Postoperative speech disorder after medial frontal surgery: role of the supplementary motor area

Pre-operative fMRI localization of the supplementary motor area and its relationship with postoperative speech deficits

INTRODUCTION

Neurosurgery of the supplementary motor area (SMA) is associated with transient speech defects. We investigated whether SMA laterality correlates with postoperative speech defects.

MATERIALS AND METHODS

The authors reviewed 17 patients with SMA-area lesion resection and preoperative language fMRI. SMA laterality was calculated by comparison of voxel activation in paired SMAs by hand-drawn regions of interest (ROIs) (drawn by a neuroradiologist), and compared with qualitative assessment by two neuroradiologists. Postoperative speech defects before and after surgery were assessed by chart review.

RESULTS

Six patients developed new speech defects that resolved within several months. Two of the patients had a pre-existing speech defect that had developed after prior SMA-area surgery. All these patients had left-sided lesions, while none of the four patients with a right-sided lesion developed a speech defect. Neuroradiologists' assessment of SMA laterality agreed with ROI calculation for the SMAs that were lateralized. However, for the SMAs in the "codominant" range by ROI, the neuroradiologists felt that all but one of the cases clearly lateralized, with the exception deemed indeterminate or codominant. No correlation between laterality of SMA and speech defect was identified. Twelve patients showed lateralization contralateral to the lesion.

CONCLUSIONS

fMRI lateralization does not correlate with transient speech defects that developed from SMA-area surgery. Qualitative/visual assessment of SMA laterality was superior to ROI calculation because of the close proximity and possible overlap of signal from midline SMA. A majority of patients showed SMA lateralization contralateral to the SMA lesion.

Somatotopic organization of the white matter tracts underpinning motor control in humans: an electrical stimulation study

The somatotopic organization of the primary motor cortex is well documented. However, a possible somatotopy of the network involved in motor control, i.e., eliciting negative motor phenomena during electrostimulation, is unknown in humans, particularly at the subcortical level. Here, we performed electrical stimulation mapping in awake patients operated for gliomas, to study the distribution of the white matter tracts subserving movement control of the lower limb, upper limb(s), and speech. Eighteen patients underwent awake surgery for frontal low-grade gliomas, by using intraoperative subcortical electrostimulation mapping to search interference with movement of the leg, arm(s), and face. We assessed the negative motor responses and their distribution throughout the tracts located under premotor areas. The corresponding stimulation sites were reported on a standard brain template for visual analysis and between-subjects comparisons. During stimulation of the white matter underneath the dorsal premotor cortex and supplementary motor area, rostral to the corticospinal tracts, all patients experienced cessation of the movement of lower and upper limbs, of bimanual coordination, and/or speech. These subcortical sites were somatotopically distributed. Indeed, stimulation of the fibers from mesial to lateral directions and from posterior to anterior directions evoked arrest of movement of the lower limb (mesially and posteriorly), upper limb(s), and face/speech (laterally and anteriorly). There were no postoperative permanent deficits. This is the first evidence of a somatotopic organization of the white matter bundles underpinning movement control in humans. A better knowledge of the distribution of this motor control network may be helpful in neurosciences and neurosurgery.

Acute effects of surgery on emotion and personality of brain tumor patients: surgery impact, histological aspects, and recovery

BACKGROUND

Cognitive effects of brain surgery for the removal of intracranial tumors are still under investigation. For many basic sensory/motor or language-based functions, focal, albeit transient, cognitive deficits have been reported low-grade gliomas (LGGs); however, the effects of surgery on higher-level cognitive functions are still largely unknown. It has recently been shown that, following brain tumors, damage to different brain regions causes a variety of deficits at different levels in the perception and interpretation of emotions and intentions. However, the effects of different tumor histologies and, more importantly, the effects of surgery on these functions have not been examined.

METHODS

The performance of 66 patients affected by high-grade glioma (HGG), LGG, and meningioma on 4 tasks tapping different levels of perception and interpretations of emotion and intentions was assessed before, immediately after, and (for LGG patients) 4 months following surgery.

RESULTS

Results showed that HGG patients were generally already impaired in the more perceptual tasks before surgery and did not show surgery effects. Conversely, LGG patients, who were unimpaired before surgery, showed a significant deficit in perceptual tasks immediately after surgery that was recovered within few months. Meningioma patients were substantially unimpaired in all tasks.

CONCLUSIONS

These results show that surgery can be relatively safe for LGG patients with regard to the higher-level, more complex cognitive functions and can provide further useful information to the neurosurgeon and improve communication with both the patient and the relatives about possible changes that can occur immediately after surgery.

Morphological derivation overflow as a result of disruption of the left frontal aslant white matter tract

The frontal aslant tract (FAT) is a recently described major connection between the preSMA and Broca's area, whose functional role remains undefined. In this study we examined a patient presenting a morphological overregularization strategy in a verb generation task during awake surgery. This specific language deficit coincided with brain tumor resection at the level of the left FAT. During the task execution the patient formed the non-existent verbs by applying a morphological derivation rule to the given nouns, instead of retrieving the appropriate verbs. DTI results confirmed left FAT damage. Neuropsychological follow-up showed that this morphological derivation impairment partially persisted after surgery, whereas the results on a wide spectrum of other language-related tasks remained satisfactory. Additionally, we compared the pre- and the post-operational fMRI activation maps for the same verb generation task. We discuss the potential role of the left FAT in the morphological derivation process and in lexical retrieval.

The impact of different aetiologies on the cognitive performance of frontal patients

Neuropsychological group study methodology is considered one of the primary methods to further understanding of the organisation of frontal 'executive' functions. Typically, patients with frontal lesions caused by stroke or tumours have been grouped together to obtain sufficient power. However, it has been debated whether it is methodologically appropriate to group together patients with neurological lesions of different aetiologies. Despite this debate, very few studies have directly compared the performance of patients with different neurological aetiologies on neuropsychological measures. The few that did included patients with both anterior and posterior lesions. We present the first comprehensive retrospective comparison of the impact of lesions of different aetiologies on neuropsychological performance in a large number of patients whose lesion solely affects the frontal cortex. We investigated patients who had a cerebrovascular accident (CVA), high (HGT) or low grade (LGT) tumour, or meningioma, all at the post-operative stage. The same frontal 'executive' (Raven's Advanced Progressive Matrices, Stroop Colour-Word Test, Letter Fluency-S; Trail Making Test Part B) and nominal (Graded Naming Test) tasks were compared. Patients' performance was compared across aetiologies controlling for age and NART IQ scores. Assessments of focal frontal lesion location, lesion volume, global brain atrophy and non-specific white matter (WM) changes were undertaken and compared across the four aetiology. We found no significant difference in performance between the four aetiology subgroups on the 'frontal' executive and nominal tasks. However, we found strong effects of premorbid IQ on all cognitive tasks and robust effects of age only on the frontal tasks. We also compared specific aetiology subgroups directly, as previously reported in the literature. Overall we found no significant differences in the performance of CVA and tumour patients, or LGT and HGT patients or LGT, HGT and meningioma's on our four frontal tests. No difference was found with respect to the location of frontal lesions, lesion volume, global brain atrophy and non-specific WM changes between the subgroups. Our results suggest that the grouping of frontal patients caused by different aetiologies is a pragmatic, justified methodological approach that can help to further understanding of the organisation of frontal executive functions.

