Abstracts

Rationale: Conscious perception refers to the mindful processing of a given piece of information. The neural mechanisms underlying conscious perception are not well-understood, although close association with spatial attention has been suggested. Some pieces of information vanish from consciousness almost immediately, while others persist long enough for an individual to report them. Focal aware seizures are defined as awareness of ictal symptoms.  Awareness alone has not been reported as symptom of focal seizures or cortical-stimulation (CS) induced after discharges (ADs). We report a case of CS induced ADs with awareness as its only symptom. Methods: An 18-years old right-handed man with focal onset intractable epilepsy and neuroradiological evidence of cortical dysplasia in the paracentral gyrus (mainly affecting the postcentral gyruswith some extension in the precentral gyrus)was implanted with 8x8 grid and two 1x6 strips covering the right fronto-parietal and superior temporal areas for localization of ictal onset zone (IOZ) and eloquent cortex (via bedside cortical stimulation (CS)).  A Grass S12 isolated biphasic stimulator was used with 50Hz pulse frequency, pulse duration of 300 microseconds/phase and stimulus duration of ~3 seconds for motor and sensory mapping. Results: During CS adjacent electrode pairs were tested and physiological motor and sensory areas were successfully mapped.  CS induced both the patient’s typical aura (“stranger than confusion” with no Ads) and electroclinical seizures in the IOZ as well as motor and sensory responses.  The above information helped localization of sensory-motor cortices (SMC) and IOZ and otherwise are not subject of this abstract.  Following stimulation at multiple sites over the wide area of fronto-parieto-temporal regions (outside of IOZ), the patient reported a sensation of 'as if confusion' while remaining otherwise asymptomatic and fully neurocognitively intact. This sensation corresponded on the ICEEG to after-discharges of variable duration (ranging from 1 second to more than 10 seconds [i.e. electrographic seizures]) and highly variable spatial distribution (affecting 3 to more than 20 electrodes).  Over multiple trials, the patient was able to reliably identify the onset and offset of ADs on the basis of this awareness alone.  Sham stimulations and CS without ADs did not result in awareness (i.e. report of “as if confusion”) Conclusions: CS resulted in ADs and focal seizures (FS) with variable temporal and spatial distribution, long enough to be perceived and reported by our patient.  Except for “as if confusion”, the ADs and FS did not result in any other motor, sensory, gastric or psychic phenomenon and had disruption of non-dominant hemispheric networks in common. Therefore we posit that our patient’s focal aware seizures were the result of ADs disrupting cortical networks involved in conscious perception and spatial attention without any other accompanying motor or sensory phenomena. Funding: No funding