Swamy, Chandra

Abstract BACKGROUND Intraoperative electrocorticography (ECoG) may aid localization of language function and help guide eloquent brain tumor resection. However, relevance of ECoG findings to language outcomes remains unclear. METHODS Fifteen patients with brain tumors (Mdn age=60; 67% high-grade glioma) underwent awake craniotomy and intraoperative language mapping. Time-frequency ECoG gamma activity was visualized in real-time followed by direct electrical stimulation (DES) across 3 paradigms (NeuroMapper Tasks: Object, Action, Auditory). Early and late ECoG gamma modulations and positive DES sites were co-registered with postoperative MRI. A subset (N=11) completed expressive language testing (Phonemic and Semantic Fluency, Confrontation Naming) prior to and <2 months following surgery. Correlational analyses and Mann-Whitney U tests examined relationships between test results and surgical impact upon expressive task-elicited gamma activity (Object and Action Naming). RESULTS Across tasks, positive DES sites were identified in 93% of cases (Auditory, 73%; Action, 71%, Object, 57%). No positive DES sites were resected. Early and/or late gamma activations were elicited in all patients, resected in 40%, and within 1 cm of surgical impact in 90%. Four patients (36%) showed reliable decline on at least 1 outcome, which was associated with Action Naming activity <1 cm of surgical impact (phi=.67, p=.035). On individual tests, Confrontation Naming and Phonemic Fluency decline were rare (9% and 18%), though Semantic Fluency declined in 36% of patients. Change in Semantic Fluency was associated with resection of Object Naming gamma sites (Z=-1.83, p=.044) and presence of Action Naming gamma features near surgical impact (Z=-2.25, p=.014). CONCLUSIONS Despite preservation DES sites and sparing of basic confrontation naming ability, verbal fluency declined in a substantial group of patients. Decline was associated with gamma features resected or near surgical impact. While preliminary, findings suggest task-based ECoG can augment DES in informing risk of surgically-acquired language decline.

Abstract BACKGROUND As an adjunct to direct electrical stimulation (DES), intraoperative electrocorticography (ECoG) can aid detection of language-eloquent cortex. However, it is unclear how surgical impact upon mapping findings relates to cognitive-linguistic outcomes. METHODS Ten patients underwent awake craniotomy for tumor resection with ECoG and DES language mapping. Mapping utilized iPad stimulus presentation coupled to an electrode array capable of both recording ECoG activity and delivering DES. Time-frequency gamma band activations were visualized (Early, Long, Late, Double Peak) for 3 naming paradigms (Object, Action, Auditory). DES was also conducted for each task. Mapping results were overlayed on postoperative MRI to examine proximity to parenchymal trauma (cavity, sulcal displacement). Patients completed cognitive-linguistic testing [WAB-R (N=3) or Neuropsychological Assessment (N=7)] prior to surgery and <2 months postoperatively. Patients with persisting aphasia at 6-month follow-up were also identified. RESULTS Postoperative language decline was found in 50% of patients, with 30% showing worsening (>1SD) in Naming and Phonemic Fluency, and 60% in Semantic Fluency. Surgery impacted ECoG features in 60% of patients and DES arrest sites in 30%. A trend was observed where Early and Late Object naming ECoG features were associated with Semantic Fluency decline [rpb(5)=-.69, p=.067]. Arrest during Auditory naming DES <1 cm of surgical effect was associated with decline in Abstraction [rpb(5)=-.83, p=.042; FET, p=.029] and Semantic Fluency [rpb(5)=-.87, p=.012; FET, p=.024]. Excluding the 3 transsulcal surgeries, arrest during Auditory naming DES <1 cm of resection was associated with general language decline [FET, p=.047]. All 3 patients with persisting aphasia had Auditory naming arrest <1 cm of resection and 2/3 patients had Object naming ECoG features resected. CONCLUSIONS While preliminary, results suggest that surgical proximity to ECoG and DES mapping results may inform risk of surgically-acquired cognitive-linguistic decline. Findings support the potential of multimethod-multitask intraoperative language mapping.

Abstract BACKGROUND Few studies have examined concordance between intraoperative electrocorticography (ECoG) and direct electrical stimulation (DES) language mapping, especially across varied naming tasks. METHODS Twelve patients (Mdn age=59; 75% HGG) underwent awake craniotomy with ECoG and DES language mapping. Mapping utilized iPad stimulus presentation coupled to a 4x8 electrode array for both ECoG and DES. Time-frequency ECoG gamma band activity (Early and Late) was visualized for 3 naming paradigms (Object, Action, Auditory). Bipolar DES was also conducted for each task at each electrode pair. ECoG activations and DES hits were overlayed on preoperative MRI. DES hits represented ground truth for eloquence. ECoG accuracy was examined for each task with 3 different criteria: exact (identical electrodes for ECoG activation and DES hits), adjacent (ECoG <1cm of DES hits), and adjacent within a predefined peritumoral region of interest (<2 cm from boundaries). RESULTS 32 DES hits (40% Auditory, 32% Action, 28% Obj) were observed across patients. Exact ECoG-DES accuracy ranged from 78%-90% [Object: Sens=11%, Spec=91%, PPV=6%, NPV=95%; Action: Sens=40%, Spec=93%, PPV=24%, NPV=97%; Auditory: Sens=69%, Spec=78%, PPV=19%, NPV=78%]. Adjacent ECoG-DES accuracy ranged from 82%-91% [Object: Sens=33%, Spec=92%, PPV=18%, NPV=97%; Action: Sens=44%, Spec=93%, PPV=25%, NPV=97%; Auditory: Sens=91%, Spec=81%, PPV=37%, NPV=99%]. When restricted to the peritumoral region, adjacent ECoG-DES accuracy ranged from 94%-97% [Object: Sens=14%, Spec=99%, PPV=25%, NPV=97%; Action: Sens=25%, Spec=99%, PPV=25%, NPV=99%; Auditory: Sens=100%, Spec=94%, PPV=54%, NPV=100%]. For patients with DES hits (N=10), all had at least 1 task activation <1 cm of DES hits, with 7/10 having convergence of activations across at least 2 tasks. CONCLUSIONS Negative ECoG mapping is strongly predictive of non-eloquence confirmed by DES for all naming tasks. Additionally, gamma band activation elicited by auditory naming within the peritumoral region is strongly predictive of eloquence. Findings support task-based ECoG language mapping for prediction of eloquence and identification of targets for DES confirmation.