Intraoperative functional mapping and monitoring during glioma surgery

Glioma surgery represents a significant advance with respect to improving resection rates using new surgical techniques, including intraoperative functional mapping, monitoring, and imaging. Functional mapping under awake craniotomy can be used to detect individual eloquent tissues of speech and/or motor functions in order to prevent unexpected deficits and promote extensive resection. In addition, monitoring the patient’s neurological findings during resection is also very useful for maximizing the removal rate and minimizing deficits by alarming that the touched area is close to eloquent regions and fibers. Assessing several types of evoked potentials, including motor evoked potentials (MEPs), sensory evoked potentials (SEPs) and visual evoked potentials (VEPs), is also helpful for performing surgical monitoring in patients under general anesthesia (GA). We herein review the utility of intraoperative mapping and monitoring the assessment of neurological findings, with a particular focus on speech and the motor function, in patients undergoing glioma surgery.

White matter connections of the supplementary motor area in humans

INTRODUCTION

The supplementary motor area (SMA) is frequently involved by brain tumours (particularly WHO grade II gliomas). Surgery in this area can be followed by the 'SMA syndrome', characterised by contralateral akinesia and mutism. Knowledge of the connections of the SMA can provide new insights on the genesis of the SMA syndrome, and a better understanding of the challenges related to operating in this region.

METHODS

White matter connections of the SMA were studied with both postmortem dissection and advance diffusion imaging tractography. Postmortem dissections were performed according to the Klingler technique. 12 specimens were fixed in 10% formalin and frozen at -15°C for 2 weeks. After thawing, dissection was performed with blunt dissectors. For diffusion tractography, high-resolution diffusion imaging datasets from 10 adult healthy controls from the Human Connectome Project database were used. Whole brain tractography was performed using a spherical deconvolution approach.

RESULTS

Five main connections were identified in both postmortem dissections and tractography reconstructions: (1) U-fibres running in the precentral sulcus, connecting the precentral gyrus and the SMA; (2) U-fibres running in the cingulate sulcus, connecting the SMA with the cingulate gyrus; (3) frontal 'aslant' fascicle, directly connecting the SMA with the pars opercularis of the inferior frontal gyrus; (4) medial fibres connecting the SMA with the striatum; and (5) SMA callosal fibres. Good concordance was observed between postmortem dissections and diffusion tractography.

CONCLUSIONS

The SMA shows a wide range of white matter connections with motor, language and lymbic areas. Features of the SMA syndrome (akinesia and mutism) can be better understood on the basis of these findings.

Insights from the supplementary motor area syndrome in balancing movement initiation and inhibition

The supplementary motor area (SMA) syndrome is a characteristic neurosurgical syndrome that can occur after unilateral resection of the SMA. Clinical symptoms may vary from none to a global akinesia, predominantly on the contralateral side, with preserved muscle strength and mutism. A remarkable feature is that these symptoms completely resolve within weeks to months, leaving only a disturbance in alternating bimanual movements. In this review we give an overview of the old and new insights from the SMA syndrome and extrapolate these findings to seemingly unrelated diseases and symptoms such as Parkinson's disease (PD) and tics. Furthermore, we integrate findings from lesion, stimulation and functional imaging studies to provide insight in the motor function of the SMA.

Contemporary model of language organization: an overview for neurosurgeons

Classic models of language organization posited that separate motor and sensory language foci existed in the inferior frontal gyrus (Broca's area) and superior temporal gyrus (Wernicke's area), respectively, and that connections between these sites (arcuate fasciculus) allowed for auditory-motor interaction. These theories have predominated for more than a century, but advances in neuroimaging and stimulation mapping have provided a more detailed description of the functional neuroanatomy of language. New insights have shaped modern network-based models of speech processing composed of parallel and interconnected streams involving both cortical and subcortical areas. Recent models emphasize processing in "dorsal" and "ventral" pathways, mediating phonological and semantic processing, respectively. Phonological processing occurs along a dorsal pathway, from the posterosuperior temporal to the inferior frontal cortices. On the other hand, semantic information is carried in a ventral pathway that runs from the temporal pole to the basal occipitotemporal cortex, with anterior connections. Functional MRI has poor positive predictive value in determining critical language sites and should only be used as an adjunct for preoperative planning. Cortical and subcortical mapping should be used to define functional resection boundaries in eloquent areas and remains the clinical gold standard. In tracing the historical advancements in our understanding of speech processing, the authors hope to not only provide practicing neurosurgeons with additional information that will aid in surgical planning and prevent postoperative morbidity, but also underscore the fact that neurosurgeons are in a unique position to further advance our understanding of the anatomy and functional organization of language.

Blood oxygen level dependent functional magnetic resonance imaging for presurgical planning

Functional magnetic resonance imaging (fMRI) has become a common tool for presurgical sensorimotor mapping, and is a significant preoperative asset for tumors located adjacent to the central sulcus. fMRI has changed surgical options for many patients. This noninvasive tool allows for easy display and integration with other neuroimaging techniques. Although fMRI is a useful preoperative tool, it is not perfect. Tumors that affect the normal vascular coupling of neuronal activity will affect fMRI measurements. This article discusses the usefulness of blood oxygen level dependent (BOLD) fMRI with regard to preoperative motor mapping.

