Page 70 - MEGIN Book Of Abstracts - 2023

RESULTS Overall, 70% of patients (14/20) in whom any Psychology, University of Texas at Austin, Texas; and; Depart-
HFC tissue was resected developed an early postopera- ment of Neurological Sciences, University of Nebraska Medi-
tive language deficit (mean 2.3 days, range 1-8 days), cal Center, Omaha, Nebraska
compared to 33% of patients (2/6) in whom no HFC
tissue was resected (p = 0.16). When bifurcated by the OBJECTIVE By looking at how the accuracy of pre-
amount of HFC tissue that was resected, 100% of pa- operative brain mapping methods vary according to
tients (3/3) with an HFC resection > 25% displayed defi- differences in the distance from the activation clusters
cits in AN, compared to 30% of patients (6/20) with an used for the analysis, the present study aimed to eluci-
HFC resection < 25% (p = 0.04). Furthermore, there was date how preoperative functional neuroimaging may
a linear correlation between the severity of AN and SYN be used in such a way that maximizes the mapping
decline with percentage of HFC sites resected (p = 0.02 accuracy.
and p = 0.04, respectively). By 2.2 months postopera-
tively (range 1-6 months), the correlation between HFC METHODS The eloquent function of 19 patients with a
resection and both AN and SYN decline had resolved brain tumor or cavernoma was mapped prior to resec-
(p = 0.94 and p = 1.00, respectively) in all patients (9/9) tion with both functional MRI (fMRI) and magnetoen-
except two who experienced early postoperative tumor cephalography (MEG). The mapping results were then
progression or stroke involving inferior frontooccipital validated using direct cortical stimulation mapping
fasciculus. performed immediately after craniotomy and prior
to resection. The subset of patients with equivalent
CONCLUSIONS Imaginary coherence measures of func- MEG and fMRI tasks performed for motor (n = 14) and
tional connectivity using MEG are able to identify HFC language (n = 12) were evaluated as both individual
network sites within and around low- and high-grade and combined predictions. Furthermore, the distance
gliomas. Removal of IES-negative HFC sites results in resulting in the maximum accuracy, as evaluated by the
early transient postoperative decline in AN and SYN, J statistic, was determined by plotting the sensitivities
which resolved by 3 months in all patients without and specificities against a linearly increasing distance
stroke or early tumor progression. Measures of func- threshold.
tional connectivity may therefore be a useful means of
counseling patients about postoperative risk and assist RESULTS fMRI showed a maximum mapping accuracy
with preoperative surgical planning. at 5 mm for both motor and language mapping. MEG
showed a maximum mapping accuracy at 40 mm
Keywords: functional connectivity, glioblastoma, high- for motor and 15 mm for language mapping. At the
grade glioma, language, low-grade glioma, magnetoen- standard 10-mm distance used in the literature, MEG
cephalography, oncology, speech showed a greater specificity than fMRI for both mo-
tor and language mapping but a lower sensitivity for
Journal of neurosurgery (2020), Vol. 134, No. 3 (32244221) motor mapping. Combining MEG and fMRI showed
(13 citations) a maximum accuracy at 15 mm and 5 mm-MEG and
fMRI distances, respectively-for motor mapping and at
a 10-mm distance for both MEG and fMRI for language
Accuracy analysis of fMRI and MEG activations mapping. For motor mapping, combining MEG and
determined by intraoperative mapping (2020) fMRI at the optimal distances resulted in a greater ac-
curacy than the maximum accuracy of the individual
Ellis, David G; White, Matthew L; Hayasaka, Satoru; predictions.
Warren, David E; Wilson, Tony W; Aizenberg, Michele R
CONCLUSIONS This study demonstrates that the accu-
Departments of1Neurosurgery and; Radiology, University of racy of language and motor mapping for both fMRI and
Nebraska Medical Center, Omaha, Nebraska; Department of MEG is heavily dependent on the distance threshold

 ontents  Index 49
C