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Neuro > EEG > Flashcards

EEG Flashcards

1
Q

From what age is EEG recordable?

A

22 weeks of gestation

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2
Q

Is there a standard EEG for all stages of development?

A

No

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3
Q

What are the types of EEG?

A

Routine awake portable

Sleep (natural, sleep deprived, drug induced)

Ambulatory

Video telemetry - long term recording

Back averaging

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4
Q

What are evoked potentials?

A

They are EEG traces recorded in response to sensory disturbances

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5
Q

What are the types of evoked potentials?

A

Visual evoked potential

Sensory evoked potential

Motor evoked potential

Brainstem evoked potential

Electroretinogram and electrooculograms

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6
Q

When do we do ambulatory EEGs?

A

When is doubt over whether they are having seizures or you want to find out seizure frequency

Good for ruling out non-epileptic attacks

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7
Q

When do we use video telemetry?

A

Used when contemplating epilepsy surgery

Less for diagnostics

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8
Q

What is back averaging?

A

Frequent epileptiform activity can be associated with twitch. You might miss one spike from myoclonus.

So you measure with EEG and average the areas showing the twitch to remove background noise

Enhances abnormality

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9
Q

What medication is used in paediatric patients to induce sleep?

A

Melatonin

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10
Q

What is a VEP?

A

Response to sensory disturbances

  • flashing checkboard pattern

Usually recorded upside down

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11
Q

What do we see in the VEP of MS patients?

A

Delayed response to visual stimulus

  • P100 is delayed if there is an optic nerve problem
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12
Q

Give an example of how an SEP would work

A

Sensory disturbance in foot or arm

Stimulate with electricity and then measure CNS response - see if it is normal

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13
Q

What do we see in the SEP of an MS patient?

A

SEP is slowed

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14
Q

What are motor evoked potentials?

A

Cortical magnetic stimulation –> check time for arm to twitch

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15
Q

When are MEPs used?

A

Spinal cord surgery

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16
Q

What is the 10/20 system?

A

23 electrodes placed symmetrically over the scalp on very specific places according to places in the cortex underneath

10 and 20 refer to distance between certain places in head

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17
Q

How do you conduct an EEG?

A
  1. Skin is prepared and electrodes are held in place with conductive paste
  2. Locations are measured and marked according to the international 10-20 system
  3. Recording for ~20 min with periods of eye opening and closing
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18
Q

How do monopolar measurements differ from the EEG montage we use?

A

Unlike the 20/10 system, it utilizes one electrode at e.g. the ear and the potential from that electrode to some another electrode often far away is measured

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19
Q

What does an EEG record?

A

Voltage differences between two points on the scalp over time

The voltage difference is the sum of a mixture of excitatory and inhibitor post-synaptic potentials in ~5cm^2 of the cortical surface

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20
Q

What are EEG electrodes made of?

A

Ag-AgCl in a state of equilibrium

AgCl- + e- = Ag + Cl-

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21
Q

What do EEG amplifiers do?

A

Compare the differences in voltage between pairs of electrodes

22
Q

What are montages?

A

Different ways EEG electrodes can be connected

23
Q

What can you do to induce seizure readings?

A

Hyperventilation - increase slow activity and reduces seizure threshold

Photic stimulation (flashing light - sometimes colour dependent) - normally elicits time locked evoked responses

Sleep: drug induced sleep deprivation

24
Q

What can be the negative side effects stimulating seizures for EEGs?

A

Someone who has not had seizures so far can lose drivers licence

Seizure can cause damage

25
Q

What kind of rhythms do we see in EEGs?

A

Alpha: 8-12 /sec

Beta: >12/sec

Theta: 4-<8/sec

Delta: <4/sec

26
Q

What is typical for alpha waves?

A

Fairly fixed, doesn’t fluctuate in the short term

Sensory stimulus suppresses it so best when eyes are closed

Comes from the thalamus (synchronised thalamocortical activity)

Seen over the occipital regions

27
Q

What is typical for beta waves?

A

Usually anterior

Low voltage

Desynchronised

28
Q

When are beta waves worrisome?

A

Lots of beta activity commonly seen in benzodiazapine use

Usually nothing pathological

29
Q

What is typical for theta waves?

