Abstract:
Objective:
To define networks affected by mesial temporal lobe epilepsy (MTLE) pathology. Background:
The brain is organized into a robust set of canonical networks that are detectable across imaging modalities and invariant to analytic method. The same functional architecture is reflected in pathology, vis-à-vis the Network Degeneration Hypothesis. Imaging studies of MTLE often focus on canonical network effects, reporting regional changes congruent with semiology. However, MTLE-specific networks remain ill-defined. Design/Methods:
A comprehensive literature search identified 45 structural and 29 resting-state-functional imaging experiments, collectively reporting 588 coordinate-foci of pathology (n=1599 MTLE subjects). Patterns of coordinate co-occurrence (within and across experiments) were computed using independent component analysis (FSL-MELODIC.v3.14). Spatial cross-correlations (FSL.v6.0.4) were computed to assess the stability of and overlap between network-patterns. Functional interpretations were obtained by regional behavioral analysis (Mango.v4.1; http://rii.uthscsa.edu/mango/plugin_behavioralanalysis.html) of healthy task-activation data (20,998 experiments; n=103,977) from the BrainMap database (https://www.brainmap.org/). Effect modification was assessed (χ2-homogeneity). Results:
Two stable (R=0.890) network-patterns were identified in the MTLE literature, bearing little resemblance to canonical architecture (R<0.3). Network-patterns overlapped at the hippocampus/MDN-thalamus but were otherwise spatially distinct (R=0.042). Network-1 (supramarginal, frontal/precentral, fusiform, temporal, and occipital gyri) was associated with verbal (speech-action: Z=8.23; speech-cognition: Z=6.85), motor (Z=6.06), and visual (Z=4.30) tasks. Network-2 (frontal, temporal and cingulate cortical areas, pulvinar, anterior-nucleus, and contralesional-parahippocampus) was associated with limbic (explicit-memory: Z=5.42; positive-emotion: Z=4.54) and executive-function (attention: Z=4.65; reasoning: Z=3.15) tasks. No effect-modification was observed (p>0.05); structural and functional data contributed equally to both networks. Conclusions:
This study identifies two distinct networks in MTLE. Seizure propagation along these networks is congruent with ictal observations of communication deficits, stereotypic behaviors, and visual hallucinosis (Network-1) as well as dyscognitive effects, transient amnesia, and pre-/post-ictal social-emotional deficits (Network-2). These cortical networks may underlie discrete behavioral phenomena manifested in MTLE; further investigation is required to determine their precise functions as they relate to the peri-ictal continuum. Disclosure: The institution of Mr. Towne has received research support from NIH T32GM113896. Dr. Eslami has nothing to disclose. Mr. Fox has nothing to disclose. Dr. Cavazos has received stock or an ownership interest from Brain Sentinel . The institution of Dr. Cavazos has received research support from NIH. Dr. Fox has received personal compensation in the range of $10,000-$49,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Wiley. The institution of Dr. Fox has received research support from NIH. Dr. Fox has received intellectual property interests from a discovery or technology relating to health care. Dr. Fox has received personal compensation in the range of $500,000-$999,999 for serving as a Reviewer with NIH. 
