Pre-surgical epilepsy evaluation using 3T MRI. Do surface coils provide additional information?

Purpose: To assess if 3T MRI can be further improved by adding surface coil imaging, in the context of detection and characterization of cerebral lesions in patients with drug-resistant epilepsy.

Methods: Twenty five patients with drug-resistant epilepsy undergoing evaluation for epilepsy surgery were examined with high resolution 3T MRI. The patients were MRI-negative (n = 15), or had unclear findings (n = 10), on previous MRI at 1.0-1.5T. Surface coils were applied over the suspected epileptogenic zone after imaging in the head coil. In MRI-negative patients, placement of the coils was defined by semiological analysis, extracranial video-EEG, and, in selected cases, subtraction ictal SPECT co-registered with MRI and PET. Coil placement was re-analyzed and graded, based on the degree of convergence between different investigational modalities.

Results: Surface coil MRI allowed visualization of the cortical lesions with somewhat better demarcation and detail, but did not contribute to detection of previously undiagnosed lesions and did not provide additional information regarding type of lesion. Possible epileptogenic lesions were detected on 3T MRI in 12 patients. No abnormalities were found in the remaining 13 patients. 3T MRI provided new or additional information about the cortex, compared with reports from previous 1.0-1.5T MRI in 5 patients (20%).

Conclusion: 3T MRI with high resolution is valuable for lesion detection, especially MCD, in patients with drug-resistant epilepsy. We question the additional contribution from supplementary surface coil imaging at 3T MRI.