Sleep activity in eeg

SLEEP ACTIVITIES By: Mohibullah Fazli KakarTrainee of Neurophysiology French Medical Institute for Children

Sleep stages•Drowsiness Alpha dropout (earliest sign)• Increased beta activity over the frontocentral regions• Diff use rhythmic theta activity with anterior predominance

• Slow eye movement• Mu rhythm, wicket wave, and 14 and 6 Hz positive spikes can be seen.

• Deep drowsiness is marked by the vertex waves and POSTS that persist during light sleep and deep sleep

• Hypnagogic hypersynchrony in 3 months to 8 years.

Sleep stages•Stage 2 sleep• Symmetric, synchronous theta rhythms with posterior predominance, 12–15/sec spindles, vertex sharp waves, K-complexes, and POSTS.

• Sleep spindles in the 12–15/sec range are hallmark of sleep onset.

Sleep stages•Stage 3 sleep Delta frequencies in the 0.75–3/sec range are prominent over the anterior regions.

• Sleep spindle in the 10–12/sec and even in the 12– 14/sec ranges are still present but gradually become less prominent.

• Rhythmic activity of 5–9/sec is common.• Rhythmic and symmetrical delta activity is noted between 20% and 50% of the recording

Sleep stages•Stage 4 sleep• Over 50% of the recording is delta rhythm.• Spindles are rare.• Arousal at this stage can be correlated with sleep

disorders (somnambulism, nocturnal terror, or enuresis), and can cause confusion.

• Occasionally, spikes in temporal lobe epilepsy will only appear in stage 3 and 4 sleep.

Sleep stages•REM sleep Low-voltage activity, polyrhythmic waves, and slower alpha waves.

• Short bursts of “saw-tooth waves” over the frontal or vertex leads and quick lateral eye movements.

• Appearance of REM sleep in routine EEG is seen in narcolepsy and in patients who are withdrawn from CNS depressants such as alcohol or phenobarbital

K-Complex• Contain 3 components including sharp, slow, and fast.• Seen in stage 2 sleep and arousal.• Largest in older children and adolescence. With

advanced age, the K-complexes show the decline in voltage with tiny superimposed spindle-like waves.

• First appears at 4 months of age. • They have high amplitude but their rise is not as abrupt

and the configuration is not as sharp as seen in older children.

Sleep spindles• Arise from synchronized activity in neuronal networks

linking the thalamus and the cortex.• Spindles result from rhythmic spike bursts in inhibitory

(GABAergic) thalamic reticular neurons that induce rhythmic rebound bursting in cortical neurons resulting in effective deafferentiation of the cerebral cortex.

• Cortical neurons show enhanced synaptic plasticity that might have a role in memory and learning processes.

• First seen at 1.5–2 months with a frequency of 14/sec.

Sleep spindles• Throughout infancy, they are maximal over the central and

parietal areas with shifting asymmetry.• They usually are electronegative with rounded positive

component that is a typical hallmark of sleep spindles in infancy.

• These surface-negative spindles with wicket or comb-like shape can be erroneously interpreted as 14/sec positive spikes

• Between the ages of 3 and 6 months, sleep spindles appear to be biphasic and as prolonged runs, up to 10– 15 sec. The prolonged run of spindles is a very useful developmental marker and is rarely seen beyond this age range

Sleep spindles• Subharmonic or harmonic of sleep spindles with a

frequency approximately half or double that of sleep spindles and notched appearance can be seen.

• In the second half of the first year of life, the spindles appear to be monophasic and are often asynchronous between the two sides.

• The frequency of spindles also changes, with 12/sec components becoming more prominent.

• Asynchronous spindles may occasionally continue from 1 to 2 year of age but rarely are seen after the age of 2 years when interhemispheric synchrony of the spindles appears.

Mitten patterns• Consist of a sharp-contoured waveform on the slope of a

slow wave of the same polarity that resembles a mitten, with a thumb of mitten formed by the last wave of a spindle and the hand portion by the slower wave component.

• Maximal at the frontocentral vertex with spread into parasagittal regions.

• The location is different from K-complexes in that it is centered anterior to the central vertex where K-complexes are maximal.

• Variant of a vertex wave or K-complex and should not be mistaken for a spike-and-wave discharge.

• It is best seen in referential montage in stage 3 sleep.

Hypnagogic hypersynchrony• Seen in early drowsiness and arousal from deeper sleep.• Characterized by bilateral synchronous, high voltage, rhythmic 3–5 Hz activity.

• The frequency of hypnagogic hypersynchrony is 3–4 Hz at the age of 2–3 months and increases to 4–5 Hz in older children.

• Asymmetric hypnagogic hypersynchrony with shifting predominance can be seen and is not considered abnormal.

• At 2–3 months, first appears.• At 9 months, more prominent and continuous.• Between 4 months and 2 years, seen in almost all infants

Hypnagogic hypersynchrony• Few infants do not show this pattern but show occipital or

widespread rhythmical and synchronous• 4–5 Hz waves of low to medium amplitude.• At 4 years, shorter in duration and more paroxysmal.• At 9–11 years, it becomes rare (10%).• Although the presence of hypnagogic hypersynchrony• at age 12 years is considered abnormal by some• authors, it may be seen in normal children up to the age of 12–

13 years.• Occasionally, small sharp or spiky discharges may be

interspersed between the theta waves. • These discharges should not be interpreted as epileptiform

activity unless they are definitely distinct from background activity and not only occur during drowsiness or at the onset of sleep but persist into deeper stages of sleep.

Hypnic myoclonia (hypnagogic jerks)• This wake-to-sleep transition event is characterized by a sudden, single, brief muscular contraction of the legs and occasionally the arms, head, and postural muscles.

• Sensory hallucinations (hypnagogic hallucinations) often occur before the hypnic myoclonia.

• Hypnic myoclonia occurs in 60–79% of normal population.

• Although it may occur at any age, 90% of patients stop these movements by age of 4 years.

• They are more common in boys than girls by 4:1.

Midline theta rhythm• Rare nonspecific finding of no clinical significance.• Rhythmic train of 5–7 Hz theta activity occurring in the

central vertex but may also be seen in the frontal vertex.• Morphology includes sinusoidal, aciform, spiky, or mu-like

appearance.• Seen during wakefulness and drowsiness.• Variable reactivity to eye opening, alerting, and limb

movement.• The rhythm usually lasts from 3 to 20 sec and does not

evolve.

