Hugues Duffau

Resection of world health organization grade II gliomas involving Broca's area: Methodological and functional considerations - Commentary

OBJECTIVEAdvances in functional mapping have enabled us to extend the indications of surgery for low-grade gliomas (LGGs) within eloquent regions. However, to our knowledge, no study has been specifically dedicated to the resection of LGGs within Brocas area. We report the first surgical series of LGGs involving this area by focusing on methodological and functional considerations. METHODSSeven patients harboring an LGG in Brocas area (revealed by partial seizures) had a language functional magnetic resonance imaging scan and then underwent operation while awake using intrasurgical electrical mapping. RESULTSThe neurological examination was normal in all patients despite mild language disturbances shown using the Boston Diagnosis Aphasia Examination. Both pre- and intraoperative cortical mapping found language reorganization with recruitment of the ventral and dorsal premotor cortices, orbitofrontal cortex, and insula, whereas no or few language sites were detected within Brocas area. Subcortically, electrostimulation allowed the identification and preservation of four structures still functional, including the arcuate fasciculus, fronto-occipital fasciculus, fibers from the ventral premotor cortex, and head of the caudate. Postoperatively, after transient language worsening, all patients recovered and returned to a normal socioprofessional life. The resection was total in three cases, subtotal in three, and partial in one patient (operated twice). CONCLUSIONOur results indicate that, in patients with no aphasia despite LGGs within Brocas area, thanks to brain plasticity, the tumor can be removed while involving this “unresectable” structure without inducing sequelae and even improving the quality of life when intractable epilepsy is relieved on the condition that subcortical language connectivity is preserved.

Speaking without Broca's area after tumor resection

We present the case of a right-handed patient who received surgical treatment for a left frontal WHO grade II glioma invading the left inferior and middle frontal gyri, the head of the caudate nucleus, the anterior limb of the internal capsule and the anterior insula, in direct contact also with the anterior-superior part of the lentiform nucleus. The tumor resection was guided by direct electrical stimulation on brain areas, while the patient was awake. Adding a narrative production task to the neuropsychological assessment, we compared pre-, peri- and post-surgical language skills in order to analyze the effects of the tumor infiltration and the consequences of the left IFG resection, an area known to be involved in various language and cognitive processes. We showed that the tumor infiltration and its resection did not lead to the severe impairments predicted by the localization models assigning a significant role in language processing to the left frontal lobe, notably Brocas area. We showed that slow tumor evolution – the patient had been symptom-free for a long time – enabled compensatory mechanisms to process most language functions endangered by the tumor infiltration. However, a subtle fragility was observed in two language devices, i.e., reported speech and relative clauses, related to minor working memory deficits. This case study of a patient speaking without Brocas area illustrates the efficiency of brain plasticity, and shows the necessity to broaden pre-, peri-, post-surgery language and cognitive assessments.

Agraphia after awake surgery for brain tumor: new insights into the anatomo-functional network of writing.

BACKGROUND Controversy still exists about neural basis underlying writing and its relation with the sites subserving oral language. Our objective is to study functional areas involved in writing network, based on the observations of different postoperative writing disorders in a population of patients without preoperative agraphia. METHODS We analyzed the postoperative agraphia profiles in 15 patients who underwent surgery for cerebral LGGs in functional language areas, using electrical mapping under local anesthesia. These profiles were then correlated to the sites of the lesions, shown by preoperative cerebral imaging. RESULTS Our findings showed that (1) spoken language and writing functions could be dissociated, and that (2) writing is subserved, at least partially, by a network of 5 areas located in the dominant hemisphere for language: the superior parietal region, the supramarginalis gyrus, the second and third frontal convolutions, the supplementary motor area, and the insula. Each of these areas seems to have a different role in writing, which will be detailed in this article. However, among the patients, only those with lesions of the supplementary motor area did not recover from agraphia in the postoperative period (in 50% of cases). CONCLUSIONS On the basis of these results, and in the light of the recent literature, we discuss the relevance of each area in this anatomo-functional network as well as the clinical implications of such better knowledge of the neural basis of writing, especially for brain surgery and functional rehabilitation.

Naming performance in two bilinguals with frontal vs. temporal glioma

Two bilingual patients had World Health Organization Grade II Gliomas removed from a language area, one in the left mesiofronto-cingular region and one in the left postero-temporal region. They performed a picture naming task in their two languages before their surgery and afterwards. Both patients showed slowness in naming in their first language but different patterns of naming performance across their first and second language. Their patterns depended upon the site of their lesion and their language experience. These data, from brain-damaged, bilingual adult patients, contribute to the neuropsychological literature on brain organization and plasticity, and highlight the importance of assessing naming speed to obtain a better understanding of impairment and recovery mechanisms.

Reversible deficit affecting the perception of tone of a human voice after tumour resection from the right auditory cortex

SummaryWe report on a young woman operated for a ganglioglioma involving the right auditory cortex (AC), presenting with auditory seizures. Despite a normal pre-operative examination, a specific post-operative disorder affecting the perception of a human voice occurred. The patient was unable to recognise the tone of familiar voices while she recognised the expressed content. A temporal lobectomy for recurrence was performed two years later. The patient recovered from the voice perception deficit. This report shows that (1) a discrete site within the AC is specifically involved in the perception of tone of the human voice (2) functional compensation is possible.

Mapping the Brain for Primary Brain Tumor Surgery

Extensive resective surgery plays a major role in prolonging survival of glioma patients. However, patient’s will is not to survive as long as possible, but rather to enjoy the longest possible «normal» life. Because glioma infiltrates functional tissue, it is necessary to define resection boundaries by functional maps rather than by tumoral imaging. In this perspective, advances in brain mapping have deeply improved the surgical management of glioma patients. In this chapter, we summarize the preoperative and intraoperative methods that allows to map the brain and we review the cortical and axonal mapping of the main cognitive functions.