Cortical calculation localization using electrostimulation.
OBJECTIVE
A naming task has been used to spare cortical areas involved in language. In the present study, a calculation task was combined with electrostimulation mapping (awake surgery) to spare cortical areas involved in calculation in patients undergoing surgery for brain lesions. The organization of language and calculation areas was analyzed in relation to these surgical data.


METHODS
Twenty patients with brain lesions close to areas possibly involved in calculation (dominant parietal lobe and F2) were prospectively studied over a 4-year period. Four patients had preoperative symptoms of acalculia and therefore were not included in the brain mapping procedure.


RESULTS
In 16 patients, direct electrostimulation caused calculation interferences in localized small cortical areas (< 2 cm(2)). Of the 53 calculation interferences found, 23 were independent of language areas, especially those in the inferior left parietal lobule. Various patterns of interference were observed (11 complete acalculia, 5 acalculia with wrong answers, 2 hesitations, and 5 mixed responses), although error patterns were fairly similar across angular, parietal, and frontal stimulation sites. Calculation areas in 4 patients could not be spared for oncological reasons; postoperatively, 3 of these patients showed significant acalculia symptoms. In contrast, none of the patients whose calculation areas were spared had arithmetic difficulties 1 month after surgery. Improvements in acalculia symptoms after surgery were also found in 3 of the 4 patients with preoperative calculation difficulties.


CONCLUSIONS
To limit the risk of personal and professional disturbances caused by acquired anarithmetia in patients undergoing surgery for brain tumors or epilepsy, the authors think it is necessary to use a calculation task during brain mapping, especially when operating in the dominant parietal lobe.
Roux
Franck-Emmanuel
FE
Institut National de la Santé et de la Recherche Médicale Unité 825 and Institut Fédératif de Recherche 96, Hôpital Purpan, France. franck.roux@club-internet.fr
Boukhatem
Leila
L
Draper
Louisa
L
Sacko
Oumar
O
Démonet
Jean-François
JF
D000328:Adult; D000368:Aged; D001931:Brain Mapping / Q000379:methods*; D001932:Brain Neoplasms / Q000473:pathology / Q000523:psychology* / Q000601:surgery*; D002540:Cerebral Cortex / Q000503:physiopathology*; D015331:Cohort Studies; D032882:Comprehension / Q000502:physiology; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D007802:Language; D008297:Male; D055641:Mathematical Concepts; D008875:Middle Aged; D011340:Problem Solving / Q000502:physiology*; D015203:Reproducibility of Results; D016896:Treatment Outcome; D055815:Young Adult