Senior Director - Neurosurgery, Neuro Critical Care & Spine Surgery, Max Super Speciality Hospital, Noida
Part 3 of 10 in Diagnosis & Management of Epilepsy & Seizures
Getting the Diagnosis Right: Why EEG and MRI Concordance Decides Who Is a Surgical Candidate
September 4, 2026
Two patients can have an identical MRI finding and receive very different surgical recommendations, because the MRI alone is never the deciding factor. What decides candidacy for Dr. Rattnani is whether the MRI, the EEG and the seizure pattern itself all agree on the same location.
What concordance looks like in practice
Concordance means the seizure semiology, the MRI location and the EEG focus are telling the same story. If an MRI shows an abnormality in the temporal lobe and the EEG also shows the seizure originating from that same temporal lobe on the same side, that is a strongly concordant case, and Dr. Rattnani describes the surgical results in these cases as extremely good.
When the scans disagree
Discordance is the harder scenario: MRI shows a subtle abnormality on one side, but the EEG focus points to the opposite side, or to a different lobe entirely, such as parietal or occipital instead of temporal. When the imaging and the electrical signal do not agree, deciding exactly what to remove becomes genuinely difficult, and a discordant case cannot be planned from imaging alone.
Electrocorticography: mapping the brain during surgery itself
For discordant cases, Dr. Rattnani uses electrocorticography, placing a grid of electrodes directly on the exposed cortical surface during the operation to record where epileptic bursts are actually originating in real time. Resection follows the tracings, not a plan made in advance: tissue is removed only from the area generating epileptic discharges, and the tracings are repeated during surgery until those discharges disappear entirely. Smaller strip electrodes extend the mapping into deeper or less accessible areas the main grid cannot reach, and if seizure activity is traced beyond the initially exposed area, the craniotomy itself may need to be extended to follow it.
Why temporal lobe epilepsy responds best
Temporal lobe epilepsy accounts for 70 to 80% of the cases that respond well to surgery, and it is also the presentation most likely to show strong EEG-MRI concordance in the first place. That combination, a common presentation with a high concordance rate, is why temporal lobectomy paired with amygdalohippocampectomy has the most predictable outcomes of any epilepsy surgery Dr. Rattnani performs.
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
This guide is based on a live Jivo Masterclass: Dr. Dinesh Rattnani taught doctors across Africa on June 29, 2025.
FROM THE LIVE Q&A
Dr. Sai
How do you reduce the risk of paralysis on the opposite side of the body after hemispherectomy?
Dr. Dinesh Rattnani
The corticospinal tracts are not cut. The disconnection stays within the white matter, which is mostly sensory and is the pathway mainly responsible for the seizure activity spreading, so the motor pathways controlling movement are preserved.
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Frequently Asked Questions
Is epilepsy surgery available only in India, and what complications can arise from it?▼
Epilepsy surgery is not unique to India. It is practiced everywhere a neurosciences centre exists, including the US, UK and Canada, and is done at a minimum of 40 to 50 centres across India alone.
What is the prognosis of epilepsy surgery, and what complications are associated with it?▼
The complications are basically infection, bleeding and meningitis, along with weakness, hemiparesis, hemiplegia and memory loss. An equally important complication is the surgery simply not achieving the expected result, meaning the seizure frequency does not come down even though the operation itself went as planned. That specific outcome happens in roughly 5% of cases.
As a layman with no medical background, if someone asks me for help, is my role simply to get an EEG and an MRI done and share the results?▼
Yes. Get the EEG and MRI done, share the reports, and the surgical team will review them and advise from there.
Which epilepsy cases actually need surgery, and can a teenager undergo it?▼
The best candidates are cases with good concordance between where the seizure semiology points, what the MRI shows, and what the EEG confirms, for example a right temporal lobe abnormality on MRI matching a right temporal EEG focus. Temporal lobe epilepsy accounts for 70 to 80% of these good-responder cases, typically treated with temporal lobectomy along with amygdalohippocampectomy. Teenagers can absolutely undergo the surgery, but medical management is always tried first.
What are the recommended antiepileptic drugs for a patient with a normal EEG and a normal MRI?▼
Sodium valproate and levetiracetam both cover a broad spectrum and rank as the top two choices for most epilepsy types, including generalised tonic-clonic and atonic seizures. For focal seizures with secondary generalisation, carbamazepine is slightly preferred, though sodium valproate also works well. Lacosamide is a newer add-on drug, used alongside a first-line drug rather than as initial therapy. Perampanel is particularly useful when the epilepsy is related to a brain tumour or damaged brain tissue.
What does it mean for a patient's EEG and MRI to show concordance?▼
It means the seizure semiology, the MRI location and the EEG focus all point to the same brain area, for example a right temporal lobe abnormality on MRI matching a right temporal EEG focus. Good concordance predicts an excellent surgical outcome.
What happens when the MRI and EEG findings disagree?▼
This is called discordance, and it makes surgical planning significantly harder, since imaging alone cannot reliably identify what to remove. These cases typically require additional intraoperative mapping.
What is electrocorticography and when is it used?▼
It is intraoperative mapping using a grid of electrodes placed directly on the exposed brain surface to record exactly where epileptic bursts are originating in real time. It is used for discordant cases where imaging alone cannot pinpoint the seizure source, and resection continues until the tracings show the discharges have stopped.
Why does temporal lobe epilepsy have the best surgical outcomes?▼
It accounts for 70 to 80% of the cases that respond well to surgery and is also the presentation most likely to show strong concordance between MRI and EEG findings, which is why temporal lobectomy with amygdalohippocampectomy has the most predictable results.
In This Series: Diagnosis & Management of Epilepsy & Seizures
- 1.Epilepsy and Seizures
- 2.When Epilepsy Becomes Drug-Resistant: Diagnosis, Workup and When to Refer
- 3.Getting the Diagnosis Right: Why EEG and MRI Concordance Decides Who Is a Surgical Candidate
- 4.Resective Epilepsy Surgery: Temporal Lobectomy and Amygdalohippocampectomy for Mesial Temporal Sclerosis
- 5.Disconnection Surgery: Hemispherectomy and Corpus Callosotomy for the Most Resistant Cases
- 6.Neuromodulation for Epilepsy: How Vagal Nerve Stimulation and Deep Brain Stimulation Work
- 7.Risks, Complications and Realistic Success Rates of Epilepsy Surgery
- 8.Antiepileptic Drug Choices and Post-Surgical Drug Tapering After Epilepsy Surgery
- 9.Can Epilepsy Surgery Make a Patient Completely Seizure-Free? Setting Realistic Expectations
- 10.The Multidisciplinary Team Behind Safe Epilepsy Surgery