[Acute ischemic optic nerve disease: Pathophysiology, clinical features and management (French translation of the article)]. / Pathologies ischémiques aiguës du nerf optique : physiopathologie, atteintes cliniques et prise en charge.

Ischemic optic neuropathies are among the leading causes of severe visual acuity loss in people over 50 years of age. They constitute a set of various entities that are clinically, etiologically and therapeutically different. Anatomically, it is necessary to distinguish anterior and posterior forms. From an etiological point of view, the diagnosis of the arteritic form due to giant cell arteritis requires emergent management to prevent blindness and even death in the absence of prompt corticosteroid treatment. When this diagnosis has been ruled out with certainty, non-arteritic ischemic optic neuropathies represent a vast etiological context that in the majority of cases involves a local predisposing factor (small optic nerves, disc drusen) with a precipitating factor (severe hypotension, general anesthesia or dialysis) in a context of vascular disease (sleep apnea syndrome, hypertension, diabetes, etc.). In the absence of specific available treatment, it is the responsibility of the clinician to identify the risk factors involved, in order to reduce the risk of contralateral recurrence that may occur even several years later. Due to their complexity, these pathologies are the subject of debates regarding both the pathophysiological and therapeutic perspectives; this review aims to provide a synthesis of validated knowledge while discussing controversial data.

Acute ischemic optic nerve disease: Pathophysiology, clinical features and management.

Ischemic optic neuropathies are among the leading causes of severe visual acuity loss in people over 50 years of age. They constitute a set of various entities that are clinically, etiologically and therapeutically different. Anatomically, it is necessary to distinguish anterior and posterior forms. From an etiological point of view, the diagnosis of the arteritic form due to giant cell arteritis requires emergent management to prevent blindness and even death in the absence of prompt corticosteroid treatment. When this diagnosis has been ruled out with certainty, non-arteritic ischemic optic neuropathies represent a vast etiological context that in the majority of cases involves a local predisposing factor (small optic nerves, disc drusen) with a precipitating factor (severe hypotension, general anesthesia or dialysis) in a context of vascular disease (sleep apnea syndrome, hypertension, diabetes, etc.). In the absence of specific available treatment, it is the responsibility of the clinician to identify the risk factors involved, in order to reduce the risk of contralateral recurrence that may occur even several years later. Due to their complexity, these pathologies are the subject of debates regarding both the pathophysiological and therapeutic perspectives; this review aims to provide a synthesis of validated knowledge while discussing controversial data.

[Value of the functional neural tractography in the reconstruction of the visual pathways in DTMRI]. / Intérêt de la neurotractographie fonctionnelle dans la reconstruction des voies visuelles en IRMTD.

OBJECTIVE: This article shows that functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) are very useful in the in vivo description of the visual pathways using today's most advanced techniques and allowing fusion between fMRI and tractography. Two complementary techniques were combined: (1) DTI coupled with the tractography and (2) fMRI. MATERIALS AND METHODS: A group of 205 cases, normal and pathological, children and adults, were studied for tractographic reconstitution of visual pathways. In addition, 11 patients underwent an acquisition in fMRI (BOLD effect), with a stimulation of a black-and-white flickering checkerboard. Acquisition was carried out on a 3.0 Tesla GEHC MRI unit. Activated arrays of fMRI are overlaid with those of neurotractography (neural tractography) having like results a functional neurotractography. RESULTS AND DISCUSSION: The main components of the visual pathways were successfully reconstructed in tractography: the optic nerves, optic chiasm, optic tracts, and optic radiations. It was also possible to visualize fiber decussation within the chiasma (possible direct pathways to the hypothalamus and thalamus were also identified). CONCLUSIONS: The tensor of diffusion is increasingly used and is a promising technology to improve the diagnosis of neurological diseases. Sophisticated algorithms contribute a new vision of the anatomy, with the possibility of isolating distinct anatomical entities. With the software used, the charts of fMRI activation are overlaid on the anisotropy charts. The tractograms that link two regions of the same functional network thus provide information on subjacent structural connectivity. Consequently, one speaks about functional neurotractography.

