ASET Q&A Flashcard Study System for EEG Card Set 2 4th edition

Where is the nasion?

Is the indentation between the forehead and the nose.

Where is the inion?

Is the bony protuberance in the middle of the back of the head; a ridge or knob that can be felt when you run your finger up the back of the neck to the skull.

List the standard skull landmarks used in the International 10-20 System.

Inion, nasion, left and right preauricular points.

If the measurement from F8 through Fz to F7 measures 24 cm, what are the measurements to mark F4 and F3 if the tape zero remains at F8?

F4= 6 cm
F3= 18 cm

If the measurement of C4 is 11 cm, (as a 50% mark from Fp2 to O2), where should F4 and P4 be marked if the tape zero remains at Fp2?

F4= 5.5 cm
P4= 16.5 cm

If the head circumference is 56 cm, what is the distance between Fp1 and Fpz, and between Fpz and Fp2?

2.8 cm

Explain the modified nomenclature of the 10-10 system.

The modified nomenclature replaces T3/T4 and T5/T6 terms with T7/T8 and P7/P8 so that all electrode positions along the sagittal line have the same number (with the exception of Fp1/Fp2 and O1/O2) and all electrodes along the same coronal line have the same letter.

What is the most valuable localizing feature in a bipolar montage?

Phase reversal

What is the most valuable localizing feature in a referential montage?

Maximum amplitude

What causes cancellation (isoelectric phase reversal) in a bipolar montage?

The voltage at input 1 is the same as the voltage at input 2.

What causes glossokinetic artifact and how do you monitor it?

Artifact from tongue movement; tip of tongue is negative, root of tongue is positive.
Monitor by placing one electrode above the mouth and one electrode below the mouth. Ask the pt to say "Lilt" "La La La" to reproduce the artifact.

Describe respiration artifact and how to monitor it.

1.) Fairly rhythmic slow activity that is synchronous with body movement related to respiration; this movement causes mechanically induced impedance changes in an electrode.
2.) Slow or sharp wave occurring synchronously with inhalation or exhalation involving only the electrodes on which the pt. is lying.
Try to eliminate by repositioning pt's head. Monitor by marking EEG recording with each inhalation and/or exhalation or use thermocouple or respirometer.

Describe EKG artifact and how to monitor it.

There is no way to eliminate EKG artifact, although using a bipolar rather than referential montage reduces the voltage. When using a referential montage to the ear leads; can average both A1 and A2 together in input 2 and this decreases the amplitude of the EKG artifact.
Try to decrease by turning pt's head relative to trunk. Monitor by recording EKG using two chest leads- one on the left upper chest; second on the right upper chest- or a lead on each wrist. Should monitor EKG on every pt throughout the entire EEG recording.

Describe pacemaker artifact and how to monitor it.

Seen as a fast spike which is the electrical stimulus delivered to the heart by an internal cardiac pacemaker.
Pacemaker artifact will be seen in the channel monitoring EKG; should monitor EKG on every pt throughout the entire EEG recording.

Describe tremor artifact and how to monitor it.

Rhythmic theta activity with myogenic potentials (muscle artifact) superimposed that occurs at 4-7 Hz as the head or body tremors; often seen in pt's with Parkinson's disease. Monitor by placing electrode over extremity with tremor, can also be directly monitored by an accelerometer. An accelerometer is an electromagnetic detector that records sudden movement and change in direction of movement.

Describe electroretinogram artifact and how to eliminate it.

Seen during photic stimulation in the prefrontal leads (Fp1 and Fp2) most often at high sensitivities needed for recording suspected electrocerebral inactivity. The artifact will match the frequency of the photic stimulation.
Hold an opaque card over the eye to block photic stimulation flash from reaching the retina.

Describe skin potential artifact and how to eliminate and monitor it.

Areas of skin with many sweat glands are electrically negative; sweat glands generate electrical potentials when active. Sweating can cause slow waves, most likely slow rolling delta waves. Try to eliminate by reducing cause of sweating, e.g, cool head, wipe area with alcohol, air conditioning.
Monitor by placing two leads on the hand; one on the palm and one on the dorsu

How are 60 Hz artifacts caused by electrostatic effects? How do you eliminate them?

Caused by capacitance between 60- Hz conductors (e.g, electrode wires, metal bed frames, the pt, or the technologist). Eliminate by determining cause of 60 Hz and remove, put on battery power, or turn off. Cover wires with sheet or towel.
Use 60 Hz filter only if absolutely unable to remove artifact and document it use on the EEG.

