Michel Desmurget’s research while affiliated with Claude Bernard University Lyon 1 and other places

This scientific commentary refers to ‘Tonic somatosensory responses and deficits of tactile awareness converge in the parietal operculum’ by Del Vecchio et al. (doi:10.1093/brain/awab384).

A therapeutic effect of vagus nerve stimulation has been reported for a wide range of neurological, medical and psychiatric conditions. New research provides evidence that this effect results from extensive increase of physiological arousal and brain activation.

The dorso-posterior parietal cortex (DPPC) is a major node of the grasp/manipulation control network. It is assumed to act as an optimal forward estimator that continuously integrates efferent outflows and afferent inflows to modulate the ongoing motor command. In agreement with this view, a recent per-operative study, in humans, identified functional sites within DPPC that: (i) instantly disrupt hand movements when electrically stimulated; (ii) receive short-latency somatosensory afferences from intrinsic hand muscles. Based on these results, it was speculated that DPPC is part of a rapid grasp control loop that receives direct inputs from the hand-territory of the primary somatosensory cortex (S1) and sends direct projections to the hand-territory of the primary motor cortex (M1). However, evidence supporting this hypothesis is weak and partial. To date, projections from DPPC to M1 grasp zone have been identified in monkeys and have been postulated to exist in humans based on clinical and transcranial magnetic studies. This work uses diffusion-MRI tractography in two samples of right- (n = 50) and left-handed (n = 25) subjects randomly selected from the Human Connectome Project. It aims to determine whether direct connections exist between DPPC and the hand control sectors of the primary sensorimotor regions. The parietal region of interest, related to hand control (hereafter designated DPPChand), was defined permissively as the 95% confidence area of the parietal sites that were found to disrupt hand movements in the previously evoked per-operative study. In both hemispheres, irrespective of handedness, we found dense ipsilateral connections between a restricted part of DPPChand and focal sectors within the pre and postcentral gyrus. These sectors, corresponding to the hand territories of M1 and S1, targeted the same parietal zone (spatial overlap > 92%). As a sensitivity control, we searched for potential connections between the angular gyrus (AG) and the pre and postcentral regions. No robust pathways were found. Streamline densities identified using AG as the starting seed represented less than 5 % of the streamline densities identified from DPPChand. Together, these results support the existence of a direct sensory-parietal-motor loop suited for fast manual control and more generally, for any task requiring rapid integration of distal sensorimotor signals.

Introduction Le jeune âge des patients traités chirurgicalement pour une tumeur de la fosse cérébrale postérieure représenterait un facteur de mauvais pronostic pour la récupération fonctionnelle. Nous rapportons une étude qui évalue ce risque. Matériel et méthodes Nous avons étudié la récupération chez 51 patients opérés d’une tumeur de la fosse cérébrale postérieure. Le suivi moyen était de 5 ans. Nous avons évalué la qualité de vie (Health-related Quality of Life -hrQol-, Performance Status -PS-), les déficits moteurs (International Cooperative Ataxia Rating Scale- ICARS -, Pegboard Purdue Test -PegBoard) et le quotient intellectuel (Full Scale Intelligence Quotient -FSIQ-). Un modèle linéaire généralisé a été utilisé pour investiguer l’impact de ces facteurs sur la récupération des patients : l’âge à la chirurgie (< 7 ans ; > 7 ans), le traitement complémentaire (radio et chimiothérapie), la préservation des noyaux profonds du cervelet, le volume tumoral et le délai entre la chirurgie et l’évaluation clinique. Résultats Le jeune âge (< 7 ans), la destruction des noyaux profonds du cervelet et l’utilisation d’un traitement complémentaire ont un effet négatif significatif indépendant sur la récupération à long terme. Le volume tumoral et le délai entre la chirurgie et l’évaluation clinique n’avaient aucun impact. L’impact de l’âge était significatif sur tous les tests : hrQoL : −18 % ; PS : −11 %, ICARS, +53 %, Pegboard, −38 %, FSIQ, −12 %. Conclusion Notre expérience prouve que le jeune âge (< 7 ans) lors de la chirurgie est un facteur indépendant de mauvais pronostic à long terme pour la récupération fonctionnelle motrice et intellectuelle des patients opérés d’une tumeur de la fosse cérébrale postérieure.

Introduction: Awake brain surgery (ABS) represents a rare surgical procedure in children as age and psychological aspects, which are considered to interfere with its feasibility and psychological outcome and limit its application. Only few pediatric case series have been reported so far, indicating a more complex translation of this surgical approach to children. However, the advances in neuropsychological testing and monitoring may have a substantial impact on ameliorating the eligibility of children undergoing awake procedures. This study addresses the condition of ABS in a pediatric cohort, focusing on its practicability and diversified outcome aspects. Methods: We performed a retrospective review and prospective outcome analysis of pediatric patients with CNS lesions undergoing ABS between 2005 and 2018, completed at the University of Lyon, France. Results: Eighteen children were considered for ABS with respect to the eloquent location of their CNS lesions documented in their pre-operative MRI. Seventeen of them underwent asleep-awake-asleep brain surgery. The cohort included 5 males and 12 females. The median age at surgery was 14.8 years, (range 9.4 to 17.6 years). Intraoperative testing included electrocortical stimulation while pursuing speech or motor activity. Most of the lesions were intrinsic tumors of glial origin. A complete tumor removal was achieved in 11 patients (65%). Post-operative neurological deficits were transiently observed in 2 patients, whereas severe psychological reactions occurred in 1 child. Persistent attention deficits were found in 2 patients. One patient experienced an infectious complication requiring antibiotic treatment. Two patients died during follow-up due to tumor progression. The mean duration of follow up was 22.2 months (range 3.4 to 46.8 months). Conclusions: ABS was shown to be beneficial in terms of efficient tumor resection besides simultaneous preservation of neurological functions. Psychological preparation of the families and the children is essential to increase the number and age range of patients, who can benefit from this technique. Neuropsychological testing before and after surgery is essential to determine cognitive outcome, which can be altered in a minority of patients.

