Fisch EEG Primer Chapter 11

Question 1

This type of rythym consists of sinusoidal waveforms >8H and <13Hz maximal over the posterior head region and is typically blocked by eye opening and disappears during drowsiness and sleep

Answer 1

The alpha rythym

Question 2

This rythym consists of waves >13Hz in either a wide distribution or limited to frontal or posterior head regions; should disappear during later stages of sleep; typically of lower amplitude than alpha

Answer 2

The beta rythym which is almost always a GOOD prognistic sign (requires normal cortical function) - can be caused by benzos/barbs

Question 3

Mu rythym (can be precipitated by scanning visual images) consists of…

Answer 3

seen in less than 5% of EEGs, arch-shaped 7-11 Hz of trains over central to central parietal regions typically in younger adults.; best seen on bipolar montage when alpha is blocked by eye opening
NOTE:previously known at ‘wicket’, ‘comb’, or ‘arceau’ rythym

Question 4

Lambda waves (can be precipitated by looking at images containing a lot of detail) consist of…(morphology, duration, phase, amplitude

Answer 4

• sawtooth shaped and positive polarity occurring primarily in occipital regions - look like POSTs
• 100-250 ms
• typically diphasic
• 50microV
• marked asymmetry is abnormal to lower amplitude side
• may be a physiologic VEP since waveform, delay, etc. same pattern

Question 5

Vertex sharp transients (V waves) consist of…

Answer 5

sharp transients of negative polarity at the vertex -commonly seen in sleep
NOTE: may be seen in awake adults/children after startle response

Question 6

Kappa rythym consists of…

Answer 6

bursts of very low amplitude waves of alpha or theta frequency seen in temporal region that are seen in subjects engaged in mental activity

Question 7

Intermittent posterior theta rythyms…

Answer 7

are more rare than alpha or beta rythyms;

Question 8

low voltage activity can sometimes be modified through the following activating procedures

Answer 8

hyperventilation, photic stimulation and sleep - low voltage EEG is considered abnormal if altered from baseline

Question 9

Alpha rythym that never exceeds 8 Hz is…

Answer 9

always abnormal

Question 10

Alpha rythym may decrease by approximately 1 Hz during…

Answer 10

drowsiness
NOTE: alpha rythym should be a constant value throghout life (same on serial recordings), decreases of 1Hz or more during adult life if abnormal even if the absolute value is still within the normal range.

Question 11

What is the phenomena of alpha rythym temporarily increasing by 1 Hz during eye closure and then rapidly returing to baseline

Answer 11

squeak phenomena

Question 12

What is the accepted range of frequency difference between the hemispheres

Answer 12

SHOULD BE THE SAME FREQUENCY, even slight difference if difference is persistent considered definitely abnormal (lower frequency hemisphere is abnormal)
NOTE: alpha frequencies do not need to be in phase

Question 13

Alpha frequency activity in the Fp1 and Fp2 regions..

Answer 13

is artifact until proven otherwise

Question 14

Asymmetric alpha amplitude typically follows this pattern…

Answer 14

right alpha rythym is typically of higher amplitude, left alpha rythym should be at least 50% of that on right. - may be caused by different thickness of occipital bones
NOTE: occasoinally higher amplitude is seen on the left

Question 15

What is Bancaud’s phenomena?

Answer 15

Unilateral blocking of the alpha rythym

Question 16

What are some reasons to test eye opening as an activating procedure?

Answer 16

1) reactivity and symmetry of alpha blocking
2) demenostrate artifacts produced
3) bring out rythyms hidden by alpha (e.g. Mu rythym
4) test other EEG reactivity
5) precipitate abnormal reaction to eye opening

Question 17

Describe a slow alpha variant

Answer 17

rythyms 3.5 - 6.5 Hz (half the frequency of normal apha) appearing in same records at different times with normal alpha rythym

Question 18

What are some maneuvers used to block frontal beta rythym?

Answer 18

blocked by movement, intention to move, and tactile stimulation. Effect often greatest when the contralateral extremity is moved.

Question 19

What are some maneuvers used to block widespread beta rythym?

Answer 19

not blocked by any stimulus

Question 20

What is another name for posterior beta rythym?

Answer 20

Fast alpha variant; beta frequency rythym usually (16-20Hz) that intermixes or alternates with alpha rythym and is blocked by same alpha blocking maneuvers

Question 21

beta rythym amplitude asymmetry between hemispheres is considered normal if homologous head regions vary by no more than…

Answer 21

35% - in the absence of a skull defect (causes breach artifact), the lower amplitude is abnormal

Question 22

What are some maneuvers used to block Mu rythym?

Answer 22

blocked by movement, intention to move, and tactile stimulation. Effect often greatest when the contralateral extremity is moved.

Question 23

When is Mu rythym considered abnormal?

Answer 23

frequent unilateral trains, amplitude asymmetry - abnromal on side of lower amplitude or frequency