Absence Seizures
When a patient suddenly stops activity and stares off, these are called absence seizures, specifically classified as "generalized nonmotor (absence) seizures" according to current International League Against Epilepsy (ILAE) terminology. 1
Clinical Characteristics
Absence seizures are brief generalized seizures characterized by:
- Sudden onset and termination with impairment of consciousness lasting only seconds 2
- Pause in activity or staring occurs in virtually all cases (99.3% of patients) 3
- Median seizure duration of 10.2 seconds, with clinical manifestations typically beginning 1.5 seconds after electrographic onset 3
Associated Features Beyond Staring
While the stare is nearly ubiquitous, it is rarely the only feature:
- Motor automatisms occur in 86.1% of patients 3
- Eye involvement (including eye fluttering, upward deviation, or eye-opening) occurs in 76.5% of patients 3, 4
- Mild myoclonic jerks, particularly of facial muscles, are common 2
- Oculomotor phenomena typically begin 1.7-3 seconds after the electrographic discharge starts 4
EEG Characteristics
The hallmark electrographic feature is:
- Generalized 3-4 Hz spike-and-wave discharges on EEG 2
- Easily precipitated by hyperventilation in approximately 90% of untreated patients 2
Clinical Context and Prognosis
Absence seizures typically:
- Start in childhood or adolescence and may remit with age or persist lifelong 2
- Are associated with increased risk of depression and anxiety (odds ratio = 4.93) 5
- Show significant intrapatient phenomenologic heterogeneity, with most patients experiencing multiple seizure subtypes 3
Common Pitfall
A critical caveat: Absence seizures are frequently underreported by patients because of their brief duration and subtle nature 6. The classification as "generalized nonmotor" does not fully convey the complex semiology that often includes motor components 7.