MAGNETIC RESONANCE IMAGING SIGNAL INTENSITY AND HIPPOCAMPAL MOSSY FIBER SPROUTING IN TEMPORAL LOBE EPILEPSY
Abstract number :
3.165
Submission category :
Year :
2002
Submission ID :
2577
Source :
www.aesnet.org
Presentation date :
12/7/2002 12:00:00 AM
Published date :
Dec 1, 2002, 06:00 AM
Authors :
Luciana T. Ribeiro, Antonio C. Santos, Andre L.M. Matos, Luciana P.A. Andrade-Valenca, Marcelo M. Valenca, Leticia V. Sales, Carlos G. Carlotti, Joao A. Assirati, Joao P. Leite. Department of Neurology, University of Sao Paulo School of Medicine at Ribeir
RATIONALE: Hippocampal sclerosis is the most frequent pathological finding in temporal lobe epilepsy (TLE) and is characterized by cell loss, gliosis and supragranular mossy fiber sprouting. Such abnormal axonal reorganization present high amounts of zinc in their glutamatergic nerve terminals. Typical MRI findings of mesial TLE are atrophy of mesial temporal lobe structures, mainly the hippocampal formation, and high signal on T2 weighted sequences. The histological basis of this hyperintensity is not completely understood. Some authors have interpreted the T2 high signal as a result of both gliosis and changes in the water tissue content. The objective of the present study was to determinate the relationship between mossy fibers sprouting and the high signal on T2 Fluid Attenuated Inversion Recovery (FLAIR) sequence.
METHODS: Twenty-seven TLE patients with hippocampal sclerosis were submitted to surgical resection of mesial structures and had their hippocampi processed the neo-Timm histochemistry, which typically marks the zinc content of nerve terminals. Mossy fiber sprouting was quantified by a semi-quantitative approach using a image analysis software (NIH Image) in specific areas, such as molecular layer and the hilar region. Data were expressed as gray value intensity (gvi, ranging from 0 to 255) and correlated with hippocampal intensity on FLAIR sequence. FLAIR images were analyzed with a semi-quantitative approach based on the index beween the mean value of gray level intensity on the hippocampus over the frontal cortex (I-H/F). Control groups were used to investigate MRI features (normal subjects, n = 18) and histological aspects (necropsy subjects without cerebral disease, n = 16).
RESULTS: Patients with TLE had an increase in the I-H/F when compared to controls (49 [plusminus] 10% and, 19 [plusminus] 6%, respectively, p[lt]0.0001, Student t test). We found a linear indirect relationship between the MRI FLAIR signal and the gray value intensity on the inner molecular layer (p=0.0053 and r2=0.3).
CONCLUSIONS: This evidence suggests that, in addition to gliosis and water tissue content, the zinc present in the nerve terminals of mossy fibers interferes on the FLAIR signal observed during the MRI investigation of epileptic subjects.
[Supported by: CNPq, PRONEX and FAPESP (Proc. 99/11729-2, 00/12951-0); Brazil.]