{"categories":[{"id":"normal","title":"Sleep and reactive rhythms","intro":"Normal transients of sleep, and a posterior rhythm that reacts.","entries":[{"id":"sleep_n1","kind":"pattern","title":"Drowsiness and N1 sleep: vertex sharp waves","text":["Vertex sharp waves are surface-negative transients of light sleep, maximal at Cz and symmetric, often with slow rolling eye movements as the posterior rhythm drops out. They can be sharp and high in voltage, especially in children, and are normal."],"look":["A negative phase reversal at Cz in the midline chain, and at Cz in the transverse chain","Slow lateral eye movements: mirror-image deflections at F7 and F8"],"notes":{"id":"normal-adult","title":"The normal adult EEG, awake and asleep"},"questions":[{"id":"bq-norm-04","sec":"The normal adult EEG, awake and asleep"},{"id":"bq-norm-40","sec":"Artifacts"}]},{"id":"sleep_n2_spindles","kind":"pattern","title":"N2 sleep: spindles and a K-complex","text":["Spindles are 11–16 Hz trains (here about 13 Hz) of waxing and waning activity over the central regions, symmetric and synchronous. A K-complex is a sharp negative wave followed by a slower positive one, lasting 0.5 s or more and maximal in front of the vertex; a spindle often rides on it."],"look":["Central spindles, the same on both sides","A frontally maximal K-complex, then a spindle","A single vertex wave"],"notes":{"id":"normal-adult","title":"The normal adult EEG, awake and asleep"},"questions":[{"id":"bq-norm-01","sec":"The normal adult EEG, awake and asleep"}]},{"id":"sleep_rem","kind":"pattern","title":"REM sleep","text":["REM sleep has a low-voltage, mixed-frequency background like drowsiness, with rapid eye movements and, often, runs of sawtooth waves at the vertex. There is no waking posterior rhythm, though alpha 1–2 Hz slower than in wakefulness can appear."],"look":["Rapid eye movements: sharp, mirror-image deflections at F7 and F8 at the same instant","Sawtooth waves: trains of triangular 2–6 Hz waves (here about 3 Hz), central and vertex most"],"notes":{"id":"normal-adult","title":"The normal adult EEG, awake and asleep"},"questions":[{"id":"bq-norm-02","sec":"The normal adult EEG, awake and asleep"}]},{"id":"icu_reactive_alpha","kind":"pattern","title":"A reactive posterior rhythm","text":["A 9 Hz posterior rhythm that blocks when the eyes are opened, here passively, and returns when they close is the EEG of a wakeful brain. In a patient who cannot move, as in locked-in syndrome from a basilar artery occlusion, a posterior rhythm that blocks with eye opening and reacts to sound strongly suggests preserved awareness rather than alpha coma, whose alpha-frequency activity is usually diffuse or frontal and unreactive."],"look":["Posterior 9 Hz rhythm with the eyes closed","It blocks within a fraction of a second of passive eye opening","The eye opening and closing show at Fp1 and Fp2"],"notes":{"id":"coma-prognosis","title":"Coma, cardiac arrest and prognosis"},"questions":[{"id":"bq-icu-37","sec":"Coma, cardiac arrest and prognosis"}]}]},{"id":"variants","title":"Normal variants","intro":"Patterns that can look abnormal or epileptiform but are not.","entries":[{"id":"variant_mu","kind":"pattern","title":"Mu rhythm","text":["An arch-shaped 7–11 Hz rhythm over the central regions, pointed on one side and rounded on the other, often independent on the two sides. It blocks when the opposite hand moves or is clenched, or even with the thought of moving it, and does not block with eye opening."],"look":["Arciform waves at C3 and C4","The left mu stops while the right fist is clenched; the right carries on"],"notes":{"id":"benign-variants","title":"Normal variants that look epileptiform"},"questions":[{"id":"bq-norm-08","sec":"Normal variants that look epileptiform"}]},{"id":"variant_wicket_spikes","kind":"pattern","title":"Wicket spikes","text":["Arch-shaped waves at 6–11 Hz over the temporal regions, in runs or singly, mostly in drowsiness and light sleep of adults over 30. A single wicket can look like a spike, but it has the shape and size of the waves of its run, no after-going slow wave and no disruption of the background."],"look":["A run at about 8 Hz at T7","A lone wicket with the same shape and size as the run's waves"],"notes":{"id":"benign-variants","title":"Normal variants that look epileptiform"},"questions":[{"id":"bq-norm-05","sec":"Normal variants that look epileptiform"}]},{"id":"variant_bets","kind":"pattern","title":"Benign epileptiform transients of sleep (small sharp spikes)","text":["Low-voltage (under 50 µV), very brief (under 50 ms) monophasic or diphasic spikes over the temporal regions in drowsiness and light sleep of adults, often independently on the two sides and sometimes synchronously, with little or no after-going slow wave. They do not disrupt the background and disappear in deeper sleep."],"look":["Tiny, brief spikes at T7 and T8, here never together","No slow wave and no change in the surrounding background"],"notes":{"id":"benign-variants","title":"Normal variants that look epileptiform"},"questions":[{"id":"bq-norm-06","sec":"Normal variants that look epileptiform"}]},{"id":"variant_rmtd","kind":"pattern","title":"Rhythmic mid-temporal theta of drowsiness","text":["Runs of 5–7 Hz theta over the mid-temporal region in drowsiness of adolescents and young adults, flat-topped and often notched by faster components (the former psychomotor variant). The rate, size and field stay the same from start to end: there is no evolution."],"look":["Notched, flat-topped 6 Hz waves at T7 for about 3 s","No change in rate or field"],"notes":{"id":"benign-variants","title":"Normal variants that look epileptiform"},"questions":[{"id":"bq-norm-07","sec":"Normal variants that look epileptiform"}]},{"id":"variant_posts","kind":"pattern","title":"Positive occipital sharp transients of sleep (POSTS)","text":["Surface-positive, often sharply contoured transients at the occipital electrodes in light sleep, singly or in trains, usually on both sides. Their positivity is the clue: in a bipolar chain they point the opposite way from a negative spike."],"look":["Trains at O1 and O2","Up in P7–O1 (O1 is input 2) and down in O1–Avg (O1 is input 1): positive"],"notes":{"id":"benign-variants","title":"Normal variants that look epileptiform"},"questions":[{"id":"bq-norm-10","sec":"Normal variants that look epileptiform"}]},{"id":"variant_lambda","kind":"pattern","title":"Lambda waves","text":["Positive occipital transients with the eyes open, each following a saccade during visual scanning, such as reading or looking at a picture. They resemble POSTS but occur in wakefulness and vanish in a dark room or with the eyes closed."],"look":["A small saccade at F7 and F8","A positive occipital transient about 100 ms later"],"notes":{"id":"benign-variants","title":"Normal variants that look epileptiform"},"questions":[{"id":"bq-norm-03","sec":"The normal adult EEG, awake and asleep"}]},{"id":"variant_breach","kind":"pattern","title":"Breach rhythm","text":["Over a skull defect, the normal rhythms arrive without the skull's attenuation and low-pass filtering, so they are higher in voltage, sharper and richer in beta on that side. It can look epileptiform; the activity is the same as on the other side, only larger and sharper, and nothing evolves. A breach does not exclude true spikes or seizures over the defect; those have a field or an after-going slow wave, or evolve."],"look":["Larger and sharper central and midtemporal activity on the right","The