Improving user experience of SSVEP BCI through low amplitude depth and high frequency stimuli design.

Steady-States Visually Evoked Potentials (SSVEP) refer to the sustained rhythmic activity observed in surface electroencephalography (EEG) in response to the presentation of repetitive visual stimuli (RVS). Due to their robustness and rapid onset, SSVEP have been widely used in Brain Computer Interfaces (BCI). However, typical SSVEP stimuli are straining to the eyes and present risks of triggering epileptic seizures. Reducing visual stimuli contrast or extending their frequency range both appear as relevant solutions to address these issues. It however remains sparsely documented how BCI performance is impacted by these features and to which extent user experience can be improved. We conducted two studies to systematically characterize the effects of frequency and amplitude depth reduction on SSVEP response. The results revealed that although high frequency stimuli improve visual comfort, their classification performance were not competitive enough to design a reliable/responsive BCI. Importantly, we found that the amplitude depth reduction of low frequency RVS is an effective solution to improve user experience while maintaining high classification performance. These findings were further validated by an online T9 SSVEP-BCI in which stimuli with 40% amplitude depth reduction achieved comparable results (>90% accuracy) to full amplitude stimuli while significantly improving user experience.

Intracranial primary synovial sarcoma mimicking a spontaneous cerebral hematoma-a case report and review of the literature.

BACKGROUND: Synovial sarcoma is a soft tissue sarcoma, of uncertain histological origin, usually located near large joints and concerning mainly young adults. Intracranial presentation in the form of metastasis from a primitive body sarcoma has been rarely reported. However, intracranial primitive synovial sarcoma (IPSS) is extremely rare and only a few cases have been reported in the literature. CASE DESCRIPTION: We present the case of a 48-year-old man, with no particular medical history, that was referred to our hospital for severe headache with a normal neurological exam and a CT cerebral scan showing a left frontal lobe hematoma. The initial cerebral CT scan didn't show any vascular malformation and the body CT scan was negative for a primitive lesion. A close follow-up with a cerebral MRI three months later, demonstrated a T1 enhanced lesion with an important volume progression. The patient underwent a complete surgical removal of this lesion and the first pathology diagnosis was compatible with a meningioma. After further proofreading by an expert and molecular analysis, the diagnosis of monophasic synovial sarcoma was confirmed. Nine months after the first surgery, the follow-up MRI showed the progressive recurrence of the lesion and in this context the patient underwent a second surgery with total resection of the tumor and frontal thin margin excision. Afterwards, the patient was treated with adjuvant radiotherapy, with a good clinical evolution, and till now the follow-up shows no recurrence. CONCLUSION: IPSS is an extremely rare sarcoma, with challenging diagnosis and difficult management. Specific molecular analysis is necessary. Complete resection followed by radiotherapy seem to be the most appropriate therapeutic approach. However, the prognosis is still poor. Our case is even rarer because of the initial presentation as a cerebral hematoma.

Long term surgical results of 154 petroclival meningiomas: A retrospective multicenter study.

BACKGROUND: Outcomes of petroclival meningiomas (PCM) (morbidity, permanent cranial nerves deficit, tumor removal and recurrence) are inconsistent in the literature, making it a challenge to predict surgical morbidity. METHODS: A multicenter study of patients with PCMs larger than 2.5cm between 1984 and 2017 was conducted. The authors retrospectively reviewed the patients' medical records, imaging studies and pathology reports to analyze presentation, surgical approach, neurological outcomes, complications, recurrence rates and predictive factors. RESULTS: There were 154 patients. The follow-up was 76.8 months on average (range 8-380 months). Gross total resection (GTR) was achieved in 40 (26.0%) patients, subtotal resection (STR) in 101 (65.6%), and partial resection in 13 (8.3%). Six (2.6%) perioperative deaths occurred. The 5-year, 10-year and 15-year progression-free survival (PFS) of GTR and STR with radiation therapy (RT) was similar (100%, 90% and 75%). PFS of STR without adjuvant radiation was associated with progression in 71%, 51% and 31%, respectively. Anterior petrosectomy and combined petrosectomy were associated with higher postoperative CN V and CN VI deficits compared to the retrosigmoid approach. The latter had a significantly higher risk of CN VII, CN VIII and LCN deficit. Temporal lobe dysfunction (seizure and aphasia) were significantly associated with the anterior petrosectomy approach. CONCLUSIONS: Our study shows that optimal subtotal resection of PCMs associated with postoperative RT or stereotactic radiosurgery results in long-term tumor control to equivalent radical surgery. Case selection and appropriate intraoperative judgement are required to reduce the morbidity.

