Diffusion-weighted MRI, dynamic susceptibility contrast MRI and ultrasound perfusion quantification of denervated muscle in rabbits.

OBJECTIVE: The purpose of this study was to assess denervated muscle perfusion using dynamic susceptibility contrast MRI (DSCMRI) and contrast-enhanced ultrasound (CEUS), and to measure denervated muscle apparent diffusion coefficient (ADC) on b1000 diffusion-weighted MRI (DWMRI) at 3 T in order to clarify whether muscle denervation leads to an increase in the extracellular extravascular space, or an increase in blood flow-or both. MATERIALS AND METHODS: Axotomy of the right sciatic nerve of six white rabbits was performed at day 0. At day 9, hind limb muscles MRI and CEUS were performed to assess the consequences of denervation and both semimembranosus muscles of each rabbit were explanted for histological studies. Signal intensity on T2- and T1-weighted MRI, ADC on DWMRI, maximum signal drop (MSD) on DSCMRI and the area under the curve (AUC) on CEUS were measured over circular regions of interest (ROI), in both semimembranosus muscles. Non-parametric Wilcoxon matched-pairs tests were used to assess the mean differences between denervated and normal muscles. RESULTS: T2 fat-saturated (FS) MRI studies showed a strong signal in the right semimembranosus muscles compared with the left side, and gadolinium enhancement was observed on T1 FS MRI. Denervated muscles show a significant increase in ADC on DWMRI (p < 0.01) and a significant signal enhancement on DSCMR imaging (p < 0.05) and on first-pass CEUS (p < 0.05). CONCLUSION: The results of this study--based on perfusion- and diffusion-weighted images--suggest that, after denervation, both increased blood flow through muscle tissue and expansion of the extracellular water volume are present.

[The spinal canal: from imaging anatomy to diagnosis]. / Espaces rachidiens intracanalaires: de l'anatomie radiologique au diagnostic étiologique.

The spinal canal is divided into epidural, subdural and subarachnoid spaces. Intraspinal processes should be correctly placed into their space of origin. MRI is the best imaging modality to achieve this task. Accurate determination of the space of origin routinely requires the acquisition of two different pulse sequences, typically T1W and T2W images, in two orthogonal planes, usually axial and sagittal. Simple imaging features can assist in determining the site of origin: changes to the epidural fat, compression or widening of subarachnoid spaces. The epidural space, bordered medially by dura, contains fat and vascular structures. The subdural space is a virtual space in between the dura and arachnoid membrane. The subarachnoid space is home to the CSF, spinal cord and nerve rootlets. An epidural process replaces the epidural fat, displaces the dura and narrows the subarachnoid space. A subarachnoid process widens the subarachnoid space and spares the epidural fat. Epidural processes usually are infectious or tumoral, either primary or secondary to spinal involvement. Subarachnoid processes include primary tumors, leptomeningeal metastases, arachnoiditis and hemorrhage. Nerve sheath tumors and meningiomas are the most frequent intradural extramedullary tumors.

[Imaging of non-traumatic and non-tumoral cord lesions]. / Imagerie des lésions médullaires non traumatiques et non tumorales.

There is a wide range of spinal cord pathologies (vascular, inflammatory, infectious, metabolic, degenerative). They present clinically as acute partial or complete cord syndromes, or chronic myelopathies (more than 4 weeks in duration). MRI examination should be undertaken with a very strict protocol. Spinal cord lesions should be evaluated with regards to their T1W and T2W signal characteristics, involvement of grey and/or white matter, axial and sagittal extension, cord volume changes, contrast uptake and associated lesions (perimedullary, radicular or brain). The correlation of MR imaging features with clinical and biological data (blood and CSF) should suggest a differential diagnosis.

[Cardiac manifestations of pheochromocytoma]. / Manifestations cardiaques des phéochromocytomes.

Pheochromocytoma is a rare cause of secondary hypertension which may have protean clinical presentations. Noteworthy, it may be revealed or complicated by cardiovascular symptoms such as arrythmia, cardiomyopathy, acute coronary syndrome and cardiogenic shock. These cardiac manifestations of pheochromocytoma may delay diagnosis and must be known in order to provide the best chance at early detection. In some cases pheochromocytoma may be associated to a large apical dyskinesia of the left ventricule apex, tako-tsubo-like which is a reversible acute myocardiopathy. These acute cardiologic manifestations appear to be induced by a toxic effect of elevated catecholamine levels.

Role of carbohydrates in rat leukemia cell-liver macrophage cell contacts.

The mechanism by which macrophages recognize tumor cells is still unknown. We have studied interactions between rat liver macrophages and rat L 5222 leukemia cells. These tumor cells, but not normal leukocytes or erythrocytes, adhere to freshly isolated macrophages in vitro. Binding of tumor cells by macrophages can be inhibited by N-acetyl-D-galactosamine, D-galactose and more potently by glycoproteins with terminal N-acetyl-D-galactosamine or D-galactose residues. Tumor cell adhesion is calcium-dependent. The relevant leukemia cell membrane structures which bear terminal beta-D-galactosyl or related residues have been determined as trypsin- and pronase-sensitive, and hence may presumably be glycoproteins. The tumor cell receptor on liver macrophages appears to be a lectin with the carbohydrate specificity N-acetyl-D-galactosamine greater than D-galactose greater than L-fucose.