same rhythms, smaller, at C3 and T7"],"notes":{"id":"benign-variants","title":"Normal variants that look epileptiform"},"questions":[{"id":"bq-norm-09","sec":"Normal variants that look epileptiform"}]},{"id":"variant_phantom_sw","kind":"pattern","title":"6 Hz spike-and-wave (phantom spike-and-wave)","text":["Brief bursts of generalized spike-and-wave at 5–7 Hz in relaxed wakefulness and drowsiness, with a tiny spike and a more obvious slow wave. The posterior, low-voltage form seen in drowsiness (often female) is benign; the anterior, higher-voltage form seen in wakefulness (often male) is more often associated with seizures."],"look":["Bursts of about 1.5 s at 6 per second, largest at O1 and O2","A spike far smaller than the wave after it"],"notes":{"id":"benign-variants","title":"Normal variants that look epileptiform"},"questions":[{"id":"bq-norm-30","sec":"Normal variants that look epileptiform"}]},{"id":"variant_14_6","kind":"pattern","title":"14 and 6 Hz positive bursts","text":["Arch-shaped, comb-like bursts at 13–17 Hz and 5–7 Hz (most often 14 and 6 Hz), surface positive, maximal at the posterior temporal electrodes, in drowsiness and light sleep, most often in adolescents. They are a normal variant."],"look":["A 14 Hz burst positive at P8, then a 6 Hz burst positive at P7","Sharp crests pointing away from each other across P8: positivity"],"notes":{"id":"benign-variants","title":"Normal variants that look epileptiform"},"questions":[{"id":"bq-norm-31","sec":"Normal variants that look epileptiform"}]},{"id":"variant_midline_theta","kind":"pattern","title":"Midline theta (Ciganek) rhythm","text":["Runs of 4–7 Hz (here 6 Hz) sinusoidal or arch-shaped waves confined to the midline, largest at Cz, in wakefulness or drowsiness, waxing and waning without evolution. It is a nonspecific, nonepileptiform pattern."],"look":["Reversal at Cz in the midline and transverse chains","The same rate in every run, and nothing over the hemispheres"],"notes":{"id":"benign-variants","title":"Normal variants that look epileptiform"},"questions":[{"id":"bq-norm-34","sec":"Normal variants that look epileptiform"}]},{"id":"variant_temporal_elderly","kind":"pattern","title":"Temporal slowing of the elderly","text":["Brief bursts of theta, with an occasional delta wave, over one or both temporal regions, most often the left, accentuated in drowsiness in healthy older adults. When it is brief and intermittent, has no sharp components and leaves the background intact, it is usually not abnormal."],"look":["Bursts of 1–2 s of 4–6 Hz theta at F7 and T7","Nothing sharp, and nothing between the bursts"],"notes":{"id":"benign-variants","title":"Normal variants that look epileptiform"},"questions":[{"id":"bq-norm-36","sec":"Normal variants that look epileptiform"}]}]},{"id":"artifacts","title":"Artifacts","intro":"Potentials from the eyes, muscles, the heart, the electrodes and the room.","entries":[{"id":"artifact_eye_blink","kind":"pattern","title":"Eye blinks","text":["With a blink the eyes roll up (Bell's phenomenon), bringing the positive cornea toward Fp1 and Fp2, which go positive together. The field falls off steeply, so it is nearly gone one electrode back."],"look":["Downward deflections in Fp1–F3 and Fp2–F4 (Fp is input 1 and positive)","Much smaller in F3–C3"],"notes":{"id":"artifacts","title":"Artifacts"},"questions":[]},{"id":"artifact_lateral_eye","kind":"pattern","title":"Lateral eye movements","text":["Looking to one side brings the positive cornea toward F7 or F8 and the negative retina toward the other, so the two sides deflect in opposite directions at the same instant. A brief burst of lateral rectus muscle potentials can mark the start."],"look":["Look left: reversal at F7, and the mirror image at F8","A tiny burst of muscle spikes at the start of a look"],"notes":{"id":"artifacts","title":"Artifacts"},"questions":[{"id":"bq-norm-13","sec":"Artifacts"}]},{"id":"artifact_eyelid_flutter","kind":"pattern","title":"Eyelid flutter","text":["Rhythmic waves, usually in the theta range (here about 5 Hz), at Fp1 and Fp2, symmetric and in phase, much smaller at F3 and F4 and absent farther back, with an unchanging rate and field. Electrodes below the eyes settle it: they record eye and eyelid potentials in opposite phase to the electrodes above, whereas a cerebral rhythm is in the same phase."],"look":["About 5 Hz at Fp1 and Fp2, in phase","Small at F3, F4, F7 and F8; nothing behind"],"notes":{"id":"artifacts","title":"Artifacts"},"questions":[{"id":"bq-norm-41","sec":"Artifacts"}]},{"id":"artifact_mains","kind":"pattern","title":"Mains interference (60 Hz)","text":["A poorly attached electrode picks up the 60 Hz of the power line (50 Hz in many countries). It appears in the two channels that share that electrode, in opposite phase, and a notch filter hides it without fixing the cause."],"look":["A dense 60 Hz band in F7–T7 and T7–P7","Mirror images in the two chains through T7"],"notes":{"id":"artifacts","title":"Artifacts"},"questions":[]},{"id":"artifact_electrode_pop","kind":"pattern","title":"Electrode pop","text":["A sudden change in one electrode's contact potential: a near-vertical jump and a slow return, at one electrode only. Because it has no field, only the two channels that share that electrode show it, equal and opposite."],"look":["Steps at T8 alone, in F8–T8 and T8–P8","No spread to neighboring electrodes"],"notes":{"id":"artifacts","title":"Artifacts"},"questions":[{"id":"bq-norm-12","sec":"Artifacts"}]},{"id":"artifact_chewing","kind":"pattern","title":"Chewing","text":["Bursts of muscle potentials from temporalis and masseter with each bite, about once a second, on both sides at once over the temporal electrodes. Muscle has no cerebral field: each electrode has its own interference pattern."],"look":["Bursts in the temporal chains with each bite","The midline chain spared"],"notes":{"id":"artifacts","title":"Artifacts"},"questions":[{"id":"bq-norm-37","sec":"Artifacts"}]},{"id":"artifact_glossokinetic","kind":"pattern","title":"Glossokinetic artifact","text":["The tongue is a dipole, its tip negative. As it moves, as in speaking, sucking or chewing, broad delta appears over the frontal and temporal electrodes, the same on both sides and in step. It can mimic frontal rhythmic delta, so video and a test (asking the patient to say \"la la la\") help."],"look":["Smooth, irregular delta, most at F7, F8, Fp1 and Fp2","Both sides identical, the background unchanged"],"notes":{"id":"artifacts","title":"Artifacts"},"questions":[{"id":"bq-norm-38","sec":"Artifacts"}]},{"id":"artifact_sweat","kind":"pattern","title":"Sweat artifact","text":["Very slow sways, under 0.5 Hz, where sweat changes the skin potential under the frontal and temporal electrodes. Each electrode drifts on its own, so there is no field, and drier posterior electrodes are often spared. Cooling the room and drying the scalp fix it."],"look":["Slow sways at the frontal and temporal electrodes, out of step","Normal background riding on them"],"notes":{"id":"artifacts","title":"Artifacts"},"questions":[{"id":"bq-norm-39","sec":"Artifacts"}]},{"id":"artifact_salt_bridge","kind":"pattern","title":"Salt bridge","text":["Two electrodes joined by a film of paste or sweat behave as one: the channel between them is nearly flat for every frequency, and in a referential montage they show the same waveform. A very low impedance is the technical clue. Cleaning the skin between them and reapplying fixes it."],"look":["P7–O1 nearly flat while