[Imaging the brain, from the cell to the organ]. / Imagerie de l'encéphale, de la cellule a l'organe.

Brain imaging has progressed over the centuries, from prehistory (surgical and sculptural empiricism), through the Middle Ages (dissection and drawings), the Renaissance (printing) and the 18th century (Spallanzani and ultrasounds), to the 19th century and the discovery of piezoelectricity by the Curie brothers and X-rays by Röntgen in 1895. The head had finally become transparent! The microscope was used by Ramon Y Cajal for histological and neuropathological brain studies. Marie Curie's discovery of radioisotopes paved the way for advances in in vivo neurophysiology. In the 20th century, technical progress accelerated with the advent of computed tomography. Injected contrast products were initially negative (air for ventriculography and pneumo-encephalography), and subsequently positive (intraventricular then intraarterial iodine, cerebral arteriography, increasingly hyperselective). Neurology and neurosurgery were followed by neuroradiology, stereotaxy, and interventional neuroradiology. G.N. Hounsfield's EMI CT scanner replaced silver salts crystals with computed pixels and voxels. Magnetic resonance imaging (MRI, 1981), which dispenses with the need for X-rays, is evolving at the same pace as computer science itself (Moore's Law) in the form of nanometric biophotonics for example. Diffusion MRI is providing precious information on neuroanatomy (axonal organization of the white matter and neuro-tractography, vascular anatomy), neurochemistry (MRS) and neurophysiology. Functional MRI of sensory activation and resting connectivity, the substrate of thought, is giving fascinating results. Functional stereotactic neurosurgery (for epilepsy, abnormal movements, etc.), stereotactic radiosurgery and endovascular interventional neuroradiology are among the latest approaches.

Endocrine pancreatic tumors in von Hippel-Lindau disease: clinical, histological, and genetic features.

OBJECTIVES: Endocrine pancreatic tumors (EPTs) in von Hippel-Lindau (VHL) disease pose difficult management problems. We aimed to assess (1) the accuracy of somatostatin receptor scintigraphy, (2) histological features with focus on malignancy and genotype-phenotype correlations, and (3) prognosis of VHL-EPT. METHODS: Thirty-five patients with EPT-VHL (20 women; median age, 37 years) from 29 families were studied. Histological diagnosis was available in 29 patients. Endocrine pancreatic tumor patients were treated surgically (n = 22), medically (n = 8), or followed (n = 5). Somatostatin receptor scintigraphy was performed in 27 patients. Germinal alterations of the VHL gene were determined. RESULTS: Tumors were malignant in 58% of patients. Somatostatin receptor scintigraphy was positive in 60% of cases, and weak expression of the somatostatin receptor type 2A was found in 47% of tumors. In operated patients, there was no mortality or tumor relapse (median follow-up, 5 [1-10] years). Mortality rate due to EPT was 6%. Germinal mutations were mainly located in exons 3 and 1, and a specific mutation (P86S) was identified. CONCLUSIONS: Most EPTs in VHL patients are somatostatin receptor scintigraphy-positive and malignant, without correlation with the VHL genotype. Surgical resection is often required, but prognosis of these EPTs seems to be fairly good.

Biomarker-based strategy for screening right ventricular dysfunction in patients with non-massive pulmonary embolism.

OBJECTIVE: To evaluate the usefulness of B-type natriuretic peptide and troponin I measurements in predicting right ventricular dysfunction (RVD) in non-massive pulmonary embolism. DESIGN: Prospective observational study. SETTING: University-affiliated emergency unit, cardiology and pneumology departments. PATIENTS: Sixty-seven patients admitted because of acute pulmonary embolism, without shock on admission, completed the study. INTERVENTIONS: Blood samples and echocardiography were obtained on admission for subsequent and independent assessment of B-type natriuretic peptide (BNP) and troponin I levels as well as RVD. MEASUREMENTS AND RESULTS: Echocardiographic RVD was diagnosed in 36 patients and was severe in 13 on admission. BNP and troponin I levels were higher in patients with RVD than in those with no RVD [62 (27-105) vs. 431 (289-556) pg/ml for BNP, p<0.001; 0.01 (0-0.09) vs. 0.16 (0.03-0.32) microg/l for troponin I, p=0.005]. The area under the receiving operating characteristic curve (AUC) for diagnosing RVD was 0.93 for BNP and 0.72 for troponin I. The troponin I level increased further when RVD was severe, compared with moderate, and the AUC was 0.91 for identifying severe RVD. Diagnoses of RVD and severe RVD were ruled out by BNP100 pg/ml and troponin I >0.10 microg/l. CONCLUSION: In hemodynamically stable pulmonary embolism, BNP/troponin I measurement is helpful on admission, especially for ruling out RVD, i.e. patients with in-hospital high-risk.

Resolution of homonymous visual field loss documented with functional magnetic resonance and diffusion tensor imaging.

A 68-year-old man developed right homonymous hemianopic paracentral scotomas from acute infarction of the left extrastriate area. He was studied over the ensuing 12 months with visual fields, conventional MRI, functional MRI (fMRI), and diffusion tensor imaging (DTI). As the visual field defect became smaller, fMRI demonstrated progressively larger areas of cortical activation. DTI initially showed that the lesioned posterior optic radiations were completely interrupted. This interruption lessened in time and had disappeared by one year after onset. fMRI and DTI are innovative measures to follow functional and structural recovery in the central nervous system. This is the first reported application of these imaging techniques to acute cerebral visual field disorders.

[The visual pathways, from anatomical MRI to physiological with (f)MRI and tractography with diffusion tensor MRI (DTMRI)]. / Les voies de la vision, de l'IRM anatomique à la physiologie (IRM(f)) et IRM en tenseur de diffusion (IRMTD) ou tractographie.

Advances in MRI technology have led to a better knowledge of visual pathways (1984-2004), with a new descriptive anatomy and functional model. The authors first describe the technical development of MRI over the last thirty years, then describe and illustrate the new descriptive anatomy. Cephalic MRI reveals brain structures that were previously invisible, on different encephalic planes, in the optic pathways, horizontally from the cornea to the calcarin fissure (neuro-ocular plane (NOP), oblique trans-hemispheric neuro-ocular (OTNOP) and neuro-opto-tractal planes (NOTP)), in their orthogonal orientation upon the oculomotor pathways: head and axonal optic nerve pack (visual deutoneurons in their meninges), optic tracts, lateral geniculate bodies, optic radiations and the calcarian fissure. Comparative anatomy with the rhesus macaque is mentioned. Functional neuroanatomy (physiology) benefits from cine-MRI for ocular motricity (OD MRI), growth by the observation of myelinization in children, blood and CSF circulation by MR angiography, local blood volumes by perfusion imaging, neuronal quantification with inflammation or myelin regeneration by spectroscopy (MRS), brain mapping by functional MR ((f)MRI) measuring local CBF enhancement by paradigmatic stimulations. The recent functional imaging method, tractography (or diffusion tensor MRI (DTMRI)), using diffusion MRI techniques, natural vector calculations with diffusion tensor and software power for morphological and statistical directional results, represents the direction of projection, association and commissural white matter tracts. Normal examples are shown and some common clinical consequences are discussed.