Sandrine de Ribaupierre

Subependymal giant-cell astrocytomas in pediatric tuberous sclerosis disease: when should we operate?

OBJECTIVEA small percentage of tuberous sclerosis patients will develop a subependymal giant-cell astrocytoma. Given the morbidity and mortality when such a lesion is left undiagnosed, successive follow-up imaging in pediatric patients has been recommended. Surgical removal of the lesion has become the procedure of choice; however, the timing of this surgery is still a controversial subject. By analyzing our own series of data, as well as other published series, we have attempted to reach a consensus on the benefits of early versus late surgery. METHODSWe retrospectively reviewed 19 patients treated surgically for intraventricular tumors in Foch Hospital and at the Fondation Adolphe de Rothschild in Paris, France, and we analyzed published pediatric reports from 1980 to 2006. RESULTSThe results from our own population, as well as from other published pediatric series (15 series), indicate that subependymal giant-cell astrocytomas have a good prognosis when a macroscopically total resection has been performed. In our series, residual lesions tended to enlarge, but residual tumors remaining stable have been reported. Careful follow-up examination should be undertaken because late recurrences do occur. Larger or symptomatic lesions tend to have a higher morbidity. CONCLUSIONWe think that any lesion fulfilling the criteria for a subependymal giant-cell astrocytoma as previously described in the literature (lesion around the foramen of Monro, greater than 5 mm, with incomplete calcifications) should be removed as soon as clear evidence of growth has been confirmed.

Hemispherotomy and other disconnective techniques

The surgical treatment of intractable epilepsy has evolved as new technical innovations have been made. Hemispherotomy techniques have been developed to replace hemispherectomy in order to reduce the complication rates while maintaining good seizure control. Disconnective procedures are based on the interruption of the epileptic network rather than the removal of the epileptogenic zone. They can be applied to hemispheric pathologies, leading to hemispherotomy, but they can also be applied to posterior quadrant epilepsies, or hypothalamic hamartomas. In this paper, the authors review the literature, present an overview of the historical background, and discuss the different techniques along with their outcomes and complications.

Measuring cognitive load: performance, mental effort and simulation task complexity

Interest in applying cognitive load theory in health care simulation is growing. This line of inquiry requires measures that are sensitive to changes in cognitive load arising from different instructional designs. Recently, mental effort ratings and secondary task performance have shown promise as measures of cognitive load in health care simulation.

Image registration of ex-vivo MRI to sparsely sectioned histology of hippocampal and neocortical temporal lobe specimens.

Intractable or drug-resistant epilepsy occurs in up to 30% of epilepsy patients, with many of these patients undergoing surgical excision of the affected brain region to achieve seizure control. Recent magnetic resonance imaging (MRI) sequences and analysis techniques have the potential to detect abnormalities not identified with diagnostic MRI protocols. Prospective studies involving pre-operative imaging and collection of surgically-resected tissue provide a unique opportunity for verification and tuning of these image analysis techniques, since direct comparison can be made against histopathology, and can lead to better prediction of surgical outcomes and potentially less invasive procedures. To carry out MRI and histology comparison, spatial correspondence between the MR images and the histology images must be found. Towards this goal, a novel pipeline is presented here for bringing ex-vivo MRI of surgically-resected temporal lobe specimens and digital histology into spatial correspondence. The sparsely-sectioned histology images represent a challenge for 3D reconstruction which we address with a combined 3D and 2D registration algorithm that alternates between slice-based and volume-based registration with the ex-vivo MRI. We evaluated our registration method on specimens resected from patients undergoing anterior temporal lobectomy (N=7) and found our method to have a mean target registration error of 0.76±0.66 and 0.98±0.60 mm for hippocampal and neocortical specimens respectively. This work allows for the spatially-local comparison of histology with post-operative MRI and paves the way for eventual correlation with pre-operative MRI image analysis techniques.

Healthcare Training Enhancement Through Virtual Reality and Serious Games

There has been an increase in the use of immersive 3D virtual environments and serious games, that is, video games that are used for educational purposes, and only recently serious games have been considered for healthcare training. For example, there are a number of commercial surgical simulators which offer great potential for the training of basic skills and techniques, if the tedium of repeated rehearsal can be overcome. It is generally recognized that more abstract problem-solving and knowledge level training needs to be incorporated into simulated scenarios. This chapter explores some examples of what has been developed in terms of teaching models and evaluative methodologies, then discusses the educational theories explaining why virtual simulations and serious games are an important teaching tool, and finally suggests how to assess their value within an educational context. The tasks being trained span several levels of abstraction, from kinematic and dynamic aspects to domain knowledge training. The evaluation of the trainee at each level of this hierarchy necessitates objective metrics. We will describe a unifying framework for evaluation of speed and accuracy of these multi-level tasks needed for validating their effectiveness before inclusion in medical training curricula. In addition, specific case studies will be presented and research results brought forward regarding the development of virtual simulations, including those for neurosurgical procedures, EMS training, and patient teaching modules.