its neighbors carry the posterior rhythm","P7 and O1 identical in the average reference"],"notes":{"id":"eeg-technique","title":"Recording technique"},"questions":[{"id":"bq-mech-26","sec":"Recording technique"}]},{"id":"artifact_pulse","kind":"pattern","title":"Pulse artifact","text":["An electrode over a pulsating scalp artery moves with each pulse and produces a rounded or sawtooth slow wave at that one electrode. It follows each QRS by a fixed delay, roughly the time the pulse wave takes to reach the scalp, and its rate follows the heart rate. ECG artifact, by contrast, is sharp, coincides with the QRS and appears in many channels."],"look":["Waves at F7 alone, mirror images in Fp1–F7 and F7–T7","Each wave about 200 ms after a QRS, at 75 per minute"],"notes":{"id":"artifacts","title":"Artifacts"},"questions":[{"id":"bq-norm-14","sec":"Artifacts"}]}]},{"id":"interictal","title":"Slowing and interictal epileptiform activity","intro":"Focal slowing, rhythmic delta with a temporal maximum, spikes and their fields, and a photoparoxysmal response.","entries":[{"id":"pathology_focal_slowing","kind":"pattern","title":"Focal polymorphic delta","text":["Continuous, irregular delta of several rates over one region that persists with alerting strongly suggests a structural lesion (it can also be transient, as after a seizure or migraine). It is generated by cortex that has lost its subcortical input, so it is most marked over lesions that involve the underlying white matter."],"look":["Irregular 1–3 Hz delta maximal at T7, reversing there","A posterior rhythm on both sides and no generalized slowing"],"notes":{"id":"ieds","title":"Interictal epileptiform discharges"},"questions":[{"id":"bq-mech-05","sec":"How seizures start and stop"},{"id":"bq-epi-03","sec":"Interictal epileptiform discharges"},{"id":"bq-epi-25","sec":"Seizures on the EEG"}]},{"id":"ied_tirda","kind":"pattern","title":"Temporal intermittent rhythmic delta activity (TIRDA)","text":["Trains of regular, sinusoidal 1–3.5 Hz delta over one anterior temporal region, in drowsiness and light sleep, with a normal background. Far more specific for temporal lobe epilepsy than polymorphic slowing, it carries about the same weight as temporal spikes; in American Clinical Neurophysiology Society (ACNS) terms it is lateralized rhythmic delta activity with a temporal maximum."],"look":["Trains of 2.6 Hz delta at F7 and T7","No spikes, no evolution, nothing on the right"],"notes":{"id":"ieds","title":"Interictal epileptiform discharges"},"questions":[{"id":"bq-epi-21","sec":"Interictal epileptiform discharges"}]},{"id":"ied_centrotemporal_dipole","kind":"pattern","title":"Centrotemporal spikes and their tangential dipole","text":["The spikes of self-limited epilepsy with centrotemporal spikes are high-voltage, diphasic and activated by sleep. Their generator in the lower rolandic cortex is oriented tangentially, so the negative end lies over C3 and T7 (where C5 would be) and the positive end over the frontal region at the same instant: one dipole, not two foci."],"look":["Negative phase reversals at C3 and at T7","Average reference: up at T7 and C3, down at Fp1 and Fz at the same moment"],"notes":{"id":"eeg-generators","title":"What the scalp can see"},"questions":[{"id":"bq-mech-08","sec":"What the scalp can see"}]},{"id":"ied_occipital_fos","kind":"pattern","title":"Occipital spikes with fixation-off sensitivity","text":["High-voltage occipital spikes that appear when central vision and fixation are removed, as with eye closure, and disappear with fixation. Fixation-off sensitivity is typical of childhood occipital visual epilepsy and also occurs in other occipital epilepsies."],"look":["No spikes with the eyes open","Frequent right occipital spikes after the eyes close, maximal at O2"],"notes":{"id":"syndromes-childhood","title":"Childhood onset"},"questions":[{"id":"bq-syn-12","sec":"Childhood onset"}]},{"id":"ied_ppr_polyspike","kind":"pattern","title":"Generalized photoparoxysmal response","text":["Intermittent photic stimulation provokes irregular generalized spike- or polyspike-and-wave, often at 3–5 Hz or faster (here 4–5 Hz), frontocentral most. A generalized response is strongly associated with idiopathic generalized epilepsies such as juvenile myoclonic epilepsy, though it is also seen in a small minority of people without epilepsy and in some developmental and epileptic encephalopathies and progressive myoclonus epilepsies. It is distinct from normal occipital photic driving."],"look":["Photic driving at the flash rate over the occipital electrodes","A 2-s run of generalized complexes at 4–5 Hz, each one to three spikes then a slow wave, during the flashes"],"notes":{"id":"activation","title":"Activation procedures"},"questions":[{"id":"bq-dx-08","sec":"Classifying the epilepsy (ILAE 2017)"}]},{"id":"ied_slow_sw","kind":"pattern","title":"Slow spike-and-wave (Lennox–Gastaut syndrome)","text":["Generalized sharp waves followed by slow waves at under 2.5 Hz, usually 1.5–2.5 Hz, frontally predominant, often near-continuous and irregular, with shifting asymmetry. In the ILAE 2022 criteria it (or a history of it) is one of the two mandatory EEG features of Lennox–Gastaut syndrome; the other is generalized paroxysmal fast activity in sleep."],"look":["Complexes at about 2 per second, frontal most","Irregular rate and size, the sides trading prominence"],"notes":{"id":"syndromes-childhood","title":"Childhood onset"},"questions":[{"id":"bq-icu-30","sec":"The ictal–interictal continuum and seizure risk"}]}]},{"id":"seizures","title":"Seizures","intro":"Ictal patterns: abrupt, evolving, brief with a clinical sign, and tonic.","entries":[{"id":"ictal_absence_3hz","kind":"pattern","title":"Typical absence seizure","text":["Generalized 3 Hz spike-and-wave that starts and stops abruptly, often a little faster at the start (3–4 Hz) and slower at the end, frontocentral most, on a normal background. Hyperventilation provokes it in most untreated children."],"look":["Abrupt onset and offset","Spike, small positive transient, slow wave, about 3 per second"],"notes":{"id":"generalized-eeg","title":"Generalized patterns and what they predict"},"questions":[{"id":"bq-epi-11","sec":"Generalized patterns and what they predict"},{"id":"bq-epi-32","sec":"Generalized patterns and what they predict"}]},{"id":"ictal_temporal_seizure","kind":"pattern","title":"Temporal lobe seizure","text":["A focal seizure that evolves: rhythmic theta appears at the temporal electrode, then slows, grows and sharpens while its field spreads. Rhythmic activity that evolves (sequential changes in frequency, morphology or location; a change in amplitude alone does not count) for at least 10 s is an electrographic seizure."],"look":["Onset: low rhythmic theta at T7","Later: slower, larger, sharper, spreading to Fp1, P7 and C3"],"notes":{"id":"ictal-scalp","title":"Seizures on the EEG"},"questions":[{"id":"bq-epi-06","sec":"Seizures on the EEG"}]},{"id":"ictal_frontal_brief","kind":"pattern","title":"Brief electroclinical seizure","text":["A run of rhythmic activity under 10 s is not an electrographic seizure by duration, but The American Clinical Neurophysiology Society (ACNS) 2021 terminology calls any pattern with a definite, time-locked clinical correlate an electroclinical seizure, whatever its length. Here the single 7-s run comes with right mouth-corner twitching that starts and stops with it. A pattern with EEG and clinical improvement after an intravenous antiseizure medication