A rostro-caudal axis for language in the frontal lobe: the role of executive control in speech production

The present article promotes a formal executive model of frontal functions underlying speech production, bringing together hierarchical theories of adaptive behavior in the (pre-)frontal cortex (pFC) and psycho- and neurolinguistic approaches to spoken language within an information-theoretic framework. Its biological plausibility is revealed through two Activation Likelihood Estimation meta-analyses carried out on a total of 41 hemodynamic studies of overt word and continuous speech production respectively. Their principal findings, considered in light of neuropsychological evidence and earlier models of speech-related frontal functions, support the engagement of a caudal-to-rostral gradient of pFC activity operationalized by the nature and quantity of speech-related information conveyed by task-related external cues (i.e., cue codability) on the one hand, and the total informational content of generated utterances on the other. In particular, overt reading or repetition and picture naming recruit primarily caudal motor-premotor regions involved in the sensorimotor and phonological aspects of speech; word and sentence generation engage mid- ventro- and dorsolateral areas supporting its basic predicative and syntactic functions; finally, rostral- and fronto-polar cortices subsume domain-general strategic processes of discourse generation for creative speech. These different levels interact in a top-down fashion, ranging representationally and temporally from the most general and extended to the most specific and immediate. The end-result is an integrative theory of pFC as the main executive component of the language cortical network, which supports the existence of areas specialized for speech communication and articulation and regions subsuming internal reasoning and planning. Prospective avenues of research pertaining to this model's principal predictions are discussed.

The presupplementary area within the language network: a resting state functional magnetic resonance imaging functional connectivity analysis

The presupplementary motor area (pre-SMA) is involved in volitional selection. Despite the lateralization of the language network and different functions for both pre-SMA, few studies have reported the lateralization of pre-SMA activity and very little is known about the possible lateralization of pre-SMA connectivity. Via functional connectivity analysis, we sought to understand how the language network may be connected to other intrinsic connectivity networks (ICNs) through the pre-SMA. We performed a spatial independent component analysis of resting state functional magnetic resonance imaging in 30 volunteers to identify the language network. Subsequently, we applied seed-to-voxel functional connectivity analyses centered on peaks detected in the pre-SMA. Three signal peaks were detected in the pre-SMA. The left rostral pre-SMA intrinsic connectivity network (LR ICN) was left lateralized in contrast to bilateral ICNs associated to right pre-SMA peaks. The LR ICN was anticorrelated with the dorsal attention network and the right caudal pre-SMA ICN (RC ICN) anticorrelated with the default mode network. These two ICNs overlapped minimally. In contrast, the right rostral ICN overlapped the LR ICN. Both right ICNs overlapped in the ventral attention network (vATT). The bilateral connectivity of the right rostral pre-SMA may allow right hemispheric recruitment to process semantic ambiguities. Overlap between the right pre-SMA ICNs in vATT may contribute to internal thought to external environment reorientation. Distinct ICNs connected to areas involved in lexico-syntactic selection and phonology converge in the pre-SMA, which may constitute the resolution space of competing condition-action associations for speech production.

Differential reorganization of three syntax-related networks induced by a left frontal glioma

The opercular/triangular parts of the left inferior frontal gyrus and the left lateral premotor cortex are critical in syntactic processing. We have recently indicated that a glioma in one of these regions is sufficient to cause agrammatic comprehension. In the present study, we aimed to show how normally existing syntax-related networks are functionally reorganized by a lesion. Twenty-one patients with a left frontal glioma preoperatively performed a picture-sentence matching task, and underwent functional magnetic resonance imaging scans in an event-related design. We established two qualitatively different types of agrammatic comprehension, depending on glioma location. Patients with a glioma in the left lateral premotor cortex had a more profound deficit in the comprehension of scrambled sentences than that of active and passive sentences. In contrast, patients with a glioma in the opercular/triangular parts of the left inferior frontal gyrus had a more profound deficit in the comprehension of passive and scrambled sentences than that of active sentences. Moreover, we found dramatic changes in the activation patterns in these two patient groups, which accompanied abnormal overactivity and/or underactivity in the syntax-related regions. Furthermore, by examining functional connectivity in the normal brain, we identified three syntax-related networks among those regions, and anatomically visualized connections within individual networks by using diffusion tensor imaging. The first network consists of the opercular/triangular parts of the left inferior frontal gyrus, left intraparietal sulcus, right frontal regions, presupplementary motor area, and right temporal regions. These regions were overactivated in the patients with a glioma in the left lateral premotor cortex only for correct responses, indicating a cognitive change. The second network consists of the left lateral premotor cortex, left angular gyrus, lingual gyrus, and cerebellar nuclei. These regions were overactivated in the patients with a glioma in the opercular/triangular parts of the left inferior frontal gyrus for both correct and incorrect responses, indicating a neuronal change. The third network consists of the left ventral frontal and posterior temporal regions. These regions were underactivated in the patients with a glioma in the opercular/triangular parts of the left inferior frontal gyrus, indicating another neuronal change. These results demonstrate that agrammatic comprehension is associated with the global reorganization of functionally distinct networks, which indeed reflects a differential change in the relative contribution of these three networks to normal syntax-related functions.

The role of secondary motor and language cortices in morbidity and mortality: a retrospective functional MRI study of surgical planning for patients with intracranial tumors

OBJECT

Functional MRI (fMRI) is commonly used by neurosurgeons preoperatively to identify brain regions associated with essential behaviors, such as language and motor abilities. In this study the authors investigated the relationship between patient morbidity and mortality and the distance from the tumor border area to functional activations in secondary motor and language cortices.

METHODS

Patients with primary or metastatic brain tumors who underwent preoperative fMRI motor and language mapping were selected from a large database of patients with tumors. The lesion-to-activation distance (LAD) was measured in each patient relative to the supplementary motor area (SMA) for motor tasks and the presupplementary motor area (pSMA) for language tasks. The association between LAD and the incidence of deficits was investigated using the Fisher exact tests of significance. The impact of other variables, including age, handedness, sex, and tumor grade, was also investigated. In a subset of patients, logistic regression was performed to identify the likelihood of deficits based on the LAD to primary and secondary regions. Finally, Mantel-Cox log-rank tests were performed to determine whether survival time was significantly related to the LAD to secondary motor and language areas.

RESULTS

A significant association was observed between the LAD to the SMA and the incidence of motor deficits, with the percentage of patients with deficits dropping for those in the LAD > 2 cm group. The relationship between the LAD to the pSMA and the incidence of language deficits was not significant. Logistic regression demonstrated that the LAD to primary sensorimotor cortex does affect the incidence of motor deficits, but that the LAD to SMA does not. Finally, the authors observed no relationship between the LAD to secondary regions and patient mortality rates.