Frontal arousal rhythm (FAR)• Rare nonspecific EEG pattern of no clinical significance.• Frontal regions (F3 and F4 electrodes with minimal

spread to nearby scalp areas) during arousal from sleep in children.

• Characterized by 30–150 μV, predominantly monophasic negative waves, occurring in bursts or runs lasting up to 13 sec (usually 1–5 sec) with a characteristic notching of the ascending or descending phase of each wave that may represent harmonics of the waveforms.

Frontal arousal rhythm (FAR)• The waxing and waning of the amplitude often leads• to a spindle-like morphology.• 70% of patients having epileptic seizures; a reported

case in which FAR representing ictal electrographic seizure activity.

Rhythmic temporal theta bursts of drowsiness, rhythmic midtemporal discharges (RMTD), psychomotor variant

• Benign variant of no clinical signifi cance.• Seen in 0.5–2.0% of normal adult population and less

common in adolescence. No prevalence in childhood.• Bursts or runs of rhythmic, 5–7 Hz or 4–7 Hz (typically• 5–5.5 Hz), theta activity with fl at-topped, sharply contoured,

often notched appearance in the temporal regions.• Maximally expressed in the mid- or anterior temporal• electrodes.• Monomorphic pattern with amplitude of 50–200 μV.• Duration: commonly 5–10 sec; vary from 1 to >60 sec with

gradual onset and off set.

Rhythmic temporal theta bursts of drowsiness, rhythmic midtemporal discharges (RMTD), psychomotor variant

• The sharper component of the wave usually has a negative polarity in the anterior temporal region.

• Unilaterally with shifting from side to side greater than bisynchronous.

• Differentiated from ictal epileptiform activity by Monomorphic and monorhythmic (no evolution into other frequencies although amplitude can vary)

• No alteration of background activity Occurrence in relaxed wakefulness and drowsiness (most common) and disappearancein deeper levels of sleep.

• Although it has no clinical significance, it was considered by some authors to be a pathologic finding in selected cases.

Fourteen and six per second positivespike discharge• Benign variant of no clinical significance.• Bursts of arch-shaped waves at 13–17 Hz and/or 5–7 Hz, most commonly at 14 and/or 6 Hz. The 14 Hz

• component is more commonly seen than 6 Hz.• Maximal over the posterior temporal and adjacent areas of one or both sides of the head.

• Amplitude <75 μV.• Appearance in deep drowsiness and very light sleep and disappearance in deeper levels of sleep.

• Electropositive of sharp component and electronegative of smooth component.

Fourteen and six per second positivespike discharge• Widespread fi eld lasting for 0.5–1 sec.• Occurs in children after age 3 to young adult but more common between 12 and 20 years with a peak at age 13–14 years.

• Best seen in contralateral ear reference montage.

• Appearance in diff use encephalopathy EEG pattern in a wide variety of encephalopathies of childhood suggesting that they are epiphenomena or a resilient normal.

• Frequency is more variable and can be elicited by alerting stimuli.

Small sharp spike (SSS) or benignepileptiform transients of sleep (BETS)• Benign variant of no clinical signifi cance.• 20–25% of a normal adult population.• Appearance in deep drowsiness and very light sleep and

disappearance in deeper stages of sleep.• Usually low voltage, short duration, single monophasic, or

biphasic spike with an abrupt ascending limb and a steep descending limb.

Six-hertz spike-wave bursts (phantom spike-wave)• Benign variant of no clinical signifi cance.• 2.5% of both adolescents and young adults; 0.5–1%

overall.• Appearance in relaxed wakefulness, drowsiness, and

light sleep and disappearance in deeper levels of sleep.• Bursts of 1–2 sec duration diff use, low voltage (<40 μV),

short duration (<30 msec), 5–7 Hz, spike-andwave• discharges, commonly bifrontal or occipital.• 25% of phantom spike and wave have repetitive rate of 4

Hz.

Six-hertz spike-wave bursts (phantom spike-wave)• At times, spikes are difficult to see.• Six-hertz spikes with minimal or no associated waves may represent a transitional pattern between

• 6-Hz spike-wave bursts and 14 and 6-Hz positive bursts.

• Waking, high-amplitude, anterior, male (WHAM) vs female, occipital, low-amplitude, drowsy (FOLD).

• WHAM is more likely to be associated with seizures if the repetitive rate is <5 Hz or amplitude of spike greater than slow wave.

Wicket waves• One of the most common over-read EEG patterns seen almost

exclusively in adults, most commonly >30 years of age and, usually, older than 50 years.

• Benign variant pattern and is not associated with epilepsy.• Rare waveform (0.9%).• It occurs in clusters or trains, but also as single sharp

transients, of 6- to 11-Hz negative sharp aciform waves with amplitude of 60–200 μV.

• Anterior or midtemporal regions.• Seen during relaxed wakefulness but facilitated by drowsiness

and may occur in light sleep.• Recently wicket waves have also been reported to occur

during REM sleep.

Wicket waves• Unilaterally with a shifting asymmetry between the• two hemispheres.• During the wakefulness, wicket waves are often masked

by background EEG activity.• Cardinal feature is a changing mode of occurrence

through any single recording, from intermittent trains of more or less sustained, aciform, discharges resembling mu rhythm, to sporadic single spikes.

• Amplitude may be high, but the transient arises out• of an ongoing rhythm and does not stand out

Wicket waves• When occurring singly, wicket waves can be mistaken for

anterior or middle temporal spikes.• Isolated wicket wave can be differentiated from epileptiform

discharge by the following criteria:• No slow wave component following the wicket wave• Occurring in trains or in isolation and do not disrupt the

background• Similar morphology to the waveforms in the train when

occurring as a single spike• More commonly seen in patients with cerebrovascular disease.• The age (younger than 30 years) and abnormal background

activity are strongly against the diagnosis of wicket waves and supportive of epileptiform activities

• In older children and adults, early drowsiness is associated with

• (1) alpha dropout (earliest sign)• (2) increased beta activity over the fronto-central regions• (3) diff use rhythmic theta activity with anterior

predominance; • and (4) slow eye movement. • Mu rhythm, wicket wave and 14- and 6 Hz positive spikes

can be seen during drowsiness.

