improving-outcomes-anteromesial-temporal-lobe-resections

Improving Outcomes in Anteromesial Temporal Lobe Resections - A Demonstration of Resecting the Temporal Piriform Cortex

Anteromesial temporal lobe resection (ATLR) is a useful treatment option for drug-resistant mesial temporal lobe epilepsy (DRmTLE). Growing evidence ...

National Hospital for Neurology and Neurosurgery

Anteromesial temporal lobe resection is the most common surgical technique used to treat drug-resistant mesial temporal lobe epilepsy, particularly when secondary to hippocampal sclerosis. Structural and functional imaging data suggest the importance of sparing the posterior hippocampus for minimising language and memory deficits. Recent work has challenged the view that maximal posterior hippocampal resection improves seizure outcome. This study was designed to assess whether resection of posterior hippocampal atrophy was associated with improved seizure outcome.

Hippocampal resection in temporal lobe epilepsy: Do we need to resect the tail?

Around 50% of patients undergoing frontal lobe surgery for focal drug-resistant epilepsy become seizure free post-operatively; however, only about 30% of patients remain seizure free in the long-term. Early seizure recurrence is likely to be caused by partial resection of the epileptogenic lesion, whilst delayed seizure recurrence can occur even if the epileptogenic lesion has been completely excised. This suggests a coexistent epileptogenic network facilitating ictogenesis in close or distant dormant epileptic foci. As thalamic and striatal dysregulation can support epileptogenesis and disconnection of cortico-thalamostriatal pathways through hemispherotomy or neuromodulation can improve seizure outcome regardless of focality, we hypothesize that projections from the striatum and the thalamus to the cortex may contribute to this common epileptogenic network. To this end, we retrospectively reviewed a series of 47 consecutive individuals who underwent surgery for drug-resistant frontal lobe epilepsy. We performed voxel-based and tractography disconnectome analyses to investigate shared patterns of disconnection associated with long-term seizure freedom. Seizure freedom after 3 and 5 years was independently associated with disconnection of the anterior thalamic radiation and anterior cortico-striatal projections. This was also confirmed in a subgroup of 29 patients with complete resections, suggesting these pathways may play a critical role in supporting the development of novel epileptic networks. Our study indicates that network dysfunction in frontal lobe epilepsy may extend beyond the resection and putative epileptogenic zone. This may be critical in the pathogenesis of delayed seizure recurrence as thalamic and striatal networks may promote epileptogenesis and disconnection may underpin long-term seizure freedom.

Thalamostriatal disconnection underpins long-term seizure freedom in frontal lobe epilepsy surgery.

Knowledge of the structural underpinnings of human verbal memory is scarce. Understanding the human verbal memory network at a finer anatomical scale will have important clinical implications for the management of patients with verbal memory impairment. In this cross-sectional study, we aimed to assess the contributions of cerebral cortex and hippocampal subfields to verbal memory encoding in temporal lobe epilepsy. We included consecutive patients ( = 84) with radiologically and pathologically defined hippocampal sclerosis (HS) (44 left-sided) and unilateral temporal lobe epilepsy, and healthy volunteers ( = 43) who were comparable regarding age and sex. The morphometric and volumetric measures of cerebral cortex and hippocampal subfields were extracted from high-resolution MRI scans. People included in this study underwent standardized neuropsychological evaluation, including measures of verbal memory assessed through the Adult Memory and Information Processing Battery. Verbal memory performances were -scores corrected by using means and standard deviations published for sample standardization. Associations between verbal learning -scores and the grey matter volume of the cerebral cortex and hippocampal subfields were investigated. Reduction of grey matter volumes in the left and right medial and dorsolateral prefrontal cortex (  < 0.0001), superior and middle temporal gyri (  < 0.0001), anterior and posterior cingulate cortex (  < 0.0001) and of the left ventrolateral prefrontal cortex (  < 0.0001) and parietal-temporal-occipital junction (  < 0.0001) were associated with worse verbal learning. These findings were consistent across both the entire cohort and in a subgroup analysis focused exclusively on HS patients. Within hippocampi, smaller volumes of the left dentate gyrus ( = 0.003), cornu ammonis 4 ( = 0.005) and cornu ammonis 3 ( = 0.03) were associated with worse verbal learning -scores. This study demonstrates that verbal learning in patients with temporal lobe epilepsy is strongly related to the volume of distinct regions of the prefrontal, temporal and cingulate cortices and left dentate gyrus, cornu ammonis 4 and cornu ammonis 3 hippocampal subfields. It provides the basis to suggest a corticohippocampal network for verbal learning in these patients, improving our understanding of human verbal memory. These biomarkers may inform attractive targets for forthcoming modulating therapies. Future work may also analyse the impact of sparing part of the left dentate gyrus, cornu ammonis 4 and cornu ammonis 3 as a protective measure against verbal memory impairment after surgery for temporal lobe epilepsy.

Article	Year
Hippocampal resection in temporal lobe epilepsy: Do we need to resect the tail? Epilepsy research\| PubMed ID: 36709527	2023
Thalamostriatal disconnection underpins long-term seizure freedom in frontal lobe epilepsy surgery. Brain : a journal of neurology\| PubMed ID: 37062539	2023
Cortico-hippocampal networks underpin verbal memory encoding in temporal lobe epilepsy. Brain communications\| PubMed ID: 40109560	2025

Roisin Finn

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