Tips and traps in neurological imaging: imaging the perimedullary spaces.

The spinal canal is frequently a source of difficulties, traps and diagnostic errors. Pitfalls related to artifacts are resolved by using appropriate sequences. Good knowledge of the appearance of certain particular anatomical structures (the cauda equina roots, the radicular veins of the lumbar spine and conus medullaris, the dorsal root ganglion) and of frequent variants (fibrolipoma of the filum terminale, common root sheaths, root cysts) will avoid a good many errors. Dilatation of epidural veins in intracranial hypotension can simulate the contrast enhancement of a tumour. An increase in epidural fat can induce pathogenic stenosis of the dural sheath.

Imaging of the facial nerve.

The facial nerve is responsible for the motor innervation of the face. It has a visceral motor function (lacrimal, submandibular, sublingual glands and secretion of the nose); it conveys a great part of the taste fibers, participates to the general sensory of the auricle (skin of the concha) and the wall of the external auditory meatus. The facial mimic, production of tears, nasal flow and salivation all depend on the facial nerve. In order to image the facial nerve it is mandatory to be knowledgeable about its normal anatomy including the course of its efferent and afferent fibers and about relevant technical considerations regarding CT and MR to be able to achieve high-resolution images of the nerve.

[Imaging spinal cord cystic lesions in adults]. / Imagerie des lésions kystiques du canal rachidien chez l'adulte.

Intrarachidian cystic lesions are frequent, with highly varied causes. They can be classified according to their location into intramedullary cystic lesions and extramedullary cystic lesions. In these two categories, they can then be regrouped according to the tissue from which they develop. MRI is the first-choice examination for the study of the intracanal contents and the differential diagnosis between the various lesions.

[Intradiploic encephalocele in an adult. A case report and review of the literature]. / Encéphalocèle intra-diploïque de l'adulte. A propos d'un cas et revue de la littérature.

We describe a rare case of parietal intradiploic encephalocele in a 51-year-old woman with no history of head trauma. The patient presented with a 1-month history of left hemiparesthesia. A hard indolent scalp lesion was palpable on examination in the right parietal area. Skull x-rays and cranial computed tomography examination demonstrated a lytic lesion that was consistent with a malignant osteolytic skull lesion. Magnetic resonance imaging of the head revealed an intradiploic cyst that included a round tissue mass contiguous with the parietal cortex. Surgery confirmed the diagnosis of encephalocele and the patient underwent surgical resection of the herniated brain, duraplasty, and cranioplasty. The presenting hemiparesthesia persisted at the 6-month follow-up. Encephaloceles of the cranial vault are a rare complication of skull fractures and rarely occur in adults. These lesions can be difficult to distinguish from congenital encephaloceles in patients with no history of head trauma. The pathogenesis, clinical and radiological nuances and the role of surgery are discussed.

Accuracy of delayed post-contrast FLAIR MR imaging for the diagnosis of leptomeningeal infectious or tumoral diseases.

AIMS: To compare unenhanced, gadolinium enhanced, delayed gadolinium enhanced FLAIR images, gadolinium enhanced and delayed gadolinium enhanced T1 images in different types of leptomeningeal diseases, and to determine the most accurate MRI sequence for the diagnosis of leptomeningeal disease. MATERIAL: and methods: Ten patients (6 men, 4 women, age: 52,7+/-16,4) clinically suspected of cerebral leptomeningeal infectious or tumoral disease underwent brain MR examination: Axial FLAIR and T1 SE images were acquired before, immediately after administration of gadobenate dimeglumine (0.1 mmol per kilogram of body weight) (early enhancement), and 20 minutes after injection of contrast media (delayed enhancement). Images were analysed to determine the more appropriate technique for the diagnosis of leptomeningeal disease. RESULTS: Early enhanced FLAIR and delayed enhanced T1 were always more or equally accurate for the diagnosis of leptomeningeal diasease, as compared to, respectively, unenhanced FLAIR and early enhanced T1 images Delayed enhanced FLAIR was always more accurate for the diagnosis of leptomeningeal disease as compared to early enhanced FLAIR images. Delayed enhanced FLAIR was in most of the cases more accurate for the diagnosis of leptomeningeal disease as compared to delayed enhanced T1 images. CONCLUSION: Delayed enhanced FLAIR MR sequence seems to improve the diagnosis of leptomeningeal infectious or tumoral diseases as compared to other MR sequences.

