basic science / EEG correlate

Question 1

if a difference in potential between to electrodes is negative, you will see a _____ deflection.

Answer 1

Upward.

Question 1

Equilibrium potential for an ion can be calculated by:

Answer 1

Nernst Equation

Question 2

Equation to determine resting membrane potential

Answer 2

Goldman-Hodgin-Katz equation

Question 3

Situations in which scalp discharges can be positive (downward deflecting) - 2

Answer 3

• Craniotomy
• infants with IVH (central)

Question 4

Non-epileptic causes for occipital discharges (2, likely more)

Answer 4

• Migraine (occipital)
• Congenital blindness

Question 5

Spike-and-wave discharges:
1.0-2.5 Hz
3-3.5 Hz
4-6 Hz

Answer 5

1.0-2.5 Hz: LGS
3-3.5 Hz: Absence Epilepsy
4-6 Hz: JME

Question 6

BiPLEDS can signify what?

Answer 6

severe brain disesase. (associated with poor prognosis)

Question 7

How to differentiate between Myoclonic-Astatic seizure and negative myoclonus (in FLE with rapid bilateral synchrony)

Answer 7

MAS: Geralizes spow spike-and-wave or polyspike-and-wave with jerk
NM: interrupts tonic activity, <500 Ms, no evidence of myoclonia during drops

Question 8

What is the intracellular pathophysiological mechanism of an epileptiform discharge?

What is the primary cause?

Answer 8

Paroxysmal depolarizing shift (PDS):
Primarily due to activation of high-frequency fast sodium channel potentials

Question 9

List five (5) ways to reduce risk of electrocution in EEG recording

Answer 9

• Small leakage currents
• short cord connection
• people NOT connected to ground
• High-resistant contacts
• one common ground electrode

Question 10

minimal surface area of the postsynaptic action potential required for recording of a spike on scalp EEG

Answer 10

6 cm2

Question 11

What determines the half-life of a resistor?

Answer 11

Time-constant

Question 12

What is aliasing?
How do you avoid it?
How do we know this?

Answer 12

What is aliasing?: erroneous representation of waveform due to low sampling rate
How do you avoid it: sampling rate should at least match double the frequency of the original signal
How do we know this? Nyquist sampling theorem

Question 13

Seizures occur in ___% of patients with :
Anterior temporal spikes

Answer 13

90%

Question 14

Seizures occur in ___% of children with rolandic spikes

Answer 14

40%

Question 15

Seizures occur in ___% of children with occipital spikes

Answer 15

40%

Question 16

SeLECTS, horizontal dipole is negative over ___ and positive is ____

Answer 16

Negative over central and temporal regions
postitive end over frontal region

Question 17

EEG features seen with syncope (2)

Answer 17

Transient high-voltage delta
complete voltage attenuation

Question 18

Factors increasing sensitivity of detection epileptiform discharges (6)

Answer 18

• longer-term monitoring
• higher yield if <24 hours since seizure
• higher seizure frequency
• lack of AED
• epilepsy syndromes
• Temporal location

Question 19

What causes:
Excitatory postsynaptic potential (EPSP)
Inhibitory postsynaptic potential (IPSP)
which is negative, which is positive?

Answer 19

EPSP: positive ions flow intracellularly (inward flow): Negative
IPSP: negative ions flow intracellularly (outward flow): Positive

Question 20

What is the passive source or sink in EEG terminology?

Answer 20

current flow in opposite direction further along the dendritic tree