[MR Features of hepatic macronodular mycobacteriosis]. / IRM des atteintes macronodulaires hépatiques à mycobactéries.

Hepatic macronodular mycobacteriosis is rare. Its diagnosis is challenging and is most often proposed on the basis of histological analysis. Final diagnosis, except for germ-proven cases, is made in conjunction with clinical, biological, and radiological arguments. We retrospectively report the MR features of ten hepatic lesions discovered on five patients. MRI is sensitive but has a low specificity in demonstrating pseudotumoral lesions most often exhibiting hypointensity on the T1-weighted sequence, hyperintensity on the T2-weighted sequence, and a slight rim enhancement after gadolinium-enhanced T1-weighted sequences.

[Dynamic MRI in the evaluation of syringomyelic cysts]. / Apport de l'exploration vélocimétrique en IRM dans l'exploration des kystes syringomyéliques.

We report the results of a MR velocity study of the cerebrospinal fluid including 36 patients with syringomyelic cysts (25 with a foraminal syringomyelia, 7 with a post-traumatic cyst, 2 with a tumoral spinal cord cyst, 2 with a spinal arachnoiditis). Velocity measurements were performed in the cysts and in the pericystic subarachnoid spaces and compared with clinical data, evolutive pattern of the disease, cyst volume, degree of stenosis of the cranio-cervical junction (in patients with Chiari I) or of the spinal canal (in post-traumatic cases), and with the extension of the cyst (post-traumatic cases). Cyst velocities correlated in the pre operative course with the clinical status of the patients and with the volume of the cyst. Correlation with the degree of foraminal stenosis was uncertain and no correlation was found with the duration of the disease course. In the post-operative course cyst velocity decreased and velocity of the subarachnoid spaces increased. Onset of the systolic peak occurred sooner in the cyst than in the subarachnoid spaces. We believe that this point may be important in the pathogenesis of the disease. We consider that systolic and diastolic cyst velocities respectively greater than 2.3 cm/s and 1.5 cm/s in the post-operative course may characterize aggressive cysts. In the future comparison of velocity measurements in patients with Chiari I without syrinx and patients with Chiari I related syringomyelia may be helpful for a better understanding of the natural history of the syringomyelia.

Idiopathic spinal cord herniation: value of MR phase-contrast imaging.

We report two patients with an idiopathic transdural spinal cord herniation at the thoracic level. Phase-contrast MR imaging was helpful in showing an absence of CSF flow ventral to the herniated cord and a normal CSF flow pattern dorsal to the cord, which excluded a compressive posterior arachnoid cyst.

[The place of MRI in the study of cerebrospinal fluid fistulas]. / Place de l'IRM dans l'exploration des fistules de liquide céphalo-rachidien.

Results of CT and MRI explorations in 8 patients with cerebrospinal fluid (CSF) fistulae are reported and compared with surgical findings in 7. Sensitivity of MRI (CISS and fast T2 spin-echo sequences) was excellent giving perfect correlations with surgical findings in 7/7 cases. CT and MRI were found to provide complementary information suggesting they should be used in combination as first intention explorations of suspected CSF fistulae. Computerized cisternography should be used if MRI is contraindicated or if a clinically and biologically proven CSF fistulae is not visualized by CT or MRI.

[Anatomic variants of Meckel's cave on MRI]. / Variantes anatomiques du cavum de Meckel en IRM.

Magnetic resonance imaging (MRI) gives an accurate analysis of Meckel's cave variability. Images were acquired in 50 patients with several sections for anatomical comparison. Using several sections, MRI is a suitable method for better analysis of the trigeminal cistern. The most frequent findings are symmetrical trigeminal cisterns. Expansion of Meckel's cave or its disappearance has pathological significance.

[Imaging cranial nerves with inframillimetric T2-weighted MRI]. / Etude des nerfs crâniens en IRM en coupes inframillimétriques T2.

Fifty files were evaluated to determine the normal anatomy of the cranial nerves. All the cranial nerves were studied including the labyrinth, in different planes with a 3DFT-CISS imaging technique. The 3DFT-CISS is especially interesting to study cranial nerves because of the excellent contrast with CSF-fluid and the possibility of thin sections. It might be essential for the diagnosis of neuralgia and cranial nerves paralysis.

[MRI symptomatology of non-tumoral myelopathies]. / Sémiologie irm des myélopathies non tumorales.

