Thalamocortical Physiology

Question 1

Absence seizures can be prompted by ______________.

Answer 1

hyperventilating

Question 2

What is the basic definition of a seizure?

Answer 2

An episode of cerebral dysfunction leading to clinical changes in motor, sensory, or autonomic function

Question 3

There are two broad categories of seizures: _______________.

Answer 3

partial (involving only a part of the brain) and generalized (involving the entire brain)

Question 4

Idiopathic generalized epilepsy is a type of generalized absence seizure. There are two subtypes. Describe them.

Answer 4

• A type in which absence seizures are the predominant form (called childhood or juvenile epilepsy)
• A type in which other seizure types are predominant (called myotonic epilepsy)

Question 5

True or false: absence epilepsy is the most common type of childhood epilepsy.

Answer 5

False. Absence epilepsy accounts for only 10% of childhood epilepsy.

Question 6

There is a ____________ genetic link to absence epilepsy.

Answer 6

strong (monozygotic concordance roughly 80%)

Question 7

Simple absence seizures have ____________ motor activity.

Answer 7

minimal (while complex absence seizures have lots)

Question 8

Simple absence seizures last between ______________.

Answer 8

5 and 15 seconds

Question 9

Which type of absence seizure (complex or simple) is more common?

Answer 9

Complex

Question 10

When does childhood absence seizure typically present?

Answer 10

Age 4 to 8

Question 11

True or false: most childhood absence epilepsy persists to adulthood.

Answer 11

False. 80% resolve

Question 12

The brand name of valproic acid is ______________.

Answer 12

Depakote

Question 13

At -85 mV, stimulating the thalamus leads to ______________.

Answer 13

slower action potential frequency due to the presence of T-type calcium channels (that produce the calcium spike)

Question 14

At -65 mB, stimulating the thalamus leads to _______________.

Answer 14

rapidly oscillating action potentials (1,000 x per second)

Question 15

Why is there a different effect in stimulating the thalamus at different initial potentials?

Answer 15

Because the T-type calcium channel’s inactivation gate is closed at -65 mV; thus, it does not have the modulating effect that it does at -85 mV.

Question 16

What anticonvulsants target the T-type calcium channel?

Answer 16

Valproic acid and ethosuximide

Question 17

Valproic acid functions when people are _________.

Answer 17

asleep

Question 18

Slow-wave sleep and seizures are characterized by an EEG that fluctuates at _______.

Answer 18

3 Hz

Question 19

Why is the resting potential of the thalamus -85 when asleep and -55 when awake?

Answer 19

Because GABA channels open during sleep that hyperpolarize the cells

Question 20

What evidence demonstrates that the T-type calcium channels are necessary to produce seizure?

Answer 20

Mice born without T-type calcium channels cannot be made to have seizures, and there are families with genetic epilepsy that have mutations in T-type channels (allowing the channels to be active when depolarized).

Question 21

How many seizures do those with simple absence seizures have daily?

Answer 21

100

Question 22

What is the generic name for keppra?

Answer 22

Levetiracetam

Question 23

Atypical absence seizures have what EEG pattern?

Answer 23

Less rhythmic than typical, with lots of random squiggles

Question 24

Absence seizure EEGs resemble those of what stage sleep?

Answer 24

IV