Cortical and subcortical functional neuroanatomy for low-grade glioma surgery.

Knowledge of the encephalon anatomy is crucial for neurosurgical practice, especially the main cortical functional structures and their connections. General organisation of the encephalon is presented with frontal, parietal, occipital, temporal, limbic and insular lobes and their Brodmann correspondence. Secondly, subcortical anatomy will be presented with main white matter fasciculi in three separated categories: association, commissural and projection fibers. Main association fibers are inferior occipitofrontal fasciculus, superior longitudinal fasciculus, arcuate fasciculus, inferior longitudinal fasciculus, uncinate fasciculus, and cingulum. Commissural fibers include anterior commissure, corpus callosum and fornix. Projection fibers are internal capsule and optic radiations.

From Vesalius to tractography.

The description of an anatomical specimen may look straightforward, but it appears that it depends in fact on several intermingled factors: technical methods for conservation, dissection and vascular injection and the anatomist skills are of course important. This is especially true when the studied organ, as for instance the brain, is subject to rapid putrefaction after death without any preservation technique. Nevertheless the possibility to reject, or at least criticize, the dominant paradigm is probably as important as these technical considerations: important changes occurred in brain representation between the early Middle Ages and the Early Modern Times, without major improvements of cadaveric preservation or dissection methods; Vesalius rejected the existence of the rete mirabile in human not only because he was a talented anatomist but also because he accepted and had the courage to fight the dominant tradition inherited from Galen. Such difficulties in the scientific approach obviously remain vivid, and should not be forgotten despite the development of modern tools for studying brain morphology and function.

Surgical anatomy of the hippocampus.

BACKGROUND AND PURPOSE: Hippocampectomy is an efficient procedure for medial temporal lobe epilepsy. Nevertheless, hippocampus anatomy is complex, due to a deep location, and a complex structure. In this didactic paper, we propose a description of the hippocampus that should help neurosurgeons to feel at ease in this region. METHODS: Embryological data was obtained from the literature, whereas adult anatomy was described after dissecting 8 human hemispheres (with and without vascular injection) and slicing 3 additional ones. RESULTS: The hippocampus is C-shaped and made of 2 rolled-up laminae, the cornu Ammonis and the gyrus dentatus. Its ventricular aspect is covered by the choroid plexus of the inferior horn excepted at the head level. Its cisternal aspect faces the mesencephalon from which it is limited by the transverse fissure. Its rostral part (head) curves dorso-caudally to form the uncus, located at the medial aspect of the temporal lobe. Its caudal part (tail) splits into the fimbria and the gyrus fasciolaris that respectively run ventral and dorsal to the corpus callosum, to become the fornix and indusium griseum. CONCLUSION: Consequences of this complex anatomy are presented, and the authors stress the need for a subpial resection. Important landmarks are provided to avoid lesions of the surrounding structures.

Anterior fossa schwannoma mimicking an olfactory groove meningioma: case report and literature review.

