Mapping the Phenotypic Spectrum of Occipital Lobe Epilepsy: A SEEG-Defined Network Classification

Area of Science:

• Neuroscience
• Epileptology
• Clinical Neurology

Background:

• Occipital lobe epilepsy (OLE) often exhibits complex symptoms beyond visual disturbances, complicating diagnosis and localization.
• Stereo-electroencephalography (SEEG) is crucial for detailed seizure investigation.

Purpose of the Study:

• To systematically characterize the seizure phenotype spectrum in OLE using SEEG.
• To elucidate the electrophysiological and anatomical basis of OLE seizure propagation.
• To correlate clinical phenotypes with specific SEEG-defined propagation networks.

Main Methods:

• Retrospective case series of 19 OLE patients undergoing SEEG.
• Classification of seizure phenotypes based on clinical manifestations.
• Coregistration of SEEG with MRI/CT for seizure onset zone and propagation pathway identification.
• Analysis of electroclinical correlations and dual-stream model for network mapping.

Main Results:

• Five distinct clinical phenotypes were identified: pure visual, visual-automatism, visual-oculomotor-motor, oculomotor onset, and behavioral arrest-motor.
• Four reproducible SEEG propagation patterns were observed: restricted, ventral stream-limbic, dorsal-medial/default mode network-limbic, and lateral occipital-temporoparietooccipital junction (TPOJ).
• The TPOJ and posterior cingulate/precuneus act as key hubs for rapid network propagation.

Conclusions:

• A preliminary anatomical-electrophysiological-clinical classification for OLE is proposed.
• OLE seizure phenotypes are associated with structured, pathway-specific network recruitment.
• A phenotype-driven SEEG approach can inform presurgical evaluation and surgical planning for OLE.