Objective: To describe pure insular ictal semiology and patterns of extra-insular spread demonstrated by stereoelectroencephalography (SEEG) according to a classification based on the insular cytoarchitecture.
Methods: We investigated the ictal semiology in 17 patients undergoing SEEG for insular epilepsy. The insular cortex was divided into three regions roughly overlapping with the agranular, dysgranular and granular regions. Ictal semiology was described accordingly: anterior insula (AI, short anterior and middle gyri), middle insula (MI, short posterior and long anterior gyri) and posterior insula (PI, long posterior gyrus).
Results: Awareness impairment occurred secondarily to extra-insular ictal spread. Subjective manifestations were constant. AI seizures (n = 3) presented with autonomic (increased heart rate [HR], respiratory changes), oropharyngeal (mainly throat sensations), emotional (fear, anguish) semiology and the "hand-to-throat" sign followed by frontal-like semiology. MI seizures (n = 8) presented with mainly non-painful paresthesia, some autonomic (respiratory, increased HR), oropharyngeal or thermic symptoms and early motor features with spread to the opercular cortex. PI seizures (n = 6) were characterized by somatosensory semiology, mainly paresthesia potentially painful, and cephalic sensations.
Conclusions: Cytoarchitectonic-based classification and the corresponding ictal features support the antero-posterior grading of insular seizures and highlight specific ictal symptoms.
Significance: This refinement of insular semiology can help optimize the planning of SEEG for presumed insular epilepsy.
Keywords: Cytoarchitecture; Functional connectivity; Insular epilepsy; Semiology; Stereoelectroencephalography.
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