDAR inhibitors (for example, memantine,
felbamate);
NR2B-specific inhibitors (ifenprodil)
AMPAR AMPAR antagonists (for example, topiramate,
talampanel, GYKI compounds)
Protein phosphatases Calcineurin inhibitors (FK506)
Protein kinases Kinase inhibitors (CaMKII inhibitor KN-62, PKA
inhibitor KT5720, PKC inhibitor chelerythrine)
Potential targets for antiepileptogenic therapy in acute stage

34. Subacute changes
1-Neuronal death:
 Status epilepticus results in progressive neuronal loss in the CA3 region of
the hippocampus in adult models of epilepsy, this neuronal loss is presumed
to alter the balance between excitation and inhibition in the limbic network.
 Subplate neurons:
 Neurons are present in the deep cortical regions during the preterm and
neonatal periods and are critical for the normal maturation of cortical
networks.
 These cells, however, lack oxidative stress defenses, so they are selectively
vulnerable to hypoxic-ischemic insults. Kainate-induced seizures cause a loss
of sub-plate neurons, and, consequently, abnormal development of
networks.
 Importantly, administration of clinically available antioxidants, such as
Erythropoietin, is neuroprotective following hypoxia-induced neonatal
seizures

35. 2-Neurotrophic factors:
 Neurotrophic factors and their receptors considered to be critical for
normal synaptic development.
A. Nerve growth factor and Brain Derived nerve growth factor (BDNF):
Activation of BDNF receptors “tropomyosin related kinase (Trk)”
reduces KCC “ potassium–chloride cotransporter” protein levels
following seizure induction.
B. Neurotrophins: could also promote Epileptogenesis via their role in
modulating the maturational onset of KCC “ Potassium–chloride
Cotransporter” expression, which enhances GABA-mediated synaptic
inhibition in dentate granule cells.

36.  In the mature brain Activation of
GABAARs hyperpolarizes neurons, by
causing an influx of chloride into the cell
aided by KCC.
 In immature neurons, the intracellular
chloride concentration is higher than the
extracellular concentration, so GABAAR
activation leads to an efflux of such ions,
thereby depolarizing the cell aided by
NKCC.
 KCC “chloride exporter” is not expressed
until the middle of the first year of life.
 The sodium–potassium–chloride
cotransporter (NKCC), a chloride
importer, NKCC expression is highest in
the human cortex at term.

37. 3-Inflammation
• Subacute inflammatory processes occur after seizures, and increased levels of
cytokines, such as interleukin (IL), IL1, IL2, IL6, tumor necrosis factor and
macrophage, colony stimulating factor, are associated with seizures.
• Seizures also directly activate microglia, triggering an inflammatory response
mediated by cytokines, complement factors and major histocompatibility class
factors. Indeed, the microglial inactivators minocycline and doxycycline protect
against neuronal death
• In the normal brain microglia were considered "resting," but it has recently become
evident that they constantly scan the brain environment and contact synapses.
Activated microglia can remove damaged cells as well as dysfunctional synapses, a
process termed "synaptic stripping"

39. In addition to rapid and early post-translational regulation of receptors and ion
channels, early-life seizures induce subacute and long-term changes in
neurotransmitter receptor transcription and expression for example:
I. GluR2 subunit expression declines following seizures. which could lead to an
increase in the number of calcium-permeable AMPARS, and, subsequently, pro-
excitatory alterations in calcium signaling and long-term synaptic potentiation.
(NB: When GluR2 expression is relatively low (or absent), AMPARs are permeable to
calcium, and Kainate receptors become more permeable to calcium when the GluR5
or GluR6 subunits are absent).
4-Transcriptional changes

40. II. Studies in the adult rat brain show that seizures cause a decrease in the
expression of the GABAAR α1 subunit, which would diminish inhibition.
III. Seizures in the immature brain also exert varying effects on expression and
hyperpolarization-activated current (Ih) function of HCN channel “Hyperpolarization-
activated cyclic nucleotide-gated (HCN) channel”. Status epilepticus leads to a functional
decrease in Ih in CA1 neurons and an increase in synaptic excitability.
IV. The cannabinoid type 1 receptor (CB1) modulates glutamatergic synaptic
function. The levels of CB1 mRNA and protein are decreased within days
following hyperthermia-induced seizures. Notably, similar decreases in CB1 and
CB1 receptor binding protein mRNA and protein levels have been observed in
human mesial temporal sclerosis tissue
Transcriptional changes “Cont.”

