Béatrice Claise

Is R2* a New MRI Biomarker for the Progression of Parkinson’s Disease? A Longitudinal Follow-Up

Purpose To study changes of iron content in basal ganglia in Parkinson’s disease (PD) through a three-year longitudinal follow-up of the effective transverse relaxation rate R2*, a validated MRI marker of brain iron content which can be rapidly measured under clinical conditions. Methods Twenty-seven PD patients and 26 controls were investigated by a first MRI (t0). Longitudinal analysis was conducted among the 18 controls and 14 PD patients who underwent a second MRI (t1) 3 years after. The imaging protocol consisted in 6 gradient echo images obtained at different echo-times for mapping R2*. Quantitative exploration of basal ganglia was performed by measuring the variation of R2* [R2*(t1) – R2*(t0)] in several regions of interest. Results During the three-year evolution of PD, R2* increased in Substantia nigra (SN) (by 10.2% in pars compacta, p = 0.001, and 8.1% in pars reticulata, p = 0.013) and in the caudal putamen (11.4%, p = 0.011), without significant change in controls. Furthermore, we showed a positive correlation between the variation of R2* and the worsening of motor symptoms of PD (p = 0.028). Conclusion Significant variation of R2* was longitudinally observed in the SN and caudal putamen of patients with PD evolving over a three-year period, emphasizing its interest as a biomarker of disease progression. Our results suggest that R2* MRI follow-up could be an interesting tool for individual assessment of neurodegeneration due to PD, and also be useful for testing the efficiency of disease-modifying treatments.

Using High Spatial Resolution to Improve BOLD fMRI Detection at 3T.

For different functional magnetic resonance imaging experiments using blood oxygenation level-dependent (BOLD) contrast, the acquisition of T 2*-weighted scans at a high spatial resolution may be advantageous in terms of time-course signal-to-noise ratio and of BOLD sensitivity when the regions are prone to susceptibility artifacts. In this study, we explore this solution by examining how spatial resolution influences activations elicited when appetizing food pictures are viewed. Twenty subjects were imaged at 3 T with two different voxel volumes, 3.4 μl and 27 μl. Despite the diminution of brain coverage, we found that high-resolution acquisition led to a better detection of activations. Though known to suffer to different degrees from susceptibility artifacts, the activations detected by high spatial resolution were notably consistent with those reported in published activation likelihood estimation meta-analyses, corresponding to taste-responsive regions. Furthermore, these regions were found activated bilaterally, in contrast with previous findings. Both the reduction of partial volume effect, which improves BOLD contrast, and the mitigation of susceptibility artifact, which boosts the signal to noise ratio in certain regions, explained the better detection noted with high resolution. The present study provides further evidences that high spatial resolution is a valuable solution for human BOLD fMRI, especially for studying food-related stimuli.

Interest of local intra-arterial fibrinolysis in acute central retinal artery occlusion: Clinical experience in 16 patients

OBJECTIVE Central retinal artery occlusion (CRAO) is a rare disease with poor visual prognosis. We evaluated clinical effectiveness of in situ fibrinolysis with original angiographic scores describing the aspect of carotid siphon, proximal ophthalmic artery, and choroid blush. METHODS Retrospective study of 16 consecutive cases of CRAO between 2007 and 2013. Fourteen underwent in situ fibrinolysis, two were excluded due to pre-occlusive internal carotid stenosis on pre-procedural diagnostic angio-CT. Fibrinolysis was performed with rt-PA (average injected dose: 35 mg), with an average onset delay of 8hours (4-17h). We reported angiographic scores pre- and post-fibrinolysis, visual acuity (VA) before and after treatment, and VA improvement evaluated by ophthalmologist 6 to 12 months after thrombolysis. RESULTS Six patients (43%) recovered post-fibrinolysis VA significally improved, superior or equal to 1/10 (1/10 to 8/10). An irregular carotid siphon (2 cases) appeared as a predictive factor of failure. Fibrinolysis procedure led to a significant improvement of angiographic permeability of proximal ophthalmic artery (P=0.0498), but this result was not accompanied by any VA improvement. The aspect of choroid blush showed no correlation with the management of thrombolysis. CONCLUSION In situ fibrinolysis was more effective than medical treatments or natural evolution of CRAO (VA improvement was respectively 40% and 20%). However, the benefit/risk ratio must be discussed, and an angio-CT of supra-aortic trunks could be systematically performed before thrombolysis, to assess the potential VA recovery compared with complications such as ischemic stroke.

