Abstracts

Rationale: Resting state functional magnetic resonance imaging (rsfMRI) has emerged over the past decade as a method to characterize network phenomena in the brain. Areas with correlated signal changes over time are deemed to be connected with one another. RsfMRI studies of epileptic patients have demonstrated alterations in typical brain connectivity within various cognitive domains including language, motor, and memory function, as well as widespread network abnormalities. For example, patients with mesial temporal lobe epilepsy have decreased connectivity within the epileptogenic temporal lobe and increased connectivity to extra-temporal sites. Malformations of cortical development (MCD) are a common cause of epilepsy and can be associated with both focal and widespread network alterations. In this study, we examined rsfMRI connectivity changes associated with MCDs in patients with epilepsy compared to healthy controlsMethods: Seven subjects diagnosed with epilepsy and MCDs confirmed by structural MRI were recruited: two subjects with focal nodular heterotopia, two with polymicrogyria, and three with focal cortical dysplasia. Each subject underwent a five-minute rsfMRI scan while looking at a projected fixation cross using a 3 T GE scanner (GE, Waukesha, WI). Regions of interest (ROIs) were generated encompassing the entire MCD for each subject. These ROIs were used to assess the connectivity between the MCD and the rest of the brain. These data were then compared to five age-matched healthy controls, looking for areas of increased or decreased connectivity at the sites of malformation.Results: In 6/7 (85%) subjects, the MCDs showed significantly less global connectivity when compared to analogous healthy tissue in the controls (Figure 1). Also, the MCDs had greater connectivity within the malformation ROI compared to the analogous site in healthy controls. One subject demonstrated significantly greater global connectivity at the MCD compared to healthy controls. The type of malformation did not impact the connectivity findings.Conclusions: Based on these data, MCDs show less connectivity to the rest of the brain compared to analogous healthy tissue. In contrast, there is increased connectivity within the MCD itself compared to healthy tissue. These data suggest that focal MCDs may cause widespread network disturbances that result in relative isolation of the malformed tissue.