41. Mechanism targeted Potential therapeutic options
Subacute changes
Inflammation Anti-inflammatory compounds (ACTH);
microglial inactivators (for example,
minocycline, doxycycline)
Neuronal injury Erythropoietin, antioxidants, nitric oxide
inhibitors, NMDAR antagonists (memantine)
HCN channels Ih-blocker (ZD7288)
CB1 CB1 receptor antagonists (for example,
SR14176A, SR141716)
Potential targets for antiepileptogenic therapy in subacute stage

43. Chronic changes
1-Sprouting:
 Dentate granule cells seem to sprout aberrant collaterals to the inner molecular layer of the
dentate gyrus. These projections form monosynaptic connections between dentate granule
cells, thereby creating a positive feedback loop and seizure focus.
2-Neurogenesis
 Human studies performed on pediatric autopsy specimens and tissue
biopsies taken during epilepsy surgery show there is an increase in
neurogenesis in individuals with epilepsy compared with controls.
 Rodent models in which chemo-convulsants are administered during the first
four weeks of life also show increased neurogenesis during either the ictal
period or postictal period.
Recurrent flurothyl-induced seizures in the first postnatal week, however,
result in a decrease in subsequent neurogenesis in dentate granule cells.
.

44. 3-Gliosis:
 Since their discovery over 100 years ago, glial cells have traditionally
been considered only as passive support cells of the nervous system
However, recent application of cellular imaging, physiology, and
genetics to astrocytes has shown that they are active participants at
the neuronal synapse.
 The processes of astrocytes are in close proximity to neuronal
membranes and express a host of receptors, transporters, and ion
channels that enable astrocytes to “listen” to the chemical
conversation at the synapse. In return, they are able to “respond” and
modify the tone of synaptic transmission by regulating the availability
of neurotransmitters and ions in the synaptic cleft, such as glutamate
and potassium.

45.  As a consequence of SE and subsequent
inflammation, astrocytes change their
morphology and protein expression in a
process termed reactive Astrogliosis “Became
hypertrophic, increase expression of
intermediate filament proteins (for example,
GFAP), and develop longer and thicker
processes”
 A number of molecules and signaling pathways
are known to trigger reactive Astrogliosis, such
as ATP and glutamate, inflammatory cytokines
such as TNF-α and Il1-β.

46. Astrocyte and Potassium Buffering:
 Astrocytes play a critical role in maintaining
neuronal homeostasis by buffering extracellular
potassium (K+) through the highly permeable
potassium channel KIR4.1.
 Neurons extrude K+ with each action potential
repolarization and during periods of high activity,
K+ concentration in the extracellular space can be
rapidly elevated. Thus, the tight regulation of
[K+] via astrocytic uptake is critical for maintaining
neuronal homeostasis.
 For instance, conditional knock-out of the KIR 4.1
channel in mice results in seizures resulting from
deficient K+ uptake in astrocytes.

47. Gap Junctions Between Astrocytes and
Epileptogenesis:
 Astrocytic gap junction is critical in maintaining
homeostatic balance of ions and molecules.
 A complete gap junction is formed by Connexons, on
two different cells. Each Connexon consists of six
Connexin (Cx) proteins with a hydrophilic pore at its
center. This pore allows transfer of ions, second
messengers, metabolites, and other small molecules.
 Recently showed that the number of coupled
astrocytes was significantly increased early in the
process of Epileptogenesis, and consistent with
that observation, CX expression was greatly
elevated.

