Epilepsy Diagnosis When the Routine Ancillary Tests Are Normal

Epilepsy is a clinical diagnosis. In a patient suspected of epilepsy, the main contribution of routine EEG is to record interictal epileptiform discharges (IEDs) which include spikes, sharp waves, spike-and-wave discharges, sharp-and-wave discharges, and multiple spike-and-wave discharges. Studies show that the first routine EEG fails to record IEDs in approximately 47–50% of patients with epilepsy. When the clinical history strongly suggests epilepsy, but the first EEG fails to record IEDs, various measures can improve EEG performance, which is the subject of this review. Similarly, in cases of suspected epilepsy, magnetic resonance imaging (MRI) has become the imaging technique of choice to identify structural brain abnormalities. However, in a significant number of cases of clinically suspected epilepsy, MRI is interpreted as “normal” even when performed according to an epilepsy-specific protocol and when evaluated by a specialized MRI reader. In such cases, a comprehensive epilepsy-targeted MRI protocol is the key factor to identify, localize, and characterize an epileptogenic lesion. In this regard, the ILAE Neuroimaging Working Group recommends using the Harmonized Neuroimaging of Epilepsy Structural Sequences (HARNESS-MRI) protocol, among other additional imaging tools, to look for such a lesion; this will be also described in detail below.