Drowsiness; Older Children and Adults

• Drowsiness must be differentiated from increased alertness after eye opening or caused by emotional stress that can cause alpha blocking.

• In such cases the slow frequency component is absent and beta frequency predominates.

• Deep drowsiness is marked by the appearance of vertex waves and POSTS that persist during light sleep and deep sleep


• In older children and adults, early drowsiness is associated with • (1) alpha dropout (earliest sign); • (2) increased beta activity over the fronto-central regions (double arrows)• (3) diff use rhythmic theta activity with anterior predominance (open

arrow)• and (4) slow eye movement (doublehead arrow). • Mu rhythm, wicket wave and 14- and 6 Hz positive spikes (*) can be

seen during drowsiness. • Drowsiness must be differentiated from increased alertness after eye

opening or caused by emotional stress that can cause alpha blocking.• In such case slow frequency component is absent and beta frequency

predominates. • Deep drowsiness is marked by the appearance of vertex waves and

POSTS that persist during light sleep and deep sleep

Drowsiness; 14-and-6 Hertz Positive Bursts

Drowsiness; 14-and-6 Hertz Positive Bursts

• Stage 2 sleep shows symmetric, synchronous theta rhythms with posterior predominance, 12–15/sec spindles, vertex sharp waves, K-complex and POSTS.

• The appearance of sleep spindles in the 12–15/sec range is a hallmark of sleep onset

Stage 2 (Light Sleep

Stage 2 (Light Sleep

• Subdural recording showing the sleep spindles in the parietal lobe during sleep.

• A harmonic of the sleep spindles is more frequently seen in intracranial EEG.

• In addition, the sleep spindles usually appear sharper in morphology as the scalp and skull act as a high-frequency filter and pass lower frequencies more efficiently than higher frequencies.

• Disappearance during wakefulness helps to differentiate the sleep spindles from low-voltage fast activity.

• All normal EEG rhythms seen in the scalp EEG can be seen in the intracranial EEG

Sleep Spindles During Subdural EEG Recording

Sleep Spindles During Subdural EEG Recording

• Delta frequencies in the 0.75–3/sec range are prominent over the anterior regions.

• Sleep spindles in the 10–12/sec and even in the 12–14/sec ranges are still present but gradually become less prominent.

• Rhythmic activity of 5–9/sec is common.• Rhythmic and symmetrical delta activity occurs during

20% to 50% of the recording

Stage 3 (Moderate Deep Sleep)

Stage 3 (Moderate Deep Sleep)

• Over 50% of the recording is delta rhythm. Spindles are rare.

• Arousal at this stage can be correlated with sleep disorders (somnambulism, nocturnal terror, or enuresis), and can cause confusion.

• Occasionally, spikes in temporal lobe epilepsy will only appear in stage 3 and 4 sleep

Stage 4 (Very Deep Sleep)

Stage 4 (Very Deep Sleep)

• EEG reveals low-voltage activity, polyrhythmic waves, slower alpha waves, and short bursts of “saw-tooth waves” over the frontal or vertex leads (Box B), and quick lateral eye movement (Box A).

• Appearance of REM sleep in routine EEG is seen in narcolepsy and in patients who are withdrawn from CNS depressants such as alcohol or phenobarbital

REM Sleep

REM Sleep

• K complexes contain 3 components including sharp, slow, and fast.

• They are seen in stage 2 sleep and arousal. • The K complexes are largest in older children and

adolescence. • With increasing age, the K complexes show the

decreasing voltage with tiny superimposed spindle-like waves

K Complexes

K Complexes

• Subdural recording showing a run of vertex waves and widely distributed K-complexes, maximally expressed in the parietal lobe during arousal.

• Harmonic of the sleep spindles is frequently seen in intracranial EEGs.

• In addition, the sleep spindles usually are sharper in morphology as the scalp and skull act as a high-frequency filter and pass lower frequencies more efficiently than higher frequencies.

• Disappearance during wakefulness• helps to differentiate the K-complexes from low-voltage fast

ctivity.• All normal EEG rhythms in the scalp EEG can be seen in the

intracranial EEG.

Subdural EEG Monitoring; K-Complex During Arousal

Subdural EEG Monitoring; K-Complex During Arousal

• The differentiation of physiologic waveforms and pathologic waveforms is extremely important in intracranial EEG recording (open arrow-epileptiform in depth electrode; arrow-sleep spindles; double arrows-vertex waves).

• Harmonic and sharp morphology of the physiologic waveforms in an intracranial EEG make distinguishing between onepileptiform and epileptiform activities more difficult.

• Disappearance of spindles and vertex waves during wakefulness, distribution, and morphology help to diff erentiate them from epileptiform activity, especially between sleep spindles and low-voltage fast epileptiform activity

Pathologic vs Physiologic Wave Forms in Intracranial EEG

Pathologic vs Physiologic Wave Forms in Intracranial EEG

• K-complex first appears at 4 months of age.• They have high amplitude but their rise is not as abrupt

and the configuration isnot as sharp as one seen in older children

Early K-Complex (16 Week CA)

Early K-Complex (16 Week CA)

• Sleep spindles arise from synchronized activity in functionally important neuronal networks linking the thalamus and the cortex.

• Spindles result from rhythmic spike bursts in inhibitory (GABAergic) thalamic reticular neurons that induce rhythmic rebound bursting in cortical neurons. This process has been shown to result in effective deafferentiation of the cerebral cortex.

• Cortical neurons show enhanced responsiveness and properties of synaptic plasticity that may have a role in memory and learning processes.

• At 1.5 to 2 months, 14/sec spindles are first seen

Normal Sleep Spindles (2 Months); Definite 14/sec Spindles

Normal Sleep Spindles (2 Months); Definite 14/sec Spindles

• EEG of an 8-week-old full-term boy shows low-voltage 22–24 Hz biphasic beta activity diffusely in the central vertex and bilateral central-parietal areas.

• This exceptional waveform most likely represents a harmonic of sleep spindles.

