Cortical Electrical Recordings

Question 1

define primary

Answer 1

genetic

Question 2

define idiopathic

Answer 2

unknown

Question 3

define symptomatic

Answer 3

known underlying cause: developmental, degenerative, inflammatory, infectious, neoplastic, traumatic

Question 4

define reactive

Answer 4

metabolic, nutritional, or toxic cause

Question 5

define reflex epilepsy

Answer 5

sensory stimuli triggers an episode

Question 6

define seizure

Answer 6

physical findings and/or changes in behavior that result from abnormal electrical activity in the brain

Question 7

what effects can a seizure include

Answer 7

motor, sensory, autonomic, or psychic effects

Question 8

define epilepsy

Answer 8

abnormal activity in cerebral cortex that results in a seizure

Question 9

what is an epileptic seizure a clinical sign of?

Answer 9

abnormal forebrain disorder

Question 10

what is status epilepticus?

Answer 10

seizure lasts 5 min or longer within a few days or 2 seizures within 24 hours

Question 11

what are cluster seizures?

Answer 11

increased frequency of seizures within a few days or 2 seizures w/in 24 hours

Question 12

what are the 3 phases of epileptic seizure?

Answer 12

prodome
ictus
post-ictal period

Question 13

what happens during the prodome period?

Answer 13

pre-ictal period; abnormal behavior may occur hours before ictus

Question 14

what happens during the ictus period?

Answer 14

seizure lasting 1-2 minutes, characterized by loss of consciousness and alteration

Question 15

what happens during the post-ictal period?

Answer 15

return to normal or altered behavior - recovery period

Question 16

what does EEGs measure?

Answer 16

collective electrical activity of these neurons in cortex

Question 17

how is the cortex organized?

Answer 17

layers and columns

Question 18

what is in the layers of the cortex?

Answer 18

Layer 1 - glia cells and dendrites of neurons in lower layer
Layers 2-6 - stellate cells relieve afferents from brainstem sensory neurons, pyramidal cells send axons to other parts of cortex
Layer 4 - receives thalamic inputs
Layer 5 - motor efferent neurons to SC
Layer 6 - projections to basal ganglia and thalamus

Question 19

what are the major cell types of the cortex?

Answer 19

pyrimidal neurons
stellate neurons
glial cells

Question 20

what is a focal seizure

Answer 20

originates in localized portion of cortex = seizure focus

Question 21

what is a generalized seizure

Answer 21

involves both hemispheres of brain
originates in thalamus with abnormal activity in thalamocortical circuit

Question 22

what is a secondary generalized seizure?

Answer 22

focal seizure start locally and spreads to rest of cortex -> generalized seizure

Question 23

what contributes to membrane potential and creation of action potentials?

Answer 23

ions
ion channels
pumps
pH

Question 24

what are the two kind of ion channels responsible for inhibitory and excitatory activity

Answer 24

voltage-gated channels
ligand-gated channels

Question 25

which ligand-gated channels causes hyperpolarization and which cause depolarization?

Answer 25

GABA - hyperpolarization AMPA & NMDA - depolarization

Question 26

when might elipesy channelopathies occur?

Answer 26

mutations to various channels -> enhanced excitability or loss of inhibition

Question 27

what is a paroxysmal depolarization shift?

Answer 27

sudden, large, long depolarization

Question 28

what does a paroxysmal depolarization shift (PDS) lead to?

Answer 28

train of AP recurrent high frequency bursts of AP

Question 29

what causes the depolarization phase in PDS?

Answer 29

calcium and glutamate channel activation

Question 30

what receptors mediate and maintain initial and sustained depolarization in PDS

Answer 30

initial - AMPA sustained - NMDA

Question 31

what causes the hyper polarization phase in PDS?

Answer 31

termination of PD -> Cl and K flux via GABA receptors

Question 32

how do PDS remain localized in healthy NS?

Answer 32

recurrent of axons affected -> active inhibitory interneurons -> dampens spread of seizure to neighboring cells

Question 33

what happens when surround inhibition breaks down?

Answer 33

seizure spreads

Question 34

when can a seizure spread?

Answer 34

neurons die - loss in inhibitory interneurons channelopathies - disorders in ion channels -> high Na, Ca & low K

Question 35

what is detected on the EEG?

Answer 35

Question 36

how do electrodes on the surface of the scalp work?

Answer 36

detect transient electrical fields when individual neurons depolarize

Question 37

what is detected in practice from the electrodes?

Answer 37

average signal of all the depolarizing neurons in the cortex under the electrode on the scalp

Question 38

what will a positive voltage change do to the EEG?

Answer 38

downward reflection

Question 39

what will a negative voltage change do to the EEG?

Answer 39

upward deflection

Question 40

what are EEGs useful in?

Answer 40

identifying and classifying epilepsies localizing lesion in cortex sleep studies legal determination of brain death

Question 41

what do the electrodes over the occipital lobe measure?

Answer 41

electrical activity related to vision

Question 42

how do alpha and beta waves look in awake EEG?

Answer 42

alpha - regular high amplitude sweeping pattern beta - irregular and low amplitude

Question 43

is this patient awake or asleep

Answer 43

awake

Question 44

what are the characteristics of a sleeping slow wave EEG?

Answer 44

delta waves - slow wave sleep

Question 45

what is paradoxial sleep characterized by?

Answer 45

low amplitude, irregular EEG

Question 46

what EEG is similar to the awake eyes closed EEG?

Answer 46

sleeping EEG

Question 47

what EEG is similar to the awake eyes open EEG?

Answer 47

paradoxical sleep

Question 48

what is this the EEG of?

Answer 48

slow wave sleep

Question 49

what is this an EEG of?

Answer 49

paradoxical sleep

Question 50

what are sleep spindles in the sleeping EEG?

Answer 50

bursts of activity from the thalamus to the cortex

Question 51

what are K complexes?

Answer 51

extensive activities in the primary sensory corticles

Question 52

what can an EEG determine?

Answer 52

focal vs generalized seizure part of cortex affected how seizure spreads through cortex over time

Question 53

Can intracranial EEGs provide future ability to forecast seizures?

Answer 53

yes

Question 54

how does flashing lights induce seizures

Answer 54

photosensitive epilepsy - brain responds excessively to certain visual stimuli

Question 55

what explains rhodesian ridgebacks sensitivity to myoclonic jerks and photosensitive epilepsy?

Answer 55

4-bp deletion in DIRAs gene