also counts."],"look":["About 6 Hz at F3 and C3, slowing to about 5 Hz and reaching Cz","Twitching that starts and stops with the run"],"notes":{"id":"ictal-scalp","title":"Seizures on the EEG"},"questions":[{"id":"bq-epi-09","sec":"Seizures on the EEG"}]},{"id":"ictal_tonic_lgs","kind":"pattern","title":"Tonic seizure","text":["A generalized decrement, then generalized paroxysmal fast activity at about 10–25 Hz that builds up, frontal and vertex most, often after a generalized slow wave. Tonic seizures are most frequent in sleep, and in Lennox–Gastaut syndrome intravenous benzodiazepines have occasionally been reported to bring them out."],"look":["Abrupt flattening of all channels","Fast activity at 14 then 12 Hz, growing, on both sides"],"notes":{"id":"syndromes-childhood","title":"Childhood onset"},"questions":[{"id":"bq-syn-29","sec":"Childhood onset"}]},{"id":"ied_ring20_delta","kind":"pattern","title":"Nonconvulsive status in ring chromosome 20 syndrome","text":["Long runs of bilateral, frontally predominant, high-voltage rhythmic delta with intermixed spikes during prolonged confusional states. With drug-resistant frontal seizures from sleep, it points to ring chromosome 20, found on a karyotype that examines many cells because of mosaicism."],"look":["Rhythmic delta at about 2.4 Hz over both frontal regions","Spikes riding on the delta"],"notes":{"id":"genetics","title":"Genetic testing and precision treatment"},"questions":[{"id":"bq-cause-24","sec":"Genetic testing and precision treatment"}]}]},{"id":"icu","title":"Critical care EEG (ACNS 2021)","intro":"Periodic and rhythmic patterns, the ictal–interictal continuum and patterns by cause.","entries":[{"id":"icu_lpds","kind":"pattern","title":"Lateralized periodic discharges (LPDs)","text":["Lateralized discharges (over one hemisphere, or both but clearly asymmetric) that recur at nearly regular intervals, here about once a second, with a clearly discernible interval between them. They usually reflect acute or subacute structural injury, but also occur with chronic lesions, infection or metabolic stress on an old lesion, and carry a high risk of seizures, more so at faster rates and with plus features."],"look":["Sharp discharges over C3 and T7 about once a second","Nothing on the right, and a lower left background"],"notes":{"id":"acns-terminology","title":"ACNS 2021 terminology"},"questions":[{"id":"bq-icu-01","sec":"ACNS 2021 terminology"},{"id":"bq-icu-07","sec":"The ictal–interictal continuum and seizure risk"},{"id":"bq-icu-38","sec":"Periodic patterns by cause"}]},{"id":"icu_uipds","kind":"pattern","title":"Unilateral independent periodic discharges (UIPDs)","text":["Two populations of periodic discharges in the same hemisphere, running at the same time and independent of each other: no fixed time relationship (often, as here, at different rates). ACNS 2021 added this main term."],"look":["Left frontal discharges about once a second","Left occipital discharges about once every 2 s, at varying delays"],"notes":{"id":"acns-terminology","title":"ACNS 2021 terminology"},"questions":[{"id":"bq-icu-24","sec":"ACNS 2021 terminology"}]},{"id":"icu_bipds","kind":"pattern","title":"Bilateral independent periodic discharges (BIPDs)","text":["Two independent, simultaneous populations of periodic discharges, one over each hemisphere. They usually mean acute bilateral injury (stroke, infection, anoxia) and carry a seizure risk similar to LPDs."],"look":["Left temporal discharges about once a second","Right parietal discharges about once every 2 s, unlinked"],"notes":{"id":"periodic-by-cause","title":"Periodic patterns by cause"},"questions":[{"id":"bq-icu-40","sec":"Periodic patterns by cause"}]},{"id":"pathology_gpds_triphasic","kind":"pattern","title":"Generalized periodic discharges (GPDs) with triphasic morphology","text":["Generalized periodic discharges with three phases, the second (positive) phase the largest and each phase longer than the one before, frontally predominant and often a little later at the back. Common in toxic-metabolic encephalopathy, they are not specific: ACNS 2021 describes them as GPDs with triphasic morphology, and seizure risk depends on rate and plus features."],"look":["About 1 per second, frontal most","Negative, then a larger positive, then a broader negative phase"],"notes":{"id":"acns-terminology","title":"ACNS 2021 terminology"},"questions":[{"id":"bq-icu-06","sec":"ACNS 2021 terminology"},{"id":"bq-icu-17","sec":"Periodic patterns by cause"}]},{"id":"icu_gpds_2hz","kind":"pattern","title":"Generalized periodic discharges at 2 Hz","text":["Generalized periodic discharges averaging more than 1 and up to 2.5 Hz fall on the ictal–interictal continuum. Without evolution and without averaging over 2.5 Hz for 10 s, they are not an electrographic seizure (nor an electroclinical one, absent a time-locked clinical sign or improvement with intravenous medication)."],"look":["20 discharges in 10 s, generalized and symmetric","No change in rate, shape or field"],"notes":{"id":"iic-and-birds","title":"The ictal–interictal continuum and seizure risk"},"questions":[{"id":"bq-icu-10","sec":"The ictal–interictal continuum and seizure risk"}]},{"id":"icu_gpds_fast","kind":"pattern","title":"Generalized periodic discharges over 2.5 Hz: an electrographic seizure","text":["Epileptiform discharges averaging more than 2.5 Hz for at least 10 s meet the ACNS 2021 definition of an electrographic seizure, however stereotyped they look."],"look":["27 discharges in 10 s","Generalized, frontally predominant, unchanging"],"notes":{"id":"acns-terminology","title":"ACNS 2021 terminology"},"questions":[{"id":"bq-icu-41","sec":"Periodic patterns by cause"}]},{"id":"icu_gpds_drug_beta","kind":"pattern","title":"Generalized periodic discharges without a plus modifier","text":["+F is coded only when the fast activity belongs to the pattern: with each discharge, or absent whenever the discharges are absent. Diffuse beta from a sedative that continues unchanged when the discharges stop is part of the background, so these are GPDs without +F."],"look":["GPDs at 1.5 Hz until about 6 s","The same 16–20 Hz beta before and after they stop"],"notes":{"id":"acns-terminology","title":"ACNS 2021 terminology"},"questions":[{"id":"bq-icu-23","sec":"ACNS 2021 terminology"}]},{"id":"icu_grda","kind":"pattern","title":"Generalized rhythmic delta activity (GRDA), frontally predominant","text":["Runs of rhythmic delta at about 2 Hz, bilateral, synchronous and symmetric, frontally predominant, with the same rate and size throughout. It is common in encephalopathy and is not by itself associated with seizures."],"look":["Two runs of 2 Hz delta, the same on both sides","Largest frontally, falling off toward the back"],"notes":{"id":"acns-terminology","title":"ACNS 2021 terminology"},"questions":[{"id":"bq-icu-08","sec":"The ictal–interictal continuum and seizure risk"}]},{"id":"icu_lrda","kind":"pattern","title":"Lateralized rhythmic delta activity (LRDA)","text":["Runs of rhythmic delta over one hemisphere, here the left temporal region at about 1.75 Hz, smooth and unchanging. LRDA carries a seizure risk similar to LPDs."],"look":["Smooth delta maximal at T7, reversing there","No sharp waves riding on it, nothing on the right"],"notes":{"id":"acns-terminology","title":"ACNS 2021 terminology"},"questions":[{"id":"bq-icu-28","sec":"The ictal–interictal continuum and seizure risk"}]},{"id":"icu_birds","kind":"pattern","title":"Brief potentially ictal rhythmic