• More commonly spindles occur independently from faster 18–25 Hz activity and both patterns may be seen at the same time

Normal Sleep Spindles (8 Weeks CA); Harmonic of Sleep Spindles

Normal Sleep Spindles (8 Weeks CA); Harmonic of Sleep Spindles

• Trace alternant disappears in the first month of life. • Sleep spindles usually appear in the second months of life

with frequency between 12 and 15/sec. Throughout infancy, they are maximal over the central and parietal areas with shifting asymmetry.

• They usually are electronegative with a rounded positive component.

• A complete absence of spindles at age 3–8 months indicates a severe abnormality

Normal Sleep Spindles (10 Weeks CA)

• Between the ages of 3–6 months, sleep spindles appear to be biphasic and occur as prolonged runs, up to 10–15 sec.

• The prolonged run of spindles is a very useful developmental marker and is rarely seen beyond this age range

Normal Sleep Spindles (3-6 Months CA); Prolonged Runs of Spindles

Normal Sleep Spindles (3-6 Months CA); Prolonged Runs of Spindles


• The prolonged run of spindles is a very useful developmental marker and is rarely seen beyond this age range

Prolonged Sleep Spindles (3-6 Months CA)


• The prolonged run of spindles is a very useful developmental marker and rarely seen beyond this age range.


• Between the ages of 3–6 months, sleep spindles appear to be biphasic and as prolonged runs, up to 10–15 sec.

• The prolonged run of spindles is a very useful developmental marker and rarely seen beyond this age range.

• Throughout infancy, sleep spindles are maximal over the central and parietal areas with shifting asymmetry.

• They usually shows electronegative with rounded positive component that is a typical hallmark of sleep spindles in infancy.

• These surface-negative spindles with wicket or comb-like shape can be erroneously interpreted as 14/sec positive spikes (below)


Sleep Spindles with subharmonic• Subharmonic of sleep spindles with a frequency approximately half that of sleep spindles with a notched appearance can be seen.

• The subharmonic has the same reaction and distribution as sleep spindles

Sleep Spindles with Subharmonic

• Mitten patterns are seen during sleep and consist of a sharply-contoured waveform on the slope of a slow wave of the same polarity that resemble a mitten, with the thumb of the mitten formed by the last wave of a spindle and the hand portion by the slower wave component.

• Mittens are a variant of a vertex wave or K-complex and should not be mistaken for a spike-and-wave discharge.

• It is best seen in the referential montage and in stage 3 sleep

Mitten Pattern

Mitten Pattern

• Hypnagogic hypersynchrony is an activity seen in early drowsiness and in arousal from deeper sleep.

• It is characterized by bilateral synchronous, high voltage, rhythmic 3-5 Hz activity.

• This activity first appears at the age of 2 to 3 months and becomes prominent and continuous at 9 months.

• At age 4 years, it becomes shorter in duration and more paroxysmal in appearance

•

Hypnagogic Hypersynchrony

• By age 9 to 11 years, it becomes rare. Although the presence of hypnagogic hypersynchrony at age 12 years is considered abnormal by some authors,21 it may be seen in normal children up to the age of 12-13 years.

• The frequency of hypnagogic hypersynchrony is 3-4 Hz at the age of 2-3 months and increases to 4-5 Hz in older children.

• This EEG also shows slow eye movement (SEM), maximally seen at F7 and F8, which is also one of the signs of drowsiness.


• Nearly continuous hypnagogic hypersynchrony in a 22-month-old infant.

• Hypnagogic hypersynchrony appears at approximately 3 months of age and is characterized by monorhythmic, slow generalized activity with the frequency of 3-4 Hz during drowsiness.

• It may be seen in olderchildren up to 12-13 years but is rare after 11 years (incidence of only 10%).

• The frequency increases to 4-5 Hz in older children


• EEG of a 25-month-old boy with asymmetric hypnagogic hypersynchrony with shifting predominance.

• The paroxysmal bursts of generalized high-voltage, rhythmically monotonous theta activity superimposed on low-voltage background activity, so-called “hypnagogic hypersynchrony,” is the hallmark of drowsiness in early childhood.

• Occasionally, small sharp or spiky discharges may be interspersed between the theta waves.

•

Asymmetric Hypnagogic Hypersynchrony

• These discharges should not be interpreted as epileptiform activity unless they are definitely distinct from background activity and not only occur during drowsiness or at the onset of sleep but also persist into deeper stages of sleep.

• Asymmetric hypnagogic hypersynchrony with shifting predominance can be seen and is not considered abnormal



• EEG of a 4-year-old boy with hypnagogic hypersynchrony.• The paroxysmal bursts of generalized high-voltage,

rhythmically• monotonous theta activity superimposed on low-voltage

background activity, so-called “hypnagogic hypersynchrony” is the hallmark of drowsiness in early childhood.

• Occasionally, small sharp or spiky discharges may be interspersed between the theta waves.

• These discharges should not be interpreted as epileptiform activity unless they are definitely distinct from background activity and not only occur during drowsiness or at the onset of sleep but also persist into deeper stages of sleep

Hypnic Myoclonia (HM) (Sleep Starts or Hypnogogic Jerks)

• Video-EEG of a 5-year-old boy with well-controlled focal epilepsy shows a burst of high-voltage 3–4 Hz delta activity intermixed with low-amplitude spikes during chin quivering (*).

• This EEG pattern is compatible with hypnagogic hypersynchrony associated with HM.

• This wake-to-sleep transition event is characterized by a sudden, single, brief muscular contraction of the legs and occasionally the arms, head, and postural muscles.

• Hypnagogic hallucinations often occur before the sleep starts, and the perception of falling may occur, ending with the myoclonic jerk.

• HM is a physiologic fi nding unless it is frequent and results in sleep-onset insomnia. It also must be diff erentiated from seizure, especially if it occurs in patients with known epilepsy.


• HM occurs in 60–79% of normal individuals. • Ninety percent of patients stop these movements by age

4 years. • It is more common in boys than in girls by 4:1.• It may be frightening when observed by a parent,• especially if associated with a vocalization or cry. • Injury from the massive movement is rare, but foot injuries

secondary to kicking a bedpost or crib rail may occur

• EEG of a 5-year-old asymptomatic boy shows 14- and 6 Hz positive spikes (arrow head) immediately after hypnagogic hypersynchrony (open arrow).

• Fourteen and six hertz positive spikes (arrow head) are commonly seen during drowsiness.

