Marc Braun

Automated cortical projection of EEG sensors: Anatomical correlation via the international 10–10 system

Several studies have described cranio-cerebral correlations in accordance with the 10-20 electrode placement system. These studies have made a significant contribution to human brain imaging techniques, such as near-infrared spectroscopy and trans-magnetic stimulation. With the recent development of high resolution EEG, an extension of the 10-20 system has been proposed. This new configuration, namely the 10-10 system, allows the placement of a high number (64-256) of EEG electrodes. Here, we describe the cranio-cerebral correlations with the 10-10 system. Thanks to the development of a new EEG-MRI sensor and an automated algorithm which enables the projection of electrode positions onto the cortical surface, we studied the cortical projections in 16 healthy subjects using the Talairach stereotactic system and estimated the variability of cortical projections in a statistical way. We found that the cortical projections of the 10-10 system could be estimated with a grand standard deviation of 4.6 mm in x, 7.1 mm in y and 7.8 mm in z. We demonstrated that the variability of projections is greatest in the central region and parietal lobe and least in the frontal and temporal lobes. Knowledge of cranio-cerebral correlations with the 10-10 system should enable to increase the precision of surface brain imaging and should help electrophysiological analyses, such as localization of superficial focal cortical generators.

An Evaluation of the Cutaneous Distribution After Obturator Nerve Block

In 1973, Winnie et al. introduced the inguinal paravascular three-in-one block, which allegedly provides anesthesia of three nerves—the femoral, lateral cutaneous femoral, and obturator nerves—with a single injection. This concept was undisputed until the success of the obturator nerve block was reassessed by using evidence of adductor weakness rather than cutaneous sensory blockade, the latter being variable in its distribution and often absent. We performed this study, therefore, to evaluate the area of sensory loss produced by direct injection of local anesthetic around the obturator nerve. A selective obturator nerve block with 7 mL of 0.75% ropivacaine was performed in 30 patients scheduled for knee surgery. Sensory deficit and adductor strength were evaluated for 30 min by using sensory tests (cold and light-touch perception) and the pressure generated by the patient’s squeezing a blood pressure cuff placed between the knees. Subsequently, a three-in-one block was performed, and the sensory deficit was reassessed. The obturator nerve block was successful in 100% of cases. The strength of adductors decreased by 77% ± 17% (mean ± sd). In 17 patients (57%), there was no cutaneous contribution of the obturator nerve. The remaining 7 patients (23%) had an area of hypoesthesia (cold sensation was blunt but still present) on the superior part of the popliteal fossa, and the other 6 (20%) had sensory deficit located at the medial aspect of the thigh. The three-in-one block resulted in blockade of the lateral aspect of the thigh in 87% of cases, whereas the anteromedial aspect was always anesthetized. By use of magnetic resonance imaging in eight volunteers, we demonstrated that the obturator nerve has already divided into its two branches at the site of local anesthetic injection. However, the injection of blue dye after having simulated the technique in five cadavers showed that the fluid regularly spread to both branches. We conclude that after three-in-one block, a femoral nerve block may have been assessed as an obturator nerve block in 100% of cases when testing the cutaneous distribution of the obturator nerve on the medial aspect of the thigh.

Brain death and transcranial Doppler: Experience in 130 cases of brain dead patients