A

Seen widespread but mostly temporal

Acceptable in young adults until 30 and in temporal areas

30
Q

When are theta waves worrisome?

A

If you have too many theta waves as an adult

31
Q

What is normal for delta waves?

A

Widespread when asleep

32
Q

When are delta waves worrisome?

A

Definitely pathological in awake patients

33
Q

When do you use EEGs?

A

Diagnostic:

  • Evidence of seizure activity
  • Seizure classification
  • Evidence of status epilepticus
  • Focal abnormalities
  • Metabolic and infective encephalopathies
  • Neurodegenerative diseases, dementia, CJD
  • Sleep disorders
  • Planning treatment

Monitoring:

  • Evidence of drug effects (in US used in operation for sedation)
  • Adequate suppression of status epilepticus

Prognostic:

  • Checking brain injury
  • In coma it is combined SEP
34
Q

How is status epilepticus different from other epilepsy?

A

Patients are in a state of epilepsy that isn’t self-limiting and neurotoxic

35
Q

Why might we need to check if someone has status epilepticus?

A

People in ICU might not wake up due to brain damage or status epileticus (find out why)

36
Q

What kind of metabolic/infective encephalopathies can be studied with EEG?

A

Helpatoencephalopathy

Triphasic waves found in encephalopathies and CJD

37
Q

What do we see in normal awake EEGs?

A

If eyes are closed maybe alpha

If child: theta

Some anterior beta

38
Q

What are the stages of sleep and what are their characteristics?

A

Stage 1: drowsiness, attenuation of alpha activity, increasing amounts of theta

Stage 2: vertex sharp waves, K complexes, sleep spindles, positive occipital sharp transients of sleep, up to 20% slow and theta activity

Stage 3: 20-50% slow and theta

Stage 4: >50% slow, deep sleep, slow wave sleep(non-REM)

Stage 5: REM

39
Q

What abnormal patterns would you see in epilepsy?

A

Focal or generalised

May be continuous (status)

PLEDs (periodic lateralised epileptiform discharges)

40
Q

What abnormal patterns would you see with drugs?

A

Activity seems slowed (usually there are many types of patterns)

Fast, beta activity - especially in barbiturates and benzodiazepines

Burst suppression: anaesthetic doses (look quite epileptiform: flat and then bursts)

Epiletiform: Clozapine and Olanzepine

41
Q

What abnormal patterns would you see with metabolic or toxic issues?

A

There are slow focal or diffuse patterns

You would expect PLEDs

42
Q

What abnormal patterns would you see with trauma?

A

It is slow, focal/generalised

Burst suppression (poor prognosis)

Breach rhythm

43
Q

What are the causes of EEG abnormalities?

A

Epilepsy

Drugs

Metabolic/toxic

Trauma

44
Q

Three types of epileptic EEGs

A

Inter-ictal

Ictal

Post-ictal

45
Q

What might you see in an inter-ictal EEG?

A

Normal in 50% of patients

Might see spike/sharp and slow wave complexes

Cannot exclude epilepsy without inter-ictal EEG

46
Q

What do you see in ictal EEG?

A

Usually you see sharp waves or spikes build up in frequency and area of distribution

Can also see attenuation or slowing immediately before or after seizure

47
Q

What can you see in post-ictal EEG?

A

Generalised

Suppression/attenuation of activity which may persist for hours or days after a seizure

48
Q

What suggests a good prognosis in coma?

A

Mix of frequencies

Reactivity: pain, suction, auditory

Variability of frequency and amplitude

Evolution to more favourable pattern over time

49
Q

A patient had brain surgery and is now on light sedation but is twitching. What could it be?

A

A seizure or left over anesthetics

You have to find out which with an EEG

50
Q

What suggests a bad prognosis in coma (off sedation)?

A

Monotonous Rhythms (alpha coma)

Lack of reactivity

Low amplitude

Burst suppression

Periodic bilateral spikes, may be associated with myoclonus

51
Q

What might we use to get accurate localisation of brain issues?

A

Multiple scalp electrodes (telemetry)

Cortical grids

Depth electrodes

Electrocorticography

PET scanning

fMRI

Neuro (23 decks)

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