Seizure Active Learning

Question 1

What is a seizure?

Answer 1

It’s abnormal synchronized electrical activity in the brain

manifests as episodes of altered consciousness, involuntary movements or convulsions

Question 2

What are the causes of secondary seizures? i.e. provoked seizures?

Answer 2

metabolic disturbances

infections

fevers

focal neurologic lesions

medications

toxins

Question 3

Epilepsy is the diagnosis for a primary seizures disorder. What would it be characterized by?

Answer 3

at least 2 episodes of UNPROVOKED seizures

note that a single seizures or cluster of seizures within a 24 hours period does NOT imply epilepsy

Question 4

How are generalized and focal seizures different?

Answer 4

generalized seizures START IN BOTH HEMISPHERES - synchronized

focal seizures have a LOCAL ONSET

Question 5

How are generalized seizures further characterized?

Answer 5

convulsive = grand mal/tonic clonic

nonconvulsive = petit mal or absence

Question 6

How are focal seizures further characterized?

Answer 6

simple = no alteration of consciousness (so just motr, autonomic or psychic)

complex = impaired or loss of consciousness

Question 7

What are some signs of a focal temporal lobe seizures?

Answer 7

• behavioral arrest
• aphasia/dysphasia
• automatisms with licking, blinking, lip smacking, etc
• auditory phenomena
• auras (deja vu, jamais vu, smells, tastes)

Question 8

What are some signs of a focal frontal lobe seizures?

Answer 8

contralateral arm extension, ipsilateral arm flexion

bizarre complex behaviors

contralateral eye deviation and head turning

Question 9

What are some signs of a focal occipital lobe seizure?

Answer 9

visual symptoms

Question 10

Describe a Jacksonian Motor Seizure.

Answer 10

it starts as an initial focal tonic seizure with motor involvement in a small area like the fingers, face on one side, or muscles of one foot.
then it spreads from the first muscles affected to those nearby on the motor homunculus - in the “jacksonian march”

Question 11

What are the 3 physiological bases for seizures?

Answer 11

1. population of pathologically excitable neurons
2. increase in excitatory GLUtaminergic activity
3. decrease in inhibitory GABAnergic projections

Question 12

How does the ion channel type number and distribution affect neuron excitability?

Answer 12

These are just examples…

the VG Na+ channels form the basis of rapid depolarization and AP, so more = more excitable

the GABA receptor complex mediates influw of Cl-, which hyperpolarizes the cell, so more = neuronal inhibiiton

Question 13

How does descreasing extracellular volume lead to increased excitability?

Answer 13

Decreased extracellular volume leads to an increased extracellular K+ concentration

this resists the otuward movement of K+ ions

thus, you don’t get the hyperpolarization of the cell after the AP, effectively increasing the excitability

Question 14

Thy synchronized bursts from a sufficient number of neurons will result in what on EEG?

Answer 14

spike discharge

Question 15

What is the paroxysmal depolarizing shift?

Answer 15

the sequence of electrical activity seen in a seizure:

1. sustained neuronald epolarization resulting in a burst of APs
2. a plateau=like depolarization at completion of the APs
3. rapid repolarization followed by hyperpolarization

Question 16

What does the bursting activity result from in terms of ion movement?

Answer 16

relatively prolonged influx of Ca2+, which leads to the opening of the VG Na+ channels, influx of Na+ and generation of repetivie action potentials

Question 17

What receptors and ions then mediate the subsequent hyperpolarizing?

Answer 17

GABA receptors with Cl- influx or K+ efflux depending on the cell type

Question 18

What is a tetanus?

Answer 18

a high frequency train of stimulations

Question 19

What is post-tetanic potentiation?

Answer 19

after a tetanus, there is a high level of residual calcium in the presynaptic cell, temporarily increasing the release probability

this increases excitability and synchronous activity wihtin neighboring neurons - so acts on groups of neurons

Question 20

What is kindling?

Answer 20

After repeated brief, low-intensity stimulation, you get a progressive intensification of seizures, culmination in tonic-clonic seizures

it reflects plasticity of the brain and synaptic connections - essentially it’s how a seizures can be “learned”

Question 21

What glutamate receptor is a particular target of AEDs and why?

Answer 21

the NMDA - because it is an activity dependent channel

if you block it, you can still get activity thoruhg AMPA, but you don’t get prolonged electrical activity - blocks seizures

Question 22

How do AEDs utilize the GABA receptor to decrease seizures?

Answer 22

Benzos and Barbs activate the GABA receptor, allowing Cl- to flow in and out. Because Cl’s reversal potential is -61, near the -70 RPM, this acts as a membrane stabilizer - making the cell less excitable

Question 23

How are use-dependant Na+ channels targeted by AEDs?

Answer 23

they will act on the inactivating plug to put the Na+ into the inactivated phase longer after firing an AP

Question 24

What types of voltage gated Ca2+ channels are where?

Answer 24

N type and P/Q type are all on the presynaptic terminal

T type is found on the postsynaptic terminal

Question 25

What does the SV2A receptor do and hwere is it located?

Answer 25

it aids in vesicle docking, so it’s located at the presynaptic axon terminal

Question 26

What receptor is important for sponging up excess GABA from the synaptic cleft?

Answer 26

GAT-1