Dynamic assessment of high-resolution MRI with multi-planar reconstruction increases the yield of lesion detection in patients with partial epilepsy

Abstract

Objective: To investigate the presence and type of lesions associated with partial epilepsies by routine high resolution MRI and multi-planar reconstruction (MPR) and correlate the MRI abnormalities with semiology and EEG findings. Methods: We studied 100 consecutive patients followed in the epilepsy clinic of our Hospital with partial epilepsy who underwent MRI investigation. The MRI protocol included 6 mm sagittal T1-weighted, 3-4 mm axial T1 and T2-weighted, 3 mm coronal T1 inversion recovery and T2-weighted images that were printed on a radiographic film for routine analysis. In addition, all patients had a volume T1-gradient echo acquisition with isotropic voxels (1-1.5 mm) for multiplanar reconstruction (MPR). The MRIs were examined in two different occasions: first using only the images printed on films, without volume T1-gradiente echo acquisition and in a second occasion in a computer workstation when all the available images and MPR were analyzed blindly to the clinical information. The clinical and EEG findings were tabulated independently, and results were compared using Chi-square of Fisher exact test when appropriate. Results: The patients were divided into 10 groups according to their etiological classification (structural lesions) established by MRI. Mesial temporal sclerosis (MTS) was the largest group (40%). There were 65 women and 35 men. Mean age was 23.9 (± 5.7) years and mean age of onset of recurrent seizures was 9.9 (± 0.8) years. The most frequent risk factors were family history of seizures (23%), head trauma (10%), peri-natal anoxia (5%) and infection (9%). High resolution MRI including thin coronal slices, in addition to a "dynamic" analysis in a workstation with MPR, allowed a significant improvement in lesion detection compared to the traditional analysis with radiographic films (94% versus 80%) (p < 0.05). The lesions previously undetected were focal cortical dysplasia and subtle MTS. There was a good concordance between MRI lesions and clinical and EEG findings. Conclusion: High resolution MRI including thin coronal slices, in addition to a "dynamic" analysis in a workstation with MPR allowed a significative improvement in lesion detection compared to the traditional analysis with radiographic films (94% versus 80%). Patients with partial epilepsy and "normal" MRI need to be investigated further with thin slices and post-processing techniques using volume acquisitions that allow adequate multi-planar re-slicing.Key words: Magnetic resonance imaging, partial seizures, partial epilepsy, cortical dysplasia, mesial temporal sclerosis, lesions. RESUMO Avaliação dinâmica em epilepsias parciais utilizando imagens por ressonância magnética (RM) de alta resolução de rotina e reconstrução multiplanar (RMP)Objetivo: Investigar a presença e tipo de lesões em pacientes com epilepsias parciais utilizando imagens por ressonância magnética (RM) de alta resolução de rotina e reconstrução multiplanar (RMP) e correlacionar as anormalidades com semiologia e EEG. Casuística e métodos: Estudamo...

Partial epilepsies: a brief overview

“…Other pathologies causing temporal lobe epilepsy are readily identified on MR images, though again, as the lesions are often small, fine contiguous slices should be used. Volumetric imaging provides information suited to the detection of both hippocampal and neocortical temporal disease, and is rapidly becoming the MR technique of choice for assessment of TLE (25,(29)(30)(31)(32) .…”