BACKGROUND AND PURPOSE Diagnosis of brain death requires confirmation of the clinical diagnosis by appropriate tests, generally electroencephalography (EEG) and angiography. The diagnostic limitations or logistical problems inherent to these tests indicate the need to develop other more appropriate methods. The results obtained with transcranial Doppler (TCD) led us to conduct this prospective study of TCD recordings in brain dead patients. METHODS 130 patients, aged 2-88 years were diagnosed as brain dead between July 1987 and June 1993. Clinical criteria were confirmed in all cases by EEG (n=88) and or angiography (n=64). Intracranial anterior circulation was insonated via temporal windows or, when impossible, via a transorbital approach. The posterior circulation was studied only in more recent patients. Examinations were made as soon as possible after brain death diagnosis and repeated for about 30 min. Vital parameters and treatments were taken into account. RESULTS There was only one false negative result, in a patient with an extended skull defect, who retained TCD and angiographic intracranial circulation despite confirmed irreversible brain death. All other patients displayed typical ultrasonic patterns of cerebral circulation arrest: an oscillating signal (n= 190, 73%), a systolic spike (n=62, 24%) or a unilateral absence of signal (n=5). Despite a total correlation for positive diagnosis, TCD and angiography may differ as to the level of circulation arrest. TCD is useful for patients under sedative drugs. No false positive result was encountered but we were unable to insonate any intracranial artery in 5 patients. CONCLUSION Data from previous studies and the results of this study indicate that TCD is a very sensitive and safe method for diagnosing cerebral circulatory arrest. TCD may be used as a confirmatory test alongside EEG and angiography. TCD is more widely applicable than EEG and may be earlier and safer than angiography.

Distinctive alterations of the cingulum bundle during aging and Alzheimer's disease

Brain imaging studies have revealed frontal disruption during aging and parieto-temporal disruption during Alzheimers disease (AD). The present study aims at developing a specific method based on precise anatomical landmarks for assessing the integrity all along the course of the cingulum bundle, so as to determine if it presents the classical aging and AD dissociation. Five regions of interest (ROIs) were placed on fractional anisotropy (FA) maps all along the cingulum in 15 young (Gyoung), 15 70-year-old (Gold), and 15 AD subjects (Galz). An age-related decrease of FA occurred in the anterior part of the bundle. Moreover, a specific alteration of the supero-posterior region of the cingulum during AD was observed since mean FA values as well as mean number of fibers were significantly decreased in Galz compared to Gold and Gyoung. This multiple ROIs placement allows for revealing distinctive alterations of the cingulum bundle during aging and AD, which could constitute the anatomical basis for the distinctive functional disconnection recently described in the literature using functional connectivity at rest.

Automatic localization and labeling of EEG sensors (ALLES) in MRI volume

Spatial localization of scalp EEG electrodes is a major step for dipole source localization and must be accurate, reproducible and practical. Several methods have been proposed in the last 15 years. The most widely used method is currently electromagnetic digitization. Nevertheless, this method is difficult to use in a clinical environment and has not been validated with a high number of electrodes. In this paper, we introduce a new automatic method for localizing and labeling EEG sensors using MRI. First, we design a new scalp EEG sensor. Secondly, we validate this new technique on a head phantom and then in a clinical environment with volunteers and patients. For this, we compare the reproducibility, accuracy and performance of our method with electromagnetic digitization. We demonstrate that our method provides better reproducibility with a significant difference (p<0.01). Concerning precision, both methods are equally accurate with no statistical differences. To conclude, our method offers the possibility of using MRI volume for both source localization and spatial localization of EEG sensors. Automation makes this method very reproducible and easy to handle in a routine clinical environment.

Discriminant study of the development of the mandibular units in a neural reference system

The mandible is a complex osteological structure composed of distinct units integrated into a single bone around the director axis of the mandibular nerve. In this study of the mandibular development, we use a method that synthesizes the contributions of each sub-unit, using the mandibular canal as reference system. This novel approach results in new informations and confirms the leading role of the mandibular nerve and of its curve in mandibular development. It would seem to be possible to explain a major part of mandibular development by the role of the nerve as guide.

Isolation of the arterial supply to the carotid and central chemoreceptors in the sheep.