Early studies on long-term functional recovery after motor and premotor lesions showed better outcomes in younger than older monkeys. This finding led to the widespread belief that brain injuries cause less impairment in children than adults. However, this view has limitations and a large body of evidence now indicates that cerebral damages can be more harmful when inflicted at young age, during critical periods of neural development. To date, this issue has been mainly investigated in the context of focal and diffuse cortical lesions. Much less is known about the potential influence of early cerebellar damages. Several studies exist in survivor of posterior fossa tumors. However, in these studies critical confounders were not always considered and contradictory conclusions were provided. We studied the impact or early cerebellar damage on long-term functional recovery in 3 groups of fifteen posterior fossa survivors, comparable with respect to their tumor characteristics (type, size, location) but operated at different ages: young (≤ 7 years), middle (> 7 years and ≤ 13 years) and older (> 13 years). Daily (Health-related Quality of Life Scale, Performance Status Scale), motor (International Cooperative Ataxia Rating Scale, Pegboard Purdue Test) and cognitive (Full Scale Intelligence Quotient) functioning were assessed. A general linear model controlling for age at surgery, radiotherapy, preservation of deep-cerebellar nuclei, tumor volume and delay between surgery and assessment, was used to investigate significant variations in outcome measures. Early age at surgery, lesion of deep cerebellar nuclei and post-operative radiotherapy had a significant, independent negative influence on long term recovery. Tumor volume and delay between surgery and assessment had no statistically detectable impact. The negative influence of early age at surgery was significant in all domains: daily functioning (Health-related Quality of Life Scale, Performance Status Scale), motor functioning (International Cooperative Ataxia Rating Scale, Pegboard Purdue Test) and cognitive functioning (Full Scale Intelligence Quotient). These results support the existence of an early critical period of development during which the cerebellar "learning machine" is of critical importance. Although the extent to which the early deficits here observed can be reversed needs now to be established, our data plead for the implementation of prompt and intense rehabilitation interventions in children operated before 7 years of age.

Awake brain surgery (ABS) in children remains a subject of controversial debate for the potential psychological limitations that are related to this type of procedure. However, the tolerance and benefits of ABS in adults advocate for increased application of ABS in children. In this study, we report the psychological assessment, evaluation algorithm, and outcome of pediatric patients, who underwent ABS for surgical treatment of lesions in eloquent areas. Psychological selection criteria and the specifications of psychological support are described. A retrospective review and analysis of psychological assessment and psychological outcome of pediatric patients, who underwent ABS between 2005 and 2018 at the Department of pediatric neurosurgery, University of Lyon, France, was performed. Long-term psychological outcomes are reported. ABS was proposed to 18 children aged between 9 and 17 years and their families. After psychological evaluation of the individual patient and their familial surrounding, five boys and 12 girls (n = 17) were accounted eligible for ABS. They underwent asleep-awake-asleep brain surgery with intraoperative testing. In 16 cases, ABS could be performed as planned. Psychological alterations were postoperatively observed in 3 patients, symptoms of a post-traumatic stress disorder in 1 patient. The precise preoperative evaluation of the risk-benefit ratio in children plays a crucial role in anticipating a good psychological outcome. Professional psychological preparation and support of the child and his or her family are the key elements for successful completion of ABS.

Synopsis This chapter reviews the role of the posterior parietal cortex (PPC) in sensorimotor control. Although relevant data from monkey literature is considered, a special emphasis is put on human studies. The text is segmented into two main sections. The first section describes the basic anatomical organization of PPC. The second reports a functional dissociation between the superior (SPL) and inferior (IPL) parietal lobules.

Objective Awake brain surgery (ABS) is poorly reported in children as it is considered having limited indications due to age and neuropsychological aspects interfering with its feasibility and psychological outcome. The aim of this article is to review the current state-of-the-art of ABS in children and to offer an objective summary of the published literature on diversified outcome aspects of pediatric awake procedures. Methods A literature review was performed using the MEDLINE (PubMed) electronic database applying the following MeSH terms to the keyword search within titles and abstracts: “awake brain surgery children,” “awake brain surgery pediatric,” “awake craniotomy children,” “awake craniotomy pediatric,” and “awake surgery children.” Of the initial 753 results obtained from these keyword searches, a full text screening of 51 publications was performed, ultimately resulting in 18 eligible articles for this review. Results A total of 18 full text articles reporting the results of 50 patients were included in the analysis. Sixteen of the 18 studies were retrospective studies, comprising 7 case series, 9 case reports, and 2 reviews. Eleven studies were conducted from anesthesiological (25 patients) and 7 from neurosurgical (25 patients) departments. Most of the patients underwent ABS for supratentorial lesions (26 patients), followed by epilepsy surgery (16 patients) and deep brain stimulation (DBS) (8 patients). The median age was 15 years (range 8–17 years). Persistent deficits occurred in 6 patients, (12%), corresponding to minor motor palsies (4%) and neuropsychological concerns (8%). An awake procedure was aborted in 2 patients (4%) due to cooperation failure and anxiety, respectively. Conclusions Despite well-documented beneficial aspects, ABS remains mainly limited to adults. This review confirms a reliable tolerability of ABS in selected children; however, recommendations and guidelines for its standardized implementation in this patient group are pending. Recommendations and guidelines may address diagnostic workup and intra-operative handling besides criteria of eligibility, psychological preparation, and coordinated neuropsychological testing in order to routinely offer ABS to children.