IRM stéréotaxique de la région sous-thalamique : optimisation d’une séquence de repérage pré-opératoire pour la mise en place d’électrodes de stimulation profonde chronique

Introduction. Optimisation d’une nouvelle sequence IRM, en conditions stereotaxiques, permettant d’identifier les noyaux de la region sous-thalamique, pour leur reperage direct, lors de la mise en place d’electrode de stimulation profonde dans la maladie de Parkinson idiopathique severe. Materiel-Methode. Nous avons optimise 3 types de sequences — inversion/recuperation (IR), 3D, turbo spin echo (TSE) —, de durees compatibles avec une application clinique (entre 10 et 20 min/sequence), chez des volontaires sains (adultes jeunes, 6 femmes et 8 hommes) sur une IRM 1,5 Tesla (Sonata, Siemens) par selection progressive a partir d’une analyse subjective des images. Puis nous avons analyse l’ensemble des images : apres anonymisation des sequences (n = 79), lecture par 3 evaluateurs independants en aveugle du type de sequence, sur 19 structures anatomiques (de la region sous-thalamique, du thalamus et du noyau lenticulaire), selon une cotation ponderee portant sur la visibilite (0 = non visible, 0,5 = intermediaire, 1 = clairement identifiable, score maximal). Resultats ou Cas rapporte. Une sequence IR, derivee d’un type CAIR (cortex attenuated inversion recovery), a obtenue le score le plus eleve de 0,93, offrant une bonne visualisation de l’ensemble des ganglions de la base : TR = 6 000 msec, TE = 13 msec, TI = 160 msec. La meme sequence adaptee aux conditions stereotaxiques (cadre en place pendant l’IRM, Leksell, Elekta) avait un score de 0,75 (TR = 4 500 msec, voxel = 0,53 ×0,62 ×2 mm3). La sequence de densite de proton (TSE) utilisee habituellement dans l’equipe avait un score de 0,55. Conclusion. L’IRM, en sequences TSE et surtout IR, peut offrir une excellente visualisation des ganglions de la base. Suite a ce travail preliminaire, nous avons introduit en routine la sequence IR en conditions stereotaxiques, pour la visee directe du noyau sous-thalamique. Un travail de comparaison entre les sequences TSE et IR, en conditions stereotaxiques, apres appariement de patients parkinsoniens, est en cours a propos des 16 premiers cas.

Toxoplasmic pachymeningitis with visual field impairment in a single-eyed patient and a literature review.

To describe the clinical features of a patient with toxoplasmic pachymeningitis and provide a review of the recent cases of pachymeningitis in the literature.Retrospective, observational case report. A one-eyed patient who presented to our institution with blurred vision, floaters, and visual field shrinkage. Review of clinical, laboratory, perimetric, and radiologic records of the patient and description of the efficacy of antibiotic therapy. The signs of ocular impairment, including visual acuity, visual field, and magnetic resonance imaging (MRI) changes. A one-eyed patient who complained of blurred vision and unexplained visual field shrinkage was evaluated. The diagnosis of toxoplasmic pachymeningitis was confirmed by existence of a toxoplasmic seroconversion, cerebrospinal fluid abnormalities, radiological features, absence of other diagnoses, improvement of symptoms, and resolution of pachymeningitis in MRI with oral trimethoprim–sulfamethoxazole combination. Pachymeningitis is a rare disease and toxoplasmic pachymeningitis has never been described. Among the various infectious causes, screening for toxoplasmosis must be performed because it can lead to pachymeningitis and sequelae. Variable features may lead to misdiagnosis and delay in the treatment of this sight-threatening and potentially fatal disease.

