module 5 Flashcards
define alpha, amplitude, arrhythmic
Alpha: EEG activity that occurs 8-12 times a second (hertz, Hz) (cycles per second cps). For
a patient to be normal, alpha must be seen in the posterior regions when the patient is awake
with their eyes closed
Amplitude- how big an EEG waveform is. It is the height or distance from the baseline to the
top of the wave in millimeters. Amplitude can be converted into voltage by taking the
distance and multiplying it by the sensitivity of the equipment. The answer is the voltage and
is expressed in uV (microvolts).
Arrhythmic- this is EEG activity that is not regular. It changes and varies throughout the
recording.
Define frequency, generalized,,
Frequency- how fast a waveform is. How many times a second a waveform appears. It
should be expressed by using a number such as 8Hz or 4Hz not a word like alpha or delta.
Generalized- means it is happening all over the brain or in every channel. The word diffuse
Define: paroxysmal, periodic, phase reversal
Paroxysmal- the sudden appearance of a wave or group of waves from a relatively organized
background and subsiding quickly. (similar to burst)
Periodic- occurring at regular intervals, such as once every 3 seconds
Phase Reversal waveforms that either point to each other or point away from each other. The phase reversal of waveforms in a bipolar montage, help us determine where the focus (source) of an
abnormality is.
state when and where we see each of the four EEG frequencies (example: alpha is seen in the occipital area in adults when patient is awake with eyes closed)
Beta: it can be seen in patients of all ages in both awake and sleep states. Unless beta only happens on one side, it is always normal. Your brain activity cannot be abnormally fast.(oociptal)
Delta- this is the slowest EEG frequency. It is activity that occurs 4 times a second or less.
(Hz or cps) Eye movement artifacts and some sleep patterns are in the delta range. If an adult
patient is awake and has delta, they are abnormal. Strokes can cause delta activity
Theta- this is EEG activity that happens 5-7 times in a second. It can be seen in kids or
during sleep. If theta is seen in an awake adult, they are abnormal. See picture below
discuss what is meant by reactivity (attenuation/blocking)
this is the blocking or attenuating (flattening) of activity after a stimulus. Alpha
activity reacts after the patient opens their eyes. Mu activity reacts when the patient clinches
the contralateral fist.
Define bilateral, biphasic
Bilateral- bi means two and lateral means side. So, bilateral means both sides. If you said
this activity is bilateral, you’re saying it happened in both hemispheres.
Biphasic- this is a waveform that has two phases to it, negative and positive. (the wave goes
up and down from the baseline)
Define: Blocked bust, continuous, contralateral, cps,
Blocked- this word could be interchanged with the word react. If you asked a patient to open
their eyes, the alpha should decrease in amplitude.
Burst- a sudden emergence or appearance of a waveform or a run of waveforms that does not
stay or continue throughout the test. You can have a burst of seizure activity. The record can
look normal, then there is one burst of waveforms that lasts a second or two, and then it goes back
to normal again. (a run is a little longer than a burst).
Define: diffuse, Epileptiform, FIRDA.
Diffuse- means generalized. It is an activity that is happening all over the brain or in every
channel of the EEG machine.
Epileptiform- resembles a waveform associated with the diagnosis of epilepsy such as
spikes, spike and wave, sharp activity, or other episodic discharges.
FRIDA- stands for frontal intermittent rhythmic delta activity. It is an abnormal delta appearing
in the frontal lobe usually due to encephalopathy or a stroke. (Newer term: RDA for rhythmic
delta activity or Frontal predominant RDA)
Define: Hz, homologous, intermittent, ipsilateral,
Hertz- is abbreviated Hz and means cycles per second or how many times in one second that
a waveform appears.
Homologous- means the same site in the opposite hemisphere. Your right pinky is
homologous to your left pinky. F7 is homologous with F8. ALL during the EEG, you should
be comparing the homologous areas.
Intermittent- means that it happens sporadically. It is an activity that comes and goes. Seizure
activity may come and go. It appears, goes away, then may come back again several pages
later.
Ipsilateral- ipsi means same and lateral means side. So, ipsilateral means the same side. F7
and F3 are on the same side of the head.
Define: lambda, lateralized, localized
Lambda- this is normal EEG activity that appears in the occipital lobe when the patient has
their eyes open scanning a picture. The activity looks like little sails in the theta or delta
range and sometimes looks pointy. It is known as a normal variant which we will learn more
about later.
Lateralized- affecting one hemisphere only or mainly. If you said the patient’s seizure
activity was lateralized, you are saying it is only on the left or only on the right.
Localized- activity that is only in one area. This is the opposite of generalized. If the patient
had localized activity, the activity is only in one lobe or only in a few electrodes.
The word focal could also be used.
Define: morphology, multi-focal, mu, OIRDA
Morphology- is the shape of a waveform. A wave could be sharp or squared off or
sinusoidal (s shaped) etc.
Multi-focal- (or Mf )- this is activity that has more than one focus or localization. The
patient could have a lesion in say the left temporal area and the right occipital area. So, the
EEG is showing two different abnormal discharges
Mu- this is a normal EEG pattern that appears in the central area and can look like theta with
beta superimposed on top of it. Mu has been described as “saw toothed” in shape. When you
see mu, you can ask the patient to clench the contralateral fist and the mu will attenuate or
block. (if the mu is at C3, you would ask the patient to clinch their right fist) This is another
normal variant.
OIRDA- stands for occipital intermittent rhythmic delta activity. This is abnormal delta that
comes and goes (intermittent) seen in the occipital area, usually after a stroke. It can also be seen in children with epilepsy, Huntington’s disease, central nervous system salmonellosis
and SSPE. (Newer term: RDA for rhythmic delta activity or Occipital Pre-Dominant RDA).
Define: PLEDs, polymorphic, reactivity, run
PLEDs- stands for periodic lateralizing epileptiform discharges. Periodic means occurring at
regular intervals, lateralizing means on one side, epileptiform means seizure activity and
discharges are a burst of activity. So, PLEDs are bursts of seizure activity happening on one
NEW TERM: It is now being called LPD
Polymorphic- poly means many and morphic means shape. So, polymorphic activity is EEG
activity with many shapes.
Run- is used to describe activity that lasts for several seconds or pages. A run is longer than a
burst but not as much as continuous. You could say a run of 3Hz seizure activity was seen
lasting 20 seconds.
Define: superimposed
Superimposed- waveforms can be made up of two different frequencies on top of each other.
The picture below shows delta with beta superimposed on top of it
Define: transient, triphasic, unilateral and voltage
Transient- shifting and changing in form and appearance, occurring only briefly. It is similar
to a burst.
Triphasic- a waveform with 3 phases. (the wave goes up, over then down)
Voltage- usually refers to the amplitude (size/height) of a wave. It is an electrical potential
expressed in volts, in the EEG it is expressed in microvolts (uV). EEG is electrical activity of
the brain. The voltage of the EEG is how big it is.