discharges (BIRDs)","text":["Focal or generalized rhythmic activity faster than 4 Hz, at least 6 waves, lasting 0.5 to under 10 s, without a definite clinical correlate, that is not a normal variant or part of burst-suppression or burst-attenuation. BIRDs are definite if they evolve or match the patient's discharges or seizures, and possible if they are only sharply contoured. These runs, sharply contoured but not evolving, are possible BIRDs."],"look":["Runs of sharply contoured 6–7 Hz at T8, each under 2 s","Abrupt on and off, no evolution"],"notes":{"id":"iic-and-birds","title":"The ictal–interictal continuum and seizure risk"},"questions":[{"id":"bq-icu-29","sec":"The ictal–interictal continuum and seizure risk"}]},{"id":"icu_birds_evolving","kind":"pattern","title":"Evolving brief potentially ictal rhythmic discharges (BIRDs)","text":["A run under 10 s that evolves, here slowing from about 7 Hz through 6 to 5 Hz before stopping abruptly, is a definite BIRD. Definite BIRDs carry a high risk of electrographic seizures."],"look":["Right frontal run at F8 and F4, about 5 s long","Rate falling from about 7 to about 5 Hz; sharp waves before and after"],"notes":{"id":"iic-and-birds","title":"The ictal–interictal continuum and seizure risk"},"questions":[{"id":"bq-icu-09","sec":"The ictal–interictal continuum and seizure risk"}]},{"id":"icu_extreme_delta_brush","kind":"pattern","title":"Extreme delta brush","text":["Near-continuous generalized rhythmic delta with a burst of 20–30 Hz beta riding on each delta wave, described in anti-NMDA receptor encephalitis. In ACNS 2021 it is rhythmic delta with superimposed fast activity (+F), not considered ictal by itself, and it typically persists despite escalating antiseizure drugs."],"look":["Rhythmic delta at about 1.5 Hz, frontal most","A burst of 20–25 Hz on every delta wave"],"notes":{"id":"periodic-by-cause","title":"Periodic patterns by cause"},"questions":[{"id":"bq-icu-18","sec":"Periodic patterns by cause"}]},{"id":"icu_sspe","kind":"pattern","title":"Periodic complexes of subacute sclerosing panencephalitis","text":["High-voltage, stereotyped, generalized complexes of sharp and slow waves recurring every several seconds, each time-locked to a myoclonic jerk or head drop, on a slow background. Raised measles antibody in the cerebrospinal fluid confirms subacute sclerosing panencephalitis."],"look":["A complex about 1.5 s long, repeated 6 s later","The same on both sides, largest in the parasagittal and midline chains; only slow background between complexes"],"notes":{"id":"periodic-by-cause","title":"Periodic patterns by cause"},"questions":[{"id":"bq-icu-19","sec":"Periodic patterns by cause"}]}]},{"id":"coma","title":"Coma and prognosis","intro":"Background patterns that carry prognostic weight, most of them after cardiac arrest.","entries":[{"id":"icu_burst_suppression","kind":"pattern","title":"Burst-suppression","text":["Bursts of mixed high-voltage activity alternating with suppression under 10 µV that fills more than half of the record. It may be induced by anesthetics; after cardiac arrest, off sedation and beyond about 24 hours, it is highly malignant, while early, nonidentical bursts are less specific."],"look":["Generalized bursts with sharp components","Suppression under 10 µV between them"],"notes":{"id":"coma-prognosis","title":"Coma, cardiac arrest and prognosis"},"questions":[{"id":"bq-icu-12","sec":"Coma, cardiac arrest and prognosis"}]},{"id":"icu_bs_identical","kind":"pattern","title":"Burst-suppression with identical bursts","text":["When the first half second or more of each burst looks the same in each channel in more than 90% of bursts, the bursts are identical. After cardiac arrest this signals severe anoxic injury and is strongly associated with a poor outcome; in the original series it was never seen in anesthesia-induced burst-suppression."],"look":["The same sharp transient and slow wave starting every burst","Under 10 µV between bursts"],"notes":{"id":"coma-prognosis","title":"Coma, cardiac arrest and prognosis"},"questions":[{"id":"bq-icu-13","sec":"Coma, cardiac arrest and prognosis"}]},{"id":"icu_gpds_suppressed","kind":"pattern","title":"Generalized periodic discharges on a suppressed background","text":["Generalized periodic discharges with nothing above 10 µV between them. Each lasts under 0.5 s, which alone makes it a discharge; a burst lasts 0.5 s or more and has at least four phases. After cardiac arrest a suppressed background with or without periodic discharges is highly malignant."],"look":["Three-phase discharges of about 250 ms every 1.5–2 s","Under 10 µV between them"],"notes":{"id":"acns-terminology","title":"ACNS 2021 terminology"},"questions":[{"id":"bq-icu-25","sec":"ACNS 2021 terminology"}]},{"id":"icu_low_voltage","kind":"pattern","title":"Low-voltage, unreactive background","text":["\"Low\" means most or all activity under 20 µV; \"suppressed\" means all under 10 µV. A continuous background at 12–18 µV is low, not suppressed. After cardiac arrest a low-voltage background and an unreactive background are each malignant features, though not highly malignant ones."],"look":["Delta and theta at 12–18 µV, compare the 50 µV bar","No change with a sternal rub or a loud voice"],"notes":{"id":"coma-prognosis","title":"Coma, cardiac arrest and prognosis"},"questions":[{"id":"bq-icu-15","sec":"Coma, cardiac arrest and prognosis"}]},{"id":"icu_beta_coma","kind":"pattern","title":"Beta coma","text":["Diffuse beta, frontal and central most, mixed with some theta and without a posterior rhythm, in a comatose patient. It is the typical EEG of sedative-hypnotic intoxication (barbiturates, benzodiazepines) and, without hypoxic injury, is usually reversible."],"look":["Continuous 15–20 Hz at 20–40 µV, frontal more than occipital","Slower and lower briefly after a sternal rub"],"notes":{"id":"coma-prognosis","title":"Coma, cardiac arrest and prognosis"},"questions":[{"id":"bq-icu-14","sec":"Coma, cardiac arrest and prognosis"}]},{"id":"icu_spindle_coma","kind":"pattern","title":"Spindle coma","text":["Sleep-like spindles, vertex waves and K-complexes on a slow background in a comatose patient: the sleep-generating circuits still work. Its meaning depends on cause and reactivity; with trauma and a reactive EEG the outlook is often good."],"look":["Diffuse 1–3 Hz delta","Central spindles, a K-complex and vertex waves, the same on both sides"],"notes":{"id":"coma-prognosis","title":"Coma, cardiac arrest and prognosis"},"questions":[{"id":"bq-icu-35","sec":"Coma, cardiac arrest and prognosis"}]},{"id":"icu_myoclonus_vertex","kind":"pattern","title":"Postanoxic myoclonus with vertex spike-and-wave","text":["After cardiac arrest, myoclonus with a continuous, reactive background and narrow vertex-maximal spike-and-wave discharges time-locked to the jerks is the phenotype with a chance of good recovery. Burst-suppression with high-voltage polyspikes in lockstep with the jerks carries a poor outcome."],"look":["A continuous 4–6 Hz background","A narrow spike-and-wave at Cz with each marked jerk"],"notes":{"id":"coma-prognosis","title":"Coma, cardiac arrest and prognosis"},"questions":[{"id":"bq-icu-16","sec":"Coma, cardiac arrest and prognosis"}]}]},{"id":"syndromes","title":"Epilepsy syndromes (ILAE 2022)","intro":"Published EEG figures from the ILAE 2022 syndrome papers, reproduced under CC BY 4.0.","entries":[{"id":"self-limited-neonatal-epilepsy","kind":"figure","title":"Self-Limited Neonatal Epilepsy (SeLNE)","text":["Interictal EEG background may be normal or show minor nonspecific abnormalities. Focal interictal epileptiform discharges are seen in approximately two thirds of cases, most commonly in centrotemporal or frontotemporal regions. A typical ictal pattern shows initial EEG attenuation lasting up to 20 seconds, followed by repetitive spike discharges (mainly centrotemporal) that are often bilateral but asynchronous with shifting laterality. The topography can change from one seizure to the next."],"look":[],"caption":"Ictal EEG in a neonate with KCNQ2-related self-limited neonatal epilepsy.","figure":{"src":"assets/images/ilae-eeg/self-limited-neonatal-epilepsy.jpg","width":2751,"height":1843,"credit":"Zuberi SM et al. Epilepsia. 