Abstracts

Rationale: Functional MRI (fMRI) has been established as a clinically useful tool. In particular, fMRI has proved to be a reliable tool for identifying sensory-motor regions and localizing language. Implementing a clinical memory paradigm for evaluation of mesial temporal function with robust results in individual patients has proven to be more challenging. Functional connectivity MRI (fcMRI) an analysis technique based on task-free resting state fMRI recording -- is an alternative approach for mapping functionally related areas of the brain. Potentially, it can be useful in assessing disruption of connectivity in certain disease states, including memory disruption in epileptic patients with hippocampal sclerosis (Frings L et al.2009). We explore the possibility of using connectivity analysis for accessing networks implicated in memory function. Methods: During the 8 min resting state fMRI scan the subjects were instructed to relax and rest while keeping their eyes closed. Siemens (Erlangen, Germany) system, 3-Tesla (Trio) scanner was used for imaging (EPIBOLD sequence, TE=30ms, flip angle = 90 ). Analysis was performed using 1000 Functional Connectomes Project scripts based on AFNI and FSL software packages. We retrospectively analyzed connectivity patterns in five healthy control subjects (ages 11 to 15) and compared these to results in two patient (age 18 and 5) with memory disruption and epilepsy due to hippocampal sclerosis. Resting state data were analyzed for connectivity with ventral precuneus (Vincent JL 2006) and retrospenial (Greicius MD 2009)cortex. Results: The figure shows connectivity patterns for ventral precuneus seed (MNI coordinates: 0, -60, 24) in one control subject and in one patient. We observed robust connectivity of this seed point with fusiform gyri, parahippocampus and hippocampus. Connectivity pattern was found to be bilateral and symmetric in control subjects, (Fig 1A), which is in agreements with literature reports. In contrast, results observed in an epileptic patients with left hippocampal sclerosis exhibited an asymmetric pattern of connectivity (Fig1B). Connectivity is decreased on the left hemisphere and appears most asymmetric in the hippocampal and parahippocampal regions. Conclusions: Connectivity in memory networks revealed with fcMRI analysis is bilateral and symmetric in control subjects. This finding appears to be sufficiently robust, so that connectivity patterns can be assessed in individual subjects. Observation in two epileptic patients with hippocampal sclerosis revealed a deviation from the typical connectivity pattern with diminished connectivity on the side ipsilateral to the MTS. We intend to collect the data in several such patients and study the relationship between the connectivity patterns, the extent and localization of hippocampal sclerosis and the degree of memory function disruption, as assessed by neuropsychological testing.