Localization Patterns in EEG Analysis

Main Terms 1 & 2

• Main Term 1 (Localization of a pattern): Options include lateralized, multifocal, bilateral asymmetric, bilateral asynchronous, generalized, unilateral independent, and bilateral independent. Regional patterns are also possible.

• Main Term 2: Options include sharply contoured, spike-and-wave/sharp-and-wave, rhythmic delta activity, irregular/polymorphic delta activity, periodic discharges, paroxysmal fast activity, and epileptiform discharges.

Pattern Duration

• A pattern is considered present if it lasts for at least 10 seconds.

Localization Patterns (Fp1, Fp2, Posterior)

• If a pattern is equally and synchronously present in Fp1 and Fp2 but not in posterior head regions (and not artifact), it's lateralized, bifrontal predominant.

• Other localization patterns include bilateral asymmetric, bilateral asynchronous, generalized frontally predominant, bilateral independent, and bifrontal maximal.

Synchronous Lower Voltage Component

• If a rhythmic or periodic pattern is primarily on the left but has a synchronous, lower voltage component on the right, it is lateralized, but bilateral asymmetric. Alternately if it is predominant on the right it is generalized, left predominant. Lateralized bilateral asynchronous is also a possibility.

Rhythmic vs. Periodic Patterns

• The main difference between rhythmic and periodic patterns is the presence or absence of an interdischarge interval.

Discontinuous EEG Records

• A discontinuous record is characterized by periods of suppression or attenuation lasting up to 10 seconds. This includes a range of percentages: 1-9%, 10-49%, and 50-99%.

PDs and RDA (Simultaneously Prominent)

• If a pattern qualifies as both periodic discharges (PDs) and rhythmic delta activity (RDA) and both are equally prominent, it's classified as PDs+RDA.

Electrographic Status Epilepticus (ESE)

• For a 60-minute EEG recording, 10 or more minutes of seizure activity needs to be present to classify this as ESE.

Ictal-Interictal Continuum (IIC)

• GPDs (Generalized Periodic Discharges) at 2 Hz, 3 Hz; fluctuating LRDA (Left Rhythmic Delta Activity) at 2 Hz, are part of the IIC. LPDs (Left Periodic Discharges) are also included at 1 Hz, 0.5 Hz and some others.

Focal Evolving Patterns (6Hz to 2Hz)

• An isolated 8-second focal evolving pattern beginning at 6 Hz and slowing to 2 Hz without clinical correlation is considered a fluctuating LRDA.

Electrographic Status Epilepticus (ESE)

• Conditions like 12-minutes of continuous, 31 minutes of continuous, or five 3-minute long electrographic seizures within an hour are all considered electrographic status epilepticus (ESE). An hour of 2Hz GPDs with complete resolution after an IV benzodiazepine is also considered for categorization.

0.5 Hz LRDA and Speech Arrest

• 8-second runs of 0.5 Hz left rhythmic delta activity (LRDA) consistently associated with speech arrest are classified as evolving LRDA.

EEG Resolution of Antiseizure Medication (1-2 Hz)

• Administering IV seizure medication to an unresponsive patient experiencing 1-2Hz GPDs+. R followed by patient responding to commands is classified as possible non-convulsive status epilepticus.

EEG Background Activity Asymmetry (70 to 50 uV)

• Consistent 6–7 Hz activity in the right hemisphere (70 uV) and the left hemisphere (50 uV) is indicated as mild asymmetry on the EEG.

Six-Hour EEG, Continuous 7 Hz, No Stimulation

• A 6-hour EEG record with uninterrupted 7 Hz activity in an unstimulated patient suggests the patient is asleep and unresponsive to stimulation.

Sporadic Epileptiform Discharges (20-30 seconds)

• Sporadic epileptiform discharges roughly every 20–30 seconds, in an irregular pattern, are described as periodic.

Rhythmic and Periodic, 8% Record

• A rhythmic or periodic pattern lasting 8% of a record duration is classified as Occasional.

EEG Pattern with Delta Wave and Twitch

• A pattern characterized by a blunt delta wave in the left hemisphere, synchronized with a twitch of the right thumb, is unusual, but not exactly defined by the available data.

Developmental and Epileptic Encephalopathy (DEE) - Electroclinical Status Epilepticus

• In DEE a sufficiently prominent increase in epileptiform discharges or frequency, compared to baseline, with an observable clinical decline, points to electroclinical status epilepticus.

EEG Stimulation Protocol - No Change

• If an EEG shows no change in cerebral rhythms despite stimulation, it's best described as unreactive. Multiple stimulations during EEG will not yield any result in cerebral rhythms.

Daily Pattern Burden (LPDs, 16 Hours and 8 Hours)

• If left periodic discharges are present for 50% of the initial 16 hours and 25% of the subsequent 8 hours, the daily pattern burden is indicated as 8 hours.

Left Hemispheric LPDs with Midline Periodic Discharges (PDs)

• Simultaneous occurrences of left hemispheric LPDs (left periodic discharges) and midline PDs (periodic discharges) should be categorized as two separate populations of LPDs.

Brief Potentially Ictal Rhythmic Discharges (BIRDS).

• To qualify as definite, BIRDS must have similar morphology and location to interictal discharges (same patient), seizures (same patient), evolution from 2 Hz to 6 Hz or 5 Hz to 3 Hz lasting less than 10 seconds.

Continuous 6 Hz Activity with Spindle-like 15 Hz Activity

• A 6-hour EEG record containing continuous 6 Hz activity alongside spindle-like 15 Hz activity, with stimulation changes to 2.5 Hz high-voltage GRDA for 30 seconds, is best described as present with normal stage N2 sleep transients.

Voltage Measurement of EEG Discharge (Bipolar Montage)

• The appropriate method for measuring the voltage of a circled EEG discharge on a bipolar montage is letter 'D'.

Pattern Characterization (26 seconds of Epileptiform Discharges)

• A series of 26 epileptiform discharges within 10 seconds is best classified as brief potentially ictal rhythmic discharges (BIRDs).

Rhythmic Delta Activity (RDA) Description

• The description of a RDA would be as it shows no plus, plus fast( RDA + F). The text does also show a possibility of an extreme delta brush pattern.

Abundant RDA Through a Record

• An abundant RDA pattern across an entire EEG record is identified as electrographic seizure.

Burst Phase Count in EEG

• A prominent burst, shown in the EEG data, has 3 distinct phases, when the EEG activity is analyzed from the image, the burst has 3 distinct phases.

This quiz focuses on the localization and characterization of EEG patterns including various terms and their significance. Test your understanding of terms such as bilateral asymmetric and spike-and-wave activity, alongside duration requirements. Familiarity with EEG patterns is essential for accurate analysis.