An Infundibular Unidentified Object (IUO): a new pituitary stalk marker?

PURPOSE: Measurement of the pituitary stalk (PS) diameter does not always solve the issue of minimal PS thickening. A previously undescribed image is found at the infundibular level on high resolution thin section T2W MRI in a large number of normal individuals. We speculate that this image-whose exact origin is still unknown-may serve as a marker of the normal infundibulum. METHODS: In the last 6 months, 350 consecutive adult patients suspected of sellar pathology or controlled after medical or surgical treatment prospectively underwent a pituitary MRI including a sagittal T2W high resolution sequence. One hundred twelwe patients presenting a pituitary mass with suprasellar extension or those whose PS was not entirely visible were excluded. RESULTS: A short focal annular T2 hypointense thickening of the wall of the infundibular recess of the third ventricle, more pronounced anteriorly was found in 151/238 patients. Additionally, a more or less tiny ventral extension was demonstrated on sagittal T2W sequence in 105/151 patients. These images were not identified on T1W or on T1W gadolinium enhanced sequences. The ring-like infundibular thickening and/or its ventral extension were not identified in 87/238 patients; in 43/87 of these patients the PS was found severely stretched mainly in case of primary or secondary empty sella. If patients with empty sella were excluded, our finding was observed in 194/238 cases, i.e. in 82%. CONCLUSIONS: A detailed appearance of the PS on T2W MRI is described for the first time. A previously unreported T2W hypointense annular focal image prolonged by a tiny spicular or nodular ventral bud is found at the lower part of the infundibulum in a majority of normal patients, but not if the PS is stretched such as in empty sella. This image has to be recognized as a normal anatomical landmark. The possible origin of this image is discussed but not totally elucidated. An ongoing research will demonstrate or not if this image may serve as a marker to improve the early diagnosis of PS lesions.

[Functional imaging and radiotherapy]. / Utilisation de l'imagerie fonctionnelle en radiothérapie.

Medical imaging plays a crucial role in the diagnosis, staging and therapeutic strategy of oncologic patients. The development of medical imaging over the last decade has allowed significant progresses in radiotherapy. Indeed, medical imaging is now considered the corner stone of radiotherapy. The main challenge for the radiation oncologist consists in the tumour identification with a view to irradiate the tumour at a curative dose while avoiding healthy tissues. To achieve these goals, the radiotherapist daily uses anatomical imaging such as computed tomography (CT) or magnetic resonance imaging (MRI). Since several years now, the development of functional imaging such as positron emission tomography (PET) combined with CT or functional MRI has opened new perspectives in the management of oncologic diseases. Indeed, these imaging techniques offer new information on tumour metabolism that may be taken into account to plan the radiotherapy treatment. This article illustrates the different imaging techniques used in radiotherapy and the role of functional imaging for establishing new therapeutic strategies in radiation oncology.

[Multidisciplinary treatment of glioblastoma]. / Le traitement multidisciplinaire du glioblastome.

Glioblastoma is a primary brain tumor that occurs most often in elderly patients. Despite improved management, the prognosis of this cancer remains poor. This review describes the multidisciplinary management of the patient with glioblastoma. It includes surgery, radiation therapy and chemotherapy.

[Cerebrotendinous xanthomatosis, a rare, severe, but treatable metabolic disorder]. / La xanthomatose cérébro-tendineuse, une maladie métabolique rare, grave mais curable.

Cerebrotendinous xanthomatosis (CTX) is a rare and treatable autosomal recessive disease. The diagnosis should be suspected in the presence of a suggestive clinical triad characterized by early-onset cataract, tendinous xanthomata and neurological symptoms and signs, notably cerebellar ataxia, mental retardation and pyramidal syndrome.The diagnosis is confirmed by demonstrating an increased blood level of cholestanol, or/and by molecular genetic analysis.In typical cases, brain MRI shows bilateral hyperintensity of the cerebellar nucleus dentatus together with cerebral atrophy and leukoencephalopathy. The treatment is based on the administration of chenodeoxycholic acid. The aim is to restore the negative feedback on the enzymatic cascade altered by mutation in the gene CYP27 which induces a 27-hydroxylase deficiency

DTI BASED STRUCTURAL DAMAGE CHARACTERIZATION FOR DISORDERS OF CONSCIOUSNESS.