2022;63:1349–1397. Figure 2. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17239"},"ilae":"ilae_classification.html#syndrome-0","notes":{"id":"neonatal-seizures","title":"Neonatal seizures"},"questions":[{"id":"bq-epi-35","sec":"Neonatal seizures"}]},{"id":"self-limited-infantile-epilepsy","kind":"figure","title":"Self-Limited (Familial) Infantile Epilepsy (SeLIE)","text":["Background EEG is normal. Focal slowing may occur postictally. The interictal EEG is typically normal, but a variant with midline spikes during slow wave sleep has been described. Ictal EEG shows focal onset with rhythmic theta or delta activity arising most commonly from the temporal or parietal regions."],"look":[],"caption":"Successive ictal EEG pages in an infant with self-limited infantile epilepsy.","figure":{"src":"assets/images/ilae-eeg/self-limited-infantile-epilepsy.jpg","width":1198,"height":1400,"credit":"Zuberi SM et al. Epilepsia. 2022;63:1349–1397. Figure 3. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17239"},"ilae":"ilae_classification.html#syndrome-2","notes":{"id":"ictal-scalp","title":"Seizures on the EEG"},"questions":[{"id":"bq-epi-27","sec":"Seizures on the EEG"}]},{"id":"myoclonic-epilepsy-infancy","kind":"figure","title":"Myoclonic Epilepsy in Infancy (MEI)","text":["Interictal EEG may be normal or show mild generalized spike-wave or polyspike-wave discharges. Ictal EEG demonstrates a brief burst of generalized spike-wave or polyspike-wave discharge coinciding with the myoclonic jerks. Ictal video-EEG is strongly recommended if the interictal sleep EEG does not show generalized spike-wave, to establish that the jerks are epileptic; it is not mandatory in every case. EMG can help characterize the movement."],"look":[],"caption":"Generalized spike-wave and synchronized EMG myoclonic jerk in myoclonic epilepsy in infancy.","figure":{"src":"assets/images/ilae-eeg/myoclonic-epilepsy-infancy.jpg","width":2655,"height":1832,"credit":"Zuberi SM et al. Epilepsia. 2022;63:1349–1397. Figure 4. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17239"},"ilae":"ilae_classification.html#syndrome-3","notes":{"id":"syndromes-infancy","title":"Neonatal and infantile onset"},"questions":[{"id":"bq-syn-05","sec":"Neonatal and infantile onset"}]},{"id":"infantile-epileptic-spasms","kind":"figure","title":"Infantile Epileptic Spasms Syndrome (IESS)","text":["Interictal EEG may show hypsarrhythmia, but focal or multifocal epileptiform discharges can also meet syndrome criteria. If hypsarrhythmia is absent, capturing the suspected spasms on EEG is important for confirmation. Ictal EEG often shows a high-amplitude slow transient followed by diffuse or regional electrodecrement, but ictal morphology varies."],"look":[],"caption":"Interictal hypsarrhythmia and an ictal spasm with a relative decrement.","figure":{"src":"assets/images/ilae-eeg/infantile-epileptic-spasms.jpg","width":1135,"height":1200,"credit":"Zuberi SM et al. Epilepsia. 2022;63:1349–1397. Figure 7. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17239"},"ilae":"ilae_classification.html#syndrome-4","notes":{"id":"syndromes-infancy","title":"Neonatal and infantile onset"},"questions":[{"id":"bq-syn-03","sec":"Neonatal and infantile onset"}]},{"id":"early-infantile-dee","kind":"figure","title":"Early Infantile DEE (EIDEE)","text":["The background is abnormal in waking and sleep. Either burst suppression or multifocal epileptiform discharges with diffuse slowing can meet the EEG criterion; burst suppression is not required in every infant. When present, high-voltage bursts alternate with marked attenuation. The EEG may change as the syndrome evolves, including evolution to infantile epileptic spasms syndrome."],"look":[],"caption":"Burst-suppression EEG in a neonate with early infantile DEE.","figure":{"src":"assets/images/ilae-eeg/early-infantile-dee.jpg","width":2281,"height":1400,"credit":"Zuberi SM et al. Epilepsia. 2022;63:1349–1397. Figure 5. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17239"},"ilae":"ilae_classification.html#syndrome-5","notes":{"id":"syndromes-infancy","title":"Neonatal and infantile onset"},"questions":[{"id":"bq-syn-02","sec":"Neonatal and infantile onset"}]},{"id":"migrating-focal-seizures-infancy","kind":"figure","title":"Epilepsy of Infancy with Migrating Focal Seizures (EIMFS)","text":["Interictal EEG shows a progressively deteriorating background with multifocal epileptiform discharges. The defining ictal feature is focal seizures that shift (migrate) from one cortical region or hemisphere to another during the same recording. Individual seizure onsets begin independently in different regions, with one seizure ending and another starting in a distant region, sometimes overlapping."],"look":[],"caption":"Successive EEG pages showing a focal seizure migrating between cortical regions in infancy.","figure":{"src":"assets/images/ilae-eeg/migrating-focal-seizures-infancy.jpg","width":915,"height":1600,"credit":"Zuberi SM et al. Epilepsia. 2022;63:1349–1397. Figure 6. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17239"},"ilae":"ilae_classification.html#syndrome-6","notes":{"id":"ictal-scalp","title":"Seizures on the EEG"},"questions":[{"id":"bq-epi-28","sec":"Seizures on the EEG"}]},{"id":"sturge-weber-syndrome","kind":"figure","title":"Sturge-Weber Syndrome (SWS)","text":["EEG characteristically shows asymmetric reduction in background voltage and focal slowing over the affected hemisphere. During the first year of life, the background may initially be normal. Interictal epileptiform discharges appear later as focal spikes or spike-wave bursts. Ictal activity varies depending on the seizure focus."],"look":[],"caption":"Hemispheric EEG suppression and left posterior electrographic seizures in Sturge–Weber syndrome.","figure":{"src":"assets/images/ilae-eeg/sturge-weber-syndrome.png","width":1215,"height":1600,"credit":"Zuberi SM et al. Epilepsia. 2022;63:1349–1397. Figure 9. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17239"},"ilae":"ilae_classification.html#syndrome-15","notes":{"id":"structural-causes","title":"Structural causes"},"questions":[{"id":"bq-cause-09","sec":"Structural causes"}]},{"id":"centrotemporal-spikes","kind":"figure","title":"Self-Limited Epilepsy with Centrotemporal Spikes (SeLECTS)","text":["Interictal EEG shows high-amplitude centrotemporal sharp-and-slow wave complexes (diphasic or triphasic morphology) on a normal background. Discharges are markedly enhanced during drowsiness and sleep and may become bilateral or shift sides. The classic 'centrotemporal spike' has a characteristic horizontal dipole. Ictal EEG shows focal rhythmic theta or delta activity in the centrotemporal region."],"look":[],"caption":"Interictal and peri-ictal EEG in self-limited epilepsy with centrotemporal spikes.","figure":{"src":"assets/images/ilae-eeg/centrotemporal-spikes.jpg","width":1063,"height":1600,"credit":"Specchio N et al. Epilepsia. 