We present a retrospective study in order to analyze the abnormalities noted on MRI in 27 cases of myelopathy excluding tumors, explored between 1994 and 1996. The different lesions were: Multiple Sclerosis (n = 11), Spondylotic myelopathy (n = 3), Neurosarcoidosis (n = 4), CMV Myelitis (n = 1), Radiation Myelopathy (n = 1), Spinal Dural Arteriovenous Fistula (n = 1), Intramedullary Cysticercosis (n = 1), Infarct (n = 5). The exams have been made on 1.5 Tesla Magnetom Vision Siemens or GE Signa machine. All patients have had axial and sagittal views with coronal complementary study in 4 cases. Sequences were Spin echo pT1 (TR: 560, TE: 12), Fast Spin echo pT2 (TR: 3 500, TE: 99 or 128), and gradient echo pT2 (TR: 700, TE: 22, Angle: 25 degrees). Intravenous injection of Gadolinium has been made in 16 cases (0.1 mmol/kg). We have studied the presence or not of a signal abnormality in pT1 and/or in pT2, of enhancement, and its topography (cervical, thoracic, lumbar). We classified lesions in central and/or peripheral and according, to their topography in anterior, posterior or lateral type. The form has been classified in four types (nodular, triangular, "pen like", plage). Extension in transversal (superior or inferior to half medullary surface) and cranio-caudal directions (inferior to one vertebrae, between one and two vertebrae, superior to two vertebrae) has been also classified. Others intra or perimedullar and encephalic abnormalities have been noted. We analyzed the results for each pathology and underline the essential diagnosis criteria noted (low cranio-caudal and transversal extension with frequent triangular form of Multiple Sclerosis lesions, frequent suggestive abnormalities of the encephale (82%) in Multiple Sclerosis, intra and perimedullar enhancement with deformations of the surface of the spinal cord in Sarcoidosis' lesions, extended dorsolumbar "pen like" lesions with inconstant enhancement of infarcts, focal plage lesions centered on degenerative changes of the spinal canal in spondylotic myelopathy, bony lipomatous involution in front of intramedullary radiation plage lesion...) and also review the literature and confront their results to it. We insist on the difficulties in classifying myelopathy (radio-clinical terminology discordances, identical signal abnormalities frequently caused by different illness, necessity to compare to pathologic results). We propose a MRI study protocol that should interest the whole spinal cord and comport T1 weighted without and after gadolinium sequences, T2 weighted sequences (with always a gradient echo type). 2 or better 3 different plans should be made. A complementary study of the brain by MRI is often useful. Clinical study, biology, evolution, MRI and when possible pathology all are necessary to better understand myelopathy's mechanisms.

[XII cranial nerve pseudoneurinoma due to spontaneous fibrous transformation of an aneurysm of the vertebral artery]. / Pseudoneurinome du XII par transformation fibreuse spontanée d'un anévrisme de l'artère vertébrale.

The authors report an exceptional case report of tumor like evolution of a completely thrombosed aneurysm of the right vertebral artery suggestive of neurinoma of the XII nerve. We describe CT, MRI, MR-angiography. The diagnosis has been established by pathologic study after surgical extraction. Our case demonstrate the possibility of growth of totally thrombosed aneurysms and we discuss various mechanisms.

[Magnetic resonance imaging of the olfactory pathways in Kallmann de Morsier syndrome]. / L'imagerie par résonance magnétique des voies olfactives dans le syndrome de Kallmann de Morsier.

INTRODUCTION: Kallmann syndrome is a disease clinically characterized by the association of hypogonadotrophic hypogonadism and anosmia or hyposmia. Most cases have been recorded among men. It is a genetic disorder with a specific gene location on the X chromosome. The cells that normally express luteinizing hormone-releasing hormone or LHRH fail to migrate the olfactory placode to the forebrain. The lateral projections of the olfactory placode also fail to induce development of the olfactory bulbs and tracts. MATERIAL AND METHODS: The aim of this study was to compare the MRI appearance of the olfactory sulci, the olfactory bulbs and frontal lobe between groups. The first reference group was composed of 20 subjects and the second group of 18 patients suffering from Kallmann syndrome. For all studies we used a 1.5 T magnet system (Signa GE). We performed two sagittal and coronal T1-weighted sequences in spin echo (TR = 600 ms, TE = 12 ms) with interleaved 3 mm slices and a 14 cm field of view. RESULTS: In the first group, the two olfactory bulbs were always seen on coronal slices just behind the crista galli measuring 2 to 3.2 mm transversally. On sagittal slices, in 60% of the cases two bulbs were seen (3 mm laterally of the pituitary stalk) and in the other 40% only one bulb was seen. The length of the bulb has been measured between 6 and 11 mm. We noticed a plat frontal lobe in 85% of the cases. In the second group the olfactory bulbs were never visible among the 18 patients suffering from Kallmann syndrome. The hypoplasic sulci were hardly visible and their size was less or equal to 1 cm and the frontal lobe was triangular in 80% of the cases. One patient had hypoplasia of corpus callosum. CONCLUSION: MRI is helpful tool to demonstrate abnormalities of the olfactory system which are always present among patients suffering from Kallmann syndrome. MRI can also show, at the same time, a possible associated brain abnormality.