Intracranial schwannomas not associated with cranial nerves account for less than 1% of surgically treated schwannomas of the central and peripheral nervous system. With only 45 cases reported to date, subfrontal schwannomas are very rare tumors, leaving the issue of their origin controversial. A 66-year-old woman presented with a 1-year history of progressive headaches. Clinical examination revealed hypoesthesia of the nasal tip. CT-scan and MRI studies revealed a large subfrontal tumor thought preoperatively to be a meningioma. Intraoperatively, a large extra-axial tumor arising from the floor of the right frontal fossa was encountered. Histopathology identified the tumor as a schwannoma. This current case gives strong clinical presumption of an origin from the anterior ethmoidal nerve. We reviewed the literature in order to establish the epidemiology of these tumors, from which there appear to be divergent profiles depending on tumor origin and histology. Despite close similarities with olfactory groove meningiomas, patient history and radiological findings provide substantial evidence for differential diagnosis.

[Evaluation of a pathway of epilepsy surgery in a polyvalent video-EEG center: retrospective analysis of a series of 295 patients]. / Évaluation d'une filière médico-chirurgicale en épileptologie au sein d'un centre de vidéo-EEG polyvalent : analyse rétrospective d'une série de 295 patients.

BACKGROUND AND PURPOSE: The supply for diagnosis and treatment is inadequate in France for epileptic patients eligible for surgery. Our institution includes a Video-electroencephalography (v-EEG) unit and a general neurosurgery department. Our objective was to evaluate the efficacy and morbidity of the surgery performed in a center non-dedicated to epilepsy surgery. METHODS: We conducted a retrospective study of a cohort of 295 patients explored with long lasting v-EEG from 1991 to 2008 in Tours in which we evaluated the efficacy and morbidity of the surgery distinguishing between hippocampal sclerosis and other epileptogenic lesions. RESULTS: Phase I directly led to surgery in 31 cases. Of them were 19 hippocampal sclerosis were operated with no surgical morbidity, and 12 other epileptogenic lesions operated with a comorbidity in two patients. Results of surgery were similar to larger studies, with 80% of patients Engel's Class I. Best results were observed in the hippocampal sclerosis group: 94.7 Class I (IA: 84%), versus 58% Class I (IA: 33%) for other etiologies. CONCLUSION: Despite the small number of operated patients, the surgical treatment keeps its efficiency without adding morbidity. v-EEG centers combined with non-specialists neurosurgical teams can contribute to improve care without reducing their quality.

The choroidal fissure: anatomy and surgical implications.

The choroidal fissure (CF) is an important landmark that allows approaches to the deepest aspects of the brain. It is the C-shaped site of attachment of the choroid plexus in the lateral ventricles, which runs between fornix and thalamus. The thinness and the absence of neural tissue between the ependyma and pia matter of this part of the medial wall of the lateral ventricles provides a surgical pathway to the third ventricle and perimesencephalic cisterns. A precise knowledge of the microsurgical anatomy of the region, particularly vascular relationships, is essential to consider surgery through the CF. We decided to present the anatomy of the CF in three distinct chapters, corresponding to three compartments of the C-shaped structure of the CF. In each compartment - rostral, dorsal and caudal - we developed the neurovascular anatomy and then discussed the clinical and surgical applications.

[Tolerance and efficacy of peripheral nerve blocks for carpal tunnel release]. / Tolérance et efficacité des blocs nerveux périphériques pour la chirurgie du canal carpien.

