Relationship between direct cortical stimulation and induced high-frequency activity for language mapping during SEEG recording

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>The authors assessed the clinical relevance of preoperative task-induced high-frequency activity (HFA) for language mapping in patients with refractory epilepsy during stereoelectroencephalography recording. Although HFA evaluation was described as a putative biomarker of cognition, its clinical relevance for mapping language networks was assessed predominantly by studies using electrocorticography (ECOG).</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>Forty-two patients with epilepsy who underwent intracranial electrode implantation during both task-induced HFA and direct cortical stimulation (DCS) language mapping were evaluated. The spatial and functional relevance of each method in terms of specificity and sensitivity were evaluated.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>The results showed that the two methods were able to map classic language regions, and a large and bilateral language network was obtained with induced HFA. At a regional level, differences were observed between methods for parietal and temporal lobes: HFA recruited a larger number of cortical parietal sites, while DCS involved more cortical temporal sites. Importantly, the results showed that HFA predicts language interference induced by DCS with high specificity (92.4%; negative predictive value 95.9%) and very low sensitivity (8.9%; positive predictive value 4.8%).</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>DCS language mapping appears to be more appropriate for an extensive temporal mapping than induced HFA mapping. Furthermore, induced HFA should be used as a complement to DCS to preselect the number of stimulated sites during DCS, by omitting those reported as HFA−. This may be a considerable advantage because it allows a reduction in the duration of the stimulation procedure. Several parameters to be used for each method are discussed and the results are interpreted in relation to previous results reported in ECOG studies.</jats:p></jats:sec>

Contributions of electrophysiology for identifying cortical language systems in patients with epilepsy

“…A meta-analysis showed that HGA measures were specific but not sensitive to localize language areas, compared to the ECS [104]. This conclusion was confirmed in a sEEG study [102]. In addition, this study revealed a larger number of regions activated by language tasks compared to those identified by positive ECS.…”

“…ECS) can be combined to better understand each of the two methods, and to better define cortical networks involved in language. Their comparison has revealed useful, if imperfect, agreements [100][101][102][103]. A meta-analysis showed that HGA measures were specific but not sensitive to localize language areas, compared to the ECS [104].…”

Electrical Stimulation Mapping of Brain Function: A Comparison of Subdural Electrodes and Stereo-EEG

“…In addition to other methodological differences, this relatively low sensitivity may reflect the wider range of language tasks used to generate the fMRI dataset compared to the single task used for SEEG ESM in our patients. Another recent study including 27 adults (50 Hz, 0.2-3 mA), reported language interference at 85/1914 (4.4%) sites, also with a topography confirming the canonical neuroanatomy (Cuisenier et al, 2020). For sensorimotor mapping, in 15 children, SEEG ESM was noted to localize anatomic sensorimotor parcels with high accuracy (0.80) and high specificity (0.86; Arya et al, 2020).…”

“…Secondly, it is common in SEEG practice to perform low frequency (1 Hz) stimulation with wider pulse durations (0.5 ms) and train duration (up to 30 s; Cossu et al, 2006;Trebuchon and Chauvel, 2016;Britton, 2018). There is a difference of opinion in the literature if low-frequency stimulation with SEEG should be performed to elicit functional responses or to reproduce habitual seizures (Cossu et al, 2006;Cuisenier et al, 2020). In our experience, low-frequency stimulation can only rarely elicit consistent functional responses.…”

“…With SEEG, the stimulation settings are fairly similar to those used with SDE, with two important differences. First, although the maximum current used with SDE ESM has varied from 10 to 20 mA, it has been lower (3-8 mA) with SEEG ESM (Trebuchon and Chauvel, 2016;Britton, 2018;Arya et al, 2019Arya et al, , 2020Cuisenier et al, 2020). The use of lower maximum current with SEEG ESM is based on calculations extrapolated from the estimates of safe current strengths for SDE ESM, and the desire to maintain similar charge density with SEEG and SDE ESM (Shannon, 1992;Britton, 2018).…”