Patrice Jissendi

MRI atlas of the human hypothalamus.

Gaining new insights into the anatomy of the human hypothalamus is crucial for the development of new treatment strategies involving functional stereotactic neurosurgery. Here, using anatomical comparisons between histology and magnetic resonance images of the human hypothalamus in the coronal plane, we show that discrete gray and white hypothalamic structures are consistently identifiable by MRI. Macroscopic and microscopic images were used to precisely annotate the MRI sequences realized in the coronal plane in twenty healthy volunteers. MRI was performed on a 1.5 T scanner, using a protocol including T1-weighted 3D fast field echo, T1-weighted inversion-recovery, turbo spin echo and T2-weighted 2D fast field echo imaging. For each gray matter structure as well as for white matter bundles, the different MRI sequences were analyzed in comparison to each other. The anterior commissure and the fornix were often identifiable, while the mammillothalamic tract was more difficult to spot. Qualitative analyses showed that MRI could also highlight finer structures such as the paraventricular nucleus, the ventromedial nucleus of the hypothalamus and the infundibular (arcuate) nucleus, brain nuclei that play key roles in the regulation of food intake and energy homeostasis. The posterior hypothalamic area, a target for deep brain stimulation in the treatment of cluster headaches, was readily identified, as was the lateral hypothalamic area, which similar to the aforementioned hypothalamic nuclei, could be a putative target for deep brain stimulation in the treatment of obesity. Finally, each of the identified structures was mapped to Montreal Neurological Institute (MNI) space.

Sex steroid hormones-related structural plasticity in the human hypothalamus.

We investigated the effects of an artificial menstrual cycle on brain structure and activity in young women using metabolic magnetic resonance imaging (MRI). We show that the activation of the hypothalamo-pituitary-gonadal axis during the pill-free interval of low-dose combined oral contraceptive use is associated with transient microstructural and metabolic changes in the female hypothalamus but not in the thalamus, a brain structure unrelated to reproductive control, as assessed by water diffusion and proton magnetic resonance spectra measurements. Our results provide neuroanatomical insights into the mechanism by which sex steroid hormones mediate their central effects and raise the intriguing possibility that specific regions of the neuroendocrine brain use ovarian cycle-dependent plasticity to control reproduction in humans. These MRI-based physiological studies may pave the way for the development of new diagnostic and treatment strategies in the central loss of reproductive competence in human syndromes, such as hypothalamic amenorrhea.

Brain areas involved in the control of speed during a motor sequence of the foot: Real movement versus mental imagery

We investigated the cerebral networks involved in execution and mental imagery of sequential movements of the left foot, both performed at slow and fast speed. Twelve volunteers were scanned with a 3T MRI during execution and imagination of a sequence of ankle movements. Overt movement execution and motor imagery shared a common network including the premotor, parietal and cingulate cortices, the striatum and the cerebellum. Motor imagery recruited specifically the prefrontal cortex, whereas motor execution recruited specifically the sensorimotor cortex. We also found that slow movements specifically recruited frontopolar and right dorsomedian prefrontal areas bilaterally, during both execution and mental imagery, whereas fast movements strongly activated the sensorimotor cerebral cortex. Finally, we noted that anterior vermis, lobules VI/VII and VIII of the cerebellum were specifically activated during fast movements, both in imagination and execution. We show that the selection of the neural networks underlying voluntary movement of the foot is depending on the speed strategy and is sensitive to execution versus imagery. Moreover, to the light of surprising recent findings in monkeys showing that the vermis should no longer be considered as entirely isolated from the cerebral cortex (Coffman et al., 2011 [2]), we suggest that the anterior vermis contributes to computational aspects of fast commands, whereas more lateral cerebellar superior lobe and lobule VIII would regulate patterning and sequencing of submovements in conjunction with movement rate. We also suggest that execution of overt slow movements, which strongly involves prefrontal executive cortex as during motor mental imagery, is associated with conscious mental representation of the ongoing movements.

Magnetic Resonance Imaging Features of the Nigrostriatal System: Biomarkers of Parkinson’s Disease Stages?

Introduction Magnetic resonance imaging (MRI) can be used to identify biomarkers in Parkinson’s disease (PD); R2* values reflect iron content related to high levels of oxidative stress, whereas volume and/or shape changes reflect neuronal death. We sought to assess iron overload in the nigrostriatal system and characterize its relationship with focal and overall atrophy of the striatum in the pivotal stages of PD. Methods Twenty controls and 70 PD patients at different disease stages (untreated de novo patients, treated early-stage patients and advanced-stage patients with L-dopa-related motor complications) were included in the study. We determined the R2* values in the substantia nigra, putamen and caudate nucleus, together with striatal volume and shape analysis. We also measured R2* in an acute MPTP mouse model and in a longitudinal follow-up two years later in the early-stage PD patients. Results The R2* values in the substantia nigra, putamen and caudate nucleus were significantly higher in de novo PD patients than in controls. Early-stage patients displayed significantly higher R2* values in the substantia nigra (with changes in striatal shape), relative to de novo patients. Measurements after a two-year follow-up in early-stage patients and characterization of the acute MPTP mouse model confirmed that R2* changed rapidly with disease progression. Advanced-stage patients displayed significant atrophy of striatum, relative to earlier disease stages. Conclusion Each pivotal stage in PD appears to be characterized by putative nigrostriatal MRI biomarkers: iron overload at the de novo stage, striatal shape changes at early-stage disease and generalized striatal atrophy at advanced disease.