MRI Diffusion Tensor Imaging (DTI) has been recently proposed as a highly discriminative measurement to detect structural damages in Disorders of Consciousness patients (Vegetative State/Unresponsive Wakefulness Syndrome-(VS/UWS) and Minimally Consciousness State-MCS). In the DTI analysis, certain tensor features are often used as simplified scalar indices to represent these alterations. Those characteristics are mathematically and statistically more tractable than the full tensors. Nevertheless, most of these quantities are based on a tensor diffusivity estimation, the arithmetic average among the different strengths of the tensor orthogonal directions, which is supported on a symmetric linear relationship among the three directions, an unrealistic assumption for severely damaged brains. In this paper, we propose a new family of scalar quantities based on Generalized Ordered Weighted Aggregations (GOWA) to characterize morphological damages. The main idea is to compute a tensor diffusitivity estimation that captures the deviations in the water diffusivity associated to damaged tissue. This estimation is performed by weighting and combining differently each tensor orthogonal strength. Using these new scalar quantities we construct an affine invariant DTI tensor feature using regional tissue histograms. An evaluation of these new scalar quantities on 48 patients (23 VS/UWS and 25 MCS) was conducted. Our experiments demonstrate that this new representation outperforms state-of-the-art tensor based scalar representations for characterization and classification problems.

Multimodal neuroimaging in patients with disorders of consciousness showing "functional hemispherectomy".

Beside behavioral assessment of patients with disorders of consciousness, neuroimaging modalities may offer objective paraclinical markers important for diagnosis and prognosis. They provide information on the structural location and extent of brain lesions (e.g., morphometric MRI and diffusion tensor imaging (DTI-MRI) assessing structural connectivity) but also their functional impact (e.g., metabolic FDG-PET, hemodynamic fMRI, and EEG measurements obtained in "resting state" conditions). We here illustrate the role of multimodal imaging in severe brain injury, presenting a patient in unresponsive wakefulness syndrome (UWS; i.e., vegetative state, VS) and in a "fluctuating" minimally conscious state (MCS). In both cases, resting state FDG-PET, fMRI, and EEG showed a functionally preserved right hemisphere, while DTI showed underlying differences in structural connectivity highlighting the complementarities of these neuroimaging methods in the study of disorders of consciousness.

Natalizumab induces a rapid improvement of disability status and ambulation after failure of previous therapy in relapsing-remitting multiple sclerosis.

BACKGROUND: Natalizumab (Tysabri) is a monoclonal antibody that was recently approved for the treatment of relapsing-remitting multiple sclerosis (RRMS). Our primary objective was to analyse the efficacy of natalizumab on disability status and ambulation after switching patients with RRMS from other disease-modifying treatments (DMTs). METHODS: A retrospective, observational study was carried out. All patients (n=45) initiated natalizumab after experiencing at least 1 relapse in the previous year under interferon-beta (IFNB) or glatiramer acetate (GA) treatments. The patients also had at least 1 gadolinium-enhancing (Gd+) lesion on their baseline brain MRI. Expanded Disability Status Scale (EDSS) scores, and performance on the Timed 25-Foot Walk Test and on the Timed 100-Metre Walk Test were prospectively collected every 4 weeks during 44 weeks of natalizumab treatment. Brain MRI scans were performed after 20 and 44 weeks of treatment. RESULTS: Sixty-two per cent of patients showed no clinical and no radiological signs of disease activity, and 29% showed a rapid and confirmed EDSS improvement over 44 weeks of natalizumab therapy. Patients with improvement on the EDSS showed similar levels of baseline EDSS and active T1 lesions, but had a significantly higher number of relapses, and 92% of them had experienced relapse-mediated sustained EDSS worsening in the previous year. A clinically meaningful improvement in ambulation speed was observed in approximately 30% of patients. CONCLUSIONS: These results indicate that natalizumab silences disease activity and rapidly improves disability status and walking performance, possibly through delayed relapse recovery in patients with RRMS who had shown a high level of disease activity under other DMTs.

