Surgical management of posterior fossa medulloblastoma in children: The Lyon experience.

INTRODUCTION: Modern approach for the treatment of posterior fossa medulloblastomas remains a challenge for pediatric neurosurgeons and pediatric oncologists and requires a multidisciplinary approach to optimize survival and clinical results. MATERIAL AND METHODS: We report the surgical principles of the treatment of posterior fossa medulloblastomas in children and how to avoid technical mistakes especially in very young patients. We also report our experience in a series of 64 patients operated from a medulloblastoma between 2000 and 2018 in Lyon. RESULTS: All patients had a craniospinal MRI. Eighty-one percent of the patients (n=50) had strictly midline tumor while 19% (n=14) had lateralized one. Eleven percent (n=7) had metastasis at diagnosis on the initial MRI. Forty-one percent (n=29) had an emergency ETV to treat hydrocephaly and the intracranial hypertension. All patient underwent a direct approach and a complete removal was achieved in 78% (n=58) of the cases on the postoperative MRI realized within 48h postsurgery. Histological findings revealed classical medulloblastoma in 73% (n=46), desmoplastic medulloblastoma in 17% (n=11) and anaplastic/large cell medulloblastoma in 10% (n=7). Patients were classified as low risk in 7 cases, standard risk in 30 cases and high risk in 27 cases. Ninety-six percent (n=61) of the patient received radiotherapy. Seventy-six percent (n=48) received pre-irradiation or adjuvant chemotherapy. At last follow-up in December 2018, 65% (n=41) of the patient were in complete remission, 12% (n=8) were in relapse and 27% (n=15) had died from their disease. The overall survival at five , ten and fifteen years for all the series was of 76%, 73% and 65.7% respectively. CONCLUSIONS: Medulloblastomas remain a chimiosensible and radiosensible disease and the complete surgical removal represents a favorable prognostic factor. The extension of surgery has also to be weighted in consideration of the new biomolecular and genetic knowledge that have to be integrated by surgeons to improve quality of life of patients.

[The default mode network: cognitive role and pathological disturbances]. / Le réseau cérébral par défaut : rôle cognitif et perturbations dans la pathologie.

INTRODUCTION: A "resting state" or "default mode network" has been highlighted in functional neuroimaging studies as a set of brain regions showing synchronized activity at rest or in task-independent cognitive state. STATE OF THE ART: A considerable and increasing number of studies have been conducted over the last few years so as to unravel the cognitive function(s) of this brain network. PERSPECTIVES: This review gives an overview of anatomical, physiological and phenomenological data regarding the default mode network. Different hypotheses have been proposed regarding the role of this network. Several studies have highlighted its involvement in autobiographical memory, prospection, self, attention, and theory of mind. The influence of the attention level and consciousness onto resting state brain network activity has also been discussed. Specific changes have been described in normal aging, Alzheimer's disease (AD) and multiple sclerosis (MS). CONCLUSIONS: These studies altogether contribute to a better definition of the default mode network, in terms of implicated brain structures, subtending mechanisms, and potential cognitive roles. For instance, similarities and relationships were found between self-related brain activity and resting-state activity in regions belonging to this network, namely posterior cingulate and prefrontal areas that may reflect introspective activity experienced, more or less consciously, when the brain is not specifically engaged in a cognitive task. As a whole, the default mode network appears as a non human-specific intrinsic functional network, active all over the life from birth until aging where it is progressively modified, and sensitive to different pathologies including AD and MS. On the other hand, many points remain to be clarified concerning this network, such as the exact part of its activity dedicated to self-related cognitive processes (introspection, imaginary mental scenario based on past autobiographical experiences) and that involved in a sentinel-like attentional process designated to react to possible environmental events. Indeed, it seems that this network is functional even in case of low level of consciousness, i.e., during light sleep. Conversely, a loss of self and environment perception as in coma, deep sleep or anesthesia might modulate its connectivity along the anteroposterior axis, i.e., frontal activity disappearance associated with a parietal reinforcement of connectivity. Since studies aiming at highlighting these points are still uncommon to date, exhaustive and objective explorations are needed to better understand all these resting state processes.

[Why a hydroxyapatite cranioplasty can be used to repair a cranial bone defect in children: Experience of 19 cases]. / Pourquoi peut-on utiliser une plastie en hydroxyapatite pour réparer une perte de substance osseuse de la boîte crânienne chez les enfants : expérience à propos de 19 cas.