48. Astrocyte and Glutamate Transporter
Function in Epileptogenesis:
• Glutamate must be actively removed via Na+
dependent glutamate transporters. Fast efficient
clearance of glutamate is essential for the prevention
of excitotoxicity.
• The main glutamate transporters, GLAST and GLT-1
are predominately expressed in astrocytes and are
responsible for >90% of the total glutamate uptake.
• In animal models, as would be expected, knock down
of GLT-1 expression in the mouse leads to neuronal loss
and seizure activity that is caused by the build up of
extracellular glutamate .
• In human tissue from patients with TLE, demonstrates
reductions in GLT-1 and GLAST expression.

49. Astrocyte and Glutamate Receptor
Expression:
 Astrocytes have been shown to express nearly
every transmitter receptor, including
metabotropic and ionotropic glutamate
receptors.
 Expression for group I mGluRs is increased in
reactive astrocytes 1 week after SE. Interestingly,
Kainate receptors (KARs) and NMDA receptors
are expressed in reactive astrocytes following
ischemia in adult animals
 increased expression of metabotropic and
ionotropic glutamate receptors in reactive
astrocytes could cause the synchronization of
neurons thus contributing to hyperexcitability.

50. Blood-Brain Barrier Disruption Following SE
• Astrocytes form close associations with the endothelial cells of capillaries
and help maintain proper function of the blood brain barrier (BBB).
Disruption of the BBB is often observed in epileptic brain regions.
• following BBB disruption, uptake of the serum protein albumin by
astrocytes through TGF-β receptors has been associated with reactive
gliosis. Albumin causes a down regulation of KIR channels “help mediate
inhibitory neurotransmitter responses” , suggesting that albumin can
directly modulate astrocyte functions and enhance excitability.
• Additionally, reductions in MCT1, a key BBB carrier molecule for
monocarboxylates and amino acids, in endothelial cell membrane
microvessels in the hippocampus of human patients with TLE.
resulting in decreased concentrations of blood-derived fuels,
as ketone bodies, which could contribute to enhanced seizure
susceptibility.

51. Astrocyte and Increased Expression of
Adenosine Kinase Following SE:
 For over 40 years, adenosine has been
recognized as an endogenous
anticonvulsant. Adenosine levels are
elevated in patients following seizures,
suggesting that adenosine is released
during a seizure and may contribute to
seizure termination
 Astrocytes regulate adenosine levels via the
production of the enzyme adenosine kinase
(ADK) and during epilepsy, reactive
astrocytes produce increased levels of ADK.
 ADK is increased in reactive astrocytes
around 1 week post SE, prior to the
development of spontaneous seizures.

52. Changes in Astrocyte Calcium Signaling
After SE:
• Astrocytic calcium activity increased during
and after SE. Interfering with the increase in
calcium activity in astrocytes that followed SE
was neuroprotective, suggesting that
glutamate release from astrocytes was
contributing to excitotoxic cell death
following SE.

53. Mechanism targeted Potential therapeutic options
Chronic changes
Sprouting Protein synthesis inhibitors (for
example, rapamycin,
cycloheximide)
Gliosis Anti-inflammatory agents (for
example, COX-2 inhibitors,
minocycline, doxycycline)
Potential targets for antiepileptogenic therapy in chronic stage:

54. Mammalian target of rapamycin pathway
changes “mTOR pathway” and
Epileptogenesis:
 mTOR is a serine/ threonine protein kinase that is
involved in multiple basic cellular functions, including
cell growth, proliferation and survival.
 mTOR regulates synaptic plasticity, neuronal
structure and the expression of various ion channels
and neurotransmitter receptors.
 mTOR overactivation produces brain abnormalities
that include dysplastic neurons, abnormal cortical
organization and Astrogliosis.
 Several preclinical and some clinical studies have
revealed that the mammalian target of rapamycin
(mTOR) signaling pathway is involved in both genetic
and acquired epilepsy syndromes.

55. mTOR pathway and genetic epilepsy:
 Genetic mutations in many components of the mTOR pathway will produce
syndromes that include epilepsy.
 Excessive activation of mTOR signaling, as a consequence of loss-of-function of
genes encoding for tuberous sclerosis complex (TSC) 1 and 2, is linked to the
development of cortical malformations and epilepsy. This mTOR
hyperactivation is associated with different epileptogenic conditions under the
term of 'mTORopathies' such as tuberous sclerosis, focal cortical dysplasia,
hemimegalencephaly and ganglioglioma..

