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.
The alpha rhythm is distributed maximally in the occipital regions, and shifts anteriorly during ______
Voltage asymmetries of >________ should be regarded as being abnormal, especially when the left side is greater than the right.
Unilateral failure of the alpha rhythm to attenuate reflects an ipsilateral abnormality. WHAT PHENOMENON?
Normally, alpha frequencies may transiently increase immediately after eye closure. This is called?
__________occurs when alertness results in the presence of alpha, and drowsiness does not.
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
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
MU RHYTHM IS ACTIVATED 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.
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
WHAT IS THE NORMAL RHYTHM SHOWN?
Bioccipital lambda waves in a 28-year-old patient with dizziness. Notice the frequent “scanning” eye movement artifact in the F7 and T8 derivations.
__________have been initially described as surface positive sharply contoured theta waves appearing bilaterally in the occipital region
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.
________sleep is defined by the presence of vertex waves, typically 200-msec diphasic sharp transients with maximal negativity at the vertex (Cz) electrode
_______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
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.
________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
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.
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.
WHAT STAGE OF SLEEP?
Slow-wave sleep. Note the intermittent POSTs and sleep
spindles against the continuous delta background