Tracings

Cerebral Function Monitor tracings

Classification
Examples
Recently Hellstrom-Westas, Rosen, de Vries and Greisen introduced a classification based on background patterns, sleep cycling activity and presence or absence of seizure activity. This classification is easy to use and is applicable to tracings whether origination from term or preterm infants (NeoReviews Vol.7 No.2 2006 e76).

Background patterns:

Continuous pattern :
In this pattern the lower border of the tracing is above 5micV (usually 7 to 10) and the upper border around 25 (up to 50).
Discontinuous pattern :
In this pattern the lower border of the tracing, though variable is below 5micV and the upper border above 10micV.
Burst Suppression :
This is a kind of discontinuous pattern where the lower border of the tracing is at 0 to 1(2)micV without variability and bursts with amplitude >25 micV.
BS+ denotes burst density 100 bursts/h
BS– means burst density <100 bursts/h
Low Voltage :
The backgroung here is depressed to a very low voltage (around or below 5 mcV).
Inactive, flat):
Primarily inactive (isoelectric tracing) background below 5 mcV.

Sleep Wake cycling :

Sleep-wake cycling in the aEEG is characterized by smooth sinusoidal variations, mostly in the minimum amplitude. The broader bandwidth represents discontinuous background activity during quiet sleep (tracé alternant EEG in term infants), and the more narrow bandwidth corresponds to the more continuous activity during wakefulness and active sleep.

No Sleep Wake Cycling :
No cyclic variation of the aEEG background.
Imminent/immature Sleep Wake Cycling :
Some, but not fully developed, cyclic variation of the lower amplitude, but not developed as compared with normative gestational age representative data.
Developed Sleep Wake Cycling :
Clearly identifiable sinusoidal variations between discontinuous and more continuous background activity, with cycle duration 20 min.

Seizures :

Epileptic seizure activity in the aEEG usually is seen as an abrupt rise in the minimum amplitude and a simultaneous rise in the maximum amplitude, often followed by a short period of decreased amplitude. The raw EEG should show simultaneous seizure activity, with a gradual build-up and then decline in frequency and amplitude of repetitive spikes or sharp-wave or activity with duration of at least 5 to 10 sec.

Single seizure :
A solitary seizure.
Repetitive seizures :
Single seizures appearing more frequently than at 30-minute intervals.
Status epilepticus :
Continuously ongoing seizure activity for >30 minutes.

Previous classifications used voltage or patterns criteria as follows:

Voltage
The semi logarithmic scale of the tracing emphasizes the lower voltages, which are important in case of brain damage. The classification according to voltage goes as follow:

Classification Minimum Maximum

Normal Voltage > 5 micro Volts >10 micro Volts
Abnormal Voltage <5micro Volts >10 micro Volts
Low Voltage <5microVolts <10micro Volts

Classification	Minimum	Maximum
Normal Voltage	> 5 micro Volts	>10 micro Volts
Abnormal Voltage	<5micro Volts	>10 micro Volts
Low Voltage	<5microVolts	<10micro Volts

Patterns
The tracings of full term neonates are also divided into six main patterns as follow:
Sleep-Wake: A normal pattern of full term newborn, always of normal voltage, with cycling between a broad band of wakefulness and narrow band of sleep.
Wave: A pattern that appears usually during the phase of recovery from an hypoxic-ischemic cerebral insult before shifting into the Sleep-Wake pattern. The pattern is of normal voltage and consists of a band fluctuating between lower and upper voltages.
No Sleep-Wake: A pattern that appears after minor insults and is usually followed by a normal Sleep-Wake tracing. The pattern is either of abnormal or normal voltage and consists of a constant width band tracing.
Burst-Suppression: A pattern that follows moderate to severe insults. The longer it lasts the worst the prognosis. It consists of a low voltage band tracing with on top of it, short burst of higher voltage.
Isoelectric: A pattern that appears after major hypoxic-ischemic events and indicates a grave prognosis. It consists of a low voltage, narrow band tracing without fluctuations over time.
Seizure: A period of continuous convulsions has to occur for an aEEG seizure pattern to appear. Seizures can be clinically apparent or sub-clinical (so called silent seizures). Shorter periods of convulsions are difficult to differentiate on the CFM tracings from artifacts, unless they are accompanied by a clinical correlate. This is where the advantage of the new monitors showing the original EEG can be appreciated, since this option contributes to our ability to differentiate artifacts from true electrical seizures. The pattern can be superimposed on any of the above patterns and consists of an abrupt rise of both the lower margin and upper margin of the tracing for a period of time and then a return to the previous voltage. After a several similar events, a saw-tooth pattern, typical of seizures, appears.

Examples

(click on picture to enlarge)
Tracing Tracing
Continuous tracing with Sleep-Wake cycling
Continuous tracing with Sleep-Wake cycling
No Sleep-Wake Cycling
Lt:discontinuous, Rt: Continuous
Burst-Supression
Lt: -, Rt: +
Lt: Inactive
Rt: Low Voltage
Seizure

This page was created by Dr. Shany Eilon
Updated: September 2006
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	Tracing	Tracing
Continuous tracing with Sleep-Wake cycling
Continuous tracing with Sleep-Wake cycling
No Sleep-Wake Cycling Lt:discontinuous, Rt: Continuous
Burst-Supression Lt: -, Rt: +
Lt: Inactive Rt: Low Voltage
Seizure