Intraoperative mapping of the cortical areas involved in multiplication and subtraction: an electrostimulation study in a patient with a left parietal glioma

Abstract

Objectives: Advances in neuroimaging studies have recently improved the understanding of the functional anatomy of the calculation processes, having in particular underlined the central role of the angular gyrus (AG). In this study, the authors applied this knowledge to the surgical resection of a glioma invading the left AG, by localising and sparing the cortical areas involved in two different components of calculation (multiplication and subtraction), using direct electrical stimulations. Methods: A calculation mapping was performed in a patient without deficit except a slightly impaired performance for serial arithmetic subtraction, during the resection under local anaesthesia of a left parieto-occipital glioma invading the dominant AG. After somatosensory and language mappings, cortical areas involved in single digit multiplications and subtractions of seven were mapped using the method of electrostimulation, before glioma removal. Results: Distinct sites specifically involved in multiplication or subtraction were detected within the left AG, with a precise spatial distribution and overlapping. All the eloquent (somatosensory, language, and calculation) areas were surgically spared. Postoperatively, the patient had a transient complete deficit for arithmetic subtraction, without either multiplication or language disturbance. The tumour removal was complete. Conclusions: These findings suggest: firstly, the usefulness of an intraoperative calculation mapping during the removal of a lesion involving the left dominant AG, to avoid permanent postoperative deficit of arithmetic processes while optimising the quality of tumour resection; secondly, the possible existence of a well ordered and dynamic anatomo-functional organisation for different components of calculation within the left AG. E ver since Henschen's seminal study, 1 evidence from neuropsychological reports in brain damaged patients [2][3][4][5][6][7][8] and functional neuroimaging studies 9-21 points toward a major involvement of inferior parietal regions in mental calculation. Moreover, there are indications that these areas include arithmetic components that may be selectively impaired or preserved following lesions. In this report, we applied this knowledge to the surgical resection of a glioma invading the left AG, by performing under local anaesthesia an intraoperative electrostimulation mapping of the cortical areas involved in calculation processes. Our goals were first to avoid permanent postoperative calculation deficit, and to study the involvement of different left parietal regions in multiplication versus subtraction, two operations that can be doubly dissociated after parietal lesions. On the basis of these findings, the anatomo-functional organisation of the AG, its integration in calculation networks, and its interaction with language and working memory functions are discussed. METHODS Case presentation PatientThe patient was a 44 year old right handed nurse. She was operated on in our institution for a left parieto-occipital low grade...

Subcortical mapping of calculation processing in the right parietal lobe

“…6 Calculation processing may be monitored during surgery in different areas, such as left frontal, temporal, and parietal cortices. 5,11,13 As far as the right hemisphere is concerned, we recently confirmed previous neuroimaging 1,2,10,12 and transcranial magnetic stimulation 14 data, suggesting a role of the right cortex in calculation processing. 4 Conversely, no surgical data have been reported in the literature on subcortical mapping of right parietal white matter so far.…”

“…Intraoperatively, cortical and subcortical mapping was performed using a bipolar stimulator. A functional cortical map was obtained using the method described by Duffau et al 5 Calculation tasks were administered as previously reported. 4 A bipolar probe with 5-mm-spaced tips delivering a biphasic current was applied to the cortex for a period of 4 seconds (with a pulse frequency of 60 Hz and a single pulse phase duration of 0.3 msec).…”

Safe Removal of Glioblastoma Near the Angular Gyrus by Awake Surgery Preserving Calculation Ability-Case Report-

“…9,21) A left parieto-occipital glioma invading the angular gyrus was successfully removed using calculation task monitoring without deterioration of the calculation ability. 9) Gerstmann's syndrome was demonstrated by direct stimulation of the left angular gyrus and is often associated with various types of aphasia, depending on the stimulation sites or lesions of the cortical areas in the left parietal lobe. 21) The six Awake Surgery to Preserve Calculation Ability monitoring tasks included standard naming, reading, calculation, finger recognition, color naming, and writing.…”

“…19) So far, very few attempts have been made to map the calculation center during surgery. 9,21) We describe a case of surgical resection of glioblastoma located near the left angular gyrus, using awake surgery with functional mapping of language and calculation functions.…”

Surgical treatment of glioblastoma multiforme localized in the motor area of the brain using the technique of cortical electrostimulation

“…of human cortex, despite the anatomical boundaries are organizationally related and surgical resection can basically considered a breach of Preoperative and intraoperative brain mapping, separating the normal from the abnormal function and allows resection of lesions that previously could not even imagine (8). Current studies recommend standard use of intraoperative electrical stimulation of the brain during operations in eloquent brain zone, a method that improves postoperative functional outcome (5,4,16,31).…”