When Epilepsy Becomes Drug-Resistant: Diagnosis, Workup and When to Refer

General physicians and neurologists manage the overwhelming majority of epilepsy cases without ever needing a surgeon. Dr. Dinesh Rattnani's message to referring doctors is correspondingly narrow: know exactly when a case has crossed the line into drug resistance, and do not refer before that line is reached.

Ruling out triggers before blaming the drugs

Before any patient is labeled drug-resistant, every trigger that can provoke a seizure independent of an underlying disease has to be excluded: stress, lack of sleep, alcohol use, hormonal changes, illness, fever, flashing lights, physical exertion and dehydration. A patient whose seizures track one of these triggers is not yet a drug-resistant epilepsy case, no matter how many medications they are already taking.

The actual definition

Once triggers are excluded, drug resistance has a specific threshold: a minimum of two antiepileptic drugs, each at the maximum dosage allowed for the patient's body weight, with seizures still occurring. Roughly 60 to 70% of epilepsy patients become seizure-free on standard drugs managed by a physician or neurologist. The remaining 20 to as much as 40% fall into this drug-resistant category, and that population, not epilepsy in general, is the surgical candidate pool.

The three-part workup

Every case that reaches this point needs the same three investigations. EEG places electrodes on the scalp to record the brain's electrical activity and localize which lobe, frontal, occipital, temporal or parietal, and which side the discharge is coming from. MRI of the brain looks for a structural cause. Video EEG addresses a practical problem with routine EEG: it only records for 5 to 15 minutes, while a seizure might not occur again for two or three days. Video EEG admits the patient for 24 to 48 hours, recording physical behavior and brain electrical activity simultaneously, so that when a seizure does occur, both are captured at once.

What a normal MRI means for referral

Idiopathic epilepsy, where the MRI is entirely normal, is the most common presentation, and Dr. Rattnani is direct about the referral implication: if the MRI is normal, continue managing the patient with standard antiepileptic drugs, dosed to body weight, rather than referring for surgery. Referral only becomes appropriate when the patient remains refractory after two or three drugs at proper dosage, or when the MRI itself shows an abnormality, such as mesial temporal sclerosis, a tumor, or scarring from a prior head injury, that could plausibly be the seizure's source.

What an abnormal MRI changes

An MRI finding changes the calculation because it gives resective surgery something concrete to target: mesial temporal sclerosis, a glioma or meningioma, a depressed bone fragment from a prior fracture, neurocysticercosis cysts, or scar tissue from a healed head injury near the motor cortex. Any of these can act as a persistent source of cortical irritation, and removing the lesion, not just adding another drug, is what stops the seizures in these cases.

This article is based on a Jivo Masterclass session conducted by Dr. Dinesh Rattnani, Senior Director - Neurosurgery, Neuro Critical Care & Spine Surgery, Max Super Speciality Hospital, Noida. The article has been summarised with the assistance of an AI tool from the original masterclass recording. Watch the full Masterclass recording

Looking for a neurosurgery consultation or a second opinion on epilepsy surgery? Get in touch with the Jivo team