[Functional amblyopia: a functional MRI evaluation of the visual cortex response after treatment]. / Amblyopie fonctionnelle : évaluation en IRM fonctionnelle de la réponse corticale visuelle après traitement.

PURPOSE: Functional MRI evaluation of the cortical response in treated amblyopic patients. MATERIAL AND METHODS: Clinical and functional MRI exploration of ten patients, seven men and three women aged from 21 to 59 years, with strabismus management during childhood. Functional evaluations were performed on a 1.5 Tesla MR device, with four monocular functional sessions, two stimulations per eye. Alternating rest and active phases displayed still and flickering black and white checkerboards with spatial and temporal frequencies of 1 degree/8Hz and 15'/4Hz. Anatomical realignment and statistical analysis were performed using SPM99 (Statistical Parametric Mapping) to compare the four sessions in individuals. RESULTS AND DISCUSSION: In patients presenting a visual acuity of the amblyopic eye less than 0.7, stimulation of this eye induced lower response in V1, V3, and V5 in comparison with the contralateral eye stimulation. Unexpectedly, in patients recovering normal or subnormal acuity, the amblyopic eye gave comparable or enhanced response in these areas. Additional response was found in the secondary visual cortex, the cuneus, the lingual gyrus, and in parietal, frontal, and orbitofrontal areas. These results suggest a variation in cortical response depending on the efficacy of the treatment. Recovered amblyopic eye, even with acuity less than the contralateral eye, may induce a reinforced cortical sensitivity to visual stimulus. Secondary visual areas may contribute to an attentional process in image perception and analysis. Cortical plasticity may be observed several years after amblyopia treatment. CONCLUSION: Our study substantiates the importance of an effective and early treatment of functional amblyopia, inducing cortical plasticity with reinforced attention and sensitivity to visual perception.

MR tractography with diffusion tensor imaging in clinical routine.

Using MRI, we demonstrated that the depiction of the cerebral white matter fiber tracts has become a routine procedure. Diffusion tensor (DT) sequences may be analyzed with combined volume analysis and tractography extraction software, giving indirect visualization of white matter connections. We obtained DT data from 20 subjects with normal MR imaging and five patients presenting cerebral diseases such as brain tumors, multiple sclerosis and stroke, with five patients explored on two different MR scanners. Data were transferred to dedicated workstations for anatomical realignment, determination of voxel eigenvectors and calculation of fiber tract orientations in a region of interest. In all subjects, axonal directions underlying the main neuronal pathways could be delineated. Comparisons between diseased regions and contralateral areas demonstrated changes in voxel anisotropy in injured regions, revealing possible preferential fiber orientations within diffuse T2 hyperintensities. Rapid data processing allows imaging of the normal and diseased fiber pathways as part of the routine MRI examination. Therefore, it appears that whenever white matter disease is suspected a tractography can be performed with this fast and simple method that we proved to be reliable and reproducible.

Acute demyelination: an insight into the effect of mitoxantrone on CNS lesions.

We report the cases of 2 severely disabled patients with large inflammatory lesions suggestive of demyelination treated with mitoxantrone. Clinical condition was improved and brain lesions volume was reduced. On serial MR spectroscopy, there were variations in peaks between 0.9 and 1.4 ppm, suggestive of free lipids and amino acids. These variations may represent neurochemical markers of clinical recovery of large inflammatory lesions in multiple sclerosis.

[Tractography of the visual pathways: routine examination in magnetic resonance imaging]. / Tractographie des voies visuelles: évaluation en routine en imagerie par résonance magnétique.

Water diffusion analysis in magnetic resonance imaging (MRI) provides an elective visualization of fiber tract orientations in cerebral white matter, especially for optic tracts. We explored 25 patients from 18 to 45 years of age, with normal MRI in 20 subjects, and radiological anomalies in five. On a 1.5 Tesla MRI apparatus, diffusion tensor acquisitions were performed in 5 minutes 58 seconds with an EPI Single Shot sequence covering the entire brain. Image displacements were precluded by patient information and adequate fixation, then digitally corrected on workstations. Volume merging and fiber tract extraction were achieved using dedicated software (Volume-One and dTV). A directional depiction was obtained for all areas in the white matter, in particular for white matter junctions. Coming from the lateral geniculate body, the optic tracts were directed posteriorly toward the occipital cortex, with numerous connections to extrastriate associative areas, and through the corpus callosum and the fornix. Diffusion tractography requires optimization of volume displacements, before and secondary to MRI acquisitions. Our diffusion tensor acquisition, with image optimization in a short-duration sequence can be routinely applied to all patients, for a specific analysis of functional connections between cortical areas of cerebral white matter.