14-and-6-Hertz Positive Spikes; Hypnagogic Hypersynchrony

14-and-6-Hertz Positive Spikes; Hypnagogic Hypersynchrony

• An 8-year-old boy with recurrent syncope without other associated symptoms suspicious of seizures or other neurologic conditions except borderline ADHD.

• There was a history of GTCS in his 4-year-old brother. • EEG during drowsiness shows hypnagogic

hypersynchrony and bilateral-independent centro-temporal spikes. Characteristic spikes over the rolandic area are regarded as neurobiological markers of BECTS.

• However, rolandic (centro-temporal) spikes have been reported in normal children without clinical seizures or neurologic manifestations.

Asymptomatic Centro-Temporal Spikes; Hypnagogic Hypersynchrony

• They are seen in 1.2–3.5% of normal healthy children in the community36,37 and 6–34% of siblings of patients aff ected by BECTS

• The risk of epilepsy is higher if rolandic spikes remain unilateral during sleep, rolandic spikes continue during REM sleep, and if they occur in the presence of generalized spike-wave discharges.

• The frequency of rolandic spikes in children with ADHD (3–5.6%) is significantly higher than expected from epidemiologic studies although how ADHD symptoms are related to rolandic spikes is still unclear


• Video-EEG of a 5-year-old boy with well-controlled focal epilepsy shows a burst of high-voltage 4 Hz delta activity intermixed with low-amplitude spike-like during right arm jerks (arrow).

• This EEG pattern is compatible with hypnagogic hypersynchrony and the right arm jerking is most likely to be hypnic myoclonia.

• Sleep starts (hypnic myoclonia) also have been termed “hypnagogic jerks”.

• This wake-to-sleep transition event is characterized by a sudden, single, brief muscular contraction of the legs and occasionally the arms, head, and postural muscles.

• Sensory hallucinations (hypnagogic hallucinations) often occur before the sleep start, and the subjective perception of falling may occur, ending with the myoclonic jerk.

Hypnic Myoclonia; Hypnagogic Hypersynchrony.

• Sleep starts are common, occur in most individuals, and are not pathologic unless they are frequent and result in sleep-onset insomnia.

• They also must be differentiated from seizure, especially if they occur in patients with known epilepsy.

• Hypnic myoclonia occurs in 60–79% of normal individuals. • Although it may occur at any age, 90% of patients stop these

movements by age 4 years. • They are more common in boys than girls by 4:1.• It may be frightening when observed by a parent, especially if

associated with a vocalization or cry.• Injury from the massive movement is rare, but foot injuries

secondary to kicking a bedpost or crib rail may occur


• Focal rhythm over the midline region, most prominent over vertex with occasional spread to adjacent electrodes

• Usually 5-7 Hz, monorhythmic, waxes and wanes • Seen in wakefulness and drowsiness- has variable

reactivity • Occurs in a heterogeneous group of patients • May be more common in frontal lobe epilepsy if pathologic

Midline theta

Midline theta

Midline Theta

• Frontal arousal rhythm (FAR) is a rare EEG rhythm, seen in the frontal regions during arousal from sleep in children.

• The FAR is characterized by 30–150 μV, predominantly monophasic negative waves, occurring in bursts or runs lasting up to 13 sec (usually 1–5 sec) with a characteristic notching of the ascending or descending phase of each wave.

• The notched appearance may represent harmonics of the waveforms. • The waxing and waning of the amplitude often leads to a spindle-like

morphology. • The FAR appears at the F3 and F4 electrodes with minimal spread to

nearby scalp areas.46 The incidence of the FAR in a normal population is unknown.

• Although it was first reported in children with minimal cerebral dysfunction or a seizure disorder, it is later considered to be a non specifi c EEG pattern of no clinical significance

Frontal Arousal Rhythm (FAR)

• EEG of an 8-year-old girl with idiopathic generalized epilepsy.• Frontal arousal rhythm (FAR) is a rare EEG rhythm, seen in the frontal regions during

arousal from sleep in children between ages 2 and 12 years, mainly 2 and 4 years. • The FAR is characterized by 30–150 μV predominantly monophasic negative waves,

occurring in bursts or runs lasting up to 13 sec (usually 1–5 sec), maximally over the frontal midline, with a characteristic notching of the ascending or descending phase of each wave.

• The notched appearance may represent harmonics of the waveforms. Waxing and waning of the amplitude often leads to a spindle-like morphology. The FAR appears at the F3 and F4 electrodes with minimal spread to nearby scalp areas.

• The incidence of the FAR in the normal population is unknown.• Although it was first reported in children with minimal cerebral dysfunction or a

seizure disorder, it is now considered to be a nonspecific EEG pattern of no clinical significance


• An 8-year-old girl with a history of GTCS. EEG demonstrates trains of rhythmic 6-Hz sharp waves in bifrontal regions during arousal state.

• Frontal arousal rhythm (FAR) is a rare EEG rhythm, seen in the frontal regions during arousal from sleep in children.

• The FAR is characterized by 30–150 μV, predominantly monophasic negative waves, occurring in bursts or runs lasting up to 13 sec (usually 1–5 sec) with a characteristic notching of the ascending or descending phase of each wave.

• The notched appearance may represent harmonics of the waveforms. The waxing and waning of the amplitude often leads to a spindle-like morphology.

• The FAR appears at the F 3 and F 4 electrodes with minimal spread to nearby scalp areas.46 The incidence of the FAR in a normal population is unknown.

• Although it was first reported in children with minimal cerebral dysfunction or a seizure disorder, it is now considered to be a nonspecific EEG pattern of no clinical significance


• EEG of a 10-year-old boy with idiopathic generalized epilepsy. • Frontal arousal rhythm (FAR) is a rare EEG rhythm, seen in the frontal regions during

arousal from sleep in children between ages 2 and 12 years, mainly 2 and 4 years. • The FAR is characterized by 30–150 μV predominantly monophasic negative waves,

occurring in bursts or runs lasting up to 13 sec (usually 1–5 sec), maximally over the frontal midline, with a characteristic notching of the ascending or descending phase of each wave.