56. The mTOR pathway and acquired epilepsy.
 Rapamycin treatment before Kainate-induced status epilepticus
prevented the development of spontaneous recurrent seizures in a
subset of rats; in those rats that did develop epilepsy, rapamycin
increased the latency to seizure development and decreased the
frequency of spontaneous seizures. When applied after the induction of
status epilepticus, rapamycin decreased cell death, mossy fiber sprouting
and aberrant dentate granule cell.
 mechanisms might include inhibition of mossy fibre sprouting,
neuroprotection and maintenance of the integrity of the blood–brain
barrier.

59. Epileptogenesis Biomarkers
 The Biomarker Concept: Biomarkers are defined as “measures” of disease
processes, that is, factors that can be objectively determined and interpreted as
indicators of pathogenic processes, such as those related to Epileptogenesis
ictogenesis.
 There are currently no validated biomarkers that would allow the reliable
prediction of increased likelihood of epilepsy development.
 Ideal biomarkers should not only be specific and sensitive, but also easily
accessible. In the case of Epileptogenesis, accessing the brain tissue of patients
at risk is typically not feasible.
 Similar to the function of molecular biomarkers for brain tumors, a transient
dysfunction of the BBB may participate in the appearance of blood or serum
biomarkers for Epileptogenesis. In CSF, molecular correlates of cellular
damage and inflammation associated with Epileptogenesis may be particularly
pronounced if the affected anatomical structures are close to the ventricles.
 Therefore, molecular biomarkers of Epileptogenesis should either be based on
brain imaging or derived from peripheral tissues.

60. Uses of biomarkers
 Predict who are likely to develop chronic seizures
 Delineate brain areas for resection
 Determine the efficacy of therapy
 Develop anti epileptogenic drugs…

61. Target mechanisms
 Epileptogenesis after a transient insult to the brain is accompanied by
pathogenic processes that may serve as the source of potential biomarkers.
These processes include:
 Cell Loss “Hippocampal Atrophy”  Axonal sprouting
 Synaptic reorganization  Neurogenesis
 Altered glial function and gliosis  Angiogenesis
 Blood–brain barrier (BBB) dysfunction  Activated microglia cells and leukocytes
 Altered expression and distribution of neurotransmitter receptors and ion channels

62. Neuroimaging biomarkers of the Epileptogenic Process:
 MRI
 Magnetic Resonance Spectroscopy
 PET
 Functional MRI

63. Magnetic Resonance Imaging:
Signal Changes
T2 signal changes: increased T2 values and T2W hyperintensity have been reported in
several brain regions, including the cortex, hippocampus, thalamus, amygdala, and piriform
piriform and entorhinal cortices, beginning as early as 2 h after SE. These acute changes
typically return to baseline within 48–72 h, and have been reported to predict the
development of epilepsy at 4 months after SE.
Common underlying pathological changes being edema, gliosis, and cell loss.
Volumetric and Morphological Analyses
volumetric and morphological changes in the hippocampus and other limbic structures
been reported in both SE.
Contrast Agents
such as manganese (Mn2+) and gadolinium (Gd3+) complexes. These agents enable the
assessment of various pathologies potentially involved in the epileptogenic process, such as
blood–brain barrier breakdown and mossy fiber sprouting..

65. Magnetic Resonance Spectroscopy
Magnetic resonance spectroscopy (MRS) is a
neuroimaging technique capable of identifying
levels of brain metabolites, such as N-acetyl
aspartate (NAA), choline, creatine (Cr), lactate,
myo-inositol, and glutathione; levels of
neurotransmitters, such as glutamate, glutamine,
and gamma-aminobutyric acid (GABA); and
other physiological changes, such as
intracerebral pH, all of which may have
relevance to Epileptogenesis.
MRS has identified acute reductions in
glutamate, glutamine, and GABA, as well as
acute and chronic reductions in NAA, a marker
of neuronal loss or dysfunction. Furthermore,
progressive increases in myo-inositol “a
metabolite inked to astrocyte activation” and
glutathione have also been detected in acute
stages after SE

