Homotopic reciprocal functional connectivity between anterior human insulae.

The aim of this study was to investigate functional connectivity between right and left insulae in the human brain. We studied a patient with implanted depth electrodes for epilepsy surgery evaluation with stereotactically placed symmetric depth electrodes in both insulae. Bipolar 1 Hz electrical stimulation of the right and left posterior short gyri in the anterior insula evoked responses in the contralateral insular structures. These responses showed a latency of 8-24 ms. This report demonstrates for the first time bi-directional homotopic and heterotopic functional connectivity between right and left anterior insulae. The short latency of the evoked responses suggests mono- or oligo-synaptic connections, most likely via the corpus callosum.

Functional connectivity between right and left mesial temporal structures.

The aim of this study is to investigate functional connectivity between right and left mesial temporal structures using cerebrocerebral evoked potentials. We studied seven patients with drug-resistant focal epilepsy who were explored with stereotactically implanted depth electrodes in bilateral hippocampi. In all patients cerebrocerebral evoked potentials evoked by stimulation of the fornix were evaluated as part of a research project assessing fornix stimulation for control of hippocampal seizures. Stimulation of the fornix elicited responses in the ipsilateral hippocampus in all patients with a mean latency of 4.6 ms (range 2-7 ms). Two patients (29 %) also had contralateral hippocampus responses with a mean latency of 7.5 ms (range 5-12 ms) and without involvement of the contralateral temporal neocortex or amygdala. This study confirms the existence of connections between bilateral mesial temporal structures in some patients and explains seizure discharge spreading between homotopic mesial temporal structures without neocortical involvement.

Can semiology predict psychogenic nonepileptic seizures? A prospective study.

OBJECTIVE: Reducing health and economic burdens from diagnostic delay of psychogenic nonepileptic seizures (PNES) requires prompt referral for video electroencephalography (VEEG) monitoring, the diagnostic gold standard. Practitioners make VEEG referrals when semiology suggests PNES, although few semiological signs are supported by well-designed studies, and most VEEG studies neglect to concurrently measure how accurately seizure witnesses can ascertain semiology. In this study, we estimate the value of eyewitness-reported and video-documented semiology for predicting PNES, and we measure accuracy of eyewitness reports. METHODS: We prospectively interviewed eyewitnesses of seizures in patients referred for VEEG monitoring, to inquire about 48 putative PNES and ES signs. Multiple, EEG-blinded, epileptologists independently evaluated seizure videos and documented the presence/absence of signs. We used generalized estimating equations to identify reliable video-documented PNES and ES signs, and we compared eyewitness reports with video findings to assess how accurately signs are reported. We used logistic regression to determine whether eyewitness reports could predict VEEG-ascertained seizure type. RESULTS: We analyzed 120 seizures (36 PNES, 84 ES) from 35 consecutive subjects. Of 45 video-documented signs, only 3 PNES signs ("preserved awareness," "eye flutter," and "bystanders can intensify or alleviate") and 3 ES signs ("abrupt onset," "eye-opening/widening," and postictal "confusion/sleep") were significant and reliable indicators of seizure type. Eyewitness reports of these 6 signs were inaccurate and not statistically different from guessing. Consequentially, eyewitness reports of signs did not predict VEEG-ascertained diagnosis. We validated our findings in a second, prospective cohort of 36 consecutive subjects. INTERPRETATION: We identified 6 semiological signs that reliably distinguish PNES and ES, and found that eyewitness reports of these signs are unreliable. We offer suggestions to improve the accuracy of eyewitness reports.