• The notched appearance may represent harmonics of the waveforms. • Waxing and waning of the amplitude often leads to a spindle-like morphology. • The FAR appears at the F3 and F4 electrodes with minimal spread to nearby scalp areas.• The incidence of the FAR in a normal population is unknown. • Although it was first reported in children with minimal cerebral dysfunction or a seizure

disorder, it is now considered to be a nonspecific EEG pattern of no clinical significance


• EEG of a 6-year-old boy with frontal lobe epilepsy during arousal from sleep.

• Frontal arousal rhythm (FAR) is a rare EEG rhythm, seen in the frontal regions during arousal from sleep in children between ages 2 and 12 years, mainly 2 and 4 years.

• The FAR is characterized by 30–150 μV predominantly monophasic negative waves, occurring in bursts or runs lasting up to 13 sec (usually 1–5 sec), maximally over the frontal midline, with a characteristic notching of the ascending or descending phase of each wave.

• The notched appearance may represent harmonics of the waveforms.

• Waxing and waning of the amplitude often leads to a spindle-like morphology.


• The FAR appears at the F3 and F4 electrodes with minimal spread to nearby scalp areas.

• The incidence of the FAR in a normal population is unknown. Although it was first reported in children with minimal cerebral dysfunction or a seizure disorder, it is now considered to be a nonspecific EEG pattern of no clinical significance.

• Its mildly abnormal character is likely, but its clinical significance was thought to be debatable

• Hughes found 70% of patients having epileptic seizures and demonstrated a case in which FAR representing ictal electrographic seizure activity


• RTTD is seen in 0.5–2.0% of normal adult population and less common in adolescence.

• It is described as bursts or runs of rhythmic, 5–7 Hz (typically 5–5.5 Hz), theta activity with flat-topped, sharply contoured, often notched appearance in the temporal regions, maximally expressed in the mid anterior temporal electrode.

• The sharper component of the wave usually has a negative polarity in the anterior temporal region.

• It can occur unilaterally, bilaterally, or shifting from side to side with gradual onset and off set.

Rhythmic Temporal Theta Bursts of Drowsiness (RTTD); Rhythmic Mid temporal Discharges (RMTD); (Psychomotor Variant)

• The pattern is distinguished from ictal epileptiform activity because it is monomorphic and mono rhythmic (no evolution into other frequencies), does not alter background activity, occurs in relaxed wakefulness and drowsiness (most common), and disappears in deeper levels of sleep.

• This pattern has no clinical significance.• However, it was considered by some authors to be a pathologic

finding in selected cases.• This pattern was previously called “psychomotor variant.• They are also now called “rhythmic mid temporal discharges (RMTDs)


• A 15-year-old girl with recurrent passing out episodes. • EEG during drowsiness shows rhythmic 5-6 Hz, theta

activity with flat-topped, sharply contoured over the temporal regions with a phase reversal in the posterior temporal electrodes.

• Rhythmic temporal theta waves of drowsiness (RTTD) is also called rhythmic mid temporal discharges (RMTDs) or psychomotor variant.

• RTTD is seen in adult and, less commonly, in adolescent.

Rhythmic Temporal Theta Bursts of Drowsiness (RTTD)

• This EEG pattern is distinguished from ictal epileptiform activity in that it is monomorphic and mono rhythmic (no evolution), does not affect background activity, and occurs in only in relaxed wakefulness and drowsiness.

• This EEG pattern is of uncertain significant


• A 16-year-old girl with recurrent vertigo who had been diagnosed with simple partial seizures and was treated with carbamazepine.

• The treatment failed to stop the symptoms and caused side effects.

• Brain MRI was unremarkable. • EEGs were performed four times in the past and were

interpreted as epileptiform activity in the temporal regions.• This EEG during drowsiness shows a burst of rhythmical

5.5 Hz theta activity in the left temporal region (open arrow) with negative polarity of the sharper component of the burst in the midtemporal region.


• Note no disruption of alpha rhythm in the left occipital region (arrow heads).

• The patient was completely normal throughout the discharge.

• This EEG pattern is compatible with RTTD and is considered a normal variant and has no clinical significance.

• The patient has done well since stopping carbamazepine


• A 17-year-old boy with recurrent headache and numbness of his right arm.

• EEG during resting wakefulness shows bilateral-independent 5.5 Hz theta activity in the temporal regions in the 2 hemispheres.

• As the discharge proceeds, the morphology does not change (monomorphic and monorhythmic).

• The discharge continues during drowsiness but disappears in stage 2 sleep.

• These differentiate the RTTD from focal ictal activity


• A 17-year-old boy with a new-onset GTCS. • EEG during drowsiness shows runs of bilateral-independent 5.5

Hz sharply-contoured theta activity in the midtemporal regions in the two hemispheres.

• As the discharge proceeds, the morphology does not change (monomorphic and monorhythmic).

• The discharge continues during drowsiness but disappears in stage 2 sleep.

• These findings differentiate the RTTD from focal ictal activity.


• EEG during drowsiness shows long runs of monomorphic and monorhythmic notched theta activity that does not evolve into other frequencies or waveforms.

• The patient was completely normal throughout the run of discharge.

• The discharge disappears during deeper states of sleep. • These findings differentiate RTTD from an electrographic

seizure.• Note an unusual morphology of the discharge that shows

positive polarity in the posterior temporal areas.


• This EEG pattern is defined as bursts of arch shaped waves at 13–17 Hz and/or 5–7 Hz, most commonly at 14 and/or 6 Hz, seen generally over the posterior temporal and adjacent areas of one or both sides of the head during deep drowsiness and very light sleep.

• The sharp peaks of its components are electropositive compared to other regions. The bursts have a widespread field and last for 0.5–1 sec.

• This EEG pattern occurs in children from the age of 3 up to young adulthood but more commonly occur between 12 and 20 years with a peak at age 13–14 years. It is best displayed in the contralateral ear reference montage.

• 14 and 6/sec positive spike discharge is a benign variant of no clinical significance

14 and 6/sec Positive Spike Discharge

• Fourteen and six per second positive spike discharge shows mainly 13 Hz positive spikes


14 and 6/sec Positive Spike Discharges; (Anterior-Posterior Bipolar)

• This EEG pattern is defined as bursts of arch shaped waves at 13–17 Hz and/or 5–7 Hz, most commonly at 14 and/or 6 Hz, seen generally over the posterior temporal and adjacent areas of one or both sides of the head during deep drowsiness and very light sleep (arrow).