CONCLUSIONS

These results demonstrate that the LAD to SMA structures does affect morbidity, although not to the extent of LAD to primary structures. In addition, motor deficits are significantly associated with LAD to secondary structures, but language deficits are not. This should be considered by neurosurgeons for patient consultation and preoperative planning.

Dynamic aphasia following low-grade glioma surgery near the supplementary motor area: a selective spontaneous speech deficit

We describe a patient (KO) with reduced spontaneous speech, resembling dynamic aphasia, after awake glioma surgery in the proximity of the supplementary motor area. Naming, repetition, and comprehension were intact. He was tested with an extensive neuropsychological test-battery and a protocol for dynamic aphasia at 1 year. He presented with postoperative reduced spontaneous speech and selective executive function deficits. Most language recovery took place at 3 months postoperatively, whereas the executive functions improved between 3 months and 1 year. Results suggest that resection near the supplementary motor area could increase the risk of cognitive disturbances at long term, especially language.

Probabilistic fiber tracking of the language and motor white matter pathways of the supplementary motor area (SMA) in patients with brain tumors

BACKGROUND AND PURPOSE

Accurate localization of anatomically and functionally separate SMA tracts is important to improve planning prior to neurosurgery. Using fMRI and probabilistic DTI techniques, we assessed the connectivity between the frontal language area (Broca's area) and the rostral pre-SMA (language SMA) and caudal SMA proper (motor SMA).

MATERIALS AND METHODS

Twenty brain tumor patients completed motor and language fMRI paradigms and DTI. Peaks of functional activity in the language SMA, motor SMA and Broca's area were used to define seed regions for probabilistic tractography.

RESULTS

fMRI and probabilistic tractography identified separate and unique pathways connecting the SMA to Broca's area - the language SMA pathway and the motor SMA pathway. For all subjects, the language SMA pathway had a larger number of voxels (P<0.0001) and higher connectivity (P<0.0001) to Broca's area than did the motor SMA pathway. In each patient, the number of voxels was greater in the language and motor SMA pathways than in background pathways (P<0.0001). No differences were found between patients with ipsilateral and those with contralateral tumors for either the language SMA pathway (degree of connectivity: P<0.36; number of voxels: 0.35) or the motor SMA pathway (degree of connectivity, P<0.28; number of voxels, P<0.74).

CONCLUSION

Probabilistic tractography can identify unique white matter tracts that connect language SMA and motor SMA to Broca's area. The language SMA is more significantly connected to Broca's area than is the motor subdivision of the SMA proper.

Intraoperative monitoring of an aspect of executive functions: administration of the Stroop test in 9 adult patients during awake surgery for resection of frontal glioma

BACKGROUND

Awake brain surgery allows extensive intraoperative monitoring of not only motor and sensory functions and language but also executive functions.

OBJECTIVE

To administer the Stroop test intraoperatively to avoid dramatic side effects such as akinetic mutism and to monitor executive functions in an attempt to optimize the benefit/risk balance of surgery.

METHODS

A series of 9 adult patients with frontal glioma were operated on for gross tumor resection under local anesthesia. All procedures involved the anterior cingulate cortex (ACC).

RESULTS

Three types of response to the Stroop test were observed: 3 patients had a Stroop effect only for stimulation of the contralateral ACC; 3 patients had a Stroop effect for stimulation of the ipsilateral ACC; and 3 patients had no Stroop effect. Preoperative and postoperative neuropsychological and surgical results are presented and discussed. Stimulation sites eliciting a Stroop effect are compared with published image-based data, and insight provided by these surgical data regarding ACC function and plasticity is discussed. No operative complication related to intraoperative administration of the Stroop test was observed.

CONCLUSION

Administration of the Stroop test during resection of gliomas involving the ACC in adult patients is an option for intraoperative monitoring of executive functions during awake surgery. Globally, these results suggest functional compensation, mediated by plasticity mechanisms, by contralateral homologous regions of the ACC in adult patients with frontal glioma.

Cerebral functional asymmetry and phonological performance in dyslexic adults

Developmental dyslexia is a frequent language-based learning disorder characterized by difficulty in reading. The predominant etiologic view postulates that reading impairment is related to phonological and orthographic dysfunction. The aim of this fMRI study was to evaluate the neural bases of phonological processing impairment in remediated dyslexic adults (DD). We used a rhyming words judgment task contrasted with an unreadable fonts font-matching judgment task to compare patterns of activation and functional asymmetry in DD and normal-reading young adults. We found evidence of a link between asymmetry in inferior frontal gyrus and performance during the phonological processing. We also observed that DD recruit a network including regions involved in articulatory control in order to achieve rhyme judgment suggesting that, due to a lack of hemispheric specialization, DD recruit the latter network to achieve rhyme judgment.

Selection of intraoperative tasks for awake mapping based on relationships between tumor location and functional networks

Intraoperative electrical brain mapping is currently the most reliable method to identify eloquent cortical and subcortical structures at the individual level and to optimize the extent of resection of intrinsic brain tumors. The technique allows the preservation of quality of life, not only allowing avoidance of severe neurological deficits but also facilitating preservation of high neurocognitive functions. To accomplish this goal, however, it is crucial to optimize the selection of appropriate intraoperative tasks, given the limited intrasurgical awake time frame. In this review, the authors' aim was to propose specific parameters that could be used to build a personalized protocol for each patient. They have focused on lesion location and relationships with functional networks to guide selection of intrasurgical tasks in an effort to increase reproducibility among neurooncological centers.

Functional imaging of cerebral perfusion

The functional imaging of perfusion enables the study of its properties such as the vasoreactivity to circulating gases, the autoregulation and the neurovascular coupling. Downstream from arterial stenosis, this imaging can estimate the vascular reserve and the risk of ischemia in order to adapt the therapeutic strategy. This method reveals the hemodynamic disorders in patients suffering from Alzheimer's disease or with arteriovenous malformations revealed by epilepsy. Functional MRI of the vasoreactivity also helps to better interpret the functional MRI activation in practice and in clinical research.

