From the Guidelines
For a new onset seizure, an MRI Head is the imaging study of choice, including coronal T1-weighted imaging, high-resolution volume acquisition, and coronal T2 and fluid-attenuated inversion recovery sequences to assess for hippocampal signal abnormality and other structural abnormalities. This recommendation is based on the American College of Radiology's Appropriateness Criteria for seizures and epilepsy 1. The use of MRI serves multiple purposes, including identifying and characterizing focal causative lesions, assessing progression, and determining prognosis and treatment strategy.
When performing an MRI for new onset seizure, the protocol should include:
- Coronal T1-weighted (3 mm) imaging perpendicular to the long axis of the hippocampus
- High-resolution volume (3-D) acquisition (T1-weighted, gradient echo) with 1-mm isotropic voxels
- Coronal T2 and coronal and axial (or 3-D) fluid-attenuated inversion recovery sequences to assess for hippocampal signal abnormality, atrophy, and loss of internal structure 1 The use of intravenous (IV) contrast is not routinely necessary but may be useful when images without IV contrast are not sufficient or if neoplasm or inflammatory condition is suspected 1.
In general, all patients with epilepsy should undergo an MRI, especially those with focal findings on neurologic examination, persistent headache, recent history of head trauma, and abnormalities on EEG, as these factors are correlated with a high probability of finding structural abnormalities 1. However, some forms of epilepsy may have a low yield of structural lesions on MRI, and in these cases, some authors do not advocate for utilizing MRI 1.
From the Research
MRI Protocols for New-Onset Seizure
The following MRI protocols are commonly used for evaluating new-onset seizures:
- T1-weighted (T1WI) imaging 2, 3
- T2-weighted (T2W) imaging 2, 3
- Fluid-attenuated inversion recovery (FLAIR) imaging 2, 3
- Diffusion-weighted imaging (DWI) sequences 2, 3
Use of Contrast in MRI for New-Onset Seizure
The use of contrast in MRI for new-onset seizure is not always necessary, as studies have shown that:
- Noncontrast sequences can detect lesional abnormalities with high sensitivity and specificity 4
- Contrast sequences may not add significant diagnostic value in patients without clinically suspected neoplasia or infection 4
Recommendations for Imaging Evaluation
The American Journal of Roentgenology recommends:
- Unenhanced CT as the initial imaging examination for adults presenting with first unprovoked seizure in the acute setting 5
- MRI for adults presenting acutely with negative CT results and for those presenting with new-onset seizure in the nonacute setting 5
Reversibility of MRI Abnormalities
Seizure-induced MRI abnormalities can be reversible, with: