Subcortical Calculation Mapping During Parietal Glioma Surgery in the Dominant Hemisphere: A Case Report

To avoid permanent neurologic deficits and preserve brain function in and near the eloquent area, intraoperative electrical stimulation mapping (IESM) is necessary. However, little is known about how these subcortical regions are involved in calculation processing function in patients with glioma.

We report the case of a 56-year-old, right-handed woman working at a primary school as a teacher who had recurrent left parietal glioma. She underwent initial surgical resection for a low-grade glioma present in the left parietal lobe 14 months before recurrence. The latest magnetic resonance imaging results revealed an enhancing lesion in the cavity of the initial resection with an infiltrating tumor in the parietal lobe. Preserving language function and calculation processing was critical; therefore, she underwent awake surgery using IESM. Thus, the calculation site was elicited by subcortical electrical stimulation at the bottom of the tumor cavity during second resection. At the same point, she could speak normally but could not calculate repeatedly when stimulated. Therefore, we stopped tumor resection. After diagnosing anaplastic astrocytoma, she underwent radiation therapy and chemotherapy. She resumed her normal life as a teacher with preserved language and calculation processing. Eventually, 31 months later, she died from disease progression.

In this report, IESM performed during awake surgery in a subcortical site demonstrated a crucial role played by the dominant parietal lobe in calculation.