EEG Ambulatory 5 — Questions and Answers
Question 1: A patient wearing an ambulatory EEG recorder reports the device became wet after showering despite instructions. The technologist's FIRST concern should be:
- Data corruption of the entire recording
- Patient electrical safety and device integrity (Correct answer)
- Re-scheduling the study from the beginning
- Increasing the recording sensitivity
Correct 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.
Question 2: Which electrode placement system is MOST commonly used for ambulatory EEG studies in the United States?
- Laplacian montage
- 10-20 International System (Correct answer)
- Queen Square System
- Bipolar longitudinal strip only
Correct answer: 10-20 International System
The 10-20 International System is the standard electrode placement system used for ambulatory EEG in the US and most international centers.
Question 3: An ambulatory EEG recording shows a sudden onset of 3 Hz spike-and-wave discharges lasting 12 seconds, coinciding with the patient pressing the event button. This is MOST consistent with:
- A generalized tonic-clonic seizure
- A typical absence seizure (Correct answer)
- A focal onset impaired awareness seizure
- A psychogenic non-epileptic seizure
Correct answer: A typical absence seizure
Classic 3 Hz generalized spike-and-wave lasting approximately 10–15 seconds with preserved consciousness is the hallmark of typical absence seizures.
Question 4: What is the PRIMARY advantage of extending ambulatory EEG from 24 hours to 72 hours?
- Higher sampling rates become available
- Greater likelihood of capturing infrequent seizures or interictal discharges (Correct answer)
- Reduced artifact burden over time
- Improved electrode adhesion after 48 hours
Correct answer: Greater likelihood of capturing infrequent seizures or interictal discharges
Longer recordings increase the probability of capturing rare events; seizure yield rises substantially with extended monitoring duration.
Question 5: A patient's ambulatory EEG diary notes going to sleep at 22:30. The technologist should expect to see which EEG pattern shortly after this time?
- Generalized paroxysmal fast activity
- Vertex sharp waves and sleep spindles (Correct answer)
- Continuous 10 Hz alpha rhythm
- High-amplitude delta with sharp transients suggesting seizure
Correct answer: Vertex sharp waves and sleep spindles
Normal sleep onset is marked by vertex sharp waves (V waves) and sleep spindles (12–14 Hz) during NREM stage N2 sleep.
Question 6: During ambulatory EEG data review, a technologist identifies a train of rhythmic sharp waves in the right temporal region lasting 45 seconds without a diary entry or event button press. The appropriate action is to:
- Discard the segment as artifact due to absence of patient report
- Flag the segment and note it in the report as a possible subclinical seizure (Correct answer)
- Immediately contact emergency services
- Re-record the study with additional electrodes
Correct answer: Flag the segment and note it in the report as a possible subclinical seizure
Subclinical seizures can occur without patient awareness; the technologist should flag and document the finding for the interpreting physician's review.
Question 7: In ambulatory EEG, the collodion electrode application technique is preferred over adhesive paste for long-term recordings because it:
- Provides lower initial impedance readings
- Ensures better electrode stability over multiple days (Correct answer)
- Eliminates the need for conductive gel
- Is required by FDA regulations for outpatient use
Correct answer: Ensures better electrode stability over multiple days
Collodion (pyroxylin) glue creates a strong mechanical bond that keeps electrodes securely attached for 24–72+ hour recordings without displacement.
EEG Ambulatory 5
A patient wearing an ambulatory EEG recorder reports the device became wet after showering despite instructions.
The technologist's FIRST concern should be: