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Neuropsychiatric Disorders > EEG Interpretation > Flashcards

EEG Interpretation Flashcards

1
Q

What are two components to examining EEG?

A

▪️ Background (ongoing activity)
▪️ Transients (brief spikes)

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2
Q

What can you look for in the background EEG signal?

A

▪️ Whether it is normal for their age/state (e.g., conscious, stage of sleep etc)
▪️ If it is abnormal, is it generalised across channels/bilateral, or is it focal?

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3
Q

What is the main distinction to make when examining transients?

A

Whether it is cerebral or not (i.e. an artefact)

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4
Q

What are the three distinctions to make when looking at cerebral transients?

A
  1. Normal for age/state
  2. Nonspecific
  3. Epileptiform (benign or significant)
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5
Q

What distinctions need to be made when examining epileptiform transients?

A

▪️ Generalised vs focal
▪️ Interictal vs ictal

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6
Q

What are interictal epileptiform discharges?

A

▪️ Paroxysmal activity clearly distinguished from the background
▪️ Abrupt change in polarity occurring during several milliseconds
▪️ Duration less than 200ms
▪️ Must have physiologic field (not an artefact)

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7
Q

What is upgoing EEG activity (e.g., height of spike)?

A

Negative

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8
Q

How do interictal epileptiform discharges appear on EEG?

A

Spike and wave patterns
▪️ Spike <70ms
▪️ Sharp waves 70-200ms
▪️ Can be generalised spike and wave, polyspike and wave, or slow spike and wave

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9
Q

What is PLED?

A

Periodic lateralised epileptiform discharges

(IED with repetitive spikes and waves, usually more associated with acute conditions such as HSV encephalitis than epilepsy but can still be associated with seizures)

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10
Q

What are the features of ictal activity in focal epilepsy?

A

▪️ Change in amplitude
▪️ Change in frequency
▪️ Propagation (spread) - reflects pathophysiology of seizures
▪️ EEG onset and offset

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11
Q

Typically, what does one bar on EEG represent?

A

One second

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12
Q

What is the hallmark EEG sign of absence epilepsy?

A

3-4 spikes per second (3-4Hz), generalised across channels

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13
Q

What is the specificity of a measure?

A

The true negative rate - the proportion of healthy subjects who do not have the sign

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14
Q

What is the sensitivity of a measure?

A

The true positive rate - the proportion of patients who show the sign

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15
Q

How long is a routine EEG recording?

A

20 minutes

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16
Q

What is the sensitivity and specificity of the first EEG?

A

▪️ 40% sensitivity
▪️ >96% specificity - very few without epilepsy will show something

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17
Q

How do we improve EEG sensitivity for epilepsy?

A

▪️ Repeat EEG - more likely then to see something that occurs randomly
▪️ Sleep EEG - increased rate of discharges, particularly in stage 2 sleep

(improves from 40% to 80-90%)

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18
Q

What is the main strength of an EEG for detecting epilepsy?

A

On the first trial, you are very unlikely to see abnormal discharges in people who don’t have epilepsy

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19
Q

Does IED/spikes always indicate epilepy?

A

No!

May be present in healthy people as well as various conditions such as neurodegeneration or when on psychotropic medication

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20
Q

Why is the false positive rate of spikes in EEG slightly higher in children?

A

▪️ Rolandic spikes (genetic phenomenon)
▪️ Asymptomatic siblings of those with rolandic epilepsy may show them but grow out of it

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21
Q

What are the main EEG recording modalities available for clinical investigation?

A

▪️ Routine and sleep VEEG
▪️ Ambulatory EEG
▪️ Polysomnographies (incl other components)
▪️ Electro-corticogram (EcoG) - mats over brain during surgery to determine function and delineate pathology
▪️ In-patient video-telemetry and home VT

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22
Q

What is video-telemetry?

A

Continuous video-EEG monitoring to record seizures

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23
Q

How long is hospital admission typically for inpatient VT?

A

3-5 days

(up to 3 weeks with implanted electrodes)

24
Q

What are the four types of VT available?

A

▪️ Inpatient VT
▪️ Home VT (HVT)
▪️ Mobile (ambulatory) HVT
▪️ Cloud based HVT

25
Q

What are the two components of VT assessment?

A

▪️ EEG activity (interictal, ictal, postictal)
▪️ Semiology (behavioural changes)

26
Q

What are the two main components of semiology examination?

A

▪️ Ictal assessment (check response, memory, ability to move and speak etc)
▪️ Signs

27
Q

What information can you get from the semiology signs using VT?

