What is a normal variant in EEG?

The phrases “electroencephalogram (EEG) variant waves” or “normal EEG variants” refer to waves that are rare or unusual but not generally abnormal. They may be unusual in shape or in distribution. These variant waveforms include waveforms and patterns that are rare or unusual but are known to be generally benign.

What is hypnagogic Hypersynchrony?

Hypnagogic hypersynchrony is a normal physiologic variant of medium to high amplitude synchronous rhythmic theta frequencies seen in light NREM sleep. NREM: non-rapid eye movement.

What is epileptiform activity on EEG?

An epileptiform activity in EEG signals including spikes, sharp waves, or spike-and-wave complexes can be evident not only during a seizure (the ictal period) but also a short time before (the preictal period) as well as between seizures (the interictal period).

What are normal variants?

A “normal variant” is defined as an incidental, usually asymptomatic, imaging finding that simulates true pathology. Given the nearly limitless spectrum of skeletal variation, a solid understanding of commonly encountered normal radiographic variants is essential to avoid mistaking one for true pathology.

Are spikes normal on EEG?

Some waveforms or activity on an EEG are normal, while others may be within normal limits for some people but not others. Spikes or sharp waves are terms commonly seen in EEG reports. If these happen only once in a while or at certain times of day, they may not mean anything.

What is wavelength lambda?

wavelength, distance between corresponding points of two consecutive waves. Wavelength is usually denoted by the Greek letter lambda (λ); it is equal to the speed (v) of a wave train in a medium divided by its frequency (f): λ = v/f.

What is Hypersynchrony?

The term hypersynchrony seemed to be first applied to seizures by Penfield & Jasper (1954), and referred to an underlying mechanism of excessive synchronization of activity in a large population of neurons manifesting as high-amplitude rhythmic epileptic discharges.

When is Hypersynchrony hypnagogic?

Hypnagogic hypersynchrony is first seen at 2-4 months of age, and is observed in approximately 30% of normal infants at 3 months of age. At this time, it is most prominent over the central regions. The distribution widens by 8-12 months.

What are the different types of EEG?

Types of EEG

Routine EEG. A routine EEG recording lasts for about 20 to 40 minutes.
Sleep EEG or sleep-deprived EEG. A sleep EEG is carried out while you’re asleep.
Ambulatory EEG. An ambulatory EEG is where brain activity is recorded throughout the day and night over a period of one or more days.
Video telemetry.

What does normal variants mean ON EEG?

Normal Variants. The term “normal variants” refers to EEG waveforms that are considered to be normal findings, but whose presence is not required for an EEG to be normal.

What is the posterior dominant alpha rhythm on EEG?

The posterior dominant alpha rhythm. The normal background EEG during wakefulness contains posteriorly dominant, symmetrical, and reactive alpha rhythm. Alpha activity is more prominent in amplitude during relaxed, eyes-closed wakefulness and demonstrates (more…) Other Features of the Normal Waking Background

What do 14 and 6 positive spikes mean ON EEG?

Taking the crown for perhaps the most uninspired name of EEG findings, 14 and 6 positive spikes describe 1-2 second bursts of sharply contoured positive waveforms that come in frequencies of either 14 Hz (13-17 Hz) or 6 Hz (5-7 Hz), or an admixture of both.

What causes transient positivity and transient negativity on EEG?

Since the positivity of the cornea rotates upward toward frontal electrode sites, a transient positivity, then negativity is recorded there. Another common artifact during the waking EEG is caused by swallowing and the related movement of the tongue, which similar to the eye is a dipole and causes a slow potential with superimposed muscle artifact.