Presurgical language mapping in children with epilepsy: Clinical usefulness of functional magnetic resonance imaging for the planning of cortical stimulation

Purpose:  Presurgical language mapping in dominant hemisphere epilepsy to evaluate the risk of postoperative deficit is particularly difficult in children. Extraoperative invasive cortical stimulation can show some areas critical to language, but not all of them, due to scarce sampling, poor cooperation, cortical immaturity, or network reorganization, whereas functional magnetic resonance imaging (fMRI) displays entire networks involved in, but not necessarily critical to, language. In a homogeneous series of children with epilepsy, we compared the contributions of language fMRI and depth electrode stimulations to optimize language mapping.

Needs assessment for simulation training in neuroendoscopy: a Canadian national survey

OBJECT In recent years, dramatic changes in surgical education have increased interest in simulation-based training for complex surgical skills. This is particularly true for endoscopic third ventriculostomy (ETV), given the potential for serious intraoperative errors arising from surgical inexperience. However, prior to simulator development, a thorough assessment of training needs is essential to ensure development of educationally relevant platforms. The purpose of this study was to conduct a national needs assessment addressing specific goals of instruction, to guide development of simulation platforms, training curricula, and assessment metrics for ETV. METHODS Canadian neurosurgeons performing ETV were invited to participate in a structured online questionnaire regarding the procedural steps for ETV, the frequency and significance of intraoperative errors committed while learning the technique, and simulation training modules of greatest potential educational benefit. Descriptive data analysis was completed for both quantitative and qualitative responses. RESULTS Thirty-two (55.2%) of 58 surgeons completed the survey. All believed that virtual reality simulation training for ETV would be a valuable addition to clinical training. Selection of ventriculostomy site, navigation within the ventricles, and performance of the ventriculostomy ranked as the most important steps to simulate. Technically inadequate ventriculostomy and inappropriate fenestration site selection were ranked as the most frequent/significant errors. A standard ETV module was thought to be most beneficial for resident training. CONCLUSIONS To inform the development of a simulation-based training program for ETV, the authors have conducted a national needs assessment. The results provide valuable insight to inform key design elements necessary to construct an educationally relevant device and educational program.

In vivo MRI signatures of hippocampal subfield pathology in intractable epilepsy

Our aim is to assess the subfield‐specific histopathological correlates of hippocampal volume and intensity changes (T1, T2) as well as diff!usion MRI markers in TLE, and investigate the efficacy of quantitative MRI measures in predicting histopathology in vivo.

Frontosphenoidal synostosis: a rare cause of unilateral anterior plagiocephaly

IntroductionWhen a child walks in the clinic with a unilateral frontal flattening, it is usually associated in our minds with unilateral coronal synostosis. While the latter might be the most common cause of anterior plagiocephaly, it is not the only one. A patent coronal suture will force us to consider other etiologies, such as deformational plagiocephaly, or synostosis of another suture. To understand the mechanisms underlying this malformation, the development and growth of the skull base must be considered.Materials and methodsThere have been few reports in the literature of isolated frontosphenoidal suture fusion, and we would like to report a series of five cases, as the recognition of this entity is important for its treatment.ConclusionFrontosphenoidal synostosis must be searched in the absence of a coronal synostosis in a child with anterior unilateral plagiocephaly, and treated surgically.

Registration of in-vivo to ex-vivo MRI of surgically resected specimens: A pipeline for histology to in- vivo registration.

BACKGROUND Advances in MRI have the potential to improve surgical treatment of epilepsy through improved identification and delineation of lesions. However, validation is currently needed to investigate histopathological correlates of these new imaging techniques. The purpose of this work is to develop and evaluate a protocol for deformable image registration of in-vivo to ex-vivo resected brain specimen MRI. This protocol, in conjunction with our previous work on ex-vivo to histology registration, completes a registration pipeline for histology to in-vivo MRI, enabling voxel-based validation of novel and existing MRI techniques with histopathology. NEW METHOD A combination of image-based and landmark-based 3D registration was used to register in-vivo MRI and the ex-vivo MRI from patients (N=10) undergoing epilepsy surgery. Target registration error (TRE) was used to assess accuracy and the added benefit of deformable registration. RESULTS A mean TRE of 1.35±0.11 and 1.41±0.33mm was found for neocortical and hippocampal specimens respectively. Statistical analysis confirmed that the deformable registration significantly improved the registration accuracy for both specimens. COMPARISON WITH EXISTING METHODS Image registration of surgically resected brain specimens is a unique application which presents numerous technical challenges and that have not been fully addressed in previous literature. Our computed TRE are comparable to previous attempts tackling similar applications, as registering in-vivo MRI to whole brain or serial histology. CONCLUSION The presented registration pipeline finds dense and accurate spatial correspondence between in-vivo MRI and histology and allows for the spatially local and quantitative assessment of pathological correlates in MRI.