White matter impairment in the speech network of individuals with autism spectrum disorder

Impairments in language and communication are core features of Autism Spectrum Disorder (ASD), and a substantial percentage of children with ASD do not develop speech. ASD is often characterized as a disorder of brain connectivity, and a number of studies have identified white matter impairments in affected individuals. The current study investigated white matter integrity in the speech network of high-functioning adults with ASD. Diffusion tensor imaging (DTI) scans were collected from 18 participants with ASD and 18 neurotypical participants. Probabilistic tractography was used to estimate the connection strength between ventral premotor cortex (vPMC), a cortical region responsible for speech motor planning, and five other cortical regions in the network of areas involved in speech production. We found a weaker connection between the left vPMC and the supplementary motor area in the ASD group. This pathway has been hypothesized to underlie the initiation of speech motor programs. Our results indicate that a key pathway in the speech production network is impaired in ASD, and that this impairment can occur even in the presence of normal language abilities. Therapies that result in normalization of this pathway may hold particular promise for improving speech output in ASD.

•

We used diffusion tensor imaging to measure white matter (WM) tracts in autism.

•

Autistic participants were high-functioning individuals with normal language skills.

•

WM between left supplementary motor and premotor areas is impaired in autism.

•

This tract is believed to be involved in the initiation of speech articulation.

•

Speech production may be impaired in the absence of language deficits in autism.

Rostral and caudal prefrontal contribution to creativity: a meta-analysis of functional imaging data

Creativity is of central importance for human civilization, yet its neurocognitive bases are poorly understood. The aim of the present study was to integrate existing functional imaging data by using the meta-analysis approach. We reviewed 34 functional imaging studies that reported activation foci during tasks assumed to engage creative thinking in healthy adults. A coordinate-based meta-analysis using Activation Likelihood Estimation (ALE) first showed a set of predominantly left-hemispheric regions shared by the various creativity tasks examined. These regions included the caudal lateral prefrontal cortex (PFC), the medial and lateral rostral PFC, and the inferior parietal and posterior temporal cortices. Further analyses showed that tasks involving the combination of remote information (combination tasks) activated more anterior areas of the lateral PFC than tasks involving the free generation of unusual responses (unusual generation tasks), although both types of tasks shared caudal prefrontal areas. In addition, verbal and non-verbal tasks involved the same regions in the left caudal prefrontal, temporal, and parietal areas, but also distinct domain-oriented areas. Taken together, these findings suggest that several frontal and parieto-temporal regions may support cognitive processes shared by diverse creativity tasks, and that some regions may be specialized for distinct types of processes. In particular, the lateral PFC appeared to be organized along a rostro-caudal axis, with rostral regions involved in combining ideas creatively and more posterior regions involved in freely generating novel ideas.

The "onco-functional balance" in surgery for diffuse low-grade glioma: integrating the extent of resection with quality of life

Diffuse low-grade glioma (DLGG) is a growing pre-cancerous tumor, often diagnosed in patients with no or only mild deficit. Maximal and early surgical resection is currently the first therapeutic option, in order to delay the malignant transformation and thus increase the overall survival. Preserving the quality of life (QoL) is nonetheless another priority. Here, our purpose is to weight the value of the extent of resection versus the neurological worsening that could be voluntarily generated by a radical resection; that is, to study the "onco-functional balance" at the individual level. To this end, we will examine DLGG involving the supplementary motor area and DLGG involving visual pathways. We will consider the benefit-risk ratio of different strategies of resection, according to the brain structures actually invaded and their plastic potential. The aim is to increase both the quantity of life and the time with a normal QoL, on the basis of strong interactions between the tumor course, brain reorganization and multistage surgical approach adapted to each patient over time. To this end, beyond the conceptual and technical issues, the most important point remains the honest and unique relationship between the surgical oncologist and the patient, based on clear and complete information about the behavior of DLGG versus the expected medical and social consequences of a resection over years. In other words, in the era of "evidence-based medicine", it is crucial to not forget "individual-based medicine" by offering tailored resections adapted to each patient.

Risk factor analysis of the development of new neurological deficits following supplementary motor area resection

OBJECT

Supplementary motor area (SMA) resection often induces postoperative contralateral hemiparesis or speech disturbance. This study was performed to assess the neurological impairments that often follow SMA resection and to assess the risk factors associated with these postoperative deficits.

METHODS

The records for patients who had undergone SMA resection for pharmacologically intractable epilepsy between 1994 and 2010 were gleaned from an epilepsy surgery database and retrospectively reviewed in this study.

RESULTS

Forty-three patients with pharmacologically intractable epilepsy underwent SMA resection with intraoperative cortical stimulation and mapping while under awake anesthesia. The mean patient age was 31.7 years (range 15-63 years), and the mean duration and frequency of seizures were 10.4 years (range 0.1-30 years) and 14.6 per month (range 0.1-150 per month), respectively. Pathological examination of the brain revealed cortical dysplasia in 18 patients (41.9%), tumors in 16 patients (37.2%), and other lesions in 9 patients (20.9%). The mean duration of the follow-up period was 84.0 months (range 24-169 months). After SMA resection, 23 patients (53.5%) experienced neurological deficits. Three patients (7.0%) experienced permanent deficits, and 20 (46.5%) experienced symptoms that were transient. All permanent deficits involved contralateral weakness, whereas the transient symptoms patients experienced were varied, including contralateral weaknesses in 15, apraxia in 1, sensory disturbances in 1, and dysphasia in 6. Thirteen patients recovered completely within 1 month. Univariate analysis revealed that resection of the SMA proper, a shorter lifetime seizure history (<10 years), and resection of the cingulate gyrus in addition to the SMA were associated with the development of neurological deficits (p=0.078, 0.069, and 0.023, respectively). Cingulate gyrus resection was the only risk factor identified on multivariate analysis (p=0.027, OR 6.530, 95% CI 1.234-34.562).

CONCLUSIONS

Resection of the cingulate gyrus in addition to the SMA was significantly associated with the development of postoperative neurological impairment.

Fronto-cerebellar fiber tractography in pediatric patients following posterior fossa tumor surgery

OBJECTIVE

Fronto-cerebellar association fibers (FCF) are involved in neurocognitive regulatory circuitry. This may also be relevant for cerebellar mutism syndrome (CMS) as a complication following posterior fossa tumor removal in children. In the present study, we investigated FCF by diffusion tensor imaging in affected children and controls.

METHODS

Diffusion-weighted MR imaging at 3 T (GE) allowed tractography of FCF using a fiber tracking algorithm software (Brainlab 2.6) in 29 patients after posterior fossa tumor removal and in 10 healthy peers. Fiber tract volumes were assessed and fiber signals were evaluated in a semiquantitative manner along the anatomical course.