Differences in BOLD responses in brain reward network reflect the tendency to assimilate a surprising flavor stimulus to an expected stimulus

&NA; External information can modify the subjective value of a tasted stimulus, but little is known about neural mechanisms underlying these behavioral modifications. This study used flavored drinks to produce variable degrees of discrepancy between expected and received flavor. During a learning session, 43 healthy young men learned 4 symbol‐flavor associations. In a separate session, associations were presented again during an fMRI scan, but half of the trials introduced discrepancy with previously learned associations. Liking ratings of drinks were collected and were analyzed using a linear model to define the degree to which discrepant symbols affected liking ratings of the subjects during the fMRI session. Based on these results, a GLM analysis of fMRI data was conducted to determine neural correlates of observed behavior. Groups of subjects were composed based on their behavior in response to discrepant symbols, and comparison of brain activity between groups showed that activation in the PCC and the caudate nucleus was more potent in those subjects in which liking was not affected by discrepant symbols. These activations were not found in subjects who assimilated unexpected flavors to flavors preceeded by discrepant symbols. Instead, these subjects showed differences in the activity in the parietal operculum. The activity of reward network appears to be related to assimilation of received flavor to expected flavor in response to symbol‐flavor discrepancy.

Advanced Neuroimaging with Computed Tomography Scanning

The x-ray computed tomography (CT) is well known as a useful imaging method and thus CT images have continuingly been used for many applications, especially in medical fields. This book discloses recent advances and new ideas in theories and applications for CT imaging and its analysis. The 16 chapters selected in this book cover not only the major topics of CT imaging and analysis in medical fields, but also some advanced applications for forensic and industrial purposes. These chapters propose state-of-the-art approaches and cutting-edge research results.

A case of bilateral stroke of the medulla oblongata

A 64-year-old woman with a history of hypertension and diabetes was admitted to the emergency room with tetraparesis which had slowly progressed over the previous week. On examination the patient presented a right-sided dominant tetraparesis, no inferior limb deep tendon jerks and upper limb paraesthesia. No sensory loss, cranial nerve impairment, or weakness of the face or tongue was noted on admission. MRI of the medulla was performed with T1 and T2 weighted sequences because of the possibility of cervical compression myelopathy. This MRI showed no medullary abnormalities except for a narrow spinal canal. Within the next 24 h the patient developed severe dysphagia. Teraparesis progressed to a right-sided …

Stimulation cérébrale profonde et déplacement d’électrode : évaluation à moyen terme

Introduction. Un eventuel deplacement des electrodes de stimulation cerebrale profonde (DBS), a distance de l’implantation, est evoque pour expliquer certaines discordances entre effets benefiques per-operatoires et en stimulation chronique. Nous avons evalue ce deplacement en nous appuyant sur des donnees d’IRM post-operatoires tardives. Materiel-Methode. Neuf patients ayant beneficie de la mise en place bilaterale d’electrodes DBS pour maladie de Parkinson idiopathique severe avec de bons resultats cliniques (amelioration motrice > 60 %) ont ete inclus. Nous nous sommes interesses aux contacts utilises en stimulation chronique (contacts effectifs, stimulation monopolaire). Les positions initiales de ces contacts (n = 18) ainsi que des electrodes (n = 18) ont ete determinees a partir de cliches teleradiographiques de fin de procedure (electrodes fixees, cadre en place) et projetees (correspondance stereotaxique) sur l’IRM pre-operatoire stereotaxique (ponderation T2, cadre en place). Une IRM realisee a distance (ponderation T1, delai de 6 a 12 mois) a ete mise en correspondance avec l’IRM pre-operatoire (algorithme d’optimisation de voxel a voxel). Pour chacun des contacts effectifs, nous avons mesure la distance entre le centre du contact identifie en radiographie et projete sur l’IRM pre-operatoire et celui determine a partir de l’artefact sur l’IRM a distance (dc). Resultats ou Cas rapporte. Dans tous les cas, la position de l’electrode, relevee sur les cliches teleradiographiques, etait situee dans les limites de l’artefact de l’electrode sur l’IRM tardive. La distance moyenne entre les positions initiales et tardives des centres des contacts (dc) etait de 1,3 mm (±0,5 mm). Conclusion. En prenant en compte les differentes incertitudes liees aux modes de recueil des coordonnees (teleradiographie et IRM), nos resultats ne semblent pas montrer de difference significative entre la position initiale des contacts effectifs et celle mesuree tardivement. Ces resultats sont discutes en fonction des donnees de la litterature