Correlating multiple MRI parameters with clinical features: an attempt to define a new strategy in multiple sclerosis.

MRI is the most powerful imaging technique in managing patients with suspected or confirmed multiple sclerosis (MS). However, conventional MRI variables show nonspecific abnormalities weakly correlated with clinical progression of the disease. New techniques, now routinely available, offer better characterisation of the pathophysiology. We combined conventional MRI, including lesion load, contrast enhancement and "black holes" with magnetisation transfer and diffusion-weighted imaging and localised proton MR spectroscopy (MRS) to study their relationship with disability, course and duration of MS. The variables that were the most significantly linked to the course of the disease (relapsing remitting versus secondary progressive) were lesion load, mean overall magnetisation transfer ratio and apparent diffusion coefficient (MGADC), the percentage of ADC in (PADCIMD), and out of (PAD-COMD) modal distribution, and the ratio N-acetylaspartate and creatine-containing compounds on MRS of the centrum semiovale. MGADC and PADCIMD were the independent factors most related to disability and duration of disease. Combining MRI techniques is clinically relevant and feasible for studies of MS and may be applied to other diseases of the central nervous system.

Normal-appearing white matter in optic neuritis and multiple sclerosis: a comparative proton spectroscopy study.

We investigated neurochemical abnormalities in the normal-appearing white matter (NAWM) on MRI of patients with optic neuritis (ON) and compared them to those of patients with multiple sclerosis (MS). Patients with ON (42) were classified into three groups according to abnormalities on brain MRI. Patients with MS (55) were divided in two groups: relapsing remitting MS (RRMS) and secondary progressive MS (SPMS). All patients underwent MRI of the brain and localised proton magnetic resonance spectroscopy (MRS) of NAWM. The results were compared to those of 15 controls. Patients with MS had significant abnormalities compared with controls and with patients with ON. Patients with RRMS and those with ON had comparable MRS parameters, while patients with SPMS had significant spectroscopic abnormalities in comparison with controls, but also with patients with RRMS. These changes consisted of a decrease in N -acetylaspartate, a neuronal marker, which may reflect axonal dysfunction and/or loss. MRS abnormalities were detected in 14 patients with ON (27 %). The main abnormalities consisted of a decrease in N -acetylaspartate, an increase in choline-containing compounds at long echo times, and the presence of free lipid peaks at short echo times. MRS of the NAWM on MRI may prove useful for detecting neurochemical brain abnormalities in ON not visible on MRI.

Minimal surface: a useful paradigm to describe the deeper part of the corpus callosum?

The aim of this magnetic resonance imaging study was to find a geometrical characterization of the deeper part of the corpus callosum. Its shape was studied in 12 middle-aged persons free of white matter pathology. Profiles of curvatures were measured showing that this surface was close to a minimal one, especially at the genu and near the splenium. To assess the effect of a white matter pathology on these geometrical features, the same measurements were performed in an extra group of nine patients with definite multiple sclerosis. The hypothesis of curvatures profiles parallelism for the two groups could be rejected at the 0.05 confidence level for the mean curvatures but not for the Gaussian ones. Curvatures profiles may give indications on balance between the cortex and the fiber bundles growth rates during the development and on large scale modifications co-occurring with multilocular white matter pathologies.

[Etiologic diagnosis of oculomotor paralysis by computerized tomography: a statistical approach. Apropos of 472 cases]. / Diagnostic étiologique des paralysies oculomotrices par Scan RX: une approche statistique. A propos de 472 observations.

