Right parietal cortex and calculation processing: intraoperative functional mapping of multiplication and addition in patients affected by a brain tumor

Clinical article

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The role of parietal areas in number processing is well known. The significance of intraoperative functional mapping of these areas has been only partially explored, however, and only a few discordant data are available in the surgical literature with regard to the right parietal lobe. The purpose of this study was to evaluate the clinical impact of simple calculation in cortical electrostimulation of right-handed patients affected by a right parietal brain tumor.


Calculation mapping in awake surgery was performed in 3 right-handed patients affected by high-grade gliomas located in the right parietal lobe. Preoperatively, none of the patients presented with calculation deficits. In all 3 cases, after sensorimotor and language mapping, cortical and intraparietal sulcus areas involved in single-digit multiplication and addition calculations were mapped using bipolar electrostimulation.


In all patients, different sites of the right parietal cortex, mainly in the inferior lobule, were detected as being specifically related to calculation (multiplication or addition). In 2 patients the intraparietal sulcus was functionally specific for multiplication. No functional sites for language were detected. All sites functional for calculation were spared during tumor resection, which was complete in all cases without postoperative neurological deficits.


These findings provide intraoperative data in support of an anatomofunctional organization for multiplication and addition within the right parietal area. Furthermore, the study shows the potential clinical relevance of intraoperative mapping of calculation in patients undergoing surgery in the right parietal area. Further and larger studies are needed to confirm these data and assess whether mapped areas are effectively essential for function.

Article Information

Address correspondence to: Alessandro Della Puppa, M.D., Department of Neurosurgery, University Hospital of Padova, Via Giustiniani 2, Azienda Ospedaliera di Padova, Padova 35128, Italy. email: alessandro.dellapuppa@sanita.padova.it.

Please include this information when citing this paper: published online August 9, 2013; DOI: 10.3171/2013.6.JNS122445.

© AANS, except where prohibited by US copyright law.



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    Images obtained in Case 1. A and B: Preoperative (A) and postoperative (B) sagittal T1-weighted MR images with Gd enhancement. C: Intraoperative image obtained during functional mapping of the right parietal area. Lettered tags were positioned over the tumor, identified with MRI neuronavigation. Tag 1 marks the functional site for hand motor response (subsequently driving the intensity threshold of stimulation [3 mA]); X tags mark functional sites for multiplication on the superior, inferior, and intraparietal sulcus; B and C tags mark the subcortical site of the tumor identified by MRI neuronavigation. D: Final view. Tags 2 and 5 lie over the motor area in front of the corticectomy chosen for tumor removal.


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