What is the recommended imaging protocol for a seizure workup, including the use of Magnetic Resonance Imaging (MRI)?

MRI Protocol for Seizure Workup

MRI without IV contrast is the preferred imaging modality for seizure workup in non-emergent settings, while CT head without contrast is appropriate for emergent situations requiring rapid assessment. 1

Initial Imaging Selection Algorithm

• Emergent Setting: CT head without IV contrast is appropriate when:

  • Rapid assessment is needed for immediate intervention 1, 2
  • Patient requires ready access during scanning 1
  • Acute trauma is suspected 1
  • Patient is unstable or requires close monitoring 1

• Non-Emergent Setting: MRI head without IV contrast is the preferred choice due to:

  • Superior sensitivity (detects up to 55% of abnormalities vs. 18-30% with CT) 1
  • Better gray-white matter differentiation 1
  • Improved detection of epileptogenic lesions 1, 2

Dedicated MRI Seizure Protocol Components

• Coronal T1-weighted imaging (3mm) perpendicular to the long axis of the hippocampus 1
• High-resolution 3D T1-weighted gradient echo (GRE) with 1mm isotropic voxels 1
• Coronal T2-weighted sequences 1
• Coronal and axial (or 3D) fluid-attenuated inversion recovery (FLAIR) sequences 1, 3
• Diffusion-weighted imaging (DWI) to assess for acute infarcts or ictal-related changes 3, 4

When to Add IV Contrast

• IV contrast is not routinely necessary for seizure evaluation 1
• Consider adding contrast when:
  • Initial non-contrast images are insufficient 1
  • Neoplasm is suspected 1, 3
  • Inflammatory condition is suspected 1
  • Infection is suspected 1

Special Considerations

• 3T MRI is preferred over 1.5T when available for improved lesion detection 1

• Patients with higher probability of structural abnormalities who should be prioritized for MRI:

  • Focal neurological deficits on examination 1, 2
  • Persistent headache 1, 2
  • Recent history of head trauma 1, 2
  • Abnormal EEG findings 1
  • Focal seizure features 1, 2

• Cases where MRI may have lower yield (but still generally recommended):

  • Typical primary generalized epilepsy 1
  • Benign focal epilepsies of childhood with characteristic EEG features 1
  • Early onset childhood epilepsy with occipital spikes and good response to antiepileptic drugs 1

Advanced Imaging Techniques for Surgical Planning

• FDG-PET/CT may be complementary to MRI for surgical planning 1

  • Particularly useful when MRI is normal but seizures persist 1
  • Sensitivity of 87-90% for temporal lobe epilepsy 1
  • Sensitivity of 38-55% for extra-temporal lobe epilepsy 1

• SPECT may be useful in presurgical planning 1

  • Provides assessment of regional cerebral blood flow 1
  • Statistical ictal SPECT co-registered to MRI can identify hyperperfusion focus in 84% of patients 1

Common Pitfalls to Avoid

• Relying solely on CT when MRI is available in non-emergent settings 2, 5

  • CT misses approximately 19% of abnormalities detected on subsequent MRI 5
  • CT has poor sensitivity for orbitofrontal and medial temporal lesions 1, 2

• Inadequate MRI protocols not optimized for seizure evaluation 1, 6

  • Standard brain protocols may miss subtle epileptogenic lesions 1
  • Dedicated epilepsy protocols with multiplanar reformatting are essential 1

• Misinterpreting seizure-induced MRI changes as structural causes 4

  • Seizure activity itself can cause transient, reversible MRI abnormalities 4
  • Follow-up imaging may be needed to differentiate seizure effects from structural causes 4