How are 60 Hz artifacts caused by electromagnetic effects? How do you eliminate them?

Caused by electrical appliances or equipment (e.g, transformers, motors, high intensity lamps, power supplies, TV sets, radio, etc). Eliminate by determining cause of 60 hertz and remove, put on battery power, or turn off. Cover wires with sheet or towel. Use 60- Hz filter only if absolutely unable to remove artifact and document its use on the EEG.

Describe an electrode malfunction artifact and how to eliminate it.

Caused by an electrically unstable electrode of high impedance. May appear as a spike or sharp wave or random slow wave with no field- an electrode "pop''.
Eliminate by repairing electrode and improving impedance.

Describe an intravenous (IV) drip artifact and how to monitor it.

Resembles EKG artifact. Monitor drip by typing an "X" on EEG recording. Eliminate by asking nurse to turn off IV or use battery power when possible.

Describe pulse artifact and how to monitor it.

Periodic slow wave that has a slight delay from but is time locked to the EKG waveform. Monitor by recording EKG; especially useful if the heart rate is irregular.

Describe muscle artifact and how to eliminate it.

Very short duration potentials that usually occur in clusters or periodic runs. They may resemble cerebral spike discharges except cerebral spikes are of much longer duration and will have a field.
To eliminate, ask patient to relax, drop the jaw, or open mouth slightly.

Why is the use of high frequency filter (HFF) not recommended to reduce muscle artifact?

Excessive high frequency filtering will reduce the amplitude of these fast potentials and will also change their form. Single muscle potentials may look like spikes and repetitive potentials might look like cerebral fast waves.

What is corneoretinal potential?

The cornea (the front of the eye) is positive relative to the retina (the back of the eye) which is negative.

List the types of cardiac artifacts and describe their morphology.

Electrocardiographic- QRS complex seen in the scalp leads.
Pacemaker- Generalized high frequency polyphasic potentials of short duration.
Pulse- Periodic slow wave that occurs after the EKG artifact's peak by about 200 msec.
Ballistocardiographic (results from head or body movements with cardiac contractions)- Similar in morphology to pulse but more widespread.

List the type of electrode artifacts and describe their morphology.

Electrode Pop- very steep rise and a more shallow fall, resembles a calibration signal.
Electrode Contact- sharp or slow waves of varying morphology and amplitude.
Electrode/lead Movement- disorganized morphology, double phase reversals of noncerebral appearance.
Perspiration- low amplitude rolling waves of greater than 2 seconds in duration.
Salt Bridge- low amplitude, typically only one channel, appears flat and close to isoelectric.

List the types of external device artifacts and describe their morphology.

50/60 Hz ambient electrical noise- medium to low amplitude monomorphic activity of 50 or 60 Hz.
Intravenous drips- spike-like EEG potential which has the regularity of the drip.
Electrical devices- IV pumps, telephone, radio, TV- high-amplitude, irregular, polyspike-like or spike-like activity.
Mechanical effects- ventilators, circulatory pumps- slow wave or a complex including a mixture of frequencies superimposed on a slow wave.

List the types of muscle artifacts and describe their morphology.

Glossokinetic (chew/swallow) - slowing with superimposed faster frequencies with maximal amplitude frontally.
Photomyogenic (photomyoclonic) - frontal and periorbital time-locked artifact that occurs with photic stimulation.
Surface electromyography (scalp/facial muscle) - rhythmic activity of high amplitude and frequency most commonly seen in the temporal and frontal electrodes.

List the types of ocular artifacts and describe their morphology.

Blink - bifrontal diphasic synchronous slow wave.
Eye flutter - run of bifrontal spike and slow wave complexes.
Lateral gaze - rhythmic slow artifact seen in the frontal and temporal leads at a frequency less than 1 Hz.
Slow roving eye movements - low amplitude slowing of opposite polarity in the left and right frontotemporal regions.
Lateral rectus spike - single motor unit potential seen at F7 or F8.
Rapid eye movements of REM sleep - asymmetric waves with a quicker rise than fall.

Why is sleep deprivation considered an activation procedure?

20 hours of continuous waking time may stress a potentially epileptogenic brain so that abnormalities will appear in the waking EEG.

What are three epilepsy syndromes with a dramatic increase in interictal discharges during sleep?

Epileptic encephalopathy with continuous spike-and-wave during sleep (CSWS), Landau-Kleffner syndrome, and childhood epilepsy with centrotemporal spikes (CECTS)
Note: Childhood epilepsy with centrotemporal spikes was previously known as benign childhood epilepsy with centrotemporal spikes.

What is hyperventilation (HV) ?

Deep and rapid breathing usually for a period of 3 to 4 minutes. Used as an activation procedure; especially potent in activating absence seizures.

What are the clinical effects of hyperventilation (HV)?

HV causes hypocapnia (decrease of CO2 in the system). Clinically characterized by cerebral symptoms including dizziness and even loss of consciousness; also by peripheral symptoms such as tingling especially in the hands and feet and around the mouth.

What electrographic changes are seen during HV?

Normal responses consist of generalized bilaterally synchronous slow waves that begin soon after HV; often called a "build-up". Abnormal responses consist of asymmetrical responses and epileptiform discharges. Spike and wave discharges of 3 Hz are often activated by HV.

What are the contraindications to hyperventilation?

1) Acute stroke
2) Recent intracranial hemorrhage
3) Large vessel stenosis
4) Recent transient ischemic attack
5) Severe cardiopulmonary disorders
6) Sickle cell disease or trait
7) Moyamoya disease

Describe a photomyogenic response.

A photomyogenic response to intermittent photic stimulation is characterized by brief, repetitive muscular spikes over the anterior regions of the head. The muscle potentials occur at the same rate as the photic stimulation and stop as soon as the photic stimulation is stopped.

Describe photic driving.

Consists of a train of occipital waves driven by repetitive strobe flashes. The photic driving response measures the ability of the occipital lobe to follow strobe flashes at varying frequencies with repetitive responses. Absence of a response is NOT considered abnormal.

Describe a photoparoxysmal aka photoconvulsive, response.

A photoparoxysmal (photoconvulsive) response is an abnormal response to intermittent photic stimulation eliciting generalized spike and wave discharges. The response may (sustained) or may not (unsustained) continue after the photic stimulation is stopped.

What is the minimal amount of recording time acceptable when performing clinical EEG?

The baseline record should contain at least 20 minutes of technically satisfactory recording.

What is the minimum number of scalp electrodes required when performing clinical EEG?

All 21 electrodes and placements following the IFCN (International Federation of Clinical Neurophysiology) should be used.

What are the appropriate filter settings when performing clinical EEG?

The LFF should be no higher than 1 Hz and the HFF should be no lower than 70 Hz.

Why is the use of the 60 Hz filter discouraged when performing EEG?

The 60 Hz filter can distort or attenuate spikes and should therefore only be used when other measures against 60-Hz interference fail.

What are the interelectrode impedance requirements when performing a clinical EEG?

With modern digital EEG recording equipment, impedances up to 10 k Ohms are acceptable, but optimal recording still requires impedances that are balanced. Impedances should also not be below 100 Ohms.

What is the correct documentation a clinical EEG record should contain?

As a minimum the EEG should have the name and age of the pt, the date of the recording, an ID number, and name or initials of the tech.

State three reasons it is important to have periods of eye opening and eye closing during the performance of a clinical EEG.

1. Some rhythms can be masked by alpha activity with eyes closed;

2. To help differentiate cerebral activity from eye movement; and

3. Some paroxysmal activity can only be seen with eye opening or closing.

What is the minimum number of scalp electrodes required when performing an EEG to determine electrocerebral silence (ECS)/electrocerebral inactivity (ECI)?

A full set of scalp electrodes should be utilized whenever possible.

What are the interelectrode impedance requirements when performing an EEG to determine electrocerebral silence (ECS) / electrocerebral inactivity (ECI)?

Interelectrode impedances should be under 10,000 Ohms but over 100 Ohms.

What is the interelectrode distance requirement when performing an EEG to determine electrocerebral silence (ECS) / electrocerebral inactivity (ECI)?

Interelectrode pair distances should be at least 10 centimeters apart.

What are the appropriate filter settings when performing an EEG to determine electrocerebral silence (ECS) / electrocerebral inactivity (ECI)?

To avoid attenuation of low-voltage fast or slow activity, the HFF should not be set below 30 HZ, and LFF should not be set above 1 Hz.

Name the 3 characteristics that define and describe EEG waveforms.

Frequency, Amplitude, Location

State the frequencies of normal scalp EEG rhythms.

