Epilepsy: Classification and Etiology

Question 1

Broadly, what part of the brain do seizures affect?

Answer 1

The cortex.

Question 2

What are 3 things that can cause a provoked seizure?

Answer 2

Fever, acute head trauma, CNS infection.

Question 3

Are provoked seizures indicative of epilepsy?

Answer 3

No.

Question 4

Is an unprovoked seizure epilepsy?

Answer 4

No.

Question 5

What is epilepsy? (simple definition)

Answer 5

Recurrent unprovoked seizures.

Question 6

How does prevalence of epilepsy vary with age?

Answer 6

Bimodal: peaks in infants/children and adults > 70 yrs.

Question 7

What did the Bible get right about epilepsy?

Answer 7

Fasting -> ketosis actually helps epilepsy sometimes. (Does this actually happen in the Bible?)

Question 8

What did the 1850’s masturbator-haters get right about epilepsy?

Answer 8

Bromide salts are an effective treatment for epilepsy (with the side effect of reduced libido).

Question 9

What’s a “Jacksonian March”?

Answer 9

Motor seizure propagating along primary motor cortex. (Jackson correlated seizure signs with anatomic location in brain)

Question 10

What was the first modern medication for epilepsy? (not bromide salts) Drug class? Mechanism?

Answer 10

Phenobarbital. A barbituate.

Acts on GABA-A to facilitate inhibitory signaling. (more coverage of this in next lecture)

Question 11

What are 2 basic rules of symmetry / asymmetry in a normal EEG?

Answer 11

Front of brain should look different from back.

Left should look the same as right.

Question 12

What do the waves on an EEG actually represent?

Answer 12

Extracellular current from summed activity from many neurons, especially pyramidal cells.

Question 13

What are 4 factors in the International League Against Epilepsy (ILAE) revised classification of epilepsy?

Answer 13

Mode of epileptic seizure onset.
Epilepsy syndrome type.
Epilepsy etiology.
Evolution over time.

Question 14

What are 3 modes of seizure onset?

Answer 14

Generalized.
Focal.
Unknown / unclear.

Question 15

What are 6 types of generalized onset seizures? Brief description of each?

Answer 15

Absence - arrest of activity, staring, unresponsive.
Myoclonic - quick muscle jerks, usu. symmetric.
Tonic-clonic - convlusions: bilateral extension progressing to rhythmic shaking.
Tonic - extremity extension and muscle stiffening.
Clonic - rhythmic shaking (without tonic phase).
Atonic - sudden loss of trunk/neck tone -> falling.
(7th bonus type = epileptic spasm/ “West syndrome”: neck and trunk flexion, extremity extension)

Question 16

How do the onsets of generalized seizures look on an EEG?

Answer 16

Left and right are the same.

Question 17

Key points of the ILAE description of the onset of generalized seizures? (3ish things)

Answer 17

Rapidly engage bilateral networks.
Bilateral networks include cortical and subcortical structures.
Doesn’t necessarily involve all cortical areas.

Question 18

Why might a seizure that looks like it had generalized onset might not actually have had one?

Answer 18

Focal onset seizures with rapid secondary generalization can mimic generalized onset seizures.

Question 19

Key points of the ILAE description of the onset of focal seizures? (2ish things)

Answer 19

Originate in networks limited to one hemisphere.

Onset consistent from one seizure to the next.

Question 20

Name 4 different localizations within the frontal lobe for focal seizures and a brief description of their signs/symptoms.

Answer 20

Motor strip: clonic shaking of contralateral limbs.
Midline premotor area near midline - complex, bilateral hypermotor activity “wild, flailing movements.”
Broca’s area - expressive language dysfunction (non-fluent aphasia).
Fronto-polar - arrest of activity, hypomotor (easy to confuse with Absence).

Question 21

Signs and symptoms of focal onset seizures localized to the temporal lobe? (4 things)

Answer 21

Aura.
Arrest of activity.
Unresponsiveness.
Motor automatisms.

Question 22

What are motor automatisms?

Answer 22

“Meaningless,” repetitive motions. Recall the guy in the video fiddling with a plastic bag. Associated with temporal lobe seizures.

Question 23

Signs and symptoms of focal onset seizures localized to the parietal lobe? (2 things)

Answer 23

Sensory signs.
Signs based on propagation to other lobes.
(Parietal seizures are subtle.)

Question 24

Signs and symptoms of focal onset seizures localized to the occiptal lobe?

Answer 24

Visual signs. Can be seeing new stuff, such as auras. Or can lose vision.

Question 25

3 broad causes of epilepsy?

Answer 25

Genetic.
Structural / metabolic.
Unknown.

Question 26

What’s a developmental structural cause of epilepsy?

Answer 26

Malformations of cortical development.

Question 27

Some epilepsy is caused by mutations in a single gene. What kind of gene are most of these?

Answer 27

Ion channels / related proteins.

Question 28

2 different classifications of an epilepsy’s evolution over time?

Answer 28

Self-limited (or not).

Treatment-responsive (or not).

Question 29

What’s one reason why it’s important to distinguish between generalized vs. focal epilepsy?

Answer 29

Treatments for them are different, and treatments for one often don’t work for the other.

Question 30

Does childhood absence epilepsy (CAE) have effects if the seizures abate? What does this tell you about epilepsy?

Answer 30

Yes. People who had CAE as children score much lower psychosocially (income, education level, emotional problems, etc. etc.) later in life than average. Suggests that seizures are a symptom of problem with brain development (which the drugs can’t fix).