Myth: If the MRI is normal, there is no structural cause for the epilepsy.
Fact: A normal MRI does not rule out epilepsy and does not prove that there is no structural abnormality. Some epileptogenic lesions are too subtle to be seen on routine imaging, can be missed without an epilepsy-specific protocol, or may only become apparent after expert re-review or with newer techniques.
Routine MRI and epilepsy MRI are not identical
Epilepsy imaging uses carefully selected sequences and slice orientation to improve detection of abnormalities such as focal cortical dysplasia, hippocampal sclerosis and other subtle lesions. The ILAE Neuroimaging Task Force recommends dedicated epilepsy protocols because standard imaging can miss clinically important findings.
MRI-negative does not mean cause-negative
The term MRI-negative is used when no responsible lesion is identified on available structural imaging. It describes what the scan shows, not whether a biological cause exists. Other evidence from EEG, seizure semiology, PET, SPECT, MEG, neuropsychology or invasive monitoring may still support localisation.
Why subtle lesions matter
Focal cortical dysplasia is a well-recognised cause of drug-resistant focal epilepsy and can be difficult to detect. Recent systematic reviews show that specialised MRI methods continue to improve detection, particularly in subtle or previously MRI-negative cases.
Sources
ILAE Neuroimaging Task Force — structural MRI recommendations
MRI techniques for detecting focal cortical dysplasia: systematic review