INTRODUCTION: The use of an autologous bone graft to repair a cranial bone defect is sometimes impossible in pediatric cases. CUSTOMBONE® made with hydroxyapatite is a good alternative in these indications for neurosurgeons. MATERIAL AND METHODS: We present a pediatric series of 19 children who benefited from a cranioplasty using CUSTOMBONE®. Their ages ranged between 8 months and 13 years with a mean of 6 years and 2 months. The most frequent indication was a cranioplasty after a post-traumatic decompressive craniectomy. RESULTS: No complications were reported. Cosmetic outcome was satisfactory in all patients. Only one plasty needed to be changed after a severe head trauma during the postoperative period. The assessment of cerebral blood flow was improved in all patients postoperatively. Complete ossification of the plasty is a long process. The mean time for the ossification to begin was 13 months (range: 3-22 months). The mean follow-up was 2.7 years. DISCUSSION: The excellent integration of the prosthesis is related to the accuracy of the reconstruction of the preoperative model. The minimum thickness of the plasty (4mm) could represent a challenge in very young children. One limitation is the cost, which remains high. CONCLUSION: CUSTOMBONE® met the criteria of protection and restoration of the normal intracranial physiology with good cosmetic results, which are necessary qualities for excellent clinical outcome.

Neuroendoscopy and pineal tumors: A review of the literature and our considerations regarding its utility.

Endoscopy has entered into the armamentarium of pineal and pineal region tumor treatment. The technique permits not only to control hydrocephalus but also to obtain tissue samples for histological diagnosis. In this paper, we explain the utility of endoscopy for the treatment of pineal tumors and as well as report some personal considerations regarding this topic.

Cranial vault expansion with the split bone flap technique in shunt-related craniosynostosis.

INTRODUCTION: Shunt-related craniosynostosis causing craniocerebral disproportion represents a particular complication of the treatment of hydrocephalus. When the modification of the shunt opening pressure does not improve the symptomatology, surgery for correction of craniocerebral disproportion is indicated. We present the results and advantages of the split bi-frontal bone technique that is a modification of the previous used frontal bone advancement technique. PATIENTS AND METHODS: We retrospectively reviewed 5 patients with iatrogenic craniosynostosis treated in our institution from 1995 to 2012. A splitting bi-frontal bone flap that is left floating posteriorly was performed to increase the cranial volume. RESULTS: All patients were cured. This technique increases the volume of the skull favoring the expansion of the brain and allows good cosmetical results. No perioperative complications were reported. DISCUSSION: The fact that the brain has a more appropriate volume allows the disappearance of the clinical symptomatology related to the split ventricle syndrome. The advantage is the respect of the fronto-orbital shape in children and adults with the same results of the classic frontal advancement in terms of volume expansion. The study of cerebral blood flow confirms the increase of the cerebral blood perfusion and the improvement of the regional cerebral blood flow in borderline regions. We preconize, for the treatment of slit ventricle syndrome, the bi-frontal split technique in children and adults for its efficacy, the low rate of complications and the respect of aesthetical constraints.

The sub-occipital transtentorial approach revisited base on our own experience.

UNLABELLED: The surgical experience of the sub-occipital approach for treatment of pineal gland and pineal region tumors is reported. This approach was originally proposed by Jamieson and modified by Lapras who by changing the shape of the bone flap obtained the elevation of the occipital lobe which consequently resulted in a better exposition of this deep region. The reason why this approach became the basis for their treatment is particularly related to the personal experience of Lapras who reported his fantastic experience of surgery in this deep area and demonstrated the advantages of the sub-occipital transtentorial approach. MATERIAL: Out of 277 patients operated from 1982 to 2012 in Lyon for a pineal tumor, 233 were treated by a sub-occipital approach: 153 males, 125 females, 75 patients of pediatric age. The majority of patients were operated on in a sitting position which represents a surgical specialty of the anesthesiological school of Lyon. RESULTS: Complete tumor removal was possible in 135 patients (58%) and partial in 60 patients (26%). For 38 patients, it was not possible to establish the quality of surgical resection. The incidence of hemianopsia decreased to less that 2% of cases while the incidence of severe pneumocephaly which requires a prolonged intensive care hospitalization was less than 4% of cases. Mortality related to this surgical approach in the Lyonnais school series was 0% during this period. CONCLUSION: In our experience the sub-occipital transtentorial approach seems to us the best approach for pineal tumors because it permits a large exposition of the pineal region favoring the removal of the tumor with a lateral extension and also for tumors extending low into the posterior cranial fossa. In fact, this is our preferred approach because it has been used in a large majority of cases. However, surgeons have to be familiar with other possible approaches to obtain the best result in terms of removal and also to decrease the rate of sequelae to improve the quality of life of these patients.

