NORMAL EEG Flashcards
In the normal EEG, a posterior dominant rhythm is represented bilaterally over the posterior head regions and lies within the _________-Hz bandwidth (alpha frequency).
8- to 13
During normal development, an 8-Hz alpha frequency appears by_______years of age.
3
The alpha rhythm is distributed maximally in the occipital regions, and shifts anteriorly during ______
drowsiness.
Voltage asymmetries of >________ should be regarded as being abnormal, especially when the left side is greater than the right.
50%
Unilateral failure of the alpha rhythm to attenuate when eyes opening reflects an ipsilateral abnormality. WHAT PHENOMENON?
Bancaud’s phenomenon
Normally, alpha frequencies may transiently increase immediately after eye closure. This is called?
alpha squeak
__________occurs when alertness results in the presence of alpha, and drowsiness does not.
Paradoxical alpha
WHAT RHYTHM IS SHOWN?
Normal 10-Hz alpha rhythm “blocked” by eye opening and returning on eye closure. Note the faster frequency immediately on eye closure
(“squeak”).
WHAT IS SEEN ON THE LEFT CENTRAL ELECTRODE?
Note the prominent left central mu rhythm during eye opening.
The mu rhythm is a centrally located arciform alpha frequency (usually 8 to 10 Hz) that represents the sensorimotor cortex at rest at C3 e C4
MU RHYTHM IS INNACTIVATED WITH?
contralateral movement of an extremity.
WHAT RHYTHM IS SHOWN?
Breach rhythm in the right temporal region (maximal at T4)
following craniotomy for temporal lobectomy.
Voltages beyond 25 μV in amplitude are abnormal.
_________, __________, _________are potent generalized beta activators of “fast activity” >50 μV for >50% of the waking tracing within the 14- to 16-Hz bandwidth
Benzodiazepines, barbiturates, and chloral hydrate
A skull defect may produce a _______with focal, asymmetrical, higher amplitudes (this relative increase may be more than three times) beta activity without the skull to attenuate the faster frequencies.
breach rhythm
WHAT RHYTHM IS SHOWN?
Normal frontocentral theta rhythm in an 18-year-old patient while awake.
Approximately one-third of normal awake, young adults show intermittent 6- to 7-Hz theta rhythms of <15 μV that is maximal in the frontal or frontocentral head regions.
The appearance of frontal theta can be facilitated by emotions, focused concentration, and during mental tasks
__________have been initially described as surface positive sharply contoured theta waves appearing bilaterally in the occipital region
Lambda waves
Lambda waves are best elicited when the________ AND __________
patient visually scans a textured or complex picture with fast saccadic eye movements
WHAT IS SEEN IN THIS EEG OF AN 84 YEAR OLD MAN?
Intermittent left mid-temporal delta during transition to drowsiness in a normal 84-year-old patient evaluated for syncope
In the waking states, delta can be considered a normal finding in the_________
Excessive generalized delta is abnormal and indicates an _______that is etiology nonspecific
very young and in the elderly.
encephalopathy
________sleep is defined by the presence of vertex waves, typically 200-msec diphasic sharp transients with maximal negativity at the vertex (Cz) electrode. Theta waves start to appearing and alpha waves < 50%
Stage 1
_______are another feature signifying stage 1 sleep.These are surface positive, bisynchronous physiological sharp waves with voltage asymmetries that may occur over the occipital regions as single complexes or in repetitive bursts that may be present in both stages 1 and 2 sleep
positive occipital sharp transients
(POSTS)
What is shown?
POSTS appearing in the lower three channels in a bipolar circle montage demonstrating positive polarity in the occipital region during sleep. Notice the surface negative vertex waves maximal at Cz.
Stage 2 sleep is defined by the presence of______ and __________
sleep spindles and K complexes.
________are transient, sinusoidal 12- to 14-Hz activity with waxing and waning amplitude seen in the central regions with frontal representation by slower frequencies of 10 to 12 Hz.
Sleep spindles
________is a high amplitude diphasic wave with an initial sharp transient followed by a highamplitude slow wave often associated with a sleep spindle in the frontocentral
region
K-complex
What stage of sleep?
Stage 2 sleep with prominent sleep spindles and POSTs.
_______sleep now best describes non-REM deep sleep and is comprised of 1- to 2-Hz delta frequencies occupying variable amounts of the background.
Slow-wave
Stage 3 previously noted delta occupying 20% to 50% of the recording with voltages of >75 μV, while stage 4
consists of delta present for________% of the recording.
>50
WHAT STAGE OF SLEEP?
Slow-wave sleep. Note the intermittent POSTs and sleep
spindles against the continuous delta background
WHAT STAGE OF SLEEP?
REM sleep with rapid eye movements associated with lateral rectus spikes is noted at the F7 and F8 derivations.
_______is characterized by rapid eye movements, loss of muscle tone, and saw-toothed waves in the EEG
REM sleep
WHAT IS THE PURPOSE OF HYPERVENTILATION IN EEG?
