Sensitivity of 1st EEG in Detecting Generalized Spike and Wave Activity in Absence Epilepsy
Hayes Fountain1, Nathan Fountain2
1University of Miami Miller School of Medicine, 2Department of Neurology, University of Virginia
Objective:
To determine the sensitivity of routine EEG (REEG) for generalized spike wave discharges (GSW) in absence seizures (ABS).
Background:
EEG-based diagnosis is generally required to identify patients with ABS. ABS often arise in childhood and can be mistaken for inattention. It is generally accepted that the 1st REEG of an untreated patient will demonstrate GSW required for diagnosis of ABS. However, the sensitivity of REEG for ABS identification has not been quantified.
Design/Methods:
We studied the 1st REEG from 80 untreated patients with an ultimate diagnosis of ABS. Subjects were extracted from the University of Virginia clinical epilepsy database of 2,648 patients based on seizure and syndrome classifications. Patients without GSW were excluded. Patients were classified as ABS alone, ABS and generalized tonic-clonic, or ABS and other seizures. We noted total number of EEGs, number of normal EEGs, number of EEGs until GSW discharges appeared, number of EEGs without epileptiform activity, and presence of focal EEG findings.
Results:
A total of 80 subjects met inclusion criteria: 21 with childhood absence epilepsy (CAE), 8 with juvenile absence epilepsy (JAE), 10 with juvenile myoclonic epilepsy (JME), and 41 with ABS due to other types of epilepsy. The 1st REEG was normal in 7 patients (sensitivity 91.2%). Sensitivity varied by syndrome: JME 100%, CAE 90%, and JME80%. The 2nd REEG had GSW on 6 of the 7 whose 1st REEG was normal; the 3rd EEG had GSW in the remaining patient.
Conclusions:
First REEG for all comers with ABS is very high, especially when due to common epilepsy syndromes. Sensitivity by the 3rd REEG is 100%. Up to 3 REEGs may be required to exclude ABS, although sensitivity of even the 1st REEG is already very high. This confirms and quantifies the high sensitivity of REEG for ABS, regardless of the cause.