[Our experience about the use of resorbable plates in the treatment of craniostenosis]. / Notre expérience de l'utilisation des plaques résorbables dans le traitement des craniosténoses.

INTRODUCTION: The use of resorbable plates increases for craniosynostosis surgery. This material, based on polymere (PLA, PGA) can replace steel wire and non resorbable plates. A few studies present surgical results about the use of this material with a long follow-up. We present our ten years experience of using resorbable material for craniosynostosis treatment in children. METHODS: Between 2002 and 2012, we operated 283 craniosynostosis (98 scaphocephalies, 55 trigonocephalies, 79 plagiocephalies et 51 craniofaciostenoses). Among these surgeries, 211 were realized with resorbable material (plates and screws). Different criteria were observed: the esthetic result, the infection rate, the re-intervention, the bone defects and the inflammatory granuloma. RESULTS: Among the 211 craniosynostosis, we found 62 plagiocephalies, 66 scaphocephalies, 50 trigonocephalies, 33 craniofaciostenoses. All the reconstructions were realized with the same resorbable material (Macropore by Medtronic). The rate of complications was low: one scar infection without participation of material for two patients (0.9%), a pseudo-meningocele for two patients (0.9%), epilepsy for four children (1.8%) and bone defect for 15 (7%). We observed no granuloma for these patients. CONCLUSION: Our experience of ten years using resorbable material is very satisfactory. This material permits to realize solid and esthetic reconstructions with a low rate of infection without dangerous reaction for children in young age.

Decompressive craniectomy in the treatment of post-traumatic intracranial hypertension in children: our philosophy and indications.

Decompressive craniotomy (DC) in children is a life-saving procedure for the treatment of refractory intracranial hypertension related to traumatic, ischemic and infectious lesions. Different surgical procedures have been proposed including uni or bilateral hemicraniectomy, bi-frontal, bi-temporal, or bi-parietal craniotomies. DC can avoid the cascade of events related to tissue hypoxia, brain perfusion reduction, hypotension and the evolution of brain edema that can be responsible for brain herniation. The monitoring of intracranial pressure (ICP) is very important to take a decision as well as the value of Trans cranial Doppler (TCD). Repeated TCD in the intensive care unit give important information about the decrease of the cerebral perfusion pressure (CPP) and facilitates the decision making. The important question is about how long time we have to wait before to perform the DC. Three conditions can be distinguished: 1) ICP stable and TCD with good parameters: the decision can be postponed; 2) ICP>20 mmHg with good TCD and without clinical signs of deterioration: the decision can be postponed; 3) ICP>20 mmHg with altered CPP and degraded TCD value and clinical signs of brain herniation: the surgical procedure is indicated. The decision of a ventricular drainage can also be discussed but in cases of slit ventricles it is preferable to realize a DC to avoid the problems of multiple taps without finding the ventricular system. In some very specific situations, DC has to be contraindicated. The first one is a prolonged cardiopulmonary arrest with a no-flow longer than 15 minutes and irreversible lesions on the TCD or on the CT-scan. The second most common situation is a patient with GCS of 3 on admission associated with bilaterally fixed dilated pupils. In this case TCD is very useful to document the decrease or the absence of diastolic flux that indicates a very poor cerebral perfusion. In case of severe polytraumatism with multiorgan failure, especially in very severe hemorrhagic shock with incontrollable coagulopathy, the realization of DC is definitely hazardous with y a high risk of cardiac arrest during the surgical procedure. The decision to realize a hemicraniectomy or a bi-frontal craniotomy is related to the presence or not of associated traumatic lesions as hemorrhagic contusions or a sub-dural or extradural hematoma. In cases of diffuse cerebral edema the bi-frontal bone flap is indicated. In all cases a closure of the dura mater with a large dural patch has to be performed avoiding compression of the nervous system. Our results showed a mortality rate of 18%. Eighty percent of the survivors have a good quality of life but only 43% in a scholar age could attend a normal program. Patients treated with DC need a long follow-up and an important rehabilitation program to improve their quality of life. Our report shows that DC in children is effective to control the post-traumatic intracranial hypertension but a long follow-up is recommended to access the sequels and quality of life of these patients.