Mixed Deck — All EEG Topics Flashcards

What are the typical high-pass and low-pass filter settings used when recording brainstem auditory evoked potentials (BAEPs)?

Answer: 100–3000 Hz

BAEP waveforms contain frequencies predominantly in the 100–3000 Hz range; these bandpass settings preserve the fast transient potentials while rejecting low-frequency muscle artifact and EEG.

Eye closure sensitivity refers to which phenomenon during EEG recording?

Answer: Epileptiform discharges triggered specifically by the act of closing the eyes, distinct from normal alpha appearance

Eye closure sensitivity is a form of reflex epilepsy where epileptiform discharges are triggered by the act of closing the eyes, as opposed to the normal alpha rhythm that appears. It is distinct from fixation-off sensitivity.

Centrotemporal spikes (rolandic spikes) in a child are associated with which EEG characteristic regarding sleep?

Answer: They increase in frequency and may become bilateral during NREM sleep

Centrotemporal spikes in benign epilepsy with centrotemporal spikes (BECTS) are markedly activated and may spread bilaterally during NREM sleep.

The standard paper speed (or digital equivalent time base) for routine EEG display is:

Answer: 30 mm/second

The standard time base for routine EEG is 30 mm/second (equivalent to displaying 10 seconds per standard screen page), which provides optimal visualization of EEG waveform morphology and temporal relationships.

A photic driving response seen on EEG during IPS is considered normal when it occurs at:

Answer: Harmonic or subharmonic frequencies of the flash rate over the occipital region

Normal photic driving is a rhythmic occipital response at the flash frequency or its harmonics/subharmonics and represents normal visual cortex activation.

A patient wearing an ambulatory EEG recorder reports the device became wet after showering despite instructions. The technologist's FIRST concern should be:

Answer: Patient electrical safety and device integrity

Patient safety is the primary concern; water ingress into recording equipment can create electrical hazards, and device integrity must be assessed before continuing.

According to the American Clinical Neurophysiology Society (ACNS) guidelines, interelectrode impedances should be within what range for a standard EEG recording?

Answer: Between 100 Ohms and 10,000 Ohms (10 kOhms)

ACNS guidelines state that interelectrode impedances should be under 10,000 Ohms (10 kOhms) but over 100 Ohms. Impedances that are too high can lead to increased noise and artifact, while impedances below 100 Ohms may suggest a salt bridge or short circuit between electrodes. While values under 5 kOhms are often recommended, the acceptable range is up to 10 kOhms.

An EEG is performed on a 32-week conceptional age premature infant. During quiet sleep, the recording shows bursts of high-amplitude mixed frequencies lasting 3-10 seconds, separated by periods of marked attenuation (<25 µV) lasting 10-20 seconds. This pattern is best described as:

Answer: Tracé discontinu

Tracé discontinu is the characteristic EEG pattern of quiet sleep in premature infants between approximately 30 and 34 weeks conceptional age. It consists of bursts of mixed-frequency activity separated by interburst intervals of significant voltage attenuation, typically less than 25 µV. [1, 2, 3] Tracé alternant is seen in older infants (around 34-44 weeks) and has a higher interburst interval amplitude (>25 µV). Burst-suppression is a profoundly abnormal pattern associated with severe encephalopathy. Hypsarrhythmia is a chaotic, high-voltage, disorganized pattern seen in infants with West syndrome.

Reflex epilepsy triggered by specific cognitive tasks (such as reading or calculating) is an example of:

Answer: Cognitive activation of seizures (thinking epilepsy or praxis-induced epilepsy)

Praxis-induced or cognitive-task-induced epilepsy is a form of reflex epilepsy where specific mental activities (reading, calculating, spatial tasks) trigger epileptiform discharges or seizures, most commonly in genetic generalized epilepsies.

An EEG recording shows a sudden, very high-amplitude, brief transient that is strictly confined to a single channel. The transient does not have a physiological field and is not time-locked to any other event. What is the most likely cause?

Answer: An electrode artifact ('pop')

The key features are its confinement to a single electrode and the lack of a physiological field (i.e., it doesn't appear in adjacent channels). This is the classic presentation of an electrode artifact, often called an 'electrode pop,' which is caused by a sudden, unstable change in impedance at that one site.

A normal adult EEG background shows a well-organized 10 Hz posterior dominant rhythm. This rhythm is categorized as which frequency band?

Answer: Alpha

10 Hz falls squarely within the alpha band (8–13 Hz), the normal posterior dominant rhythm of a relaxed, eyes-closed adult.

Triphasic waves with anterior-to-posterior phase lag are most classically associated with which metabolic condition?

Answer: Hepatic encephalopathy

Triphasic waves — high-amplitude, anteriorly dominant complexes with three phases and an anterior-to-posterior time lag — are the classic EEG hallmark of hepatic (portosystemic) encephalopathy, though they can also appear in renal failure and other toxic-metabolic states. Recognizing this pattern and its metabolic context is essential for accurate reporting.

When applying EEG electrodes using collodion, what substance is used to remove them after the recording?

Answer: Acetone

Acetone is used to dissolve collodion and safely remove electrodes from the scalp after the EEG recording.

What distinguishes a polyspike-and-wave complex from a single spike-and-wave complex?

Answer: Polyspike-and-wave contains multiple spikes (2 or more) preceding the slow wave component

Polyspike-and-wave complexes contain a burst of two or more spikes before the slow wave, and are particularly associated with juvenile myoclonic epilepsy and other generalized epilepsies with myoclonic seizures.

Lateralized periodic discharges (LPDs), formerly called PLEDs, are most often associated with:

Answer: Acute hemispheric structural lesions such as stroke or herpes encephalitis

LPDs typically reflect acute or subacute focal cortical injury and are a common finding in herpes simplex encephalitis and hemispheric stroke.

Which VEP component is most commonly used clinically to detect demyelinating disease of the optic nerve?

Answer: P100

The P100 component of the VEP is the most clinically relevant peak; a delayed latency (>115 ms) strongly suggests optic nerve demyelination.

Which EEG feature is a normal finding in drowsiness in adults?

Answer: Vertex sharp waves

Vertex sharp waves (V waves) are normal transients that appear over the vertex during drowsiness and light sleep.

Before beginning a routine EEG, the technologist should first:

Answer: Review the clinical history and indication for the study on the requisition

Reviewing the clinical indication and patient history before beginning allows the technologist to tailor the recording protocol, anticipate relevant findings, and take appropriate precautions.

Which EEG pattern is characterized by a spike followed by a slow wave complex occurring at approximately 3 Hz?

Answer: Generalized 3 Hz spike-and-wave

The classic 3 Hz spike-and-wave pattern is the hallmark of childhood absence epilepsy, appearing as generalized, synchronous, bilateral discharges.

Wave with a single deviation from the baseline, either up or down.

Answer: Monophasic

Monophasic waves have only one deflection from the baseline, either up or down. This indicates that there is just one phase or direction of deflection for the wave. Unlike the other alternatives, it does not contain many phases or deflections (transient, polyphasic, paroxysmal, epileptiform).