Quantitative EEG (qEEG) and Trend Analysis Flashcards

A compressed spectral array (CSA) displays EEG information by showing:

Answer: Power spectral density plotted over time, with frequency on one axis and time on the other

A CSA (also called a density spectral array or DSA depending on color coding) uses Fast Fourier Transform (FFT) to decompose the EEG into its component frequencies and plots the power at each frequency band over time. This allows hours of EEG to be reviewed at a glance for trends in frequency content, making it useful for detecting delayed cerebral ischemia, seizures, and drug effects.

Amplitude-integrated EEG (aEEG) is most commonly used in which clinical setting?

Answer: Neonatal intensive care units for continuous cerebral monitoring of high-risk newborns

aEEG was developed specifically for continuous cerebral function monitoring in neonates. It compresses and amplitude-integrates the EEG into a single trend channel, making it practical for bedside nurses and neonatologists to monitor brain activity, detect seizures, and assess background continuity in premature and term newborns with hypoxic-ischemic encephalopathy.

On a qEEG trend panel, a sudden increase in the seizure probability (SP) line coincides with a visible change on the rhythmic run detector. The NEXT step for the EEG technologist should be:

Answer: Review the corresponding raw EEG segment to confirm whether the trend reflects a true electrographic seizure or artifact

qEEG trend algorithms are sensitive but not specific — they detect rhythmic and high-amplitude events but cannot distinguish between a true electrographic seizure and chewing artifact, electrode pop, or patient movement. The mandatory next step is always to review the raw EEG underlying the flagged epoch before any clinical action is taken.

On a density spectral array (DSA) in a patient following subarachnoid hemorrhage, which finding would raise concern for delayed cerebral ischemia (DCI)?

Answer: Progressive loss of alpha and sigma power with increase in delta power over the affected hemisphere

DCI produces neuronal dysfunction that manifests on the DSA as a loss of faster frequencies (alpha 8–13 Hz, sigma 12–15 Hz) and an increase in slow delta power over the at-risk hemisphere. This qEEG signature can precede clinical deterioration by hours, making continuous trend monitoring valuable for early DCI detection in subarachnoid hemorrhage patients.

Spectral edge frequency (SEF95) is defined as the frequency below which what percentage of the total EEG spectral power is contained?

Answer: 95%

SEF95 is the frequency at or below which 95% of the total spectral power lies. It is a single-number summary of the 'upper edge' of EEG activity and is used in anesthesia monitoring and ICU trend analysis to track shifts in dominant frequencies over time. A falling SEF95 indicates slowing of brain activity.

A patient's qEEG panel shows the asymmetry index trending toward the right hemisphere for 45 minutes. This means:

Answer: The right hemisphere has relatively more power (amplitude) than the left during this period

An asymmetry index that trends toward one hemisphere indicates that hemisphere has proportionally greater spectral power. Persistent rightward asymmetry over 45 minutes could reflect focal seizure activity, cortical spreading depression, or a structural lesion increasing amplitude on that side. It triggers review of the raw EEG to determine the cause, but by definition it means relatively higher power on the right.