• The sharp peaks of its components are positive with respect to other regions.

• This pattern occurs in the children after age 3 to young adult with a peak at age 13–14 years.

• This pattern is a benign variant of no clinical significance

14 and 6/sec Positive Spike Discharges; (Anterior-Posterior Bipolar)

14 and 6/sec Positive Spike Discharges; (Contralateral Ear Reference)

• The 14 and 6/sec positive spike discharges are best seen during a contralateral ear reference run

14 and 6/sec Positive Spike Discharges; (Contralateral Ear Reference)

• A 12-year-old boy with symptomatic Lennox-Gastaut syndrome after the treatment of status epilepticus with intravenous midazolam.

• EEG showed continuously diff use polymorphic delta activity with superimposed “14-and-6-Hertz positive spikes.”

• Although 14- and 6 Hz positive spikes in diff use encephalopathy EEG pattern was once thought to be seen exclusively in coma due to Reye’s syndrome

• in other encephalopathies of childhood as well suggesting that they are epiphenomena or a resilient normal.

• The 14- and 6 Hz positive spikes are best seen in contralateral ear reference montage.

14-and-6-Hertz Positive Spikes; Diffuse Encephalopathy

14-and-6-Hertz Positive Spikes; Diffuse Encephalopathy

• With contralateral ear reference, 14- and 6 Hz positive spikes (arrow head) are diffusely seen over both hemispheres but maximal in the right posterior temporal region.

• The opposite polarity in the EEG electrodes over the left hemisphere may be suggestive of the dipole character of this waveform

14-and 6-Hz Positive Spikes

14-and 6-Hz Positive Spikes

• Diff use 14 and 6/sec positive spike discharges with right hemispheric predominance during referential run in a 12-year-old adolescent girl with non epileptic events

14 and 6/sec Positive Spike Discharge; Referential Montage

14 and 6/sec Positive Spike Discharge; Referential Montage

• When a 14 and 6/sec positive spike discharge is intermixed with diff use delta or theta slowing, it can simulate spike-wave or poly spike-wave activity

14 and 6/sec Positive Spike Discharge; Poly spike-Wave-Like Discharge

14 and 6/sec Positive Spike Discharge; Poly spike-Wave-Like Discharge

• Fourteen and six hertz positive spikes (**) can be mixed with sleep spindles (*). • These 2 waveforms can be differentiated from each other by configuration and

distribution. • Fourteen and six hertz positive spikes occur predominantly during drowsiness

and light sleep and consist of short trains of arch-shaped waveforms with alternating positive spiky components and a negative, smooth, rounded waveform.

• a 14 and 6/sec positive spike maximal amplitude over the posterior temporal region.

• Sleep spindles occur predominantly during stage 2 sleep and consist of trains of sinusoidal waveforms.

• It usually has maximal amplitude over the fronto-central region

14-and-6-Hertz Positive Spikes

14-and-6-Hertz Positive Spikes

• During a subdural EEG recording in the patient with right neocortical temporal lobe epilepsy, 14 and 6/sec positive spikes are noted in the right anterior temporal region (open arrow) outside of the epileptogenic zone (blue).

• This is an uncommon location of this EEG pattern that is usually seen in the posterior temporal region.

• This may be due to brain plasticity. • The patient has been seizure free since the epileptogenic

zone, excluding the area containing 14 and 6/sec positive spike discharge, was resected.

• This strongly supports the benign nature of this EEG pattern. • The 14 and 6/sec positive spikes EEG pattern has never been

reported in the literature.

14-and 6-Hertz Positive Spikes (Subdural EEG Monitoring)

14-and 6-Hertz Positive Spikes (Subdural EEG Monitoring)

• Small sharp spike (SSS) is a benign EEG pattern that is seen in 20–25% of a normal adult population.

• SSS are seen in adults during drowsiness or light sleep. • They are usually low voltage, short duration, single

monophasic or biphasic spike with an abrupt ascending limb and a steep descending limb.

• The prominent after coming slow wave may not occur.• SSS occur unilaterally or bilaterally

Small Sharp Spikes (SSS); Benign Epileptiform Transients of Sleep (BETS

Small Sharp Spikes (SSS); Benign Epileptiform Transients of Sleep (BETS

• A 16-year-old girl with a history of migraine who presented with recurrent passing out episodes. EEG obtained during light non-REM sleep shows low voltage, short duration, biphasic spikes with an abrupt ascending limb and a steep descending limb.

• The negative and positive components are of approximately equally spiky character.

• The spikes are widely distributed in both hemispheres (*). • Small sharp spikes (SSS) or BETS occur almost

exclusively during drowsiness or light non-REM sleep.

Small Sharp Spikes (SSS); Benign Epileptiform Transients of Sleep (BETS)

• A prevalence of 1.36% was found in adult with a peak between ages 30 and 40.

• It is uncommonly seen in adolescents.• There is a debate whether this is a normal or an

epileptogenic pattern. • In nonepileptics, these discharges may be seen in stroke,

syncopal attacks, and psychiatric patients


• A 17-year-old-right-handed girl with recurrent episodes of deja vu. The presurgical work-up was consistent with right mesio-temporal epilepsy.

• EEG shows frequent small sharp spikes (SSS) during drowsiness and light sleep (arrow head).

• The patient has been seizure free since the right anterior temporal lobectomy.

• “Small sharp spikes (SSS)” is a benign EEG pattern that is seen in 20–25% of

• a normal adult population.

Small Sharp Spikes (SSS); Benign Epileptiform Transients of Sleep (BETS); Benign Sporadic Sleep Spikes (BSSS)

• SSS are seen in adults during drowsiness or light sleep, usually low voltage (less than 50 μV), short duration, single monophasic or biphasic spikes with an abrupt ascending limb and a steep descending limb.

• The prominent after coming slow wave may not occur. • SSS are almost always bilaterally represented, either ccurring

independently or having reflection to the opposite hemisphere. • The bilateral occurrence of the SSS should not be

misinterpreted as bilateral epileptogenic foc


• A 9-year-old girl with right mesio-temporal epilepsy caused by mild MCD.

• She has been seizure free since the left temporal lobectomy. EEG during drowsiness shows diff use SSS, predominantly in the left hemisphere.

