Altered Functional Network May Cause Cognitive Impairment in Temporal Lobe Epilepsy Patients

VANCOUVER, British Columbia — New research suggests that an altered functional network involving both ipsilateral and contralateral hippocampal areas was associated with cognitive impairment in patients with temporal lobe epilepsy (TLE).

The results were presented at the 2016 annual meeting of the American Academy of Neurology (AAN).

According to the investigators, human brain functional connectivity has been implicated in normal and abnormal brain functions, including epilepsy.

“In TLE, alteration in functional connectivity may involve both seizure generation and comorbid cognitive impairment, especially memory dysfunction,” the researchers wrote in the abstract. “This study aimed to investigate functional connectivity alteration related to epileptic activities and cognitive functions in TLE patients.”

The study included 99 patients—36 with left TLE, 33 with right TLE, and 30 controls — who underwent electroencephalography, 3-Tesla structural and functional brain magnetic resonance imaging (MRI), and neuropsychologic evaluations.

Researchers assessed FC data based on resting state functional MRI (rs-fMRI), utilizing left/right hippocampal regions of interest. Furthermore, neuropsychologic performance was determined with the Korean version of the California Verbal Learning Test (K-CVLT), the Rey-Kim Complex Figure Test (CFT), the Controlled Oral Word Association Test, the Boston Naming Test (BNT), and the Stroop test.

Researchers reported lower neuropsychologic performance scores in patients with TLE compared with controls. The results indicated that K-CVLT and BNT were more impaired in left vs right TLE (P=.025 and P<.005, respectively), and that CFT was more impacted in the poor seizure control group than the good seizure control group (P=.017).

Additional analysis suggested that functional connectivity between the left and right hippocampus to the whole brain was reduced in TLE, although the researchers noted relatively higher hippocampal connectivity in the lesion side (ipsilateral) compared with the intact side (contralateral) in left and right TLE (corrected P<.005 for both).

There was also an association between more preserved verbal memory scores and higher hippocampal connectivity in ipsilateral and contralateral sides (corrected P<.001 for both), which may suggest possible compensatory mechanisms along with pathophysiologic changes in these areas.

“Cognitive impairment in TLE patients can be related to altered functional network involving both ipsilateral and contralateral hippocampal areas as measured by functional connectivity analysis based on rs-fMRI,” the researchers concluded. “These findings support the concept of functional network involvement in TLE, not only for epileptogenesis, but also for comorbid memory dysfunction.”

Click here for more coverage from the 68^th Annual Meeting of the American Academy of Neurology, April 15-21, 2016, in Vancouver, British Columbia, Canada.

Reference

Jung A, Park C, Choi YS, Yoo JH, Lee HW. Functional brain connectivity and memory impairment in temporal lobe epilepsy. Presented at: The 68th Annual Meeting of the American Academy of Neurology; April 15-21, 2016; Vancouver, British Columbia, Canada. Abstract I7.007.