A 28-year-old woman presents with a 2-year history of recurrent unprovoked seizures characterized by sudden loss of consciousness followed by generalized tonic-clonic movements lasting 1–2 minutes. She has no prior head injury, infection, or metabolic derangement. Routine blood investigations and non-contrast head CT are normal. Which investigation is most appropriate to confirm the diagnosis and guide long-term management?

Explanation

## Investigation of Choice for Suspected Epilepsy **Key Point:** EEG is the gold standard and most appropriate first-line investigation for confirming epilepsy in a patient with recurrent unprovoked seizures and normal structural imaging. ### Why EEG is the Answer 1. **Diagnostic yield**: EEG can detect interictal epileptiform discharges (spikes, sharp waves, spike-and-wave complexes) in 50–80% of patients with generalized epilepsy, even between seizures. 2. **Seizure classification**: EEG helps classify the seizure type (generalized vs. focal) and epilepsy syndrome, which guides antiepileptic drug (AED) selection. 3. **Cost-effective and non-invasive**: Unlike PET or MEG, EEG is widely available, inexpensive, and safe. 4. **Ictal recording**: If a seizure occurs during EEG monitoring, the characteristic ictal pattern (e.g., generalized spike-and-wave at 3 Hz for absence seizures, or low-amplitude fast activity for tonic-clonic seizures) confirms the diagnosis. ### Role of Other Investigations | Investigation | Role in Epilepsy | Limitations | | --- | --- | --- | | **EEG** | First-line; detects interictal/ictal discharges | May be normal between seizures | | **PET brain** | Localizes hypometabolic foci in drug-resistant focal epilepsy | Expensive; not first-line; requires seizure-free period | | **MEG** | Research tool; high temporal resolution | Not routinely available; not first-line | | **fMRI** | Maps eloquent cortex pre-operatively | Not diagnostic; used only in surgical candidates | **High-Yield:** In a patient with clinical seizures and normal CT, EEG is the next step. If EEG is normal but seizures persist, MRI (not PET) is indicated to exclude subtle structural lesions (mesial temporal sclerosis, focal cortical dysplasia). **Clinical Pearl:** Hyperventilation and photic stimulation during EEG can provoke epileptiform activity and increase diagnostic yield, particularly in generalized epilepsy syndromes.