Electroencephalographic Atlas of Epileptiform Abnormalities

Soheyl Noachtar

Elaine Wyllie

Electroencephalography (EEG) is generally considered the single most important laboratory tool in the evaluation of patients with epilepsy. This atlas of material from patients seen at the Cleveland Clinic Foundation illustrates some of the EEG findings discussed throughout this book. Additional EEG atlases and textbooks are listed in the bibliography at the end of this chapter.

METHODS

These tracings were made following American Electroencephalographic Society guidelines (1), with electrodes placed according to the International 10-20 Electrode Placement System (2). Additional closely spaced electrodes (Fig. 13.1) were used in some cases to better define a focal epileptogenic zone. The combinatorial electrode nomenclature used here is that recently proposed by the American Electroencephalographic Society (3) and the International Federation of Clinical Neurophysiology (4).

For consistency and ease of interpretation, we displayed most tracings with the same longitudinal bipolar montage (Fig. 13.2). Occasionally, the activity was best shown with a transverse bipolar montage (Fig. 13.3), a longitudinal bipolar montage with anterior temporal or sphenoidal electrodes (Fig. 13.2), or a referential montage.

PART I: NORMAL EEG PATTERNS AND VARIANTS SOMETIMES CONFUSED WITH EPILEPTIFORM ACTIVITY

For epileptologists to fulfill the basic obligation to “do no harm,” they must avoid “overreading” normal variants on EEG (5,6). This section includes several normal patterns that may be easily mistaken for epileptiform discharges, resulting in an incorrect diagnosis of epilepsy and inappropriate recommendations for antiepileptic medication.

Small sharp spike	Figure 13.4
14- and 6-Hz positive spikes	Figure 13.5
6-Hz “phantom” spike and wave	Figure 13.6
Wicket spikes	Figure 13.7
Subclinical rhythmical electrographic discharges of adults	Figure 13.8
Rhythmic temporal theta bursts of drowsiness	Figure 13.9
Hypnagogic hypersynchrony	Figure 13.10
V-waves and positive occipital sharp transients (POSTS)	Figure 13.11
Sleep spindle	Figure 13.12
Hyperventilation effect	Figure 13.13
Photic driving	Figure 13.14
Breach rhythm	Figure 13.15

PART II: ELECTROENCEPHALOGRAM ABNORMALITIES OF THE GENERALIZED EPILEPSIES

Childhood Absence Epilepsy

Absence seizure	Figures 13.16 and 13.17
Absence status epilepticus	Figures 13.18 and 13.19

Figure 13.1 Electrode positions and nomenclature of the combinatorial system proposed by the American Electroencephalographic Society. (Adapted from Sharbrough F, Chatrian GE, Lesser RP, et al. American EEG Society: Guidelines for standard electrode position nomenclature. J Clin Neurophysiol 1991;8:200-202, with permission.)

Juvenile Myoclonic Epilepsy

Myoclonic jerk with photic stimulation	Figure 13.20
Cluster of myoclonic jerks	Figure 13.21

Infantile Spasms

Hypsarrhythmia	Figure 13.22
Seizure	Figure 13.23

Lennox-Gastaut Syndrome

Generalized sharp- and slow-wave complexes	Figure 13.24
Generalized paroxysmal fast and polyspikes in sleep	Figure 13.25
Atonic seizures	Figure 13.26

Figure 13.2 Longitudinal bipolar montages, left-sided electrodes. The “double-banana” montage used for almost all the tracings in this atlas includes the channels shown with filled arrows, ordered as follows: left temporal chain, right temporal chain, left parasagittal chain, and right parasagittal chain. The “anterior temporal” montage used in some of the tracings is modified to include the channels shown with broken arrows to reflect anterior, basal, or mesial temporal discharges.

Intractable Epilepsy with Multifocal Spikes

Intractable epilepsy with multifocal spikes

Figure 13.27

Stimulation-Related Epilepsy

Reading-induced spike-and-wave complexes

Figure 13.28

Figure 13.3 Transverse bipolar montage, vertex view. Channels are arrayed in order, as follows: frontal chain, temporocentral chain, and parietal chain.

PART III: ELECTROENCEPHALOGRAM ABNORMALITIES OF THE FOCAL EPILEPSIES

Localization-related (partial, focal, or local) epilepsies (7) involve seizures arising from a cortical region within one hemisphere. The first several illustrations are from children who had benign epileptiform discharges of childhood on EEG, with or without clinical seizures. The rest of the figures are from patients with symptomatic epilepsy and focal seizures arising from specific cortical regions, grouped by location of the epileptogenic zone. For most of the titles and legends, we use terminology from the most recent seizure and epilepsy classification systems of the International League Against Epilepsy (7,8). Some additional terms are also used here, such as “aura” instead of “simple partial seizure with special sensory symptoms” and “focal clonic seizure” instead of “simple partial seizure with focal motor signs.” Some newer terms were also included; these are discussed further in Chapter 14.

Benign Focal Epileptiform Discharges of Childhood

Centrotemporal sharp waves	Figure 13.29
Dipole potential	Figure 13.30
Occipital sharp waves	Figure 13.31
Left and right central sharp waves	Figure 13.32

Temporal Lobe Epilepsy

Temporal sharp wave	Figure 13.33
Complex partial (“hypomotor”) seizure	Figure 13.34
Bitemporal sharp waves	Figures 13.35 and 13.36
Complex partial seizure with automatisms	Figures 13.37 and 13.38