A comparison of resting state functional magnetic resonance imaging to invasive electrocortical stimulation for sensorimotor mapping in pediatric patients

Abstract

Localizing neurologic function within the brain remains a significant challenge in clinical neurosurgery. Invasive mapping with direct electrocortical stimulation currently is the clinical gold standard but is impractical in young or cognitively delayed patients who are unable to reliably perform tasks. Resting state functional magnetic resonance imaging non-invasively identifies resting state networks without the need for task performance, hence, is well suited to pediatric patients. We compared sensorimotor network localization by resting state fMRI to cortical stimulation sensory and motor mapping in 16 pediatric patients aged 3.1 to 18.6 years. All had medically refractory epilepsy that required invasive electrographic monitoring and stimulation mapping. The resting state fMRI data were analyzed using a previously trained machine learning classifier that has previously been evaluated in adults. We report comparable functional localization by resting state fMRI compared to stimulation mapping. These results provide strong evidence for the utility of resting state functional imaging in the localization of sensorimotor cortex across a wide range of pediatric patients.

Keywords: Functional MRI; Mapping; Neurosurgery; Pediatric; Resting state.

Graphical abstract

Fig. 1

Methods diagram. The diagram demonstrates functional imaging analysis proceeding in parallel to clinical mapping and subsequent convergence of results.

Fig. 2

Individual r-fMRI and ECS mapping. Each individual's MLP score for the SMN map is projected onto their reconstructed cortical surface. Subjects are organized in row order with Subject A at top left and Subject P at bottom right. ECoG electrodes are color-coded according to positive (white) or negative (black) ECS results for motor and sensory function.

Fig. 3

ROC analysis. ROC across a range of thresholds for the r-fMRI analysis for each subject shown in light grey and the mean in bold black. AUC for the mean ROC curve is shaded in grey. Youden's J statistic identified with red dash-dot line. Chance performance marked with dashed black diagonal line.

Fig. 4

Group SMN maps. The SMN maps after threshold applied are plotted on a pediatric representative T1-weighted atlas. Color indicates voxels where the SMN mapped to for >2 individuals and shows areas of common network localization. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 5

Functional and anatomic mapping. Thresholded r-fMRI maps of the SMN are projected onto each individual's cortical surface in red. Anatomic labeling is shown in blue. Common areas where the two maps overlap is shown in green. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 6

Anatomic map and ECS results. Anatomic map of pre-central, post-central, and para-central gyri is shown in blue. ECoG electrodes are overlaid and color-coded for positive (white) and negative (black) ECS motor mapping results. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 7

Comparison of functional and anatomic maps. (A) Overlap of functional and anatomic maps are evaluated by Dice coefficient across the full range of MLP thresholds and plotted for each individual in grey. The max Dice overlap is identified by open circle. The mean Dice curve is plotted in bold black. The max Dice for each individual is plotted against age (B) and amount of movement during the r-fMRI scan (C), showing no significant correlation for either. (D) The max Dice for each individual grouped by need for sedation during r-fMRI scan is plotted and summarized by box-and-whisker plots where the middle line represents the median, ends of box are 25th and 75th percentiles, and whiskers show the range.