7.1 Seizures, Epilepsy & Syndromes

Why Seizures and Syndromes Are Tested

The ABRET (American Board of Registration of Electroencephalographic and Evoked Potential Technologists) content outline lists Seizures (classification, clinical manifestations, syndromes) as a knowledge area in the Pre-Study domain and correlation of history with EEG patterns / electrographic correlates under Performing the Study. The registered technologist does not diagnose epilepsy, but must recognize the electroclinical pattern in real time, choose the montage and activation that best capture it, and annotate the semiology so the physician can classify it.

The ILAE Seizure Classification Framework

The International League Against Epilepsy (ILAE) 2017 classification is the modern framework the exam expects. Seizures are first grouped by onset, then by features.

The older terms (grand mal -> generalized tonic-clonic; petit mal -> absence; simple/complex partial -> focal aware/impaired-awareness) still appear on the exam, so know both vocabularies. A focal seizure that spreads to both hemispheres is now called focal to bilateral tonic-clonic rather than 'secondarily generalized.'

Generalized Epilepsies and Their EEG Signatures

Generalized epilepsies produce bisynchronous, symmetric discharges. The technologist links each to its hallmark pattern and the activation that provokes it.

Worked recognition example: A 7-year-old develops a 9-second behavioral arrest during hyperventilation. The tracing shows a generalized, frontally maximal, regular 3-Hz spike-and-wave burst that stops abruptly and the child resumes activity with no postictal confusion. This is the classic electroclinical signature of childhood absence epilepsy. The technologist's correct actions: keep recording, mark the ictal start/stop, test responsiveness during the event (a word to recall), and note that hyperventilation provoked it.

Why Activation Choice Follows the Suspected Syndrome

Because the indication on the order frequently hints at the syndrome, the technologist tailors the study: extend hyperventilation when absence epilepsy is suspected, emphasize photic stimulation for JME and photosensitive epilepsy, and prioritize sleep capture for LGS, West syndrome, and focal epilepsies, where sleep dramatically increases epileptiform yield.

Focal Epilepsies and Localization-Related EEG

Focal (localization-related) epilepsies produce lateralized or regional epileptiform discharges. The technologist's localization skills (phase reversal, montage switching) are directly tested here.

• Mesial temporal lobe epilepsy (MTLE): the most common focal epilepsy in adults, often from hippocampal sclerosis. Interictal anterior temporal sharp waves are maximal at F7/F8 and the true anterior temporal electrodes T1/T2. Sphenoidal electrodes may be added by a physician. Discharges are best captured in drowsiness and sleep, so optimizing sleep is the single most useful technologist strategy.
• Frontal lobe epilepsy: brief, often nocturnal, hypermotor seizures; frontal sharp waves that may be obscured by eye-movement and muscle artifact - clean frontal electrodes and an eye-monitor channel matter.
• Benign epilepsy with centrotemporal spikes (BECTS / Rolandic): a common childhood focal epilepsy with high-amplitude centrotemporal (C3/C4, T-region) sharp waves that markedly increase in drowsiness and sleep and often show a horizontal dipole.
• Occipital epilepsies: occipital spikes that may attenuate with eye opening (fixation-off sensitivity).

Status Epilepticus and Nonconvulsive Seizures

Status epilepticus (SE) is a prolonged seizure or repeated seizures without recovery between them and is a medical emergency. Nonconvulsive status epilepticus (NCSE) has minimal or no motor signs and is detectable only on EEG, which is why ICU continuous EEG is ordered in comatose or fluctuating patients. The technologist must recognize evolving rhythmic or periodic patterns, optimize the recording, and notify the team per critical-value protocol.

Interictal Versus Ictal Recording

The exam expects you to distinguish two recording situations. An interictal epileptiform discharge (IED) is a brief spike or sharp wave between seizures - it supports a diagnosis of epilepsy but is not a seizure itself. An ictal recording captures the seizure as it happens: a rhythmic discharge that evolves in frequency, amplitude, and spatial distribution, usually accompanied by clinical signs. When an ictal event begins, the technologist's priorities are, in order, patient safety, then capturing the electrographic onset on the best localizing montage, then testing and documenting responsiveness and semiology.

A clean ictal-onset recording is the single most valuable product for seizure classification and surgical localization.

Worked Correlation Example

An order reads 'rule out epilepsy; staring spells.' During hyperventilation the technologist sees a generalized 3-Hz spike-and-wave burst and the child stops counting mid-sentence. The technologist should: continue the recording, mark the start time, ask the child a question to test awareness, note the lack of postictal confusion, document that hyperventilation provoked it, and recognize this as a critical, reportable event. The same disciplined sequence applies whether the suspected syndrome is absence, JME, or a focal temporal epilepsy.

Critical Values and Provider Notification

The outline lists electrographic changes requiring provider notification (critical values). The technologist immediately alerts the supervising physician/team for: an electrographic or clinical seizure, evolving status epilepticus (including nonconvulsive status in a comatose patient), a new pattern suggesting acute deterioration, or onset of a photoparoxysmal response (stop the strobe first). Recognizing the pattern, optimizing capture, and escalating - without attempting a diagnosis - is exactly the competency ABRET tests.