Beta: Greater then 13 Hz
Alpha: 8-13 Hz
Theta: 4-7 Hz
Delta: 0 to less than 4 Hz

Describe mu and its occurrence.

Negative arch-shaped 7 to 11 Hz rhythmic activity most often located in C3 and C4. Can occur unilaterally or bilaterally often shifting from side to side. Does not attenuate with eye opening.
Occurs in the wake state, attenuated by making a fist with the contralateral arm

Describe the Third rhythm (temporal alpha rhythm) and its occurrence.

Alpha range activity located in the temporal region.
Occurs in the wake state. Seen only in some patients who have a skull defect.

Describe slow alpha variant and its occurrence.

A sub-harmonic of the posterior dominant alpha rhythm often notched and occurring at 4.5-5 Hz
Occurs in the wake state with eyes closed; attenuates (blocks) with eye opening.

Describe fast alpha variant and its occurrence

16 to 20 Hz posterior rhythm; can be harmonic (twice as fast as) of the patient's alpha rhythm.
Occurs in the wake state with eyes closed; attenuates (blocks) with eye opening.

Describe subclinical rhythmic electrogrpahic discharge of adults (SREDA) and its occurrence.

Periodic sharp activity that progresses into a monorhythmic theta pattern of sharply contoured theta.
Occurs in the waking state of older pt's; pt's have no symptoms or clinical changes associated with the discharge.

Describe rhythmic midtemporal theta of drowsiness and its occurrence.

Sharply contoured trains of 5-7 Hz theta activity of temporal and central localization; often has a notched appearance.
Occurs in a state of drowsiness or relaxed wakefulness.

Describe 14 and 6 Hz positive spikes and their occurrence.

Sharply contoured trains of 14 and 6 Hz spikes in the posterior region maximal at T5 (P7) and T6 (P8). Best recorded from widely spaced electrodes so best seen on a referential montage to the contralateral ear.
Occur in a state of drowsiness or N1 sleep.

Describe positive occipital sharp transients of sleep (POSTS) and their occurrence.

Surface positive 4-5 Hz theta waves in the occipital regions.
Occur in N1 and N2 stages of sleep.

Describe lambda and its occurrence.

Surface positive waves in the occipital regions that are transient activity associated with saccadic eye movements while the pt's eyes are open and that block with eye closure. "Scanning image/reading"

Describe wicket spikes and their occurrence.

Sharply contoured waves located in the temporal region; seen bilaterally or independently; no slow wave following the sharply contoured wave.
Occur in a state of drowsiness or stage 1 sleep.

Describe phantom spike and wave (6-Hz spike and wave) and its occurrence.

Parietal or occipital low voltage spike-and-wave complexes that occur as a single wave or in brief bursts; the spike is very low voltage in comparison with the slow wave.
Occurs in drowsiness.

Describe benign epileptiform transients of sleep (BETS), also called small sharp spikes (SSS) and their occurrence.

Low voltage sharp waves that occur on one or both sides in the temporal and frontal regions; may mimic EKG artifact; seen most often on referential montages.
Occur in N1 and N2 sleep.

What EEG finding in a neonate is highly suggestive of a focal lesion, such as a neonatal stroke or cerebral dysgenesis?

Unilateral seizures.

What EEG finding is most often associated with early infantile epileptic encephalopathy (EIEE)?

Burst-suppression

What EEG finding is most often associated with infantile spasms?

Hypsarrhythmia.

What EEG finding is most often associated with Lennox-Gaustaut Syndrome?

1 to 2.5/sec spike-and-wave complexes; a.k.a, slow spike and wave.

What EEG finding is most often associated with childhood absence epilepsy?

Generalized 3-Hz spike-wave discharges

What interictal EEG findings are most often associated with generalized tonic-clonic seizures?

Generalized multiple spike-wave bursts; photoparoxysmal response.

What EEG finding is most often associated with childhood epilepsy with centrotemporal spikes?

Centrotemporal spikes or sharp-and-slow complexes activated by sleep. The spikes show a tangential dipole in a referential montage with maximum negativity in the centrotemporal region and maximum positivity in the frontal region.

Describe the seizures of Panayiotopoulos syndrome.

Seizures are characterized by autonomic symptoms such as vomiting, pallor, nausea, cyanosis, etc. The seizure might end in hemiconvulsion, generalized motor activity, or Jacksonian march.

What EEG finding is most often seen during an infantile spasm?