INTRODUCTION: Several peripheral nerve block techniques (PNB) are performed for hand surgery. Their tolerance by patients or their efficacy are poorly described. We evaluated them for blocks at the wrist and at the brachial canal. PATIENTS AND METHODS: Cohort of outpatients undergoing open carpal tunnel release under PNB with arm tourniquet. Various anaesthetic protocols existed in our staff. The primary end points were a moderate to severe pain (greater than 3/10 on a numerical rating scale) felt during needle puncture, nerve stimulation, mepivacaine injection, at the surgical site (intraoperatively) or at the arm tourniquet, an intraoperative lidocaine supplementation, the occurrence of vasovagal events. For each primary end point, a logistic regression analyzed: the effects of gender, age, operated side, Emla(®)application, sedation before PNB (midazolam-sufentanil), wrist or brachial canal approach, musculocutaneous or radial block were using. RESULTS: Between January 2007 and June 2010, 551 consecutive patients were analyzed. Puncture pain, mepivacaine injection pain, pain tourniquet and vasovagal events were associated with wrist block (P=0.003, relative risk=1.86; P<0.001, RR=4.22; P<0.001, RR=4.52; P=0.035, RR=6.40). An intraoperative pain greater than 3/10 at the surgical site, or a supplementation by the surgeon were associated with the absence of musculocutaneous block (P=0.013, RR=2.44; P=0.013, RR=2.51). DISCUSSION: Wrist blocks are less tolerated than brachial canal blocks. The musculocutaneous nerve might often participate in the palm sensitive innervation. For open carpal tunnel release, median, ulnar and musculocutaneous nerves blocks at the brachial canal should be preferred.

The dural sheath of the optic nerve: descriptive anatomy and surgical applications.

The aim of this work was to clarify the descriptive anatomy of the optic dural sheath using microanatomical dissections on cadavers. The orbit is the rostral part of the extradural neural axis compartment; the optic dural sheath forms the central portion of the orbit.In order to describe this specific anatomy, we carefully dissected 5 cadaveric heads (10 orbits) up to the meningeal structure of the orbit and its contents. 1 cadaveric head was reserved for electron microscopy to add to our knowledge of the collagen structure of the optic dural sheath.In this chapter, we describe the anatomy of the interperiostal-dural concept and the anatomy of the orbit. The optic dural sheath contains three portions: the intracranial, the intracanalicular and the intraorbital segment. Each one has specific anatomic relations which result in particular surgical considerations.

Cemento-ossifying fibroma involving paranasal sinuses and skull base.

INTRODUCTION: Ossifying fibroma is a rare benign fibro-osseous lesion that usually affects mandible and maxillary bone. Their localisation to paranasal sinus and skull base is uncommon. MATERIAL AND METHOD: We report a huge recurrence of ossifying fibroma of the ethmoid paranasal sinus involving the skull base. CASE REPORT: Ten years after the removal of ossifying of the ethmoid 34 year old man presented headache with diplopia. Computed tomography (CT) and magnetic resonance imagery (MRI) showed a recurrent tumour witch extended to the nasal cavity, the sphenoid and the posterior ethmoid sinuses, and the skull base. The tumour was totally removed using an anterior subcranial approach with removal of the orbital rim. Histopathology confirmed an ossifying fibroma. Two years later a subdural empyema with frontal suppuration necessited to remove the frontal bone flap, which was re-constructed 12 months later using a synthetic material. CONCLUSION: Ossifying fibroma is a rare, benign tumour witch may recur if incomplete resection is performed. A long follow up with CT scan and MRI is required.

The persistent left superior vena cava: anatomical study, pathogenesis and clinical considerations.

The persistence of a left superior vena cava (LSVC) is an intrinsically cardiac anomaly, which can lead to serious complications during catheterization via the subclavian or internal jugular vein. We found this anomaly during dissection associated with an abnormal origin of the vertebral artery originating from the aortic arch between the left common carotid and subclavian arteries. The LSVC coursed towards the right atrium through a very dilated coronary sinus ostium. No abnormality of the azygos system was found. A thorough anatomic description was then made with external and internal morphology. The embryonic development and variations are described. Radiological and clinical implications are discussed.

A cultivation technique for E. coli fed-batch cultivations operating close to the maximum oxygen transfer capacity of the reactor.

A cultivation strategy combining the advantages of temperature-limited fed-batch and probing feeding control is presented. The technique was evaluated in fed-batch cultivations with E. coli BL21(DE3) producing xylanase in a 3 liter bioreactor. A 20% increase in cell mass was achieved and the usual decrease in specific enzyme activity normally observed during the late production phase was diminished with the new technique. The method was further tested by growing E. coli W3110 in a larger bioreactor (50 l). It is a suitable cultivation technique when the O2 transfer capacity of the reactor is reached and it is desired to continue to produce the recombinant protein.

