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Open Access Highly Accessed Research article

Asymmetrical hippocampal connectivity in mesial temporal lobe epilepsy: evidence from resting state fMRI

Fabrício RS Pereira1, Andréa Alessio12, Maurício S Sercheli2, Tatiane Pedro1, Elizabeth Bilevicius1, Jane M Rondina12, Helka FB Ozelo2, Gabriela Castellano2, Roberto JM Covolan2, Benito P Damasceno1 and Fernando Cendes1*

Author Affiliations

1 Neuroimaging Laboratory, Department of Neurology, University of Campinas - UNICAMP, Cidade Universitária, Campinas, SP, Brazil

2 Neurophysics Group, Gleb Wataghin Institute of Physics, P.O. Box 6165, University of Campinas - UNICAMP, Zip Code 13083-970, Campinas, SP, Brazil

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BMC Neuroscience 2010, 11:66  doi:10.1186/1471-2202-11-66

Published: 2 June 2010

Abstract

Background

Mesial temporal lobe epilepsy (MTLE), the most common type of focal epilepsy in adults, is often caused by hippocampal sclerosis (HS). Patients with HS usually present memory dysfunction, which is material-specific according to the hemisphere involved and has been correlated to the degree of HS as measured by postoperative histopathology as well as by the degree of hippocampal atrophy on magnetic resonance imaging (MRI). Verbal memory is mostly affected by left-sided HS, whereas visuo-spatial memory is more affected by right HS. Some of these impairments may be related to abnormalities of the network in which individual hippocampus takes part. Functional connectivity can play an important role to understand how the hippocampi interact with other brain areas. It can be estimated via functional Magnetic Resonance Imaging (fMRI) resting state experiments by evaluating patterns of functional networks. In this study, we investigated the functional connectivity patterns of 9 control subjects, 9 patients with right MTLE and 9 patients with left MTLE.

Results

We detected differences in functional connectivity within and between hippocampi in patients with unilateral MTLE associated with ipsilateral HS by resting state fMRI. Functional connectivity resulted to be more impaired ipsilateral to the seizure focus in both patient groups when compared to control subjects. This effect was even more pronounced for the left MTLE group.

Conclusions

The findings presented here suggest that left HS causes more reduction of functional connectivity than right HS in subjects with left hemisphere dominance for language.