Drug-Resistant Epilepsy,
Patient Selection for Surgical Treatment

You’ve been diagnosed with drug-resistant epilepsy—what does that mean in practice?

If your neurologist tells you that you have drug-resistant epilepsy (DRE), it does not mean there is nothing else that can be done. It means that:

• standard medication management has reached its practical limits,
• the chance that an additional medication will render you completely seizure-free is low,
• it is time to consider specialized surgical or interventional strategies.

The goal is not only to reduce seizures, but also to:

• improve quality of life, independence, and daily functioning,
• reduce the risk of injury, sudden unexpected death in epilepsy (SUDEP), and prolonged hospitalizations,
• minimize overall medication burden (side effects, interactions, etc.) whenever safely possible.

What is epilepsy surgery, and who is a candidate?

Epilepsy surgery refers to a group of procedures designed either to remove a small brain region that reliably generates seizures (resective surgery), or to modulate neural networks that enable seizure propagation (neurostimulation, neuromodulation, or selected disconnection procedures).

A patient is typically considered a candidate when:

• epilepsy has been confirmed by a neurologist/epileptologist,
• seizures persist despite two appropriately tried antiseizure medication regimens,
• there is evidence that seizures arise from a defined region (a seizure focus) that can be safely removed or modulated without unacceptable impact on language, motor function, memory, vision, or other critical abilities.

Evaluation is performed by a multidisciplinary epilepsy team (epileptologist, neurosurgeon, neuropsychologist, neuroradiologist, and others).

Which causes and epilepsy types can be treated surgically?

Epilepsy is not a single disease—it is a syndrome with multiple underlying causes and patterns.

Common surgically treatable focal syndromes

• Temporal lobe epilepsy (TLE)—the most common focal epilepsy treated surgically. It is frequently associated with mesial temporal sclerosis (MTS).
• Frontal lobe epilepsy—the most common extratemporal focal epilepsy.

Potential underlying etiologies

• Cortical malformations (focal cortical dysplasia, polymicrogyria, schizencephaly, etc.)
• Mass lesions (benign or malignant), including low-grade tumors
• Tuberous sclerosis, vascular malformations (AVMs), cavernous malformations
• Post-traumatic lesions, post-stroke epilepsy
• Remote sequelae of infections (e.g., herpes encephalitis, neurocysticercosis)
• In many patients, epilepsy remains cryptogenic (no clear MRI lesion).

In general, the more discrete and well-localized the epileptogenic region is (e.g., classic MTS), the higher the likelihood of successful surgical treatment.

What do seizures “look like,” and why does semiology matter?

Seizure semiology (what you feel, what observers see, and the sequence of events) provides critical clues about where seizures originate:

• visual aura → may suggest occipital lobe involvement,
• rising epigastric sensation, déjà vu, sudden fear or “strange feeling” → often seen in mesial temporal seizures,
• preserved speech during a seizure → may suggest involvement of the non-dominant temporal lobe,
• loss of speech → may indicate involvement of the dominant (often left) temporal lobe,
• forced head/eye version to one side → often points to a focus in the opposite hemisphere.

The more stereotyped and consistent seizures are, the more likely there is a single, discrete focus. Multiple distinct seizure types may indicate a more diffuse network problem.

How does the presurgical evaluation work? (Video-EEG, MRI, and more)

1. Prolonged Video-EEG monitoring (Phase I evaluation)

You are admitted to a dedicated Epilepsy Monitoring Unit (EMU) for several days. Monitoring typically includes:

• continuous video recording (clinical semiology),
• continuous EEG recording,
• often a carefully supervised medication adjustment to help capture typical seizures.

Goals include:

• confirming seizures are epileptic (and not psychogenic nonepileptic events),
• correlating the clinical event with the EEG pattern,
• identifying the most likely region of seizure onset.

2. High-resolution epilepsy-protocol brain MRI

Specialized sequences (thin cuts, FLAIR/T2, 3D T1, etc.) help:

• detect MTS (hippocampal atrophy, signal change, temporal horn enlargement),
• identify cortical malformations, heterotopias, vascular lesions, tumors, and other structural causes.

3. Neuropsychological evaluation

4. Functional and advanced studies (when indicated)

• fMRI for language, memory, and sensorimotor mapping,
• FDG-PET to detect interictal hypometabolism around the focus,
• SPECT (especially ictal SPECT) to identify regions of hyperperfusion during seizures,
• EEG–fMRI in specialized centers,
• MEG for higher-precision spatial localization of epileptiform activity.