RESULTS

Volumes of FCF revealed significant diminished values in pediatric patients with symptoms of CMS (19.3 ± 11.7 cm(3)) when compared with patients without symptoms of CMS (26.9 ± 11.9 cm(3)) and with healthy peers (36.5 ± 13.82 cm(3)). In medulloblastoma patients, the volume of FCF was also significantly reduced in patients with symptoms of CMS despite having the same antitumor therapy. In semiquantitative analysis of the fiber tract signals, differences were observed in the superior cerebellar peduncles and midline cerebellar structures in patients with symptoms of CMS.

CONCLUSION

Using DTI, which allows the visualization of fronto-cerebellar fiber tracts, lower FCF tract volumes and diminished fiber signal intensities at the level of the superior cerebellar peduncles and in midline cerebellar structures were identified in patients with postoperative symptoms of CMS. Our study refers to the role of a neural circuitry between frontal lobes and the cerebellum being involved in neurocognitive impairment after posterior fossa tumor treatment in children.

Spontaneous speech of patients with gliomas in eloquent areas before and early after surgery

BACKGROUND

Glioma patients often complain about problems in daily conversation. A detailed spontaneous speech analysis could provide more insight in these communicative problems; no previous studies are reported.

OBJECTIVE

To select sensitive parameters in spontaneous speech pre- and post-operatively in patients with gliomas in eloquent areas.

METHODS

We included 27 patients and 21 healthy controls. In addition to a naming and category fluency test, spontaneous speech was collected 1 month pre-operatively and 3 months post-operatively, and analysed with the variables: Self-corrections, Repetitions, Lexical Diversity, Incomplete Sentences and Mean Length of Utterance (MLUw). A correlation analysis was performed between the linguistic variables and tumour characteristics (grade, localisation and volume), treatment related factors, and between the linguistic variables and the language tasks.

RESULTS

Pre-operatively, patients produced more Incomplete Sentences than the controls (p < 0.001). Post-operatively, patients' utterance length (MLUw) (p < 0.05) was also deviant. The quality of the spontaneous speech was influenced by tumour grade and localisation. There was no influence of tumour volume or treatment-related factors. Pre- and post-operatively, patients' performance on the naming and the fluency task deviated from normal (p < 0.001). The majority of the linguistic variables did not correlate with the language tasks, pointing to a measurement of distinct linguistic aspects.

CONCLUSION

Pre- and post-operatively there was a disorder in naming, category fluency and spontaneous speech, partly influenced by tumour characteristics. A spontaneous speech analysis appeared to be a valuable addition to standardised language tasks. Both measurements are important tools to obtain a complete linguistic profile.

Epilepsy surgery of the cingulate gyrus and the frontomesial cortex

BACKGROUND

Epilepsy surgery involving the cingulate gyrus has been mostly presented as case reports, and larger series with long-term follow-up are not published yet.

OBJECTIVE

To report our experience with focal epilepsy arising from the cingulate gyrus and surrounding structures and its surgical treatment.

METHODS

Twenty-two patients (mean age, 36; range, 12-63) with a mean seizure history of 23 years (range, 2-52) were retrospectively analyzed. We report presurgical diagnostics, surgical strategy, and postoperative follow-up concerning functional morbidity and seizures (mean follow-up, 86 months; range, 25-174).

RESULTS

Nineteen patients showed potential epileptogenic lesions on preoperative magnetic resonance imaging (MRI). All patients had noninvasive presurgical workup; 15 (68%) underwent invasive Video-electroencephalogram (EEG)-Monitoring. In 12 patients we performed extended lesionectomy according to MRI; an extension with regard to EEG results was done in 6 patients. In 4 patients, the resection was incomplete because of the involvement of eloquent areas according to functional mapping results. Eight pure cingulate resections (36%, 3 in the posterior cingulate gyrus) and 14 extended supracingular frontal resections were performed. Nine patients experienced temporary postoperative supplementary motor area syndrome after resection in the superior frontal gyrus. Two patients retained a persistent mild hand or leg paresis, respectively. Postoperatively, 62% of patients were seizure-free (International League Against Epilepsy [ILAE] 1), and 76% had a satisfactory seizure outcome (ILAE 1-3).

CONCLUSION

Epilepsy surgery for lesions involving the cingulate gyrus represents a small fraction of all epilepsy surgery cases, with good seizure outcome and low rates of postoperative permanent deficits. In case of extended supracingular resection, supplementary motor area syndrome should be considered.

Characterization of the supplementary motor area syndrome and seizure outcome after medial frontal lobe resections in pediatric epilepsy surgery

BACKGROUND

In adults, resection of the medial frontal lobe has been shown to result in supplementary motor area (SMA) syndrome, a disorder characterized by transient motor impairment. Studies examining the development of SMA syndrome in children, however, are wanting.

OBJECTIVE

To characterize the development of SMA syndrome and to analyze seizure outcomes after surgery in the medial frontal lobe for medically intractable epilepsy.

METHODS

Thirty-nine patients with medically intractable epilepsy who underwent surgery in the medial frontal lobe were reviewed retrospectively. The progression of neurological impairment and seizure outcome after surgery was recorded, and the extent of cortex resected was analyzed.

RESULTS

After resection in the region of the SMA, 23 patients (59%) developed postoperative neurological impairment; 17 (74%) were identified as SMA syndrome. No neurological impairment was found after surgery in 16 patients (41%). Six patients (15%) experienced permanent neurological impairment. The majority of patients (82%) who developed SMA syndrome had resolution of their symptoms by 1 month postoperatively. Preoperative magnetic resonance imaging finding of lesional cases was associated with a significantly decreased likelihood of developing SMA syndrome (P = .02). Seizure outcome was favorable after surgery in most patients.

CONCLUSION

Surgery for medically intractable epilepsy in the region of the medial frontal cortex is effective and associated with reversible neurological impairment in children. All patients had resolution of their SMA syndrome by 6 months postoperatively.

Complex epileptic palilalia: a case report

Palilalia is a kind of motor perseveration involving speech, consisting in the continuous repetition of words or phrases, or both. Rarely it occurs in seizure disorders as ictal or post-ictal manifestation. We report a case of epileptic palilalia in a 71-year-old patient with a previous history of intracerebral haemorrhage in the left frontal region, characterized by the continuous repetition of the same speech sequence for few minutes. EEG recordings during NREM sleep and wakefulness showed recurrent and prolonged focal subclinical epileptiform paroxysms in the left mesial frontal region. Our case confirms the role of the left frontal lobe, reliably of the supplementary motor area (SMA), as neuroanatomic origin of ictal palilalia.