The aim of our study was to develop and validate a simple surgical model in the sheep which allows control of the gas composition of the blood supplying the carotid and central chemosensitive area independently of the rest of the body. This approach was made possible due to the specific features of the cranial circulation in the sheep. An extracorporeal circuit, consisting of a pump and a gas exchanger, was placed at the level of the two common carotid arteries to create a pressure gradient between the carotid and the systemic systems and to reverse blood flow in the vertebral vessels via the occipital arteries. When a pressure gradient of about 40 Torr was created between the systemic and carotid circulation, we found that no blood could reach the carotid bodies and the medulla without passing though the extracorporeal circulation. This was established (1) by measuring vertebral blood flow; and (2) by injecting either a coloured suspension or particles labelled with 99m*Tc into the systemic or the carotid circulation. The slope of the relationship between minute ventilation (V̇E) and systemic arterial PCO2 (Pa,CO2) during high CO2 inhalation in seven hyperoxic vagotomised and anaesthetised sheep was dramatically reduced, but remained above zero, when Pa,CO2 was maintained constant in the cephalic circuit (0.11 ± 0.15 vs. 0.70 ± 0.35 l min−1 Torr−1 for the control tests). This residual V̇E response to CO2 inhalation remains to be explained since it could not be accounted for by any of the chemical or circulatory changes occurring in the cephalic circulation. Nevertheless, this preparation provides an easy method of maintaining chemical and circulatory homeostasis at the chemoreceptor level.

Paralysie vélopalatine isolée aiguë réversible de l’enfant

Resume Introduction La paralysie velopalatine unilaterale de l’enfant est une situation rare qui pose principalement le probleme de son diagnostic etiologique et donc de l’extension du bilan pour y parvenir. Observation Nous rapportons les cas des deux enfants âges respectivement de 10 et 11 ans, jusque-la en bonne sante, presentant une paralysie velopalatine transitoire unilaterale, associee dans un cas a une paralysie de l’hemipharynx homolateral. Resultats La confrontation des donnees de ces deux observations a celles de la litterature suggere le diagnostic d’une neuropathie peripherique idiopathique. Conclusion Compte tenu de la rarete de ce tableau clinique, il parait necessaire de colliger d’autres cas similaires afin d’affirmer le caractere benin de l’affection, et d’eviter la multiplication d’examens complementaires invasifs.

Simulation training for emergency teams to manage acute ischemic stroke by telemedicine.

AbstractTelemedicine contributes to initiating early intravenous recombinant tissue plasminogen activator (rt-PA) treatment for patients with acute cerebral infarction in areas without a stroke unit. However, the experience and skills of the emergency teams in the spokes to prepare patients and administer rt-PA treatment are ill-defined. Improving these skills could vastly improve management of acute stroke by telemedicine. We developed a medical simulation training model for emergency teams to perform intravenous rt-PA treatment in a telestroke system.From February 2013 to May 2015, 225 learners from 6 emergency teams included in the telestroke system “Virtuall”—in Lorrain (northeastern France)—received a standardized medical simulation training module to perform rt-PA treatment. All learners were assessed with the same pretraining and posttraining test consisting of 52 items. The percentage of right answers was determined for every learner before and after training.Median percentages of right answers were significantly higher in the posttraining test overall (82 ± 10 vs. 59 ± 13% pretraining; P < 0.001), but also in all professional subgroups: physicians (88 ± 8 vs. 67 ± 12%; P < 0.001), paramedical staff (80 ± 9 vs. 54 ± 12%; P < 0.001), nurses (80 ± 8 vs. 54 ± 12%; P < 0.001), and auxiliary nurses (76 ± 17 vs. 37 ± 15%; P = 0.002).We describe for the first time a training model for emergency teams in a telestroke system. We demonstrate significant gain in knowledge for all groups of healthcare professionals. This simulation model could be applied in any medical simulation center and form the basis of a standardized training program of spokes in a telestroke system.

Addendum to “Automated cortical projection of EEG sensors: Anatomical correlation via the international 10–10 system” [NeuroImage 46 (2009) 64–72]

Addendum to “Automated cortical projection of EEG sensors: Anatomical correlation via the international 10–10 system” [NeuroImage 46 (2009) 64–72] L. Koessler , L. Maillard , A. Benhadid , J.P. Vignal , J. Felblinger , H. Vespignani , M. Braun a,c,d,⁎ a INSERM U947, Nancy University, France b Neurology Department, University Hospital, Nancy, France c Neuroradiology Department, University Hospital, Nancy, France d Anatomy Department, Nancy University, France