Instabilities and routes to turbulence in rotating disc boundary layers and cavities.

Studied for more than a century, first in the field of geophysics, flows over rotating discs present a great diversity of complex instability behaviours that are not yet fully understood. While the primary instabilities are now well characterized experimentally, theoretically and numerically, their role in the transition mechanisms to turbulence remains an open question that still challenges the scientific community. This article brings together the main results of the literature related to the instabilities over rotating discs, but also in the connected problem of rotating cavities, and reviews the main scenarios currently assumed to describe the flow breakdown to turbulence. A particular focus is on more recent studies of generic flows in rotating cavities bounded by two coaxial rotating discs, that occur in many industrial systems, the performances of which and their improvement are linked to a better understanding of these mechanisms. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (part 1)'.

[Amyloidoma of the central nervous system: CT and MR aspects]. / Amyloïdome primitif du cerveau: aspect TDM et IRM.

PURPOSE: To report a case of tumor like amyloïd formation (amyloidoma) of the brain with etiologic discussion. MATERIAL: and Methods. A 46-year-old female had a 7 year history of epilepsy. CT scan and MRI revealed two enhancing lesions in the white matter of the right temporal and frontal lobes. RESULTS: Stereotactic biopsy examination showed large amyloid deposits surrounded by sparsely scattered lymphocytes, few matures plasma cells, macrophages and rare foreign body type giant cells. The congophilic amyloid was found in the interstitium as well as within the walls of blood vessels with close connection to the choroid plexus. No significant abnormalities were noted on routine laboratory studies. DISCUSSION: Unlike all other types of amyloid, AL amyloid can produce both systemic amyloidosis and solitary amyloidoma. Amyloidomas are rare and usually found in the lung, skin, lower urinary tract. The location in the brain is extremely rare, with only 16 cases reported in the literature. All this cases as well as our example in the current study to some extent involved deep white matter. The association with choroid plexus is possible. The relatively indolent course of this amyloidomas is noted. Our study showed a presence of monotypic lambda producing plasma cells. Thus this lesion could be the result of monoclonal B cell neoplasm capable of terminal differentiation and the existence of AL amyloid producing low grade B lymphomas of the brain could be discussed.

[Neurotrichinosis: a case report with MRI evaluation]. / Neurotrichinose: à propos d'une observation documentée par IRM.

Neurological complications are rare in trichinosis. A case of trichinosis involving the central nervous system documented by MRI is presented. To our knowledge, only three cases of neurotrichinosis with MRI abnormalities have been already reported. The physiopathological mechanism are discussed (transport of the parasite through the blood-stream, immuno-allergic reaction or eosinophilic neurotoxic effect).

Metastases from a pituitary adenoma: MRI.

Few cases of pituitary adenoma with metastases have been reported. We report a case with histologically benign intracranial and cauda equina metastases. We compare it to the others in the literature.

Periganglionic foraminal steroid injections performed under CT control.

PURPOSE: The purpose of our study was to evaluate the efficacy of direct intraforaminal steroid injections into the periganglionic space in the treatment of radicular pain. METHODS: Periganglionic infiltrations were performed in 41 patients with acute or chronic radicular pain. Neuroradiologic imaging in all patients showed foraminal stenosis due to degenerative disorders or herniated disk. All injections were performed under CT control. RESULTS: Seventy percent of patients had significant pain reduction, with the greatest success (90% of patients) in those whose foraminal stenosis was due to degenerative disorders; 45% of patients with foraminal herniated disks had pain relief. CONCLUSION: Intraforaminal steroid injection is useful in the treatment of radicular pain, particularly in cases of foraminal degenerative stenosis.

Magnetization transfer imaging in AIDS-related brain diseases.

MT makes it possible to characterize tissue destruction in several CNS diseases, including AIDS-related diseases such as PML or HIV encephalitis. MR may be helpful in establishing diagnosis, disease burden, prognosis, and therapeutic efficacy. MT may also contribute to the investigation of the natural history of the diseases. The other application is in improving contrast after the injection of gadolinium chelates. This contrast improvement can be achieved routinely on any device and may be a good alternative to other methods, such as increasing dose or delay.

[Agenesis of the internal carotid artery associated with an aneurysm of the anterior communicating artery]. / Agénésie de l'artère carotide interne associée à un anévrisme de l'artère communicante antérieure.

We report a case of agenesis of the internal carotid artery which was revealed by a subarachnoid hemorrhage. Angiography showed a ruptured aneurysm of the anterior communicating artery and unilateral absence of the left internal carotid artery. Both the left anterior and middle cerebral arteries were perfused from the right carotid artery via the anterior communicating artery. Absence of the left carotid canal was proved on bone CT. Such an association is discussed. An hemodynamic stress on a congenital defect of the cerebral arterial wall could be the origin of the aneurysm development.

[Diagnosis of extrapontine myelinolysis preceding central pontine myelinolysis]. / Diagnostic d'une myélinolyse extrapontine précédant l'apparition d'une myélinolyse centropontine.

An MR study performed on a patient who presented a tetraplegia after liver transplantation, revealed bilateral hypersignal of internal globus pallidus on T2 weighted images. Diagnosis of extrapontine myelinolysis was proposed based on clinical presentation and lesions topography, although absence of natremic disorders. Confirmation of diagnosis was obtained on an MR study performed a month later, which demonstrated a pontine extension. Extrapontine myelinolysis can precede pontine involvement. Diagnosis of myelinolysis should be evoked although MR normal appearance of the pons.