Ultra-fast recovery from right neglect after 'awake surgery' for slow-growing tumor invading the left parietal area

It is now possible to perform resections of slow-growing tumors in awake patients. Using direct electrical stimulation, real-time functional mapping of the brain can be used to prevent the resection of essential areas near the tumor. Simple clinical observations of patients with a resection of slow-growing tumors have demonstrated substantial recovery within a few days of such 'awake surgery'. The aim of this study was to investigate the kinetics of recovery following the resection of slow-growing tumors invading the left parietal area and to focus mainly on its rapidity. Two patients were assessed by standard line bisection tests and compared with eight healthy individuals. Independently of the pure nature of the symptoms, we report that the patients rapidly and substantially recovered from pronounced right neglect. They were tested 48 hours after the surgery and the recovery was significant for both patients after less than 4 hours. Strikingly, for one patient, recovery was ultra fast and substantial in the first practice session within less than 7 minutes: it occurred without verbal feedback and was substantially retained during the following testing session. Its rapidity suggests a process of unmasking redundant networks. With the slow growth of the lesion, the contralesional hemisphere is probably progressively prepared for rapid unmasking of homologue networks. These results have major clinical implications. For patients with an invading left-side tumor, it is now clear that line bisections are required before, during, and after awake surgery to: plan the surgery, control the quality of the resection, and also optimize the rehabilitation of the patient.

Intrasurgical mapping of complex motor function in the superior frontal gyrus

A lesion to the superior frontal gyrus (SFG) has been associated with long-lasting deficits in complex motor functions. The aim of this study was to analyze the functional role of the SFG by means of electrical cortical stimulation. Direct intraoperative electrical stimulation was used in a group of 21 subjects with lesions within or close to the SFG while they performed three motor tasks that require high skills or bimanual synergy. The results were compared to functional magnetic resonance imaging (fMRI). Ninety-four of the 98 (94.9%) labels identified were located on the convexity surface of the SFG and only four (4.1%) labels were located on the middle surface of the SFG. Areas of blockage of the three tasks were identified in six of the 12 (50%) hemispheres with lesions that had infiltrated the SFG, compared to all 10 of the 10 hemispheres (100%) with lesions that spared the SFG. The difference between these two proportions was statistically significant (P=0.015). fMRI activation was mainly located on the medial aspect of the SFG. We show that the convexity surface of the SFG has an important role in bilateral control of complex movements and in bimanual coordination. The infiltration of the posterior part of the SFG by a lesion disturbs some of the complex hand motor functions, which may be assumed by the contralesional homologous area. Finally, the current study emphasizes the discrepancies between fMRI and intraoperative electrical stimulation maps in complex hand motor function.

Imaging of brain tumors: functional magnetic resonance imaging and diffusion tensor imaging

The eloquent brain can be identified using functional MR (fMR) imaging for the gray matter and diffusion tensor (DT) imaging for the white matter. fMR imaging and DT imaging are especially important for patients with tumors near the important motor and language centers of the brain, where the normal anatomic references may be distorted by the tumor and associated edema. This article explains fMR imaging and DT imaging techniques and illustrates their clinical applications and limitations.

Interactions between auditory and visual semantic stimulus classes: evidence for common processing networks for speech and body actions

Incongruencies between auditory and visual signals negatively affect human performance and cause selective activation in neuroimaging studies; therefore, they are increasingly used to probe audiovisual integration mechanisms. An open question is whether the increased BOLD response reflects computational demands in integrating mismatching low-level signals or reflects simultaneous unimodal conceptual representations of the competing signals. To address this question, we explore the effect of semantic congruency within and across three signal categories (speech, body actions, and unfamiliar patterns) for signals with matched low-level statistics. In a localizer experiment, unimodal (auditory and visual) and bimodal stimuli were used to identify ROIs. All three semantic categories cause overlapping activation patterns. We find no evidence for areas that show greater BOLD response to bimodal stimuli than predicted by the sum of the two unimodal responses. Conjunction analysis of the unimodal responses in each category identifies a network including posterior temporal, inferior frontal, and premotor areas. Semantic congruency effects are measured in the main experiment. We find that incongruent combinations of two meaningful stimuli (speech and body actions) but not combinations of meaningful with meaningless stimuli lead to increased BOLD response in the posterior STS (pSTS) bilaterally, the left SMA, the inferior frontal gyrus, the inferior parietal lobule, and the anterior insula. These interactions are not seen in premotor areas. Our findings are consistent with the hypothesis that pSTS and frontal areas form a recognition network that combines sensory categorical representations (in pSTS) with action hypothesis generation in inferior frontal gyrus/premotor areas. We argue that the same neural networks process speech and body actions.

Activation of frontal neocortical areas by vocal production in marmosets

Primates often rely on vocal communication to mediate social interactions. Although much is known about the acoustic structure of primate vocalizations and the social context in which they are usually uttered, our knowledge about the neocortical control of audio-vocal interactions in primates is still incipient, being mostly derived from lesion studies in squirrel monkeys and macaques. To map the neocortical areas related to vocal control in a New World primate species, the common marmoset, we employed a method previously used with success in other vertebrate species: Analysis of the expression of the immediate early gene Egr-1 in freely behaving animals. The neocortical distribution of Egr-1 immunoreactive cells in three marmosets that were exposed to the playback of conspecific vocalizations and vocalized spontaneously (H/V group) was compared to data from three other marmosets that also heard the playback but did not vocalize (H/n group). The anterior cingulate cortex, the dorsomedial prefrontal cortex and the ventrolateral prefrontal cortex presented a higher number of Egr-1 immunoreactive cells in the H/V group than in H/n animals. Our results provide direct evidence that the ventrolateral prefrontal cortex, the region that comprises Broca's area in humans and has been associated with auditory processing of species-specific vocalizations and orofacial control in macaques, is engaged during vocal output in marmosets. Altogether, our results support the notion that the network of neocortical areas related to vocal communication in marmosets is quite similar to that of Old world primates. The vocal production role played by these areas and their importance for the evolution of speech in primates are discussed.

Prediction of neurological deficits and recovery after surgery in the supplementary motor area: a prospective study in 26 patients

OBJECT

Resection of lesions involving the supplementary motor area (SMA) may result in immediate postoperative motor and speech deficits that are reversible in most cases. In the present study the authors aimed to determine the critical involvement of SMA in the lesioned and healthy hemispheres in this functional recovery. They hypothesized that compensatory mechanisms take place following surgery in the SMA, and that these mechanisms can involve either the lesioned or the non-lesioned hemisphere. In addition, they hypothesized that a correlation will be present between the functional MR imaging (fMR) imaging-related activation in the SMA and the occurrence of a functional deficit during intraoperative cortical stimulation.

