Ferrao Santos, Susana
[UCL]
Liberati, Giulia
[UCL]
Klöcker, Anne
[UCL]
Maia da Cunha Oliveira Safronova, Marta
[UCL]
Ribeiro Vaz, José Géraldo
[UCL]
Raftopoulos, Christian
[UCL]
Mouraux, André
[UCL]
Introduction : Insular epilepsy is rare and difficult to diagnose. Surface electroencephalography is not modified by specific insular epileptiform activity (EA), and there are few clinical features pointing specifically to an insular ictal onset zone (IOZ). Functions attributed to the insula include autonomic regulation and somesthesic integration. Furthermore, the insula is thought to play a major role in the perception of pain, a multi-dimensional experience, including sensory, affective, and cognitive components. We recently found that nociceptive stimuli elicit consistent gamma-band oscillations (GBO) in the human insula (manuscript in preparation: Pain specific gamma-band oscillation in the human insula. Same authors). Because non-nociceptive stimuli do not elicit a similar response, these high frequency oscillations could reflect activity specific for nociception. Here we analysed how EA affects GBO within insular cortex. Methods : Intracerebral activity was recorded from a total of 8 insulae in 7 patients with deep multicontact electrodes, implanted for the presurgical evaluation of focal epilepsy. Other brain regions were also recorded, according to clinical hypotheses for IOZ. Patients received stimulation belonging to four different sensory modalities: thermonociceptive, tactile, auditory, and visual. Interictal EA was characterized as specific insular activity when present only within insular contacts. Insular IOZ was determined as an electroclinical onset specific to the insula, or simultaneous with other brain regions. Results: In 4/8 patients, nociceptive stimuli consistently elicited a clear enhancement of GBO power at insular contacts, peaking 245 ms ± 12 ms after stimulus onset, but not at other intracerebral contacts. Vibrotactile, auditory, and visual stimuli did not elicit such high frequency responses at any of the recorded contacts. Three out of 4 insulae with nociceptive-specific GBOs did not show any specific insular interictal EA (Table 1). Conversely, when specific insular interictal EA was present, only 1/5 insulae showed nociceptive-specific GBOs. Insular IOZ was found in 2 patients, one showing nociceptive-specific GBOs (Table 1). Conclusion: Nociceptive stimuli elicit consistent GBOs in some, but not all observed insulae. Preliminary results show that presence of specific interictal EA might contribute to the variability of this response. Further analysis is necessary to confirm our observations, and to explore possible clinical implications in clinical pain perception or in ictal semiology.


Bibliographic reference |
Ferrao Santos, Susana ; Liberati, Giulia ; Klöcker, Anne ; Maia da Cunha Oliveira Safronova, Marta ; Ribeiro Vaz, José Géraldo ; et. al. The insular cortex displays pain-specific gamma-band oscillations, possibly disrupted by epileptiform activity.69th Annual Meeting of the American Epilepsy Society (AES) (Philadelphia, du 04/12/2015 au 08/12/2015). |
Permanent URL |
http://hdl.handle.net/2078.1/170000 |