66. Positron Emission Tomography
• Positron emission tomography (PET) uses
radiotracers to visualize and quantify functional
processes in the brain.
• [18F]FDG–PET: is the glucose analogue
[18F]FDG–PET, a biomarker for glucose uptake
and brain metabolism.
• A significant relationship has been reported
between the degree of hypometabolism on
[18F]FDG–PET in the entorhinal cortex early
following SE in the rat and the chance of later
developing spontaneous recurrent seizures,
suggesting that this may be a biomarker of early
epileptogenesis following a brain insult

67. a-[11C]Methyl-L-tryptophan “AMT PET”:
• AMT PET measures brain serotonin
synthesis.
• (AMT) is able to pinpoint the epileptic
focus itself in the interictal state, by
revealing a focus of increased AMT
uptake, even when an MRI or glucose
metabolism PET demonstrates normal
findings.
• AMT PET appears to be particularly
useful in patients with tuberous sclerosis
complex and in patients with cortical
developmental malformations.

69. Functional MRI
As with PET, functional MRI (fMRI) allows
for the assessment of functional brain
activity.
the basic principle of fMRI, that MRI signal
is sensitive to changes in blood oxygenation
levels As neuronal activity leads to increased
blood flow and changes in blood oxygenation
levels, or the blood oxygenation level-
dependent (BOLD) signal, fMRI allows for
the investigation of the location and networks
of brain function. As epilepsy is known to
involve abnormalities in neural activity and
circuitry, fMRI represents a promising tool in
the study of Epileptogenesis.

70. MRI signal abnormalities induced by seizures:

71. Peripheral tissues biomarkers of the Epileptogenic Process

72. Molecule Biomaterial Remarks [reference]
Neuron-specific
enolase
Serum Levels correlate with neurologic outcome after trauma and
reflect neuronal damage after SE
Myelin basic protein Serum Released in the course of brain trauma.
Ubiquitin carboxyl-
terminal
Hydrolase L1
CSF Increase in CSF correlates with epileptogenesis.
S100 calcium binding
protein B;
Serum/CSF Levels correlate with injury severity after trauma and have
predictive value on neurological outcome
Glial fibrillary acidic
protein
Serum/CSF Levels correlate with injury severity after trauma and have
predictive value on neurologic outcome; increase in CSF
correlates with Epileptogenesis stage in the kainic acid SE
model
Tau Serum/CSF Released in the course of brain trauma; predictive value for
Epileptogenesis to be determined
MicroRNA-9 Serum/Brain Increased after traumatic injury
Prolactin Serum/CSF Transiently increased in SE animal model in early
Epileptogenesis.

73. Antiepileptogenic Drugs

75. Models of acquired Epileptogenesis—SE models
Drug Mechanism Antiepileptogenesis
Atipamezole α2-adrenergic antagonist YES
Celecoxib COX-2 inhibition YES
Erythropoietin Erythropoietin receptor YES
FGF-2 and BDNF
gene therapy
FGF receptors, TrkB YES
Rapamycin mTOR inhibition YES
Bumetadine NKCC1 inhibitor NO
Aspirin COX-2 inhibition YES
Fingolimod anti-inflammatory YES
Adenosine Reduced DNA methylation YES
Melatonin Antioxidant YES
Parecoxib COX-2 inhibition YES

76. Models of acquired Epileptogenesis—TBI models
Drug Mechanism Antiepileptogenesi
s
Ceftriaxone Stimulation of glutamate
transporter
YES
Rapamycin mTOR inhibition YES
Phenytoin Na+-channel blocker Raises seizure
threshold but
ineffective in
preventing
epileptogenes

77. Genetic epilepsies
Drug Mechanism Antiepileptogenesis
Levetiracetam Binding to synaptic vesicle
protein SV2A
YES
Ethosuximide T-type calcium-channel
blocker
YES
Zonisamide Na+-channel blocker YES
Vigabatrin GABA transaminase
inhibitor
YES
Carbamazepine Na+-channel blocker YES
Rapamycin mTOR inhibition YES