Question:hard
A 15 year old boy has 10-12 partial complex seizures per day despite an adequate 4-drug antiepileptic regimen. He gives a history of repeated high grade fever in childhood. MRI done for the epilepsy protocol shows a normal brain scan. What should be the best non-invasive strategy to make a definite diagnosis, so that he can be prepared to undergo epilepsy surgery?
A 15 year old boy has 10-12 partial complex seizures per day despite an adequate 4-drug antiepileptic regimen. He gives a history of repeated high grade fever in childhood. MRI done for the epilepsy protocol shows a normal brain scan. What should be the best non-invasive strategy to make a definite diagnosis, so that he can be prepared to undergo epilepsy surgery?
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When MRI is normal in drug-resistant epilepsy, injecting the tracer right at seizure onset (ictal SPECT) plus video EEG gives the sharpest localization.
Updated On: Jul 8, 2026
- Interictal scalp EEG
- Video EEG
- Interictal 18F-FDG PET
- Video EEG with ictal 99mTc-HMPAO brain SPECT
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The Correct Option is D
Solution and Explanation
This question is about presurgical workup for drug-resistant epilepsy when the MRI is normal. We need the non-invasive test combination that best finds the seizure onset zone. Let's look at each option.
- Interictal scalp EEG: Recorded between seizures, it can show spikes suggesting an irritable area of cortex, but spikes do not always sit exactly over the true seizure onset zone, so this alone is not definite enough for surgical planning.
- Video EEG: This captures the actual clinical seizure and its scalp EEG pattern, confirming the semiology and rough region of onset, but scalp electrodes can struggle to localize precisely, especially with a normal MRI and possibly deep or subtle pathology.
- Interictal 18F-FDG PET: Done between seizures, it shows an area of low glucose use around the epileptic focus. It is useful, but the hypometabolic zone it shows is usually larger and less sharply defined than the actual onset zone.
- Video EEG with ictal 99mTc-HMPAO SPECT: The tracer is injected right when the seizure starts, catching the sudden rise in blood flow at the true onset zone before it fades, and video EEG times this precisely against the clinical and electrical seizure onset. Combined, this pairing gives the sharpest, most reliable non-invasive localization when MRI is unremarkable.
Because it captures the transient ictal blood flow surge together with exact electro-clinical timing, video EEG with ictal HMPAO SPECT is the best strategy here.
Let's summarize:
- Interictal tests (scalp EEG, FDG-PET) give useful but blurrier localization.
- Ictal SPECT paired with video EEG captures the seizure onset zone at its sharpest, which is why it is chosen in MRI-negative, drug-resistant epilepsy.
So the correct answer is video EEG with ictal 99mTc-HMPAO brain SPECT.
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