MRI Seizure Protocol: Plain vs. Contrast-Enhanced Imaging
For most seizure evaluations, plain MRI (without IV contrast) is sufficient and is the recommended approach, as IV contrast is not routinely necessary for detecting epileptogenic lesions. 1, 2
When Plain MRI is Adequate
- The American College of Radiology explicitly states that IV contrast is not routinely necessary for seizure protocol imaging. 1
- Plain MRI with a dedicated seizure protocol detects the vast majority of epileptogenic lesions including focal cortical dysplasia, polymicrogyria, mesial temporal sclerosis, gliosis, encephalomalacia, and developmental abnormalities. 1, 2
- A proper seizure protocol should include specific sequences without contrast: coronal T1-weighted imaging (3mm) perpendicular to hippocampal long axis, high-resolution 3D T1-weighted gradient echo with 1mm isotropic voxels, coronal T2-weighted sequences, and coronal/axial FLAIR sequences. 2
- Complex partial seizures specifically require evaluation of frontal lobes and hippocampus for mesial temporal sclerosis, which are optimally evaluated with FLAIR imaging without contrast. 3
When to Add IV Contrast
Add IV contrast only in specific clinical scenarios: 1, 2
- When initial non-contrast images are insufficient or inconclusive 1, 2
- When neoplasm (primary brain tumor or metastases) is suspected - particularly in new-onset seizures in adults or worsening of chronic seizures 1, 3
- When inflammatory conditions are suspected (such as autoimmune encephalitis or demyelinating disease) 1, 2
- When infection is suspected (such as encephalitis or abscess) 2
Evidence Supporting Plain MRI Approach
- Plain MRI detects potentially epileptogenic lesions in 23-28% of patients with new-onset seizures, with the highest yield (53%) in focal-onset seizures. 4
- In a prospective study of 764 patients, MRI revealed epileptogenic lesions in 177 patients (23%), with the most common findings being gliosis/encephalomalacia (49%), tumors (15%), cavernomas (9%), and mesial temporal sclerosis (9%) - most detectable without contrast. 4
- MRI established the underlying cause for acute seizures in 44% of patients, with plain sequences detecting the majority of structural abnormalities. 5
Common Pitfalls to Avoid
- Do not assume contrast is always needed - this exposes patients to unnecessary gadolinium administration and cost without improving detection of most epileptogenic lesions. 1, 2
- Ensure a dedicated seizure protocol is used rather than a standard brain MRI, as specific sequences and slice orientations are critical for detecting subtle cortical dysplasias and hippocampal abnormalities. 2
- Consider 3T MRI over 1.5T when available for improved lesion detection, particularly for subtle cortical malformations. 2
- Remember that subacute contusions can enhance due to blood-brain barrier disruption - if trauma history exists, contrast may reveal findings not visible on plain sequences. 1