Clinical Manifestations of Insular Lobe Seizures: A Stereo‐electroencephalographic Study

Abstract

Summary:Purpose: In this study, we report the clinical features of insular lobe seizures based on data from video and stereo-electroencephalographic (SEEG) ictal recordings and direct electric insular stimulation of the insular cortex performed in patients referred for presurgical evaluation of temporal lobe epilepsy (TLE).Methods: Since our first recordings of insular seizures, the insular cortex has been included as one of the targets of stereoelectroencephalographic (SEEG) electrode implantation in 50 consecutive patients with TLE whose seizures were suspected to originate from, or rapidly to propagate to, the perisylvian cortex. In six, a stereotyped sequence of ictal symptoms associated with intrainsular discharges could be identified.Results: This ictal sequence occurred in full consciousness, beginning with a sensation of laryngeal constriction and paresthesiae, often unpleasant, affecting large cutaneous territories, most often at the onset of a complex partial seizure (five of the six patients). It was eventually followed by dysarthric speech and focal motor convulsive symptoms. The insular origin of these symptoms was supported by the data from functional cortical mapping of the insula by using direct cortical stimulations.Conclusions: This sequence of ictal symptoms looks reliable enough to characterize insular lobe epileptic seizures (ILESs). Observation of this clinical sequence at the onset of seizures on video-EEG recordings in TLE patients strongly suggests that the seizure-onset zone is located not in the temporal but in the insular lobe; recording directly from the insular cortex should occur before making any decision regarding epilepsy surgery.

Generalized epileptic discharges show thalamocortical activation and suspension of the default state of the brain

“…The insula is a region of convergence of multisensory inputs that has recently been implicated in focal seizures (13) but not in generalized discharges. The insula has widespread thalamic connections, however (14), which may explain its activation during generalized spike-and-wave.…”

Parallel Processing of Nociceptive A-δ Inputs in SII and Midcingulate Cortex in Humans

“…Among other sites, these patients had electrodes chronically implanted in the cingulate cortex and the second somatosensory area (SII) for the recording of their seizures. The decision to explore these areas resulted from the observation during scalp video-EEG recordings of ictal manifestations suggesting the possibility of seizures propagating to or originating from these regions (for a complete description of the rationale of electrode implantation, see Isnard et al, 2000Isnard et al, , 2004. This procedure, performed routinely before epilepsy surgery in patients implanted with depth electrodes, is completed by the functional mapping of potentially eloquent cortical areas using evoked potentials recordings and cortical electrical stimulation [for a description of the stimulation procedure, see Ostrowsky et al (2002) and Mazzola et al (2006)].…”

The Hippocampus Codes the Uncertainty of Cue–Outcome Associations: An Intracranial Electrophysiological Study in Humans

“…The procedure did not entail any additional risk for the subjects and was thus ethically acceptable according to French regulation. The target structures implanted with depth electrodes to identify the potential epileptogenic foci before eventual functional surgery were defined on the basis of noninvasive videoscalp EEG recordings, structural MRI, 18 fluorodeoxyglucose (18FDG) positron emission tomography (PET), and ictal SPECT (single photon emission computed tomography) [for a complete description of the rationale of electrode implantation, see the study by Isnard et al (2004)]. Structural MRI and 18FDG PET scans showed no hippocampal atrophy or hypometabolism in any of the three subjects.…”