2022;63:1398–1442. Figure 2. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17241"},"ilae":"ilae_classification.html#syndrome-17","notes":{"id":"syndromes-childhood","title":"Childhood onset"},"questions":[{"id":"bq-syn-08","sec":"Childhood onset"}]},{"id":"childhood-absence","kind":"figure","title":"Childhood Absence Epilepsy (CAE)","text":["Typical absences have regular generalized spike-wave, usually 3 Hz (range 2.5-4 Hz), on a normal background. Hyperventilation is an important activation procedure. Sleep deprivation, drowsiness, and sleep enhance epileptiform discharges; sleep often fragments generalized spike-wave so it can look focal or multifocal. Consistent abnormalities in the same focal region warrant evaluation for another cause. Test responsiveness during a discharge to establish its clinical effect; duration alone does not establish an absence seizure."],"look":[],"caption":"Typical absence seizure with generalized spike-wave in childhood absence epilepsy.","figure":{"src":"assets/images/ilae-eeg/childhood-absence.jpg","width":2486,"height":1230,"credit":"Hirsch E et al. Epilepsia. 2022;63:1475–1499. Figure 2. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17236"},"ilae":"ilae_classification.html#syndrome-21","notes":{"id":"generalized-eeg","title":"Generalized patterns and what they predict"},"questions":[{"id":"bq-epi-30","sec":"Generalized patterns and what they predict"}]},{"id":"eyelid-myoclonia","kind":"figure","title":"Epilepsy with Eyelid Myoclonia (EEM)","text":["Eye closure in a well-lit room and intermittent photic stimulation elicit brief (1-6 seconds) generalized polyspikes or polyspike-and-wave complexes at 3-6 Hz on a normal background. The discharges are time-locked to eyelid myoclonia. Eye closure is the most consistent trigger. Self-induction through voluntary eye closure with upturned gaze may be seen. Ictal EEG during absences shows generalized 3-4 Hz spike-wave."],"look":[],"caption":"Eye-closure-associated generalized polyspike-wave with eyelid myoclonia.","figure":{"src":"assets/images/ilae-eeg/eyelid-myoclonia.jpg","width":2864,"height":1402,"credit":"Specchio N et al. Epilepsia. 2022;63:1398–1442. Figure 4. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17241"},"ilae":"ilae_classification.html#syndrome-22","notes":{"id":"generalized-eeg","title":"Generalized patterns and what they predict"},"questions":[{"id":"bq-epi-13","sec":"Generalized patterns and what they predict"}]},{"id":"myoclonic-absences","kind":"figure","title":"Epilepsy with Myoclonic Absences (EMA)","text":["Interictal EEG shows a normal or mildly slow background with generalized spike-wave discharges similar to CAE. Ictal EEG demonstrates regular 3 Hz generalized spike-and-wave that is time-locked (1:1 correlation) with rhythmic myoclonic jerks of the upper limbs, distinguishing it from typical absence seizures. Polygraphic EMG recording shows rhythmic deltoid contractions synchronized with each spike-wave complex."],"look":[],"caption":"Generalized 3 Hz spike-wave with bilateral deltoid EMG jerks during myoclonic absence.","figure":{"src":"assets/images/ilae-eeg/myoclonic-absences.jpg","width":2848,"height":1270,"credit":"Specchio N et al. Epilepsia. 2022;63:1398–1442. Figure 5. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17241"},"ilae":"ilae_classification.html#syndrome-23","notes":{"id":"generalized-eeg","title":"Generalized patterns and what they predict"},"questions":[{"id":"bq-epi-12","sec":"Generalized patterns and what they predict"}]},{"id":"myoclonic-atonic-seizures","kind":"figure","title":"Epilepsy with Myoclonic-Atonic Seizures (EMAtS)","text":["Interictal EEG shows a normal or mildly slow background with prominent posterior theta rhythms (4-7 Hz, Doose rhythm). Generalized spike-wave or polyspike-wave discharges at 2-3 Hz are seen. Photosensitivity is common. Ictal EEG during myoclonic-atonic seizures shows a brief burst of generalized spike-wave or polyspike-wave followed by a brief period of diffuse attenuation or slowing corresponding to the atonic component (fall). Importantly, slow spike-wave <2.5 Hz and generalized paroxysmal fast activity (GPFA), which are hallmarks of LGS, are NOT features of EMAtS."],"look":[],"caption":"Interictal and ictal EEG with EMG in epilepsy with myoclonic-atonic seizures.","figure":{"src":"assets/images/ilae-eeg/myoclonic-atonic-seizures.png","width":1351,"height":1400,"credit":"Specchio N et al. Epilepsia. 2022;63:1398–1442. Figure 6. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17241"},"ilae":"ilae_classification.html#syndrome-24","notes":{"id":"syndromes-childhood","title":"Childhood onset"},"questions":[{"id":"bq-syn-26","sec":"Childhood onset"}]},{"id":"lennox-gastaut","kind":"figure","title":"Lennox-Gastaut Syndrome (LGS)","text":["Interictal EEG shows diffuse slow spike-and-wave complexes at 1.5-2.5 Hz (slower than the 3 Hz pattern of typical absences), which are the hallmark awake pattern. During NREM sleep, generalized paroxysmal fast activity (GPFA, 10 Hz or faster) is seen — this is highly characteristic and often associated with subtle tonic seizures. Background activity is diffusely slow and poorly organized. Ictal EEG during tonic seizures shows a generalized electrodecremental response or diffuse fast activity. Atypical absences show irregular slow spike-wave."],"look":[],"caption":"Interictal and ictal EEG patterns in Lennox–Gastaut syndrome.","figure":{"src":"assets/images/ilae-eeg/lennox-gastaut.jpg","width":939,"height":1400,"credit":"Specchio N et al. Epilepsia. 2022;63:1398–1442. Figure 7. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17241"},"ilae":"ilae_classification.html#syndrome-25","notes":{"id":"syndromes-childhood","title":"Childhood onset"},"questions":[{"id":"bq-syn-10","sec":"Childhood onset"}]},{"id":"spike-wave-activation-sleep","kind":"figure","title":"DEE/EE with Spike-and-Wave Activation in Sleep (DEE-SWAS / EE-SWAS)","text":["Slow spike-wave activity (1.5-2 Hz) becomes markedly activated in NREM sleep. The discharges may be diffuse, focal, or multifocal; they need not be bilaterally continuous. A sleep EEG is required, and an overnight recording may be necessary if a brief sleep sample is unrevealing. Background slowing and disrupted sleep architecture vary with the etiology. Interpret the sleep activation together with a temporally related developmental plateau or regression rather than applying the historical 85% spike-wave index as a universal cutoff."],"look":[],"caption":"Awake and sleep EEG in epilepsy with spike-and-wave activation in sleep.","figure":{"src":"assets/images/ilae-eeg/spike-wave-activation-sleep.jpg","width":1858,"height":1791,"credit":"Specchio N et al. Epilepsia. 2022;63:1398–1442. Figure 9. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17241"},"ilae":"ilae_classification.html#syndrome-26","notes":{"id":"syndromes-childhood","title":"Childhood onset"},"questions":[{"id":"bq-syn-09","sec":"Childhood onset"}]},{"id":"juvenile-absence","kind":"figure","title":"Juvenile Absence Epilepsy (JAE)","text":["EEG background is normal. Generalized spike-wave or polyspike-wave discharges at 3-5.5 Hz (often faster and more irregular than CAE's regular 3 Hz pattern). Discharges are enhanced by hyperventilation and drowsiness. A photoparoxysmal response may be seen. Interictal discharges may be more fragmented and less rhythmic than CAE. During sleep, discharges may appear focal or multifocal but are not consistently in one region. Slow spike-wave (<2.5 Hz) is exclusionary."],"look":[],"caption":"Typical absence seizure with generalized spike-wave in juvenile absence epilepsy.","figure":{"src":"assets/images/ilae-eeg/juvenile-absence.jpg","width":2494,"height":1391,"credit":"Hirsch E et al. Epilepsia. 