A

▪️ Evolution of the seizure
▪️ Lateralisation
▪️ Localisation

28
Q

Is EEG needed for the diagnosis/definition of epilepsy?

A

No!

29
Q

What is EEG used for in epilepsy?

A

The CLASSIFICATION (focal vs generalised, idiopathic vs symptomatic)

30
Q

How many unprovoked seizures are necessary for diagnosis and treatment of epilepsy?

A

Two

31
Q

What are generalised polyspike waves a typically sign of?

A

Juvenile myoclonic epilepsy

32
Q

Does interictal EEG prove the presence of epilepsy?

A

No! - some spikes seen in other conditions

33
Q

Does a normal EEG exclude epilepsy?

A

No! - low sensitivity during first recording (60% will show up normal)

34
Q

What is the most common form of reflect epilepsy?

A

Photosensitive epilepsy

35
Q

What are the three main indicators of photosensitive epilepsy following intermittent photic stimulation?

A
  1. Photic following at flash rate
  2. Photic following at harmonics
  3. Orbito-frontal photo-myoclonia
36
Q

Photosensitivity is a ________________ and refers to patients with ___________________

A

▪️ EEG marker
▪️ Reflex epilepsy

37
Q

What are the main types of photosensitivity syndromes?

A

▪️ Pure photosensitive epilepsy (seizures only in response to light flashes)
▪️ Epilepsy with photosensitivity (58%)
▪️ Photosensitivity without epilepsy (may be genetic marker)

38
Q

What form of idiopathic generalised epilepsy is most commonly associated with photosensitivity?

A

Juvenile myoclonic epilepsy (JME) - 30%

(Followed by childhood absence epilepsy and GTCS on awakening)

39
Q

How can video EEG telemetry be used for presurgical evaluation in epilepsy?

A

Can help with other measures to determine the epileptogenic zone to be removed (and whether it can be removed without deficits)
▪️ Interictal EEG - indicate irritative zone
▪️ Ictal EEG - indicate ictal onset zone

40
Q

What are the two main contacts measured by an implanted electrode for EEG?

A

▪️ EP = entry point
▪️ T = target (1) - inner aspect

(can have more contacts in between)

41
Q

When is alpha activity seen on EEG?

A

On eye closure

(Responsive but relaxed)

42
Q

What is the main EEG sign of dissociative seizure?

A

Alpha activity but unresponsive

43
Q

What is the activation procedure for NES?

A

Suggestion with non-epileptic stimulation approach that cannot commonly induce epileptic discharges/seizures

Sometimes with hyperventilation

44
Q

What happens during activation clinic?

A
  1. 30 minute EEG obtained
  2. History including witness account
  3. Activation procedure
  4. Event reviewed by witness
  5. Diagnosis not typically discussed
45
Q

How can EEG be used for diagnosis of non-epileptic/dissociative seizures?

A

Activation clinic

46
Q

What are the two important clinical components of consciousness and how can we determine these in disorder of consciousness?

A

▪️ Awareness - do they have memory of the event (e.g., seizure)?
▪️ Responsiveness - ask a witness whether they were able to respond (e.g., during the seizure)

47
Q

What disorders/states of consciousness can EEG be useful for?

A

▪️ Coma
▪️ Sleep
▪️ Wakefulness
▪️ Seizures
▪️ Parasomnias
▪️ General anaesthesia
▪️ Locked in syndrome
▪️ Non-epileptic seizures (but complicated balance of awareness/responsiveness)

48
Q

What disorders/states of consciousness does EEG struggle with?

A

▪️ Minimal consciousness - can look almost normal
▪️ Dementias
▪️ Vegetative state

49
Q

When is alpha generated?

A

On eye closure

50
Q

What can you conclude if someone is not reaching alpha (theta instead)?

A

They are drowsy

51
Q

What does alpha on eye opening and eye closure indicate?

A

An arousal response

(Following drowsiness/theta)

52
Q

What are Stimulus-induced, period, rhythmic, or ictal discharges (SIRPID) important for?

A

▪️ Determining ictal interictal continuum (seizure activity)
▪️ Differential diagnosis in status epilepticus
▪️ Prognosis of poor outcome after cardiac arrest (in unresponsive patients)

53
Q

What does more slow EEG indicate?

A

More severe abnormality/encephalopathy

54
Q

What are the main indicators of more severe abnormality?

A

▪️ Slower activity
▪️ Less reactive
▪️ Less sleep architecture

55
Q

What is are main differential diagnosis for slower and less reactive EEG?

A

▪️ Drowsiness
▪️ Drugs

Neuropsychiatric Disorders (30 decks)

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