Among 4,538 neuroradiology cases gathered at the NOHC of the XV-XX, an oculomotor paralysis is the 3rd (37.65%) clinical circumstances justifying a computerized tomography (directional plane by the neuro-ocular plane or PNO). The interpretation of the investigations requires to index them in 7 groups of items, therefore a computerized access follows (cross-sorting data). The injury of the VI overcomes (39.61%) followed by the one of the III (33.68%), and the IV (6.35%). In spite of limitations, the study puts forward and debates about etiological frequencies sometimes different from those in the literature.

The accessory middle cerebral artery (AMCA). Diagnostic and therapeutic consequences.

The existence of the accessory middle cerebral artery (AMCA) is a rare anatomical variation with an estimated incidence of 0.31%. The embryological development of this artery is unknown. Three anatomical subtypes are described: in the type 1 variety the AMCA arises from the internal carotid artery; in the type 2, the AMCA originates from the proximal part of the anterior cerebral artery; in type 3, the AMCA arises from the distal part of the anterior cerebral artery. The use of endovascular techniques to treat cerebral vascular malformations requires knowledge of the anatomical subtype of AMCA and the brain regions it supplies (cortex, basal ganglia).

Radiological anatomy of the vascularization of cranial dural arteriovenous malformations.

Knowledge of the radiological anatomy of the cranial dural vascularization allows a flexible and appropriate approach to the pretherapeutic investigation of cranial dural arteriovenous malformations. The variability of the origin of these arteries requires that several possible sources of vascular supply be investigated - internal carotid, internal maxillary, ascending pharyngeal, occipital and vertebral - and that each of their meningeal branches be known in detail. Finally, familiarity with the radiological anatomy of these vessels allows one to identify on routine angiography those vessels that may be a source of risk when performing techniques of endovascular therapy (pedicles supplying the cranial nerves, internal carotid and vertebral anastomoses). Each foramen at the base and vault of the cranium contains an artery to the dura mater. Accordingly, very precise topographical study, in particular of the cavernous region, can be made.

[Tomodensitometry of severe acute pancreatitis]. / Tomodensitométrie des pancréatites aiguës graves.

90 computed tomographic examinations were performed to 57 patients referred at Hospital Saint-Louis for an acute pancreatitis. 32 patients were operated or autopsied. Among these 32 patients, 19 patients had 21 examinations before surgery or autopsy; the other 13 patients had their computed tomographic examinations after one or more surgical procedures. During a severe acute pancreatitis the pancreas is always large either locally or diffusely. A pancreatic reaction is visible around and possibly at distance of the pancreas. When extraluminal gas is visible (3/5) it signifies gangrenous pancreatitis but it is necessary to eliminate a digestive fistulous tract and/or a communication between a pseudocyst and the digestive tract. Except gangrenous it is not possible to precise the nature of pancreatic reaction. The diagnosis of pseudocyst was easy 9/10, difficult 1/10; we did a false positive diagnosis of pseudocyst. Computed tomography and ultrasounds were compared in ten patients for the search of gallbladder lithiasis. Computed tomography can show large and small (2/4) biliary calculus in the gallbladder that cannot be shown by ultrasounds. A normal pancreas in a normal retroperitoneal space exclude the diagnosis of a severe acute pancreatitis. CT aspects of acute pancreatitis must be considered as a good diagnostic test of an acute pancreatitis.

[Computed x-ray tomographic aspects of intra-orbital hydatid cyst. Apropos of 10 cases]. / Aspects tomodensitométriques du kyste hydatique intra-orbitaire. A propos de 10 observations.

Echinococcus taenia occurs in human accidentally after contamination by infected dust of dog. Although it may localize in all parts of the body as a hydatic cyst, liver, lung and kidney are the most frequent sites. Intra-orbital localization is rare since all statistical studies estimate it to be one per cent of orbital tumours. Using computerized axial tomography (C.A.T. Scanner) ten cases of intra-orbital hydatic cyst originating from Algiers, Tunis Hospitals and C.N.O. des Quinze-Vingts of Paris were studied. The inclusion of C.A.T. scanning in the orbital evaluation enables more positive preoperative diagnosis and facilitates the choice of the most efficient surgical approach.