EEG Activation Procedures 5 — Questions and Answers
Question 1: During sleep activation, which sleep stage is most important to capture for evaluating interictal epileptiform discharges in temporal lobe epilepsy?
- REM sleep
- Stage N1 (NREM 1)
- Stage N2 (NREM 2) (Correct answer)
- Stage N3 (slow-wave sleep)
Correct answer: Stage N2 (NREM 2)
Stage N2 sleep is the most important stage for activating interictal epileptiform discharges in temporal lobe epilepsy, as spikes are significantly enhanced during NREM sleep.
Question 2: A photic driving response seen on EEG during IPS is considered normal when it occurs at:
- Frequencies above 60 Hz
- Harmonic or subharmonic frequencies of the flash rate over the occipital region (Correct answer)
- Frontal regions only at any frequency
- Only during simultaneous HV
Correct 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.
Question 3: Which of the following would prompt the technologist to STOP hyperventilation immediately?
- The patient reports mild tingling in the fingertips
- The patient develops a tonic-clonic seizure (Correct answer)
- The patient exhibits build-up of generalized slow waves
- The patient appears slightly drowsy
Correct answer: The patient develops a tonic-clonic seizure
A tonic-clonic seizure requires immediate cessation of HV and initiation of seizure safety protocols and notification of supervising physician.
Question 4: For a patient who cannot perform volitional hyperventilation (e.g., young child), an alternative activation method may include:
- Bilateral carotid massage
- Having the child blow on a pinwheel or blow bubbles (Correct answer)
- Administering IV benzodiazepines
- Applying cold water to the face
Correct answer: Having the child blow on a pinwheel or blow bubbles
Having young children blow on a pinwheel or blow bubbles is a standard pediatric technique to elicit sustained hyperventilation without requiring volitional cooperation.
Question 5: Eye closure during photic stimulation testing serves what purpose?
- It eliminates all photic driving responses
- It enhances the photoparoxysmal response by removing fixation suppression (Correct answer)
- It prevents retinal damage from the strobe light
- It produces delta wave artifacts that mimic epileptiform activity
Correct answer: It enhances the photoparoxysmal response by removing fixation suppression
Eye closure removes fixation suppression, making it easier to elicit photoparoxysmal responses in susceptible individuals during IPS.
Question 6: What is the recommended minimum distance between the photic stimulator and the patient's eyes during IPS?
- 5 cm
- 10 cm
- 30 cm (Correct answer)
- 1 meter
Correct answer: 30 cm
The photic stimulator is typically placed approximately 30 cm (about 12 inches) from the patient's eyes to ensure adequate luminance without discomfort or retinal risk.
Question 7: Which activation procedure is particularly valuable for diagnosing juvenile myoclonic epilepsy (JME)?
- Sleep deprivation followed by drowsiness recording
- Hyperventilation alone
- Intermittent photic stimulation (Correct answer)
- Cognitive task activation
Correct answer: Intermittent photic stimulation
Intermittent photic stimulation is especially effective for provoking generalized spike-wave discharges in juvenile myoclonic epilepsy due to its high photosensitivity prevalence.
EEG Activation Procedures 5
During sleep activation, which sleep stage is most important to capture for evaluating interictal epileptiform discharges in temporal lobe epilepsy?