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36 Cards in this Set
- Front
- Back
What are seizures?
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Changes in behavior associated with a disturbance in the electrical activity of the brain
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How does the CNS "design" predispose it to seizures?
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Recurrent collaterals
feed forward connections |
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What is epileptogenesis
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General processes occurring in the brain before patient develops spontaneous seizures after an insult
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Generally, what do anti-epileptic drugs block?
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seizures, NOT the development of epilepsy
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In the normal brain, are the connections skewed toward excitation or inhibition?
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Slightly towards excitation
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What are the 2 main excitatory NT's in the brain?
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Glutamate
Aspartate |
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What is the main inhibitory NT in the brain?
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GABA
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In the epileptic brain, what happens to the excitation/inhibition balance?
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Skewed too far towards excitation
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Generally, what can cause the change in excitation/inhibition balance?
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Either increase in excitation or decrease in inhibition
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What are 3 things can can cause increased excitation?
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1. Mossy fiber sprouting
2. Changes in Excitatory Amino Acid receptors 3. Presynaptic changes |
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What 3 things can occur in terms of inhibition to cause epilepsy?
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1. GABA receptor change
2. Loss of interneurons 3. Change of interneuron activity |
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In terms of structure, what can cause seizures?
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Structural Lesions
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What are the 2 types of structural lesions?
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Acquired - tumor, stroke, trauma, hemorrhage
Developmental - malformation, dysplasia |
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Apart from structural alterations, what other type of alterations can lead to seizures?
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Functional changes in neurons
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What are the 2 main types of developmental functional changes?
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1. Channelopathies
2. Synaptic alteration |
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What is the functional unit of a seizure?
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Paroxysmal Depolarization Shift (PDS)
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What is a PDS?
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Sustained neuronal depolarization resulting in bursts of APs
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What is the PDS formed by?
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Plateau-like depolarization (Ca+ influx), Na dependent AP burst, and finally, rapid repolarization followed by hyperpolarization
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When is the PDS prominent?
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After hyperpolarization due to opening of calcium dependent potassium channels
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What, in combination, causes loss of inhibitory control and runaway excitation?
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The fact that EPSPs sum with repetitive neuronal firing and IPSPs decline with repetitive activation
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What is the main similarity and difference between generalized and focal seizures?
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Both can have similar clinical presentations
BUT Have very different onsets |
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What brain structure is involved in the onset of generalized seizures?
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Thalamo-cortical involvement because the whole brain has to go at once
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What thalamic nuclei is involved in a generalized seizure?
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Intralaminar nuclei: has diffuse cortical projections
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What channel in the intralaminar nuclei is involved in producion of generalized bursts in seizures?
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T-type Ca++ channel
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Hyperpolarization that activates T-type Ca++ channels does what?
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Allows for prolonged depolarization
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What are 2 potential mechanisms for the development of early onset epilepsies?
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1. GABA is excitatory during development
2. NMDA receptors develop before AMPA receptors |
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Why is GABA excitatory during development?
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Because chloride concentration is switched, and is higher in the cell, thus flows out when GABA opens Cl channels
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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)
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GDPs are mediated by what NT?
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GABA
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Do epilepsy medications cure underlying epileptic condition?
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NO, only treats the symptoms of seizures
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What are the 5 main MOAs of anti-epileptics?
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1. Blockers of repetitive activation of Na channels
2. GABA enhancers 3. Glutamate modulators 4. Ca channel blockers 5. Synaptic transmission modulators |
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What are the 2 MOA of GABA enhancers (agonists)?
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1. Prolong GABA mediated chloride channel openings
2. Increase frequency of GABA mediated chloride channel openings |
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What are the 2 main types of surgical therapies?
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1. Resection of epileptic zone
2. Corpus callostomy |
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Corpus collastomy is used for what type of seizure?
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Generalized
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What are the two types of surgical stimulations?
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1. Vagal nerve stimulator
2. Brain stimulation (Ant nuc of thalmus) |
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What are 3 alternative (non-surgical) epilepsy therapies?
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Ketogenic Diet
Low glycemic index diet Vitamin Therapy (B6) |