A moderate voltage slow wave followed by relative flattening (electrodecrement). Low voltage spikes are present but are often obscured by muscle artifact during the clinical seizure.

What is the usual age of onset for childhood absence epilepsy?

Between 4 and 8 years of age.

What EEG finding is most often associated with Acquired Epileptic Aphasia or Landau-Kleffner Syndrome?

Electrical status epilepticus of sleep (ESES)

What is the duration of a sharp wave?

70-200 milliseconds

What is the duration of a spike?

Less than 70 msec.

Temporal intermittent rhythmic delta activity (TIRDA) is associated with what clinical finding?

Temporal lobe epilepsy

What EEG finding is most often associated with juvenile myoclonic epilepsy (JME)?

4 to 5 Hz generalized spike-wave discharges and high voltage polyspikes in sleep.

List the Lennox-Gastaut triad.

1) Mixed seizures including atypical absence seizures, atonic seizures, tonic seizures, and myoclonic seizures.
2) Cognitive dysfunction.
3) Slow spike and wave pattern at 2 to 2.5 Hz on the EEG.

What EEG finding is most often associated with locked-in syndrome?

Normal awake and sleep patterns.

What EEG pattern is often seen in the acute/subacute stage of severe, focal destructive lesions (e.g., massive cerebral infarction, herpes simplex encephalitis).

Lateralized Periodic Discharges (LPDs), formerly known as periodic lateralized epileptiform discharges (PLEDS)

What EEG finding is most often associated with infarction within the territory of the posterior cerebral artery?

Loss or decrease of alpha rhythm on the side of the stroke along with focal slowing in the posterior temporal, parietal, and occipital regions.

What EEG finding is historically associated with metabolic, especially hepatic, encephalopathy?

Triphasic waves.
Note: Triphasic waves are not exclusive to metabolic encephalopathy and can be seen in many other metabolic, toxic, or anoxic encephalopathies.

What EEG finding is most often associated with subacute sclerosing panencephalitis (SSPE)?

Bilaterally symmetric and synchronous, high amplitude, periodic bursts every 4 to 15 seconds.

What EEG finding is most often associated with herpes simplex encephalitis (HSE)?

Lateralized periodic discharges (LPDs) or bilateral independent periodic discharges (BIPDs). PDs may be predominantly temporal.

What EEG finding, when not induced by anesthetic drugs, implies the deepest level of coma preceding brain death? (Hint:often seen in severe anoxic encephalopathy.)

Burst-suppression

What EEG finding is most often associated with Creutzfeldt-Jakob disease?

Initially the EEG shows slower than normal activity with loss of normal background. With disease progression, bursts of moderate voltage biphasic and triphasic sharp waves at intervals of 2 to 1 or less than 1 per second.

What EEG finding is most often associated with a cerebral abscess?

Highly localized polymorphic delta waves over area of abscess.

Describe the EEG findings in a patient during acute alcohol withdrawal.

A desynchronized low voltage pattern. LPDs may be seen in patients who have pre-existing focal lesions.

What EEG effect is seen with diazepam?

Diffuse high amplitude beta.

What EEG changes are seen with phenobarbital?

Frontocentral beta activity.

What is the single most important step taken to avoid contamination and spreading infection?

Hand hygiene.

List the major types of infectious organisms.

Bacterial, viral, fungal and parasitic; bacterial and viral are the most common.

When should neurodiagnostic technologists wear gloves?

Always, the best policy is to use gloves for electrode application and removal of all patient contact regardless of risk.

List the 5 main modes of infection transmission.

Contact, Droplet, Airborne, Common Vehicle, Vector-borne (animals and insects)

What is the maximum leakage current allowed at the chassis when the ground wire is disabled?

300 microamperes (uA).

List precautions to protect patients from electrical shock.

Use a 3 prong plug.
Plug all power cords from all equipment touching the patient into the same receptacle.
Never use an extension cord.
Make sure all equipment attached to the patient has a current safety inspection sticker.
Remove 2 prong plug devices (radio, clock) from the patient's room.
Turn on the EEG instrument before attaching electrodes.
Disconnect the patient before turning the EEG instrument off.

Define macroshock.

Macroshock is the passage of current from one part of the body to another. A lethal macroshock current resulting in ventricular fibrillation must exceed 100 to 300 mA.

Define microshock.

Microshock is defined as the passage of current through intracardiac conductors, cardiac catheters. Ventricular fibrillation may result at currents less than 100 uV.