Linking Memory Impairment to Structural Connectivity in Extrahippocampal Temporal Lobe Epilepsy Surgery

Area of Science:

• Neuroscience
• Epileptology
• Cognitive Neurology

Background:

• Temporal lobe epilepsy (TLE) is the most common epilepsy syndrome, often refractory to medication.
• A significant portion of TLE cases originate from extrahippocampal lesions, necessitating tailored surgical interventions.
• While surgery offers seizure control, postoperative memory decline remains a concern, particularly after lesionectomy.

Purpose of the Study:

• To investigate the relationship between structural connectivity and memory performance after surgery in patients with extrahippocampal TLE.
• To identify specific brain structures and white matter pathways associated with cognitive outcomes post-lesionectomy.

Main Methods:

• Evaluated 55 patients with extrahippocampal TLE undergoing hippocampal-sparing surgery using pre- and postoperative neuropsychological testing.
• Utilized Human Connectome Project tractography data intersected with lesion volumes.
• Employed voxel-based and connectome-informed lesion-symptom mapping to assess structural connectivity and its link to cognitive function.

Main Results:

• Widespread structural disconnection of major white matter pathways was observed post-surgery.
• These disconnections significantly correlated with deficits in verbal memory and delayed recall.
• Disconnection of ipsilateral temporal lobe white matter was additionally associated with hippocampal atrophy.

Conclusions:

• Structural connectivity alterations play a crucial role in postoperative memory decline following extrahippocampal TLE surgery.
• Findings emphasize the importance of broader structural networks beyond hippocampal integrity for memory function.
• Connectome-informed, individualized surgical strategies may be beneficial for protecting neurocognitive function.