2. • Seizures are transient events that include
symptoms and/or signs of abnormal excessive
hypersynchronous activity in the brain
• definition of epilepsy requires at least two
unprovoked seizures more than 24 hours
apart. 2005
3. • 2014, Epilepsy was defined as a disease of the
brain defined by any of the following
conditions:
• (1) at least two unprovoked (or reflex)
seizures occurring >24 hours apart, or
• (2) one unprovoked (or reflex) seizure and a
probability of further seizures similar to the
general recurrence risk (at least 60%) after
two unprovoked seizures, occurring over the
next 10 years, or
• (3) diagnosis of an epilepsy syndrome.
10. Functional and perhaps structural
changes occur in the postsynaptic
membrane
Altering the character of receptor
protein - conductance channels
Favoring development of paroxysmal
depolarizing shift (PDS) and enhanced
excitability
11. Functional and perhaps structural
changes occur in the postsynaptic
membrane
Altering the character of receptor
protein - conductance channels
Favoring development of paroxysmal
depolarizing shift (PDS) and enhanced
excitability
12. Functional and perhaps structural
changes occur in the postsynaptic
membrane
Altering the character of receptor
protein - conductance channels
Favoring development of paroxysmal
depolarizing shift (PDS) and enhanced
excitability
13.
14.
15.
16. Ca++
• Latent Ca++ channels are used, that the efficacy
of Ca++ channels is increased
• or that the number of Ca++ channels is
chronically elevated
23. EXCITABILITY ARISING FROM
NEURONAL MICROENVIRONMENT
• Both functional and structural alterations
occur in epileptic foci (both neurons and glia)
Change
in
concentrations of cations
and anions
Metabolic alterations
neurotransmitter levels
29. Mechanisms of interictal-ictal
transition
synaptic
• Depression of GABA-ergic
inhibition
• NMDA receptor activation ;
voltage-dependent EPSPs
• Frequency potentiation of
EPSPs
• Actions of modulators
Non synaptic
• Alterations in ionic
microenvironment
• Decreases in size of
extracellular space
• Failure of ion transport :
Na+-K+ pump or Cl--K+ co-
transport
• Presynaptic terminal
bursting
• Ephaptic interactions
30. Non synaptic
• Alterations in ionic microenvironment ; e.g.
increased extracellular K+, decreased
extracellular Ca++
• Failure of ion transport : Na+-K+ pump or Cl--
K+ co-transport
37. Definitions
• Epileptogenesis: sequence of events that converts a
normal neuronal network into a hyperexcitable
network
• Epileptogenesis: is the process by which a brain
network that was previously normal is functionally
altered toward increased seizure susceptibility, thus
proba togenerate
(Dudek and Staley
havinganenhancedprobability spontaneous
recurrentseizuresS(R)sS
2012;Goldstein and Coulter2013.)