"A Clinician's Guide to EEG" Flashcards
What does EEG stand for?
Electroencephalogram (EEG)
Explain the electrode placement in EEG
-
Capital Letter - reflects brain lobe/region
- F = Frontal
- T = Temporal
- P = Parietal
- O = Occipital
- C = Central
-
Number or lower case letters denote position:
- Odd – left
- Even - right
- p - fronto-polar
- z – midline
Cz important electrode
Explain what happens in an EEG
- Pain free
- Non-invasive
- ~20-30mins
- Electrodes onto different areas of the head
-
Electrodes connected to an amplifyer
-
Amplifier connected to a computer
- Physiologist interprets computer
-
Amplifier connected to a computer
-
Electrodes connected to an amplifyer
- EEG records somated electrical activity (made by many neurons) from cortex
- Records in ccolumns
- 1 electrode sits over ~400 functional columns
- Hard for EEG pick up exact electrical activity due to background noise, skull (in the way), background noise
Explain differential amplifiers in EEG
- Magnifies the voltage input (easier to interpret)
- Subtracts the common components in signals between two inputs and amplifies this.
- Useful in biological systems
- Can detect small differences between two inputs
Explain the montage in EEG & types
Subtract from each other calculating differential amplifiers & describes the direction of the electrodes and way of calculation of differential amplifications
2 types:
-
Longitudinal (LEFT)
- Good at looking at temporal lobes
- Transverse (RIGHT)
Explain this EEG
Green lines = time measurement
Red lines = records when a change is made e.g. eyes open/eyes closes/sneeze/hyperventilation (make patient blow paper windmill)
How to work out differential amplifications?
What needs to be done when interpretting EEGs?
- Age of patient (different waves in different aged individuals)
- Clinical state of patient e.g. awake, drowsy, asleep
- Montage
- Wave forms
Explain the types of wave formations in EEG
If … waves appear on an EEG, one should be worried
Delta waves
What is the typical story when somene has a seizure?
- Collapsed without warning
- Witnessed to become stiff, and then started jerking. Foaming at mouth, and became cyanosed. Breathing pattern changed Incontinent of urine (INCREASE motor activity)
- Lasted 2 minutes
- Recovered slowly over 30 minutes, and was confused afterwards
- Headache, tongue biting
How to assess someone who has had a seizure?
LEARN soring system in picturee
- Risk classification will determine if someone gets treated
- EEG NOT used for diagnosis
- Looks at risk of seizure happening again
What to look for on an EEG when looking for epileptic activity?
- Typically looking for inter-ictal epileptiformdischarges (IEDs): asymptomatic epileptic abnormalities occurring between seizures
- Ictal = epileptic discharge producing clinical seizure
- Spikes or sharp waves, superimposed on background rhythms
- Localised versus generalised patterns : essential role in classifying the type of seizure disorder.
Types of waves in epileptic activity
- Sharp waves
- Spikes = short in guration
- Spikee & wave
- Polyspike
- Polyspike & wave
What independant variables would you introduce in order to see epileptic activity on an EEG?
- Hyperventilation (good test in childhood - blow windmill)
- Photic stimulation
-
Sleep deprivation
- 30% patients able to see epileptic activity thanks to this (easier diagnosis)
When would you start treatment for epilepsy & when would you give it?
After 2 events give anti-convusant treatment
What are the seizure classifications? & explain them
-
Focal onset (LEFT)
-
Doesn’t start bilaterally
- Involes _uni_lateral networks (can spread and engage bilateral networks
-
Doesn’t start bilaterally
-
Generalised onset (RIGHT)
- Seizure originating with BIlaterally distributed networks
- Types:
-
Absence
- S**udden ON & OFF onset
- Myoclonic
- Brief jerk movements especially in upper limbs
-
Atonic
- Loses ALL postural control (falls to ground)
- Clonic
- Sustained rhythmical jerking
- Clonic-tonic
- Stiffness onset followed by jerking
-
Absence
- Unknown onset
What kind of seizure is this?
Ictal-EEG
What kind of seizure is this?
Inter-ictal EEG (as separate)
What kind of differential amplitudes would this give?
What is this seizure?
Continuous seizure activity
What is status epilepticus? & types
- Continuous seizure activity for > 5-30+ minutes
-
2 types:
-
Convulsive Status Epilepticus - urgeent treatment (ICU)
- Obvious motor features
- Clinical diagnosis – no EEG required (usually)
-
Non-Convulsive Status Epilepticus
- No obvious motor features
- Confusion/Altered consciousness
- Consider in patient with epilepsy
- EEG
-
Convulsive Status Epilepticus - urgeent treatment (ICU)
What is videotelemetry?
- Patient continuously monitored ~2 weeks with EEG & video recording
- Used for diagnosing difficult seizures (UNKNOWN ones)
- & understand where they arise from
- Common in focal epilepsy to locate and then do surgery
What is advanced EEG (electrocorticography)?
- NO scalp/skull blocking signals
- Done so during surgery minimal amount of tissue is removed
- Understand WHERE seizure is starting
- Able to stimulate are they think is affected
- Is a grid of electrodes that is placed DIRECTLY over the cortex in order to monitor which areas are affected
What is a dissociation seizure?
- Many seizures everyday ~20 a day
- Start and stop (& recover rapidly)
What is Prion Disease & explain it
- Group of rare, uniformly fatal neurodegenerative diseases
- Sporadic (85-90%); Genetic (10-15%) and acquired (<1%)
- Symptoms include: difficulty walking (with falls), confusion, poor memory, ataxia, myoclonic jerks
- Good see on EEG = TRIphasic complexes
What is narcolepsy?
-
Tetrad (symptoms)
- Daytime sleepiness
- Cataplexy (sudden, brief loss of voluntary muscle tone triggered by strong emotions such as laughter)
- Sleep paralysis
- Hypnagogic/hypnopompic hallucinations
-
Multiple Sleep Latency Test (MSLT) - can do after treatment (see if medication has worked)
- 5 separate EEG recordings
- Dark, quiet room
- Sleep latency usually 10-20mins
- Abnormal mean latency <8mins –> will be in REM sleep very fast
- SOREMP on minimum 2 occasions (need 2 readings)
