EEG Non-Epileptiform Abnormalities 2

Question 1

Focal polymorphic delta activity (PDA) over the right temporal region in an awake adult most strongly suggests:

Accepted Answer

A structural lesion in the right temporal area

Answer

Focal polymorphic delta activity is a highly localizing finding indicating structural pathology (tumor, stroke, abscess) disrupting normal cortical-subcortical connections in the region where it appears.

Question 2

Generalized background slowing with intermittent frontal rhythmic delta activity (FIRDA) in an adult typically indicates:

Accepted Answer

Diffuse encephalopathy or deep midline dysfunction

Answer

FIRDA (now called generalized rhythmic delta activity with frontal predominance or GRDA) is a non-specific finding indicating diffuse cerebral dysfunction from metabolic, toxic, or structural causes affecting deep midline structures.

Question 3

An asymmetry in the posterior dominant rhythm amplitude, with the right side consistently 50% lower than the left, suggests:

Accepted Answer

Possible structural or functional abnormality of the right hemisphere

Answer

Amplitude asymmetry greater than 50% of the posterior dominant rhythm suggests dysfunction on the lower-amplitude side, potentially from a structural lesion, prior surgery, or cortical atrophy.

Question 4

Generalized voltage attenuation (low-voltage EEG) with amplitudes below 20 µV throughout may be caused by:

Accepted Answer

Scalp edema, subdural fluid, or certain medications such as barbiturates

Answer

Generalized low voltage can result from physical barriers between brain and electrodes (scalp edema, subdural effusions, thick skull) or from cortical suppression by medications like barbiturates, hypothermia, or severe diffuse brain injury.

Question 5

Excessive beta activity (above 25 µV) generalized across the recording is most commonly associated with:

Accepted Answer

Sedative or anxiolytic medication use such as benzodiazepines

Answer

Generalized excessive beta activity is most commonly a pharmacological effect of benzodiazepines, barbiturates, or other sedative-hypnotic medications, which enhance GABAergic inhibition and increase fast cortical activity.

EEG - Electroencephalography Practice Test

EEG - Electroencephalography Practice Test

EEG Non-Epileptiform Abnormalities 2