42 - Cerebral Cortex and Epilepsy

Question 1

Grand Mal Seizure

Answer 1

Generalized Compulsive Seizure

Question 2

Paleocortex

Answer 2

Hippocampus & Olfactory Regions

3 Layers

Question 3

Neocortex

Answer 3

6 Layers

Majority of the cortex

Question 4

Layers

Answer 4

Organize inputs of cortical neurons

Organize the outputs

Question 5

Excitatory Neurons

Answer 5

Spiny

Glutamatergic

Question 6

Inhibitory Neurons

Answer 6

Smooth or Sparesly Spiny
GABAergic (Glycinergic rare in neocortex)
Biophysical properties differ from excitatory cells

Question 7

Pyramidal Neurons

Answer 7

Main excitatory neurons

Polarized (Apical dendrite extending to pial surface)
Large - Layers 3 & 5
Small - Layers 2, 3, 4 & 6
Long-range axons projecting to other cortical regions

Question 8

Spiny Stellate Cells

Answer 8

Excitatory interneurons

Small
Multipolar
Layer 4
Axons usually project only to local cortical region

Question 9

Basket Cells

Answer 9

Inhibitory interneurons

Layers 3 & 4

Question 10

Chandelier Cells

Answer 10

Inhibitory interneurons
Layer 3
Synapse on axon initial segment of pyramidal cells

Question 11

Double Bouquet Cells

Answer 11

Inhibitory Interneurons

Layers 2, 3 & 4

Question 12

Three molecular markers that account for nearly all neocortical inhibitory cells

Answer 12

PV
SST
5HT3aR

Question 13

Alpha Rhythm

Answer 13

The first wave observed

Most dominant rhythm in humans

Question 14

Beta Rhythm

Answer 14

Higher frequencies

Signify alert, working, thinking

Question 15

Theta Rhythm

Answer 15

Drowzy

Relaxed

Question 16

Delta Rhythm

Answer 16

Sleeping

Question 17

Factors influencing whether or not you can MEASURE cortical potentials with an EEG

Answer 17

Voltage of cortical discharge
Area of cortex involved in synchronous activity
Degree of synchrony

Question 18

Complications in measuring an EEG

Answer 18

Complex geometry of brain & head
Emphasis on radially-orientated pyramidal neurons
Many cytoarchitectural differences reflected in cortical layering
Conductivity varies in different directions
Not all cells behave in the same manner

Question 19

Normal

Answer 19

Excitation and inhibition balance each other out

Question 20

Seizure

Answer 20

Excitation outweighs inhibition

Question 21

Cellular changes contributing to seizure

Answer 21

Membrane properties
Synaptic strength
Connectivity
Glia (ionic homeostasis, NT uptake)
Metaboloic changes
Cell death
Trauma, infection, dysplasia, infarcts

Question 22

Epilepsy

Answer 22

Not a single disorder, but a group
All contain seizures
Definition: >1 unprovoked seizure (3% of US population)
Some acquired
Some idiopathic
Genetic factors sometimes but not always
Seizure semiology is highly variable
Extent/duration vary
Different brain areas involved in different manifestations
Seizures are intermittent
Brain immaturity modifies clinical and EEG expressions of seizures

Question 23

Seizure

Answer 23

Paroxysmal change in behavior due to abnormal electrical brain activity
10% of the US population

Question 24

Interictal EEG abnormalities

Answer 24

Marker of seizure susceptibility

Question 25

Generalized onset seizures

Answer 25

Tonic-clonic (convulsive) Absence (non-convulsive) Myoclonic (muscle jerks, +/- loss of consciousness)

Question 26

Focal (partial) seizures

Answer 26

Simple partial seizures (no loss of consciousness) Complex partial seizures (consciousness altered or lost) Focal seizures with secondary generalization

Question 27

Focal epilepsy - Idiopathic

Answer 27

Benign focal epilepsy of childhood Central midtemporal spikes (rolandic) Occipital spikes

Question 28

Focal epilepsy - Symptomatic

Answer 28

Epilepsia partialis continua (Rasmussen's Syndrome) Temoral lobe epilepsy AD frontal lobe epilepsy

Question 29

Generalized onset seizures - Idiopathic

Answer 29

Childhood absence epilepsy Juvenile myoclonic epilepsy Other generalized idiopathic epilepsies

Question 30

Generalized onset seizures - Symptomatic

Answer 30

West syndrome (infantile spasms) Lennox-Gastaut syndrome Landau Kleffner syndrome

Question 31

Interictal

Answer 31

Phenomenon happening between seizures Spikes and hsarp waves (epileptiform discharges) Focal vs. generalized Sometimes multifocal

Question 32

Ictal

Answer 32

Seizures event, itself

Question 33

Cellular basis of EEG epileptiform discharges

Answer 33

Paroxysmal Depolarizing Shift (PDS)

Question 34

Interictal PDS

Answer 34

AMPA and NMDA excite GABA inhibits Excitatory signals are encased in an "inhibitory surround" When this breaks down, we have an ictal event.

Question 35

Cortical Circuit

Answer 35

Excitatory input coupled to tandem inhibitory input. There is also autoinhibition coupled to the nerve's output All this helps to refine the signal

Question 36

Cellular Events during a seizure

Answer 36

Tonic Phase: AMPA and NMDA are ON ON ON ON ON ON ONNNNN GABA is on. Clonic Phase: AMPA and GABA alternate which one is dominant Leads to rhythmic bursts

Question 37

Untreated Recurrent Seizures

Answer 37

Hippocampal Sclerosis: Granule Cell Layer ragged and deformed Pyramidal cells missing

Question 38

Hippocampal Sclerosis

Answer 38

Profound loss of CA1 and CA3 pyramidal cells Profound loss of neurons in the dentate hilus Relative survival of CA2 pyramidal cells and dentate granule cells

Question 39

Untreated Recurrent Seizures - Cellular Effects

Answer 39

Cell death, initially selective Synaptic reorganization Structural remodeling Neurogenesis (?!) Changes in intrinsic protective or trophic mechanisms Effects on future seizure susceptibility Interference with normal neuronal development

Question 40

Untreated Recurrent Seizures - Outcomes

Answer 40

``` Developmental delays (infancy & early childhood) Failure to acquire interpersonal and vocational skills (adolescence and young adulthood) Specific cognitive dysfunction Memory deficits (temporal lobe epilepsy) Language deficits (Landau-Kleffner syndrome) Other cognitive defects (CSWS) Psychiatric disturbances, especially depression Higher mortality rate ```

Question 41

Absence Seizure

Answer 41

3Hz spike wave running through entire brain Often misdiagnosed for ADD Kid just zones out for a sec

Question 42

3 Key Elements of Thalamocortical Circuitry that contribute to an Absence Seizure

Answer 42

Reciprocal connectivity Specific synaptic mechanisms Intrinsic burst-firing capability in key neurons

Question 43

Thalamocortical Neurons

Answer 43

Relay neurons in the thalamus Intertwined with reticular neurons Low threshold Ca2+ channels Burst when inhibited strongly

Question 44

Reticular Neurons

Answer 44

Inhibitory regulators of thalamocortical neurons | STRONG

Question 45

Epilepsy

Answer 45

IT IS A CHANNELOPATHY Too much sodium influx OR Not enough potassium efflux

Question 46

Twins

Answer 46

Um not always paired with epilepsy Maybe environment Maybe de novo mutations