basic science / EEG correlate Flashcards
Equilibrium potential for an ion can be calculated by:
Nernst Equation
Equation to determine resting membrane potential
Goldman-Hodgin-Katz equation
Situations in which scalp discharges can be positive (downward deflecting) - 2
- Craniotomy
- infants with IVH (central)
Non-epileptic causes for occipital discharges (2, likely more)
- Migraine (occipital)
- Congenital blindness
Spike-and-wave discharges:
1.0-2.5 Hz
3-3.5 Hz
4-6 Hz
1.0-2.5 Hz: LGS
3-3.5 Hz: Absence Epilepsy
4-6 Hz: JME
BiPLEDS can signify what?
severe brain disesase. (associated with poor prognosis)
How to differentiate between Myoclonic-Astatic seizure and negative myoclonus (in FLE with rapid bilateral synchrony)
MAS: Geralized slow spike-and-wave or polyspike-and-wave with jerk
NM: interrupts tonic activity, no evidence of myoclonia during drops
What is the intracellular pathophysiological mechanism of an epileptiform discharge?
What is the primary cause?
Paroxysmal depolarizing shift (PDS):
Primarily due to activation of high-frequency fast sodium channel potentials
List five (5) ways to reduce risk of electrocution in EEG recording
- Small leakage currents
- short cord connection
- people NOT connected to ground
- High-resistant contacts
- one common ground electrode
minimal surface area of the postsynaptic action potential required for recording of a spike on scalp EEG
6 cm2
What determines the half-life of a resistor?
Time-constant
What is aliasing?
How do you avoid it?
How do we know this?
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
Seizures occur in ___% of patients with :
Anterior temporal spikes
90%
Seizures occur in ___% of children with rolandic spikes
40%
Seizures occur in ___% of children with occipital spikes
40%
SeLECTS, horizontal dipole is negative over ___ and positive is ____
Negative over central and temporal regions
postitive end over frontal region
EEG features seen with syncope (2)
Transient high-voltage delta
complete voltage attenuation
Factors increasing sensitivity of detection epileptiform discharges (6)
- longer-term monitoring
- higher yield if <24 hours since seizure
- higher seizure frequency
- lack of AED
- epilepsy syndromes
- Temporal location
What causes:
Excitatory postsynaptic potential (EPSP)
Inhibitory postsynaptic potential (IPSP)
which is negative, which is positive?
EPSP: positive ions flow intracellularly (inward flow): Negative
IPSP: negative ions flow intracellularly (outward flow): Positive
What is the passive source or sink in EEG terminology?
current flow in opposite direction further along the dendritic tree
if a difference in potential between to electrodes is negative, you will see a _____ deflection.
Upward.
