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36 Cards in this Set

  • Front
  • Back
What are seizures?
Changes in behavior associated with a disturbance in the electrical activity of the brain
How does the CNS "design" predispose it to seizures?
Recurrent collaterals

feed forward connections
What is epileptogenesis
General processes occurring in the brain before patient develops spontaneous seizures after an insult
Generally, what do anti-epileptic drugs block?
seizures, NOT the development of epilepsy
In the normal brain, are the connections skewed toward excitation or inhibition?
Slightly towards excitation
What are the 2 main excitatory NT's in the brain?
Glutamate

Aspartate
What is the main inhibitory NT in the brain?
GABA
In the epileptic brain, what happens to the excitation/inhibition balance?
Skewed too far towards excitation
Generally, what can cause the change in excitation/inhibition balance?
Either increase in excitation or decrease in inhibition
What are 3 things can can cause increased excitation?
1. Mossy fiber sprouting

2. Changes in Excitatory Amino Acid receptors

3. Presynaptic changes
What 3 things can occur in terms of inhibition to cause epilepsy?
1. GABA receptor change

2. Loss of interneurons

3. Change of interneuron activity
In terms of structure, what can cause seizures?
Structural Lesions
What are the 2 types of structural lesions?
Acquired - tumor, stroke, trauma, hemorrhage

Developmental - malformation, dysplasia
Apart from structural alterations, what other type of alterations can lead to seizures?
Functional changes in neurons
What are the 2 main types of developmental functional changes?
1. Channelopathies

2. Synaptic alteration
What is the functional unit of a seizure?
Paroxysmal Depolarization Shift (PDS)
What is a PDS?
Sustained neuronal depolarization resulting in bursts of APs
What is the PDS formed by?
Plateau-like depolarization (Ca+ influx), Na dependent AP burst, and finally, rapid repolarization followed by hyperpolarization
When is the PDS prominent?
After hyperpolarization due to opening of calcium dependent potassium channels
What, in combination, causes loss of inhibitory control and runaway excitation?
The fact that EPSPs sum with repetitive neuronal firing and IPSPs decline with repetitive activation
What is the main similarity and difference between generalized and focal seizures?
Both can have similar clinical presentations

BUT

Have very different onsets
What brain structure is involved in the onset of generalized seizures?
Thalamo-cortical involvement because the whole brain has to go at once
What thalamic nuclei is involved in a generalized seizure?
Intralaminar nuclei: has diffuse cortical projections
What channel in the intralaminar nuclei is involved in producion of generalized bursts in seizures?
T-type Ca++ channel
Hyperpolarization that activates T-type Ca++ channels does what?
Allows for prolonged depolarization
What are 2 potential mechanisms for the development of early onset epilepsies?
1. GABA is excitatory during development

2. NMDA receptors develop before AMPA receptors
Why is GABA excitatory during development?
Because chloride concentration is switched, and is higher in the cell, thus flows out when GABA opens Cl channels
What are the large depolarizations that are believed to synchronize large cortical areas so that networks function together?

Recall: Neurons that fire together wire together
Giant Depolarizing Potentials (GDPs)
GDPs are mediated by what NT?
GABA
Do epilepsy medications cure underlying epileptic condition?
NO, only treats the symptoms of seizures
What are the 5 main MOAs of anti-epileptics?
1. Blockers of repetitive activation of Na channels

2. GABA enhancers

3. Glutamate modulators

4. Ca channel blockers

5. Synaptic transmission modulators
What are the 2 MOA of GABA enhancers (agonists)?
1. Prolong GABA mediated chloride channel openings

2. Increase frequency of GABA mediated chloride channel openings
What are the 2 main types of surgical therapies?
1. Resection of epileptic zone

2. Corpus callostomy
Corpus collastomy is used for what type of seizure?
Generalized
What are the two types of surgical stimulations?
1. Vagal nerve stimulator

2. Brain stimulation (Ant nuc of thalmus)
What are 3 alternative (non-surgical) epilepsy therapies?
Ketogenic Diet

Low glycemic index diet

Vitamin Therapy (B6)