[Duplication of the inferior vena cava: anatomical dissection and clinical implications]. / Dédoublement de la veine cave inférieure: dissection anatomique et applications cliniques.

The duplication of the inferior vena cava is often incidentally discovered during radiological studies. The presence of this anomaly can be mistaken for retroperitoneal adenopathy. Its knowledge allows to avoid hemorrhagic complications during retroperitoneal surgery. An anatomical dissection of a duplication of the inferior vena cava is presented. Embryogenesis and variations are described. Radiological and clinical implications are discussed.

Intra-operative mapping of the subcortical visual pathways using direct electrical stimulations.

Despite the risk of postoperative visual field defect following surgery within the temporo-parieto-occipital region, visual mapping has rarely been described, in particular at the subcortical level. In this report, we successfully performed a subcortical mapping of the visual pathways using intra-operative electrical stimulations (IES), during surgery under local anesthesia for a low-grade glioma invading the whole temporal lobe and the temporo-occipital junction. The optic radiations then constituted the posterior and deep functional boundary of the resection, avoiding the occurrence of a post-operative hemianopsia, in spite of an asymptomatic quadrantanopsia. This preliminary experience illustrates the possibility to use intra-operative direct electrical stimulation during surgery of lesions involving the posterior afferent visual system, in order to identify and then preserve the visual pathways, as previously reported for sensorimotor and language subcortical fibers.

Production of heterologous thermostable glycoside hydrolases and the presence of host-cell proteases in substrate limited fed-batch cultures of Escherichia coli BL21(DE3).

Metabolic stress is a phenomenon often discussed in conjunction with recombinant protein production in Escherichia coli. This investigation shows how heterologous protein production and the presence of host cell proteases is related to: (1) Isopropyl-beta- D-thiogalactopyranoside (IPTG) induction, (2) cell-mass concentration at the time of induction, and (3) the presence of metabolites (glutamic acid or those from tryptone soy broth) during the post-induction phase of high cell density fed-batch cultivations. Two thermostable xylanase variants and one thermostable cellulase, all originating from Rhodothermus marinus, were expressed in E. coli strain BL21 (DE3). A three-fold difference in the specific activity of both xylanase variants [between 7,000 and 21,000 U/(g cell dry weight)], was observed under the different conditions tested. Upon induction at high cell-mass concentrations employing a nutrient feed devoid of the metabolites above, the specific activity of the xylanase variants, was initially higher but decreased 2-3 h into the post-induction phase and simultaneously protease activity was detected. Furthermore, protease activity was detected in all induced cultivations employing this nutrient feed, but was undetected in uninduced control cultivations (final cell-mass concentration of 40 g/l(-1)), as well as in induced cultivations employing metabolite-supplemented nutrient feeds. By contrast, maximum specific cellulase activity [between 700 and 900 U/(g cell dry weight)] remained relatively unaffected in all cases. The results demonstrate that detectable host cell proteases was not the primary reason for the decrease in post-induction activity observed under certain conditions, and possible causes for the differing production levels of heterologous proteins are discussed.

Anatomical study of the length of the human intestine.

Although preoperative assessment of the length of the intestine may be of interest to avoid postoperative consequences of large intestinal resection, measurements of the intestine are quite rare and results variable in the literature. This anatomical study aimed to assess the length of the different intestinal segments, their variation and their correlation with sex, age, weight and height. Two hundred non-fixed adult cadavers (100 men, 100 women) who willingly gave their bodies for scientific purposes were studied. The post mortem average length of the whole intestine was 795.5+/-129 cm and was significantly longer in men and in young subjects. It was correlated with the subject's weight but not height. Multivariate analysis demonstrated that the factor showing the strongest correlation with intestinal length was body weight. This latter parameter may be useful in the preoperative assessment of intestinal length.