The purpose is to create cerebral vasoconstriction
through respiratory means promoting systemic hypocarbia
Hyperventilation normally produces a bilateral increase in theta and delta frequencies (build-up) that is ______________, and often of high amplitude.
frontally predominant
WHAT ACTIVATION PROCEDURE WAS DONE?
Normal build-up during hyperventilation
RESULT OF HV ON FOCAL LESIONS?
Hyperventilation may produce focal slowing in patients with an underlying structural lesion
Intermittent photic stimulation normally produces potentials
exquisitely time locked to the frequency of the intermittent light
stimulus, and is referred to as________
photic driving
Photic driving is usually greatest in the_____________, in frequencies approximating the alpha rhythm, when the
eyes are closed.
occipital location
__________consist of a frontally dominant muscle artifact that occurs when the flash evokes repetitive local contraction of the frontalis musculature (photomyogenic).
Photomyoclonic (or photomyogenic) responses
WHAT ACTIVATION PROCEDURE?
Photic driving at 20 Hz seen in the P3-O1, P4-O2, T5-O1,
and T6-O2 derivations.
Rhythmic temporal theta bursts of drowsiness is now the preferred term for what was previously described as a________
psychomotor variant.
It is an interictal pattern that does not evolve spatially or temporally, although it may be represented bilaterally or independently over both hemispheres. It is seen in adolescents and adults in relaxed wakefulness.
Rhythmic temporal theta burst
WHAT BENIGN VARIANT?
Rhythmic temporal theta bursts of drowsiness. Note the
sharply contoured morphology
While morphologically it may resemble a mu rhythm, it is not similarly reactive, and is slower in frequency, and occurs both in drowsiness or the alert state
Central theta
WHAT IS SHOWN?
Central theta (maximal at Cz) seen during the awake state in a 35-year-old patient with migraine headaches
Spike-and-wave discharges at 6 Hz were first known as______________ The acronyms WHAM (wakefulness, high amplitude, anterior, male) and FOLD (female, occipital, low amplitude, drowsy) were used to describe the two primary subtypes
“phantom spike-and-waves.”
WHAT IS SHOWN?
A 6-Hz (phantom) spike-wave burst with frontal predominance
in the 5th second of this EEG in an awake patient with temporal lobe
epilepsy.
Fourteen- and 6-Hz positive bursts (originally called 14 and 6-Hz positive spikes) have also been called______
ctenoids
They are most common during adolescence, although they may persist into adulthood and decrease with age. The bursts are usually unilateral or bilaterally asynchronous with a shifting predominance involving one hemisphere to a greater degree
Fourteen- and 6-Hz
WHAT PATTERN?
Fourteen- and 6-Hz positive bursts maximal in the T6 electrode derivation in a linked-ears reference montage. Note the downward deflection and prominent 14-Hz frequency
This benign variant of uncertain significance has the morphology of a spike, although it has an rapidly ascending limb and steep descending limb best seen in the anterior to mid-temporal derivations during non-REM sleep
BETS
DISTINGUISHING FEATURE OF BECTS
DISAPPEAR DURING SLEEP
WHAT IS SHOWN?
A right benign epileptiform transients of sleep (BETS) in the
temporal region during stage 2 sleep. Note the higher amplitude in the T1 and
T2 channel with a longer interelectrode distance.
________are most commonly seen in adults >30 years of age. They occur within the 6- to 11-Hz band, and can obtain amplitudes of up to 200 μV. They are seen over the temporal regions during drowsiness and light sleep and are usually bilateral and independent.
Wicket spikes
WHAT BENIGN VARIANT?
Wicket waves maximal at T3 and T4.
In contrast to many of the patterns of uncertain significance that mimic IEDs, _______________is a pattern that mimics the epileptiform characteristics of a subclinical seizure
subclinical rhythmic electrographic discharge in adults (SREDA)
WHAT EEG PATTERN? (Adulto de 50 anos com sonolencia)
SREDA
Padronização do EEG:
O ritmo teta, quando de predominio nas regiões________________ do cortex, são preocupantes clinicamente
Posteriores
tabela ritmos normais EEG
Beta: frontocentral
Alfa: posteriores
O que são 1,2 e 3?
1- onda aguda do vertex
2- espiculas do sono
3- complexo K
que isso?
BETS
Onda aguda positiva, de baixa amplitude, bilateral e
síncrona, observada na região occipital durante a vigília, na exploração
visual (sacadas exploratórias), quem é?
Lambda
Ondas agudas positivas, de baixa amplitude, bilaterais, observadas nas regiões occipitais durante o sono, a partir da primeira década de vida.
POSTS
8 anos de idade. Qual o padrao de ritmo do paciente nas regiões posteriores?
Onda lenta da juventude com atividade delta
Qual atividade não pode aparecer na vigilia do adulto?
atividade delta
Como diferenciar onda aguda epileptiforme da lambda?
pede pro paciente fechar os olhos, se for onda lambda, ela vai desaparecer
Que isso?
ondas agudas do vertex
Estagios do sono e padrão de EEG
