Abstracts

Rationale: To describe sleep structures and localize their intracranial generators on subdural electrodes (SDE) during monitoring for epilepsy surgery. Analysis of sleep structures including spindles, V-waves, K-complexes, as recognized on simultaneous scalp and SDE recordings Methods: K complexes, Spindles and Vertex waves on Cz surface recordings were correlated with areas of the cortex on implanted electrodes. Maximum amplitude was assessed using the contra-lateral ear electrode as reference. Sleep architecture was defined according to the AASM Manual for the Scoring of Sleep and Associated Events. Fifteen of the sleep elements each were analyzed per patient. SDE localization was divided as: perirolandic (superior, middle and inferior pre and post-central area); frontal (lateral, mesial, anterior, orbito-frontal), parietal, occipital and temporal (lateral, mesial, basal) coverage. The electrode location was confirmed in seven patients using MRI 3D reconstruction and in the remaining seven patients by 3D CT reconstruction Results: Fourteen patients, ages of 3 to 21 years (mean 11.4years; 8 males) were analyzed. Twelve patients had SDE placement involving the perirolandic area, one had exclusively temporal coverage and one had posterior SDE. The etiology of the epilepsy included developmental lesions in six, recognized acquired lesions in five and unknown mechanism in three. Spindles were visualized maximally in the central peri-sulcal region, but also seen in the frontal regions, including the mesial areas. Vertex waves and K complex were also seen maximally in the perirolandic area with field in the anterior regions. They were not seen in electrodes representing the hippocampus and mesial temporal areas. Cortical surface location in patients with MRI 3D reconstruction included: spindles and vertex waves in the middle frontal gyrus (n=2), precentral gyrus (n=2) and post-central gyrus (n=1). K complexes were seen in the middle frontal gyrus (n=1) and in the pre-central gyrus (n=4). Conclusions: This study provides the first description of sleep architecture using SDE coverage. Results have to interpreted in the setting of SDE location. Neuronal generators related to different sleep components have different locations and our preliminary data shows that there is a good cortical representation of sleep architecture correlating with traditional scalp electrodes.