Characterization of postsurgical functional connectivity changes in temporal lobe epilepsy

Abstract

OBJECTIVESeizure outcome after mesial temporal lobe epilepsy (mTLE) surgery is complex and diverse, even across patients with homogeneous presurgical clinical profiles. The authors hypothesized that this is due in part to variations in network connectivity across the brain before and after surgery. Although presurgical network connectivity has been previously characterized in these patients, the objective of this study was to characterize presurgical to postsurgical functional network connectivity changes across the brain after mTLE surgery.METHODSTwenty patients with drug-refractory unilateral mTLE (5 left side, 10 female, age 39.3 ± 13.5 years) who underwent either selective amygdalohippocampectomy (n = 13) or temporal lobectomy (n = 7) were included in the study. Presurgical and postsurgical (36.6 ± 14.3 months after surgery) functional connectivity (FC) was measured with 3-T MRI and compared with findings in age-matched healthy controls (n = 44, 21 female, age 39.3 ± 14.3 years). Postsurgical connectivity changes were then related to seizure outcome, type of surgery, and presurgical disease parameters.RESULTSThe results demonstrated significant decreases of FC from control group values across the brain after surgery that were not present before surgery, including many contralateral hippocampal connections distal to the surgical site. Postsurgical impairment of contralateral precuneus to ipsilateral occipital connectivity was associated with seizure recurrence. Presurgical impairment of the contralateral precuneus to contralateral temporal lobe connectivity was associated with those who underwent selective amygdalohippocampectomy compared to those who had temporal lobectomy. Finally, changes in thalamic connectivity after surgery were linearly related to duration of epilepsy and frequency of consciousness-impairing seizures prior to surgery.CONCLUSIONSThe widespread contralateral hippocampal FC changes after surgery may be a reflection of an ongoing epileptogenic progression that has been altered by the surgery, rather than a direct result of the surgery itself. This network evolution may contribute to long-term seizure outcome. Therefore, the combination of presurgical network mapping with the understanding of the dynamic effects of surgery on the networks may ultimately be used to create predictors of the likelihood of long-term seizure recurrence in individual patients after mTLE surgery.

Large-scale resculpting of cortical circuits in children after surgical resection

“…faces). In addition, given that FC changes have been reported for subcortical structures 15 , we also included two anatomically demarcated vision-relevant subcortical ROIs: the lateral geniculate nucleus (LGN) and the pulvinar (see Materials and Methods: Defining the functional category-specific ROIs for details). Next, in the analysis of anatomically defined ROIs, we used affine and non-linear transformations to register the HCP atlas and derive anatomical parcellations in each participant’s native volumetric space (see Materials and Methods: Anatomical parcellation for details).…”

“…Many studies have documented altered post-surgical FC among networks or ROIs. For example, Morgan et al 15 reported that post-surgical FC, especially that of thalamus and hippocampus, may contribute to long-term seizure outcome and Liao et al 16 revealed differences in FC in patients, especially in the temporoparietal junction and its connection with the ventral prefrontal cortex. Typical language localization after surgery has also been associated with better functional integration of various networks including the default mode network 17 and Ivanova et al 18 described at least partial preservation of FC of language areas in the intact right hemisphere.…”

Remote effects of temporal lobe epilepsy surgery: long-term morphological changes after surgical resection

“…This may suggest a structural analog to the compensatory mechanism previously observed. Furthermore, recent work has demonstrated a long term functional connectivity changes in the contralateral hippocampus after surgery 48 .…”

All hands on deck: Large-scale (re)sculpting of cortical circuits in post-resection children

“…Many studies have documented altered post-surgical FC among networks or ROIs. For example, Morgan et al (2019) reported that post-surgical FC, especially that of thalamus and hippocampus, may contribute to long-term seizure outcome and Liao et al (2016) revealed differences in FC in patients, especially in the temporoparietal junction and its connection with the ventral prefrontal cortex. Typical language localization after surgery has been associated with better functional integration of various networks including the default mode network (Ibrahim et al, 2015) and Ivanova et al (2017) described at least partial preservation of FC of language areas in the intact right hemisphere.…”

“…faces). In addition, given that FC changes have been reported for subcortical structures (Morgan et al, 2019), we also included two anatomically demarcated vision-relevant subcortical ROIs:…”