**Abstract**

Drug-resistant epilepsy (DRE) is defined as failure of two adequate trials of appropriately chosen and administered antiepileptic drugs. Approximately about 30% of epilepsy patients are drug resistant. Accountable reasons to treatment failure including failure to recognize epilepsy syndrome, poor drug compliance, lifestyle factors, etc. In modern era of medicine, DRE patient should be encouraged to have early referral to tertiary epilepsy centre for presurgical evaluation. Comprehensive neurophysiology, structural neuroimaging, and neuropsychological and psychiatric assessment are regarded as essential elements. Invasive electroencephalography (EEG) monitoring in terms of subdural electrodes, depth electrodes, foramen ovale electrodes, and more advanced technique using stereoelectroencephalography (SEEG) are strong armamentarium for epilepsy surgeon. Epilepsy surgery in terms of resection, disconnection, or neuro-modulation should be recommended after a multi-disciplinary agreement.

**Keywords:** epilepsy surgery, drug resistant epilepsy, presurgical evaluation, anatomo-electro-clinical hypothesis

## **1. Introduction**

Drug-resistant epilepsy (DRE) is defined as failure of two adequate trials of appropriately chosen and administered antiepileptic drugs. Approximately about 30% of epilepsy patients are drug resistant. Accountable reasons to treatment failure including failure to recognize epilepsy syndrome, poor drug compliance, lifestyle factors etc. In modern era of medicine, DRE patient should be encouraged to have early referral to tertiary epilepsy centre for presurgical evaluation. Comprehensive neurophysiology, structural neuroimaging, neuropsychological and psychiatric assessment are regarded as essential elements. Invasive electroencephalography (EEG) monitoring in terms of subdural electrodes, depth electrodes, foramen ovale electrodes, and more advanced technique using stereoelectroencephalography (SEEG) are strong armamentarium for epilepsy surgeon. Epilepsy surgery in terms of resection, disconnection or neuro-modulation should be recommended after a multi-disciplinary agreement.