[Normal and abnormal meningeal enhancement: MRI features]. / Les prises de contraste méningées normales et pathologiques en IRM.

The authors describe normal imaging of the meninges and meningeal spaces and MR (magnetic resonance) imaging findings in tumoral and nontumoral diseases. Dural or/and pial enhancement may be related to tumoral, infectious or granulomatous diseases.

[Imaging in acute toxic encephalopathy]. / Imagerie des encephalopathies toxiques aigues.

Neuroimaging, particularly MR imaging, plays a major role for the diagnosis of many acute toxic encephalopathies. Toxic disorders are related to drugs (immunosuppressive agents, chemotherapeutic agents, anti-epileptic drugs, heroin...), to metals (lead, manganese, mercury...), and to industrial and environmental chemicals (solvent, carbon monoxide...). MR imaging with diffusion and perfusion imaging provides information regarding brain lesions induced by the toxic agents (vasogenic edema, cytotoxic edema, infarction, hemorrhage, demyelination...).

[Spinal extradural meningiomas: MRI findings in two cases]. / LES MENINGIOMES RACHIDIENS EXTRADURAUX: DONNEES IRM A PROPOS DE DEUX OBSERVATIONS.

Spinal extradural meningiomas are rare and may be easily confused with malignant neoplasms. We report two unusual cases of epidural spinal meningioma one within the left C6-C7 foramen and the other within the left posterolateral epidural space at the T3-T4 level. Low signal intensity of the tumor on T2-wi, thickening and enhancement of the dura with only the possibility of bone erosion are the most characteristic MR findings.

[Brain MR imaging of chronic alcoholism]. / Imagerie par résonance magnétique (IRM) des complications encéphaliques de l'alcoolisme.

Brain complications from chronic alcoholism (Wernicke encephalopathy, central pontine myelinolysis, Marchiafava-Bignami disease, Korsakoff's syndrome, hepatic encephalopathy, cerebellar atrophy, hemorrhagic and ischemic brain lesions) may be diagnosed by MR imaging.

Sporadic and familial blepharophimosis -ptosis-epicanthus inversus syndrome: FOXL2 mutation screen and MRI study of the superior levator eyelid muscle.

The analysis of the FOXL2 gene (3q23) in a series of two families and two sporadic cases affected with Blepharophimosis-Ptosis-Epicanthus Inversus Syndrome (BPES) is presented. This study detected two novel FOXL2 mutations (missence and nonsens mutations) and confirmed the recurrence of a previously described duplication. Magnetic Resonance Imaging (MRI) of the orbit, in one family, showed absence or hypotrophy of the eyelid superior levator muscle suggesting a possible role of FOXL2 in the development of this extra-ocular muscle.

[Aspects of FLAIR sequences, 3D-CISS and diffusion-weight MR imaging of intracranial epidermoid cysts]. / Aspects en séquences FLAIR, CISS-3D et en imagerie de diffusion des kystes épidermoïdes intracrâniens.

We propose to assess the usefulness of diffusion-weighted MR Imaging (DWI), fluid-attenuated inversion recovery (FLAIR) and constructive interference in steady state (CISS) sequences in depicting epidermoid cysts (EC). FLAIR, CISS and DWI were obtained in 7 patients among 22. All patients were studied with T1 and T2 sequences. On Spin Echo images, EC demonstrate signal similar to LCS, which may lead to difficult differentiation between EC and arachnoid cyst (AC), specially for inexperienced radiologists. EC appear with a heterogeneous signal on T1 images (32%), irregular limits (91%) and with extension through foramen of Pacchioni in 18% of cases. On FLAIR sequence, the tumors were heterogeneous, different from void signal of CSF in 86% of cases. On CISS sequence, the tumors appear heterogeneous, hyperintense but less than LCS and with irregular limits in all cases. Some more, CISS images allowed to appreciate exact tumor extension and their relations with nerves and vessels. On DWI images, signal is hyperintense in all cases. Our study exhibited the great usefulness of DWI, CISS and FLAIR sequences in diagnosis of EC and in differentiating EC from AC.

[Contribution of 3D CISS MRI for pre- and post-therapeutic monitoring of obstructive hydrocephalus]. / Intérêt des séquences IRM "CISS 3D" dans le bilan pré- et post-thérapeutique des hydrocéphalies non communicantes.