2022;63:1475–1499. Figure 3. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17236"},"ilae":"ilae_classification.html#syndrome-29","notes":{"id":"generalized-eeg","title":"Generalized patterns and what they predict"},"questions":[{"id":"bq-epi-14","sec":"Generalized patterns and what they predict"}]},{"id":"juvenile-myoclonic","kind":"figure","title":"Juvenile Myoclonic Epilepsy (JME)","text":["EEG background is normal. Generalized polyspike-and-wave discharges at 3-5.5 Hz (polyspikes are more prominent than in CAE or JAE). Discharges are frequently irregular and may have fragmentary polyspike-wave. Enhanced by sleep deprivation, drowsiness, and photic stimulation. Photic sensitivity is seen in 30-40% of patients. Focal EEG features (brief focal spikes or lead-in) may be seen but are not consistent to one region. Slow spike-wave (<2.5 Hz) is exclusionary. Ictal EEG during myoclonic jerks shows generalized polyspike-wave bursts, often 10-16 Hz polyspikes preceding the slow wave."],"look":[],"caption":"Generalized polyspike-wave interictally and during myoclonic seizures in juvenile myoclonic epilepsy.","figure":{"src":"assets/images/ilae-eeg/juvenile-myoclonic.jpg","width":2494,"height":1376,"credit":"Hirsch E et al. Epilepsia. 2022;63:1475–1499. Figure 4. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17236"},"ilae":"ilae_classification.html#syndrome-30","notes":{"id":"syndromes-adult","title":"Adolescence, adulthood and variable age"},"questions":[{"id":"bq-syn-15","sec":"Adolescence, adulthood and variable age"}]},{"id":"sleep-related-hypermotor-epilepsy","kind":"figure","title":"Sleep-Related Hypermotor Epilepsy (SHE)","text":["Scalp EEG is often normal or shows only subtle frontal sharp transients during wakefulness. Ictal scalp EEG captures abnormalities in only about 50% of cases due to the deep frontal location of many seizure foci. When abnormal, it shows focal frontal theta or delta activity, or runs of low-amplitude fast activity. Video-EEG with multiple nocturnal events is required for diagnosis in many cases. Stereo-EEG may be needed for surgical planning. Interictal sharp waves may be seen over frontal regions during sleep."],"look":[],"caption":"Interictal anterior epileptiform discharges and nocturnal hypermotor seizure EEG.","figure":{"src":"assets/images/ilae-eeg/sleep-related-hypermotor-epilepsy.jpg","width":2425,"height":2224,"credit":"Riney K et al. Epilepsia. 2022;63:1443–1474. Figure 2. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17240"},"ilae":"ilae_classification.html#syndrome-32","notes":{"id":"syndromes-adult","title":"Adolescence, adulthood and variable age"},"questions":[{"id":"bq-syn-32","sec":"Adolescence, adulthood and variable age"}]},{"id":"mesial-temporal-hippocampal-sclerosis","kind":"figure","title":"Mesial Temporal Lobe Epilepsy with Hippocampal Sclerosis (MTLE-HS)","text":["Interictal EEG may show focal anterior temporal sharp waves or spikes, but these can be absent in routine EEGs. Temporal intermittent rhythmic delta activity (TIRDA; temporal LRDA in ACNS terminology) may be seen and has high specificity for MTLE. Ictal EEG shows rhythmic temporal theta activity (5-7 Hz) with temporal onset, often starting unilaterally before spreading. Background may be normal or show mild asymmetric temporal slowing."],"look":[],"caption":"Interictal and ictal EEG in mesial temporal lobe epilepsy with hippocampal sclerosis.","figure":{"src":"assets/images/ilae-eeg/mesial-temporal-hippocampal-sclerosis.jpg","width":2217,"height":986,"credit":"Riney K et al. Epilepsia. 2022;63:1443–1474. Figure 3. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17240"},"ilae":"ilae_classification.html#syndrome-34","questions":[]},{"id":"reading-induced-seizures","kind":"figure","title":"Epilepsy with Reading-Induced Seizures (EwRIS)","text":["Interictal EEG may be normal or show generalized spike-wave discharges similar to other IGE syndromes. Ictal EEG during reading shows bilateral, predominantly perirolandic or frontoparietal polyspike-wave discharges coinciding with the jaw/perioral myoclonus. Activation by reading aloud (especially unfamiliar or difficult text) is the key diagnostic test. A photoparoxysmal response may be seen in some patients."],"look":[],"caption":"Polygraphic EEG of reading-induced perioral myoclonia and generalized spike-wave.","figure":{"src":"assets/images/ilae-eeg/reading-induced-seizures.jpg","width":2217,"height":1619,"credit":"Riney K et al. Epilepsia. 2022;63:1443–1474. Figure 8. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17240"},"ilae":"ilae_classification.html#syndrome-37","notes":{"id":"syndromes-adult","title":"Adolescence, adulthood and variable age"},"questions":[{"id":"bq-syn-34","sec":"Adolescence, adulthood and variable age"}]},{"id":"progressive-myoclonus-epilepsy-example","kind":"figure","title":"Progressive Myoclonus Epilepsies (PME)","text":["EEG demonstrates progressive background slowing as the disease advances. Generalized spike/polyspike-and-wave discharges are seen, often photosensitive and enhanced by photic stimulation. In Unverricht-Lundborg disease, there is marked photosensitivity with giant somatosensory evoked potentials (SEPs). In Lafora disease, occipital predominant discharges may be seen early. The extent of EEG abnormalities progresses with disease course. At advanced stages, EEG may show severe disorganization with near-continuous epileptiform activity."],"look":[],"caption":"Polygraphic EEG and EMG in Unverricht–Lundborg disease, one progressive myoclonus epilepsy subtype.","figure":{"src":"assets/images/ilae-eeg/progressive-myoclonus-epilepsy-example.jpg","width":2217,"height":1565,"credit":"Riney K et al. Epilepsia. 2022;63:1443–1474. Figure 9. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17240"},"ilae":"ilae_classification.html#syndrome-39","notes":{"id":"syndromes-adult","title":"Adolescence, adulthood and variable age"},"questions":[{"id":"bq-syn-35","sec":"Adolescence, adulthood and variable age"}]},{"id":"rasmussen-syndrome","kind":"figure","title":"Rasmussen Syndrome (RS)","text":["EEG commonly shows slowing and multifocal epileptiform discharges over the affected hemisphere, with progressive asymmetry over time. Electrographic correlates of epilepsia partialis continua may be intermittent, subtle, or absent on scalp EEG. Independent contralateral abnormalities can occur, particularly later, so EEG is integrated with the clinical course and serial MRI rather than treated as a strictly unilateral diagnostic test."],"look":[],"caption":"Focal interictal EEG in a child with Rasmussen syndrome.","figure":{"src":"assets/images/ilae-eeg/rasmussen-syndrome.jpg","width":2204,"height":1372,"credit":"Riney K et al. Epilepsia. 2022;63:1443–1474. Figure 5. CC BY 4.0. Embedded figure image reproduced without alteration.","url":"https://doi.org/10.1111/epi.17240"},"ilae":"ilae_classification.html#syndrome-40","notes":{"id":"syndromes-adult","title":"Adolescence, adulthood and variable age"},"questions":[{"id":"bq-syn-33","sec":"Adolescence, adulthood and variable age"}]}]}]}