METHODS

Twenty-six patients scheduled for resection of space-occupying lesions involving, or in the vicinity of, the SMA were recruited. Patients underwent an fMR imaging examination that included finger-tapping and verb-generation tests to assess for motor and language functions. Intraoperatively direct cortical stimulation (DCS) of the SMA region was performed while patients were monitored for language and motor functions using tests similar to those used for the fMR imaging. Task dysfunction during DCS assessed the critical involvement of the SMA in the tested functions. Neurological evaluations were performed prior to surgery and at 3 time points within a month following surgery. A region of interest-based approach was used to evaluate fMR imaging blood oxygen level-dependent activation level and asymmetry in the SMA. These measurements were later compared with the intraoperative DCS and neurological findings.

RESULTS

Functional MR imaging showed greater activation and dominance of the SMA in the lesioned hemisphere in patients who exhibited no motor or language dysfunction during DCS. In addition, patients with the highest activation of the SMA in the lesioned hemisphere for language and motor tests showed stronger coupling of this region with ipsilateral motor and language networks. In contrast, activation in the nonlesioned hemisphere did not correspond with DCS results.

CONCLUSIONS

The authors' findings demonstrate the necessity of activation in the vicinity of the lesioned SMA for functional compensation in motor and language tasks. It is possible that more effective functional coupling of the SMA with motor and language areas in the same hemisphere prevents dysfunctions following surgical intervention. Importantly, fMR imaging activation in the unaffected SMA was not sufficient for development of functional compensation and, if anything, indicated decompensation.

Distinct representations of phonemes, syllables, and supra-syllabic sequences in the speech production network

Functional neuroimaging studies have converged on a core network of brain regions that supports speech production, but the sublexical processing stages performed by the different parts of this network remain unclear. Using an fMRI adaptation paradigm and quantitative analysis of patterns of activation rather than contrast subtractions alone, we were able to identify a set of neural substrates predominantly engaged in phonemic, syllabic, and supra-syllabic levels of processing during speech. Phoneme-level processes were found in the left SMA, pallidum, posterior superior temporal gyrus, and superior lateral cerebellum. Syllable-level processes were found in the left ventral premotor cortex, and supra-syllabic processes related to phonological chunking were found in the right superior lateral cerebellum. Active regions that were not sensitive to sublexical manipulations included primary motor and auditory cortical areas, and medial cerebellum. These results offer a quantitative technique for localizing sublexical neural processes that are difficult to dissociate using non-invasive imaging techniques and provide the beginnings of a "brain map" for language output.

Agrammatic comprehension caused by a glioma in the left frontal cortex

It has been known that lesions in the left inferior frontal gyrus (L. IFG) do not always cause Broca's aphasia, casting doubt upon the specificity of this region. We have previously devised a picture-sentence matching task for a functional magnetic resonance imaging (fMRI) study, and observed that both pars triangularis (L. F3t) of L. IFG (extending to pars opercularis (L. F3op)) and the left lateral premotor cortex (L. LPMC) are selectively involved in syntactic processing. The present study with lesion-symptoms mapping was conducted to examine whether the function of these regions is indeed critical for syntactic comprehension. Using the same picture-sentence matching task, we examined 21 patients with a glioma in the left frontal cortex but with no apparent disability in verbal/written communication or intelligence quotient. This task included three main conditions of sentence types: canonical/subject-initial active sentences, non-canonical/subject-initial passive sentences, and non-canonical/object-initial scrambled sentences. The patients preoperatively underwent a high-resolution 3D-MRI, and voxel-based lesion-symptom mapping was employed for the error rates data. We found that the patients with a lesion in L. F3op/F3t or L. LPMC showed differential patterns of condition-selective deficits in the comprehension of sentences. More specifically, the L. F3op/F3t-damaged patients had more profound deficits in the comprehension of non-canonical sentences, whereas the L. LPMC-damaged patients had more profound deficits in the comprehension of object-initial scrambled sentences. These results establish that a lesion in L. F3op/F3t or L. LPMC is sufficient to cause agrammatic comprehension.

Gliomas of the cingulate gyrus: surgical management and functional outcome

Object

In this paper, the authors' goal was to summarize their experience with the surgical treatment of gliomas arising from the cingulate gyrus.

Methods

The authors analyzed preoperative data, surgical strategies, complications, and functional outcome in a series of 34 patients (mean age 42 years, range 12–69 years; 14 females) who underwent 38 operations between May 2001 and November 2008.

Results

In 7 cases (18%) the tumor was located in the posterior (parietal) part of the cingulate gyrus, and in 31 (82%) the tumor was in the anterior (frontal) part. In 10 cases (26%) the glioma was solely located in the cingulate gyrus, and in 28 cases (74%) the tumor extended to the supracingular frontal/parietal cortex. Most cases (23 [61%]) had seizures as the presenting symptom, 8 patients (24%) suffered from a hemiparesis/hemihypesthesia, and 4 patients (12%) had aphasic symptoms.

The authors chose an interhemispheric approach for tumor resection in 11 (29%) and a transcortical approach in 27 (71%) cases; intraoperative electrophysiological monitoring was applied in 23 (61%) and neuronavigation in 15 (39%) cases. A > 90% resection was achieved in 32 (84%) and > 70% in another 5 (13%) cases. Tumors were classified as low-grade gliomas in 11 cases (29%). A glioblastoma multiforme (WHO Grade IV, 10 cases [26%]) and oligoastrocytoma (WHO Grade III, 9 cases [24%]) were the most frequent histopathological results.

Postoperatively, patients in 13 cases suffered from a transient supplementary motor area syndrome (34%), all of whom had tumors in the anterior cingulate gyrus. In the early postoperative period (30 days) a new deficit occurred in 5 cases (13%, mild motor deficits or aphasic symptoms). One patient had a major bleeding episode 2 days after surgery and was in a persistent vegetative state.

Conclusions

Gliomas arising from the cingulate gyrus are rare. A gross-total resection is often possible and acceptably safe; intraoperative monitoring and neuronavigation are helpful adjuncts. In case of resection of gliomas arising from the anterior cingulate gyrus a supplementary motor area syndrome has to be considered, particularly when the tumor extends to the supracingular cortex

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.