Abstract
BackgroundVersive seizure characterized by conjugate eye movement during epileptic seizure has been considered commonly as one of the most valuable semiological signs for epilepsy localization, especially for frontal lobe epilepsy. However, the lateralizing and localizing significance of ictal eye deviation has been questioned by clinical observation of a series of focal epilepsy studies, including frontal, central, temporal, parietal and occipital epilepsy.Case presentationTwo epileptic cases characterized by ipsiversive eye deviation as initial clinical sign during the habitual epileptic seizures are presented in this paper. The localization of the epileptogenic zone of both of the cases has been confirmed as inferioposterior temporal region by the findings of ictal stereoelectroencephalography (SEEG) and a good result after epileptic surgery. Detailed analysis of the exact position of the key contacts of the SEEG electrodes identified the overlap between the location of the epileptogenic zone and human MT/MST complex, which play a crucial role in the control of smooth pursuit eye movement.ConclusionIpsiversive eye deviation could be the initial clinical sign of inferioposterior temporal lobe epilepsy and attribute to the involvement of human MT/MST complex, especially human MST which was located on the anterior/dorsal bank of the anterior occipital sulcus (AOS).
Highlights
Versive seizure characterized by conjugate eye movement during epileptic seizure has been considered commonly as one of the most valuable semiological signs for epilepsy localization, especially for frontal lobe epilepsy
Ipsiversive eye deviation could be the initial clinical sign of inferioposterior temporal lobe epilepsy and attribute to the involvement of human middle temporal (MT)/medial superior temporal (MST) complex, especially human MST which was located on the anterior/ dorsal bank of the anterior occipital sulcus (AOS)
Inspired by the physiological and functional evidence from macaque and the human brain, and the precise anatomical localization of the human MST and MT based on the data from neurophysiologic and functional neuroimaging studies, we hypothesized that the mechanisms of epileptic semiology of ipsiversive eye deviation in the two cases, whose epileptogenic zone has been confirmed to be located in the inferoposterior temporal region, can be explained by involvement of the cortical network of eye movement control, in terms of the smooth pursuit movement
Summary
These are the first cases reports focusing on the epileptic ipsiversive eye deviation by using SEEG recordings. According to the neurophysiologic and functional neuroimaging evidence mentioned above, the core anatomical marker and probable boundary of the cortical location of human MST/MT is the AOS (the ascending limb of the ITS), which had been explored adequately with the exploration of its adjacent and related cortical areas in the two cases. The relationship of exact location of epileptogenic zones of the two cases and AOS convinces us that the manifestation of epileptic ipsiversive eye deviation should be attributed to the neurophysiologic and neuropsychological characteristics of MT+, especially area MST, and its functional role in cortical control of smooth pursuit eye movements
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