Functional connectivity in the default network during resting state is preserved in a vegetative but not in a brain dead patient.

Recent studies on spontaneous fluctuations in the functional MRI blood oxygen level-dependent (BOLD) signal in awake healthy subjects showed the presence of coherent fluctuations among functionally defined neuroanatomical networks. However, the functional significance of these spontaneous BOLD fluctuations remains poorly understood. By means of 3 T functional MRI, we demonstrate absent cortico-thalamic BOLD functional connectivity (i.e. between posterior cingulate/precuneal cortex and medial thalamus), but preserved cortico-cortical connectivity within the default network in a case of vegetative state (VS) studied 2.5 years following cardio-respiratory arrest, as documented by extensive behavioral and paraclinical assessments. In the VS patient, as in age-matched controls, anticorrelations could also be observed between posterior cingulate/precuneus and a previously identified task-positive cortical network. Both correlations and anticorrelations were significantly reduced in VS as compared to controls. A similar approach in a brain dead patient did not show any such long-distance functional connectivity. We conclude that some slow coherent BOLD fluctuations previously identified in healthy awake human brain can be found in alive but unaware patients, and are thus unlikely to be uniquely due to ongoing modifications of conscious thoughts. Future studies are needed to give a full characterization of default network connectivity in the VS patients population.

[MRI in coma survivors]. / Imagerie par résonance magnétique chez des patients survivant à un coma.

Traumatic and non-traumatic brain injured disorders of consciousness patients are still challenging for diagnosis, prognosis, ethical and socio-economic reasons. Currently, there remains a high rate of misdiagnosis of the vegetative state (Schnakers, et al. 2009). Recent advances in MRI techniques (diffusion tensor, magnetic resonance spectroscopy and functional imaging) provide data that could improve the diagnostic and prognostic evaluation and management of these patients.

Intrinsic brain activity in altered states of consciousness: how conscious is the default mode of brain function?

Spontaneous brain activity has recently received increasing interest in the neuroimaging community. However, the value of resting-state studies to a better understanding of brain-behavior relationships has been challenged. That altered states of consciousness are a privileged way to study the relationships between spontaneous brain activity and behavior is proposed, and common resting-state brain activity features observed in various states of altered consciousness are reviewed. Early positron emission tomography studies showed that states of extremely low or high brain activity are often associated with unconsciousness. However, this relationship is not absolute, and the precise link between global brain metabolism and awareness remains yet difficult to assert. In contrast, voxel-based analyses identified a systematic impairment of associative frontoparieto-cingulate areas in altered states of consciousness, such as sleep, anesthesia, coma, vegetative state, epileptic loss of consciousness, and somnambulism. In parallel, recent functional magnetic resonance imaging studies have identified structured patterns of slow neuronal oscillations in the resting human brain. Similar coherent blood oxygen level-dependent (BOLD) systemwide patterns can also be found, in particular in the default-mode network, in several states of unconsciousness, such as coma, anesthesia, and slow-wave sleep. The latter results suggest that slow coherent spontaneous BOLD fluctuations cannot be exclusively a reflection of conscious mental activity, but may reflect default brain connectivity shaping brain areas of most likely interactions in a way that transcends levels of consciousness, and whose functional significance remains largely in the dark.

[Hurst acute haemorrhagic leukoencephalitis: MRI findings]. / Leucoencephalite aigue hemorragique de Hurst: imagerie IRM.

A case of autopsy-proven acute hemorrhagic leukoencephalitis is reported. Early magnetic resonance imaging showed extensive bilateral asymmetrical demyelinating lesions and foci of microhemorrhage sparing the cortex ribbon. Fulminant disease culminated in coma and death within twenty-four hours. A comprehensive correlation between pathological findings of acute haemorrhagic leukoencephalitis and both classical and advanced neuroimaging findings is provided.

[Diagnosis of internal carotid artery dissection. Two case reports]. / Approche diagnostique de la dissection carotidienne. A propos de deux cas.

Two cases of acute internal carotid dissection are presented. Typical symptoms, pathogeny and imaging features are reviewed. Magnetic Resonance is actually the best technique for the diagnosis of internal carotid artery dissection, which should be searched in young patients presenting neurologic and cervico-facial symptoms.