Detecting interictal discharges in first seizure patients: ambulatory EEG or EEG after sleep deprivation?

Uncertainty about recurrence after a first unprovoked seizure is a significant psychological burden for patients, and motivates the need for diagnostic tools with high sensitivity and specificity to assess recurrence risk. As the sensitivity of a routine EEG after a first unprovoked seizure is limited, patients often require further diagnostics. Here, we study if ambulatory EEG (aEEG) has similar diagnostic accuracy as sleep deprived EEG (sdEEG).

In this retrospective cohort, we included patients with an unprovoked first seizure and a normal routine EEG who subsequently underwent an sdEEG or aEEG. All EEGs were reviewed for the presence of interictal epileptiform discharges (IEDs). We calculated specificity and sensitivity of sdEEG and aEEG, using the clinical diagnosis of epilepsy as golden standard. All patients had a follow-up of one year.

We included 104 patients. Sensitivities for sdEEG and aEEG were 45% (specificity 91%) and 63% (specificity 95%), respectively. Independent risk factor for recurrent seizure were IEDs on the additional EEG, with a relative risk of 1.5 of having a recurrent seizure within a year.

Diagnostic accuracies of sdEEG and aEEG are similar and depending on patients' and clinicians' preference both can be considered in patients with a first seizure and a normal routine EEG to determine recurrence risk.