Hippocampal spindles and barques are normal intracranial electroencephalographic entities

Objective: To assess whether hippocampal spindles and barques are markers of epileptogenicity. Methods: Focal epilepsy patients that underwent stereo-electroencephalography implantation with at least one electrode in their hippocampus were selected (n = 75). The occurrence of spindles and barques in the hippocampus was evaluated in each patient. We created pairs of pathologic and pathology-free groups according to two sets of criteria: 1. Non-invasive diagnostic criteria (patients grouped according to focal epilepsy classification). 2. Intracranial neurophysiological criteria (patient's hippocampi grouped according to their seizure onset involvement). Results: Hippocampal spindles and barques appear equally often in both pathologic and pathology-free groups, both for non-invasive (P-spindles = 0.73; P-barques = 0.46) and intracranial criteria (P-spindles = 0.08; P-barques = 0.26). In Engel Class I patients, spindles occurred with similar incidence both within the noninvasive (P = 0.67) and the intracranial criteria group (P = 0.20). Barques were significantly more frequent in extra-temporal lobe epilepsy defined by either non-invasive (P = 0.01) or intracranial (P = 0.01) criteria. Conclusions: Both spindles and barques are normal entities of the hippocampal intracranial electroencephalogram. The presence of barquesmayalso signify lack of epileptogenic properties in the hippocampus. Significance: Understanding that hippocampal spindles and barques do not reflect epileptogenicity is critical for correct interpretation of epilepsy surgery evaluations and appropriate surgical treatment selection. (C) 2021 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Automated summary

The study evaluated whether hippocampal spindles and barques are markers of epileptogenicity in epilepsy patients. The results show that both spindles and barques are normal entities in the hippocampal intracranial electroencephalogram and do not indicate epileptogenic properties. Understanding this is crucial for the correct interpretation of epilepsy surgery evaluations and the selection of appropriate surgical treatments.