This report describes the use of the recent three-dimensional Fourier transform constructing imaging in the steady state (CISS) MR sequence in the management of obstructive hydrocephalus. It is a gradient-echo imaging technique with high resolution which remains sensitive to flow. It enables locating the obstruction and determining the upstream impact. It provides anatomical information about third ventricle (V3) morphology and relationships useful before ventriculostomy. Twenty patients with obstructive hydrocephalus at the level of cerebral aqueduct or posterior V3 underwent sagittal 3DFT-CISS acquisition, supplemented by frontal, axial and coronal reformations in the cerebral aqueduct axis. 9 patients were examined after ventriculostomy with the same protocol. CISS-3DFT allows good visualization of the cerebral aqueduct and diagnosis of the underlying cause of obstruction (malformation, tumor), sometimes better than classical sequences. In case of complete obstruction, the flow-related signal void is usually absent in the cerebral aqueduct or V3. The position of V3 floor and its relationship with the tip of basilar artery are well analyzed. The dilatation of the anterior V3 recesses is a better sign of activity of hydrocephalus - and then of therapeutical indication - than classical transependymal resorption signs which are not always present in chronic longstanding adult hydrocephalus. Of the 9 ventriculostomy patients seven had linear flow-related signal void through V3 floor, from anterior V3 to basal cisterns on the postoperative MR study. This flow void confirms patent ventriculostomy.

Spectrophotometric determination of nitrite and nitrate using phosphomolybdenum blue complex.

A method for spectrophotometric determination of nitrite and nitrate is described. This method is based on the reduction of phosphomolybdic acid to phosphomolybdenum blue complex by sodium sulfide. The obtained phosphomolybdenum blue complex is oxidized by the addition of nitrite and this causes a reduction in intensity of the blue color. The absolute decrease in the absorbance of the blue color or the rate of its decrease is found to be directly proportional to the amount of nitrite added. The absorbance of the phosphomolybdenum blue complex is monitored spectrophotometrically at 814 nm and related to the concentration of nitrite present. The effect of different factors such as acidity, stability of the complex, time, temperature, phosphate concentration, molybdenum concentration, sodium sulfide concentration and the tolerance amount of other ions have been reported. Maximum absorbance is at 814 nm. The range of linearity using the conventional method is 0.5-2.0 ppm with molar absorptivity of 1.1 x 10(4) l mol(-1) cm(-1). and a relative standard deviation of 2.6% for five measurements. The range of linearity using the reaction rate method is 0.2-3.6 ppm with a relative standard deviation of 2.4% for five measurements. The method is applied for determination of nitrite and nitrate in water, meat products and vegetables.

Properties of the coat protein of a new tobacco mosaic virus coat protein ts-mutant.

Amino acid substitutions in a majority of tobacco mosaic virus (TMV) coat protein (CP) ts-mutants have previously been mapped to the same region of the CP molecule tertiary structure, located at a distance of about 70 A from TMV virion axis. In the present work some properties of a new TMV CP ts-mutant ts21-66 (two substitutions I21=>T and D66=>G, both in the 70-A region) were studied. Thermal inactivation characteristics, sedimentation properties, circular dichroism spectra, and modification by a lysine-specific reagent, trinitrobenzensulfonic acid, of ts21-66 CP were compared with those of wild-type (U1) TMV CP. It is concluded that the 70-A region represents the most labile portion of the TMV CP molecule. Partial disordering of this region in the mutant CP at permissive temperatures leads to loss of the capacity to form two-layer aggregates of the cylindrical type, while further disordering induced by mild heating results also in the loss of the ability to form ordered helical aggregates.

[Study of the process of thermal aggregation of several representative tobamovirus coat proteins]. / Izuchenie protsessa termicheskoi agregatsii belkov obolochki neskol'kikh predstavitelei tobamovirusov.

The role of the specific region of the tobacco mosaic virus (TMV) coat protein (CP) molecule (called "70A degree-region") in the regulation of ordered and unordered CP aggregation was investigated. CPs of the wild type TMV (strain U1), of temperature sensitive mutant with two amino acid substitutions in the "70A degree-region", and of cucumber virus 3 which is related to TMV but has a completely different structure in the "70A degree-region" were used. With the help of two different tests the processes of temperature-induced unordered aggregation of these three CPs were compared in solutions of different ionic strength and pH. On the basis of the data obtained it was concluded that the "70A-region" represents the most thermolabile region in the TMV CP molecule and that local thermal denaturation of this region results in unordered aggregation, when solution conditions (ionic strength and pH) favor formation of relatively large ordered aggregates (20S-"disks" or helical repolymerized protein).