• “Small sharp spikes (SSS)” is a benign EEG pattern that is seen in 20–25% of a normal adult population.

• SSS are seen in adults during drowsiness or light sleep, usually low voltage, short duration, single monophasic or biphasic spikes with an abrupt ascending limb and a steep descending limb. The prominent after coming slow wave may not occur. SSS occur unilaterally or bilaterally.

• Some authors believed this pattern indicates a “moderate degree of epileptogenicity.

Small Sharp Spikes (SSS)

Small Sharp Spikes (SSS)

• This EEG pattern can be seen in 2.5% of both adolescents and young adults.

• It occurs during relaxed wakefulness, drowsiness, and light sleep and disappears during deeper stages of sleep.

• It is described as bursts of 1–2 sec duration, diff use, low voltage, 5–7 Hz, spike-and-wave discharges, commonly bifrontally or occipitally.

• At times, spikes are difficult to see. • This EEG pattern is regarded as a benign variant of uncertain• significance.• Six-hertz spikes with minimal or no associated waves may

represent a transitional pattern between 6-Hz spike-wave bursts and 14 and 6 Hz positive bursts.

Six-Hertz Spike-and-Wave Bursts; (Phantom Spike-and-Wave Discharge)

Six-Hertz Spike-and-Wave Bursts; (Phantom Spike-and-Wave Discharge)

• Six-hertz spike and wave bursts in an 11-year-old girl with recurrent syncopal attacks associated with migraine.

• Six-hertz spike and wave bursts (arrow) can be very difficult to distinguish from atypical spike-wave activity.

• The clue to make a distinction is that benign 6-Hz spike and wave bursts occur during relaxed wakefulness and drowsiness and disappear during deeper stages of sleep.

• Two types of 6-Hz-spike-and-wave discharges have been described, FOLD (Female, Occipital, Low amplitude, Drowsiness) and WHAM (Wake, High-amplitude, Anterior, Male).

• FOLD is more benign, and WHAM is more likely to be associated with seizures

Six-Hertz Spike-and-Wave Bursts

Six-Hertz Spike-and-Wave Bursts

• Wicket waves are one of the most common over-read EEG patterns64 seen almost exclusively in adults, most commonly >30 years of age and, usually older than 50 years.

• Wicket waves are relatively rare with an incidence of 0.9%. • It occurs in clusters or trains, but also as single sharp transients, of 6- to

11-Hz negative sharp aciform waves with amplitude of 60–200 μV. • They are seen over the anterior or midtemporal regions during relaxed

wakefulness but facilitated by drowsiness and may occur in light sleep. • Wicket waves occur unilaterally with a shifting asymmetry between the

two hemispheres. • During the waking portion of the record, wicket waves are often• masked by background EEG activity.• Recently, wicket waves have also been reported to occur during REM

sleep

Wicket Wave

• Their cardinal feature is a changing mode of occurrence through any single recording, from intermittent trains of more or less sustained, aciform, discharges resembling mu rhythm, to sporadic single spikes.

• Amplitude may be high, but the transient arises out of an ongoing rhythm and does not stand out.

• When occurring singly, wicket waves can be mistaken for anterior or mid-temporal spikes. • Isolated wicket wave(s) can be differentiated from epileptiform discharge (s) by the

following criteria: • (1) no slow wave component following the wicket wave;• (2) occurring in trains or in isolation• and do not disrupt the background;• (3) having a similar morphology to the waveforms in the train when they occur as a single

spike. • Wicket wave is considered a benign variant pattern and is not associated with epilepsy

Wicket Wave

Wicket Wave

• A 12-year-old-right-handed boy with medically intractable epilepsy caused by nonaccidental trauma in infancy.

• Interictal EEG shows trains of negative sharp arciform waves in the right anterior temporal region (box), continuously low-amplitude polymorphic delta activity (PDA), and suppression of background activity over the right hemisphere, maximal in the temporal region.

• The trains of sharp waves are similar to “wicket waves.” • MRI demonstrates multifocal encephalomalacia but maximal over the right

anterior temporal region (open arrow).• Wicket waves are most commonly seen in individuals older than 30 years of age. • Wicket waves are relatively rare with a prevalence of 0.9% in adults but unknown

in children.• They occur in clusters or trains, but also as single sharp transients, of mid- or

anterior temporal 6–11 Hz negative sharp arciform waves with amplitude of up to 200 μV.

Wicket-Wave Like Waveform; Non accidental Trauma

• Wicket waves can be differentiated from temporal lobe epileptiform discharges based on the following criteria:

• (1) no slow wave component following wicket spikes; • (2)occurring intrains or in isolation and do not disrupt the

background; • (3) having a similar morphology to the waveforms in the

train when they occur as a single spike.• Wicket waves are more commonly seen in patients with

cerebrovascular disease.• In this EEG, the age and abnormal background activity

are strongly against the diagnosis of wicket waves and supportive of epileptiform activities.


• A 4-month-old boy who developed a right-sided focal motor seizure after cardiac surgery for complex congenital heart defects.

• MRI with DWI shows cerebral infarction in the left fronto-temporal region.

• Interictal EEG shows trains of negative sharp arciform waves in the left posterior temporal region (box) and suppression of background activity over the left hemisphere.

• The trains of sharp wave configuration are similar to “wicket waves.”

• Wicket waves are most commonly seen in individuals older than 30 years of age.

Wicket-Wave Like Waveform; Left Frontal-Temporal Infarction

• Wicket waves are relatively rare with a prevalence of 0.9% in adult but unknown in children.

• They occur in clusters or trains, but also as single sharp transients, of mid- or anterior temporal 6–11 Hz negative sharp arciform waves with amplitude of up to 200 μV.

• Wicket waves can be differentiated from temporal lobe epileptiform discharges based on the following criteria:

• (1) no slow wave component following wicket spikes;• (2) occurring in• trains or in isolation and do not disrupt the background; • (3) having a similar morphology to the waveforms in the train when

occurs as a single spike.


• In this EEG, the age and abnormal background activity are strongly against the diagnosis of wicket waves but supportive of epileptiform activities.

• In adult, wicket waves are more common seen in patients with cerebrovascular disease


Reference: Atlas of pediatric EEG

Sleep activity in eeg

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