What drug-resistant epilepsy means
Drug-resistant epilepsy is defined by the International League Against Epilepsy (ILAE) as failure of adequate trials of two tolerated and appropriately chosen anti-seizure medications (ASMs) — whether as monotherapy or in combination — to achieve sustained seizure freedom. This definition applies whether the patient has focal or generalised epilepsy, and regardless of seizure type. Approximately 30–40% of people with epilepsy meet this criterion, and continued medication cycling without surgical referral exposes these patients to ongoing seizure risk, injury, sudden unexpected death in epilepsy (SUDEP), medication side effects and reduced quality of life.
Identifying drug-resistant epilepsy early is clinically important because it triggers referral for presurgical evaluation rather than endless medication trials. The distinction between truly drug-resistant epilepsy and pseudo-resistance (non-adherence, incorrect diagnosis, untreated comorbidities such as sleep deprivation or alcohol use, or suboptimal medication selection) requires careful specialist assessment. At Kathmandu Neurology Clinic & Cognitive Center, Dr. Jitendra Prasad Yadav (NMC 8029) reviews seizure diaries, medication history, adherence patterns and comorbidities before discussing surgical candidacy.
- ILAE definition — failure of two appropriately chosen ASMs
- Approximately 30–40% of people with epilepsy are drug-resistant
- Pseudo-resistance must be excluded (adherence, diagnosis, comorbidities)
- Early identification prevents unnecessary medication cycling
Related: Epilepsy Doctor → · Dr. Jitendra Knowledge Hub → · ICHD-3 Topic →
Presurgical evaluation process
Presurgical evaluation is a structured, multi-phase process designed to answer three questions: is this truly drug-resistant focal epilepsy? Where exactly does the seizure originate (localisation)? And is the seizure-onset zone resectable without unacceptable functional deficit? Evaluation typically begins with prolonged video-EEG monitoring to capture seizures and characterise the electroclinical pattern. High-resolution MRI of the epilepsy protocol (thin-cut coronal sequences through the temporal lobes) identifies structural lesions — hippocampal sclerosis, focal cortical dysplasia, low-grade tumours or vascular malformations — that may be the seizure-onset zone.
When non-invasive evaluation is concordant — meaning EEG localisation, MRI lesion and clinical semiology all point to the same region — surgical planning may proceed directly. When results are discordant or the seizure-onset zone lies in eloquent cortex (language, motor or visual areas), additional investigations are considered: PET (ictal vs interictal hypometabolism), SPECT (ictal hyperperfusion), magnetoencephalography (MEG) or intracranial EEG (stereoelectroencephalography, SEEG) for invasive localisation. Wada testing (intracarotid amobarbital procedure) or functional MRI (fMRI) assesses language and memory lateralisation when temporal resection is planned. The multidisciplinary epilepsy team — neurologist, neurosurgeon, neuroradiologist, neuropsychologist — reviews all data before recommending surgical strategy.
- Prolonged video-EEG monitoring — capture and characterise seizures
- Epilepsy-protocol MRI — hippocampal sclerosis, dysplasia, tumours
- PET, SPECT, MEG or SEEG when non-invasive evaluation is discordant
- fMRI or Wada testing for language/memory lateralisation
- Multidisciplinary team discussion before surgical planning