MAGNETIZATION TRANSFER IMAGING DETECTS ABNORMALITIES IN FOCAL EPILEPSY PATIENTS WITH NORMAL CONVENTIONAL BRAIN MRI
Abstract number :
1.217
Submission category :
Year :
2003
Submission ID :
3889
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Tuuli M. Salmenpera, Mark R. Symms, Fergus J. Rugg-Gunn, Philip A. Boulby, Gareth J. Barker, Tarek A. Yousry, John S. Duncan MRI Unit, The National Society for Epilepsy, Chalfont St Peter, Buckinghamshire, United Kingdom; Neuroimaging Research Group, Inst
Thirty percent of all patients with epilepsy develop refractory seizures, and are therefore candidates for surgical treatment. However, no relevant structural pathology is identified in 20 % of these patients with current conventional optimal magnetic resonance imaging (MRI) scans, comprising T1- and T2-weighted, proton density (PD) and FLAIR images. Magnetization transfer imaging (MTI) is a new imaging technique which visualises protons tightly bound to macromolecular structures. The exchange of magnetization between bound protons and free water is quantified by magnetization transfer ratio (MTR) which provides a measure of macromolecular structural integrity. Our objective was to examine whether MTI can identify areas of abnormal MTR in patients with intractable focal epilepsy and normal conventional MRI.
Fifty-two patients with focal epilepsy and unremarkable conventional MRI scans and ictal videotelemetry recordings were scanned with MTI. Statistical parametric mapping was used to compare the cerebral structure of an individual patient to a template created from the MTI data of 30 control subjects.
MTR was significantly reduced in 22 of the 52 intractable focal epilepsy patients with no visual abnormality on the conventional MRI. Additionally, 4 of the 52 patients showed an MTR signal increase. Proton density was decreased in 2 of the 22 patients with abnormally decreased MTR. In one of these patients the decreased proton density co-localized with the decrease in MTR signal.
Observed decreases in MTR may reflect either focal lesion in cerebral tissue or localized atrophic change. Our findings suggest that advanced MRI sequences such as MTI are promising techniques for identifying cerebral lesions which were previously not demonstrable with MRI in patients with intractable focal epilepsy. The successful identification of a focus aids the assessment of possible surgical treatment in these patients.
[Supported by: Academy of Finland, Action Research, Emil Aaltonen Foundation, Vaajasalo Foundation]