A 34-year-old man from Uttar Pradesh presents with a 3-year history of unprovoked seizures occurring 2–3 times per month. He has tried phenytoin and carbamazepine, each for 6 months at therapeutic doses, but seizures persist. Neuroimaging (MRI brain) is normal. He reports no significant side effects from either drug. His seizure semiology is consistent with focal onset seizures with secondary generalization. What is the most appropriate next step in management?

Explanation

## Clinical Diagnosis: Drug-Resistant Epilepsy (DRE) **Key Point:** This patient meets the definition of drug-resistant epilepsy: failure of adequate trials of two or more antiepileptic drugs (AEDs) — either as monotherapy or in combination — to achieve seizure freedom. The next step is formal evaluation for surgical candidacy. ### Definition and Epidemiology **High-Yield:** Drug-resistant epilepsy is defined by the International League Against Epilepsy (ILAE) as failure of two appropriately chosen and tolerated AED regimens (monotherapy or combination) to achieve sustained seizure freedom. Approximately 30% of patients with epilepsy are drug-resistant. **Clinical Pearl:** In drug-resistant epilepsy with focal seizure onset (as suggested by secondary generalization), temporal lobe epilepsy (TLE) is the most common surgically remediable form. Even with normal MRI, electrocorticography and functional imaging (PET, fMRI) may identify a surgical target. ### Management Algorithm for DRE ```mermaid flowchart TD A[Seizures persist after 2 AED trials]:::outcome --> B{Seizure onset focal or generalized?}:::decision B -->|Focal onset| C[Evaluate for surgery]:::action B -->|Generalized| D[Consider combination therapy or newer AEDs]:::action C --> E[Detailed history, video-EEG, structural imaging]:::action E --> F{Surgical candidate?}:::decision F -->|Yes| G[Temporal or extratemporal resection]:::action F -->|No| H[Optimize medical therapy or device-based options]:::action D --> I[Add third AED or consider VNS/DBS]:::action ``` ### Why Surgery is Considered | Feature | Significance | |---------|-------------| | **Focal seizure onset** | Suggests a localized epileptogenic zone amenable to resection | | **Secondary generalization** | Indicates propagation from a focal source | | **Normal MRI** | Does not exclude surgical candidacy; lesional and non-lesional TLE can both be surgically remediable | | **Failed two AED trials** | Meets ILAE definition of DRE; surgery should be offered | **Mnemonic:** **FOCAL** criteria for surgical evaluation in DRE — **F**ailed two AEDs, **O**nset focal, **C**andidate assessment (EEG/imaging), **A**nalysis of seizure semiology, **L**ocalization of epileptogenic zone. [cite:Harrison 21e Ch 369; Robbins 10e Ch 28]