These data are integrated to build a coherent hypothesis about the location and extent of the epileptogenic zone (EZ).

What is the role of neuropsychological testing, the Wada test, and fMRI?

Neuropsychological assessment

Specialized testing of memory, attention, language, and executive function:

• helps lateralize or localize dysfunction (e.g., verbal memory patterns suggesting dominant temporal involvement),
• assesses what has already been affected by long-standing epilepsy,
• estimates what may change after resection, guiding risk counseling and planning.

Wada test (Intracarotid Amobarbital Procedure)

An interventional study in which a short-acting anesthetic is delivered into the internal carotid artery to temporarily “inactivate” one hemisphere at a time:

• to determine which hemisphere is dominant for language,
• to assess whether the contralateral side can support memory after a planned resection.

Today, in many programs, Wada is supplemented or partially replaced by language and memory fMRI, interpreted alongside neuropsychological profiles.

What is intracranial EEG monitoring (Phase II), and when is it needed?

If the combined information from semiology, Video-EEG, MRI, PET, and related studies is inconclusive or insufficient, the next step may be:

• implantation of intracranial electrodes (subdural strips/grids or depth electrodes—stereo-EEG, SEEG),
• followed by an additional period of monitoring with electrodes in direct contact with cortical or deep structures.

Goals include:

• precise delineation of the epileptogenic zone (EZ),
• distinguishing critical functional cortex (language, motor) from tissue considered for resection,
• cortical mapping through electrical stimulation.

What surgical and interventional options are available?

1. Focal resection / partial lobectomy

• Anterior temporal lobectomy / mesial temporal resection (including removal of the hippocampus and amygdala on the affected side when appropriate).
• Goal: seizure freedom in patients with well-established unilateral mesial temporal epilepsy and concordant testing.

2. Extratemporal resections

• frontal, parietal, or occipital lobe resections,
• resection of cortical dysplasia, benign tumors, cavernous malformations, and related lesions.

3. Neurostimulation and palliative procedures

• Vagus nerve stimulation (VNS)— implantation of a pacemaker-like device that stimulates the vagus nerve to reduce seizure frequency and severity.
• Corpus callosotomy— partial or complete disconnection of the corpus callosum to reduce drop attacks when no resectable focus is present.
• Responsive neurostimulation (RNS)— an implanted system that detects early seizure activity and delivers targeted stimulation to disrupt it.

The optimal option depends on:

• the type and location of the seizure onset region,
• whether it involves language, motor, memory, or visual networks,
• overall health status, age, and individual goals and priorities.

What are the chances of success, and what are the risks?

Outcomes vary by syndrome, patient-specific factors, and center expertise. In broad terms:

• in carefully selected patients with unilateral mesial temporal sclerosis (MTS), rates of sustained seizure freedom can be very high,
• in extratemporal resections or cortical dysplasia, outcomes are more heterogeneous, but many patients achieve substantial seizure reduction,
• VNS/RNS typically reduce seizure frequency and severity, but complete seizure freedom is less common.

Potential risks

• general surgical risks (infection, bleeding, thrombosis),
• procedure-specific deficits (language, memory, motor function, visual fields),
• cognitive or psychological effects (especially with dominant-hemisphere resections),
• incomplete seizure control or recurrence after a period of improvement.

For this reason, the decision is made jointly with you and your family, after a detailed discussion of expected benefits and individualized risk.

Daily life after surgery: driving, work, and long-term care

After successful epilepsy surgery:

• many patients may gradually reduce medications (never abruptly; always under epileptologist supervision),
• driving eligibility may change depending on local regulations and seizure control,
• independence in work, education, and social activities often improves over time,
• support from a neuropsychologist can be helpful as patients adjust to a new baseline.

Even when complete seizure freedom is not achieved, a meaningful reduction can translate into:

• fewer injuries and hospitalizations,
• fewer missed days of work or school,
• improved emotional well-being and participation in daily life.

When does epilepsy become an emergency—what should I watch for?

Seek emergency medical help immediately if:

• a seizure lasts longer than 5 minutes (status epilepticus),
• there are repeated seizures without full recovery in between,
• a seizure occurs in water, at height, or in a setting with high risk of injury,
• after the seizure, the person does not gradually regain awareness or has difficulty breathing,
• there is head trauma or other serious injury.