4H syndrome: a rare cause of leukodystrophy.

A 24-year-old woman suffered from gait unsteadiness and tetraparesis since childhood. Her medical history was characterized by a normal delivery of non-consanguineous parents. Walking with support was acquired at 10 months. Childhood development was characterized by occurrence of a progressive cerebellar ataxia, short stature, mental development retardation (IQ = 46), and hypodontia (i.e., absence of deciduous teeth eruption and short tooth roots). Walking without support was never acquired. At the age of 14, a partial growth hormone (GH) deficit (insufficient peak of GH in standard condition and with stimulation tests) and an hypogonadotropic hypogonadism [absence of luteinizing hormone (LH) and follicle stimulating hormone (FSH), lack of response to LH-releasing hormone (LH-RH) injection with LH peak at 0.6 UI/l and FSH peak at 1.4 UI/l] were found. Dental panoramic radiographs showed short tooth roots and absence of dental pulp chamber (Fig. 1). At the age of 24, neurological examination observed a severe static and kinetic cerebellar syndrome, spastic tetraparesis, multidirectional nystagmus, vertical down and up-gaze palsy, and mental retardation. Walking perimeter was 10 m with human assistance. Neuro-ophthalmologic examination confirmed vertical gaze palsy, and revealed amblyopia (with visual acuity of 4/10 on both sides), severe myopia, and bilateral temporal papillary atrophy. Nerve conduction studies and electromyography were normal. Neuroimaging performed at 3 Tesla (Philips, Best, The Netherlands) showed marked atrophy of the corpus callosum (reflecting the global white matter (WM) volume) and the cerebellum. In addition, spinal cord atrophy was moderate (data not shown). Myelinated areas including the pyramidal tracts, the internal capsule, the deep cerebellum, and the brainstem were hyperintense relative to cortical grey matter (CGM) on T1-WI and hypomyelinated areas (=rest of the white matter) were diffusely hypointense relative to CGM on T1-W1 (Fig. 2a–c). On T2-FLAIR images, the myelinated area appeared iso/hypointense relative to CGM and the hypomyelinated area appeared diffusively hyperintense relative to CGM (Fig. 2d–f). The pons appeared small with widening of the prepontine cystern, which was probably due to hypomyelinated corticopontine tracts as well as atrophy of crossing cerebellar tracts (Fig. 2a, c, d, f). Single voxel proton-magnetic resonance spectroscopy (HMRS) spectra showed low choline/creatine and N-acetylaspartate/creatine ratios within the left semi-ovale WM, left basal ganglia and pons. A prominent myo-inositol peak was also found within the pons (Fig. 2g). Tractography obtained from a Diffusion O. Outteryck (&) D. Devos L. Hopes P. Vermersch Department of Neurology, Salengro Hospital, Universite Lille Nord de France, CHRU Lille, Rue Emile Laine, 59037 Lille Cedex, France e-mail: Olivier_outteryck@hotmail.com

Reorganization of large-scale cognitive networks during automation of imagination of a complex sequential movement

We investigated the functional reconfiguration of the cerebral networks involved in imagination of sequential movements of the left foot, both performed at regular and fast speed after mental imagery training. Thirty-five volunteers were scanned with a 3T MRI while they imagined a sequence of ankle movements (dorsiflexion, plantar flexion, varus and valgus) before and after mental practice. Subjects were distributed in two groups: the first group executed regular movements whereas the second group made fast movements. We applied the general linear model (GLM) and model-free, exploratory tensorial independent component analytic (TICA) approaches to identify plastic post-training effects on brain activation. GLM showed that post-training imagination of movement was accompanied by a dual effect: a specific recruitment of a medial prefronto-cingulo-parietal circuit reminiscent of the default-mode network, with the left putamen, and a decreased activity of a lateral fronto-parietal network. Training-related subcortical changes only consisted in an increased activity in the left striatum. Unexpectedly, no difference was observed in the cerebellum. TICA also revealed involvement of the left executive network, and of the dorsal control executive network but no significant differences were found between pre- and post-training phases. Therefore, repetitive motor mental imagery induced specific putamen (motor rehearsal) recruitment that one previously observed during learning of overt movements, and, simultaneously, a specific shift of activity from the dorsolateral prefrontal cortex (attention, working memory) to the medial posterior parietal and cingulate cortices (mental imagery and memory rehearsal). Our data complement and confirm the notion that differential and coupled recruitment of cognitive networks can constitute a neural marker of training effects.

Neuroimaging features and pathology of mixed glioblastoma--AVM complex: a case report.

This report is of a rare case of glioblastoma coexisting with an arteriovenous malformation in a 65-year-old man. Multimodal magnetic resonance imaging (MRI) performed at 3T revealed a necrotic and cystic lesion in the left hemisphere; morphological and metabolic findings were consistent with an infiltrating high-grade glioma, but the presence of dark vessel-like signals on T2* and susceptibility-weighted imaging (SWI) suggested the coexistence of a vascular malformation. The arteriovenous malformation was confirmed by MR angiography and cerebral angiography. The patient was operated on, and histological examination revealed atypical cells characteristic of glioblastoma multiforme and, in the same area, arteriovenous malformation. The possible role of angiogenic factors in this case is also addressed.