[MRI in the diagnosis of Rathke's cleft cyst]. / IRM dans le diagnostic des kystes de la poche de Rathke.

PURPOSE: Rathke's cleft cysts are non neoplastic lesions of the sellar area that seldom are symptomatic. Their incidence has been underestimated before magnetic resonance imaging (MRI). The aim of this work was to assess the value of MRI in the diagnosis and differential diagnosis of Rathke's cleft cyst based on a retrospective review of 12 cases and a review of the literature. PATIENTS AND METHODS: We retrospectively reviewed the MRI features of 12 patients with Rathke's cleft cyst collected over 4.5 years. Patients included ten females and two males (mean age: 39 years). The most common presentation was the association of dysmenorrhea and pituitary dysfunction. MRI examinations were performed using a 1.5 Tesla system, T1 and T2 weighted sequences performed before and after Gd- DTPA injection. Signal intensity, shape, size and location of the lesion were analyzed. RESULTS: In all cases, MRI examination showed a cystic lesion of variable size and signal intensity. The cyst was purely intrasellar in nine cases and a suprasellar extension was noted in three cases. Five patients underwent surgery providing pathological confirmation, four underwent routine follow-up and three were lost of follow-up. CONCLUSION: We conclude that MRI is an efficient tool for diagnosis, allowing appropriate medical decision making.

[MR Sialography]. / SIALO-IRM.

Indications for sialography have became rare and radiologists are less and less experienced for salivary gland cannulation. MR Sialography allows opacification of salivary ducts without any cannulation and could replace residual indications for sialography. The purpose of this paper is to review the principle of the technique, the normal and pathologic aspects of MR Sialography and to emphasize advantages and limitations compared to other techniques.

Unusual lesions of the cerebellopontine angle: a segmental approach.

Tumors of the cerebellopontine angle (CPA) are frequent; acoustic neuromas and meningiomas represent the great majority of such tumors. However, a large variety of unusual lesions can also be encountered in the CPA. The site of origin is the main factor in making a preoperative diagnosis for an unusual lesion of the CPA. In addition, it is essential to analyze attenuation at computed tomography (CT), signal intensity at magnetic resonance (MR) imaging, enhancement, shape and margins, extent, mass effect, and adjacent bone reaction. CPA masses can primarily arise from the cerebellopontine cistern and other CPA structures (arachnoid cyst, nonacoustic schwannoma, aneurysm, melanoma, miscellaneous meningeal lesions) or from embryologic remnants (epidermoid cyst, dermoid cyst, lipoma). Tumors can also invade the CPA by extension from the petrous bone or skull base (cholesterol granuloma, paraganglioma, chondromatous tumors, chordoma, endolymphatic sac tumor, pituitary adenoma, apex petrositis). Finally, CPA lesions can be secondary to an exophytic brainstem or ventricular tumor (glioma, choroid plexus papilloma, lymphoma, hemangioblastoma, ependymoma, medulloblastoma, dysembryoplastic neuroepithelial tumor). A close association between CT and MR imaging findings is very helpful in establishing the preoperative diagnosis for unusual lesions of the CPA.

Visibility of the central canal on MRI.

The central canal of the spinal cord is present at birth and becomes progressively obliterated. Cadaver studies have shown that it may persist partially or completely. To our knowledge, this entity has not been described on MRI. We reviewed 794 MRI studies of the spinal cord, and found 12 patients (aged 14 to 65 years) who had an intramedullary cavity. The cavity was at the junction of the ventral 1/3 and dorsal 2/3 of the spinal cord, except at the level of the lumbar enlargement, where it was central. It was filiform in most cases, although sometimes fusiform (3 to 4 mm in diameter), and had regular contours. The cavity were thoracic in 69 % of cases. The clinical features were totally unrelated to the image, and there were no anatomical factors (Chiari malformation, dysraphism) predisposing to syringomyelia. The images were perfectly compatible with a persistent central canal, which we interpret as a variant of normal anatomy. Therefore it is important to regard these findings as normal, to avoid unnecessary treatment and follow-up.

CSF flow measurement in syringomyelia.

BACKGROUND AND PURPOSE: CSF circulation has been reported to represent a major factor in the pathophysiology of syringomyelia. Our purpose was to determine the CSF flow patterns in spinal cord cysts and in the subararachnoid space in patients with syringomyelia associated with Chiari I malformation and to evaluate the modifications of the flow resulting from surgery. METHODS: Eighteen patients with syringomyelia were examined with a 3D Fourier encoding velocity imaging technique. A prospectively gated 2D axial sequence with velocity encoding in the craniocaudal direction in the cervical region was set at a velocity of +/- 10 cm/s. Velocity measurements were performed in the larger portion of the cysts and, at the same cervical level, in the pericystic subarachnoid spaces. All patients underwent a surgical procedure involving dural opening followed by duroplasty. Pre- and postoperative velocity measurements of all patients were taken, with a mean follow-up of 10.2 months. We compared the velocity measurements with the morphology of the cysts and with the clinical data. Spinal subarachnoid spaces of 19 healthy subjects were also studied using the same technique. RESULTS: A pulsatile flow was observed in syrinx cavities and in the pericystic subarachnoid spaces (PCSS). Preoperative maximum systolic cyst velocities were higher than were diastolic velocities. A systolic velocity peak was well defined in all cases, first in the cyst and then in the PCSS. Higher systolic and diastolic cyst velocities are observed in large cysts and in patients with a poor clinical status. After surgery, a decrease in cyst volume (evaluated on the basis of the extension of the cyst and the compression of the PCSS) was observed in 13 patients. In the postoperative course, we noticed a decrease of systolic and diastolic cyst velocities and a parallel increase of systolic PCSS velocities. Diastolic cyst velocities correlated with the preoperative clinical status of the patients and, after surgery, in patients with a satisfactory foraminal enlargement evaluated on the basis of the visibility of the cisterna magna. CONCLUSION: CSF flow measurement constitutes a direct evaluation for the follow-up of patients with syringomyelic cysts. Diastolic and systolic cyst velocities can assist in the evaluation of the efficacy of surgery.

[Imaging of syringomyelia]. / Imagerie des syringomyélies.

MRI is the best imaging method to evaluate syringomyelia. It is important to study from the posterior cranial fossa to the sacro-lumbar region and also the supra-tentorial structures. This complete analysis is essential to classify the syringomyelia and to investigate other associated malformations. Radiographs and CT scan are useful to analyze bone structures. For MRI, the new sequences with phased-array coils are also very important to study the entire spinal cord and the posterior fossa. It is essential to study the spinal cord with sagittal and axial spin echo T1 and fast spin echo T2 weighted images with sometimes coronal view, particularly when the patient presents a scoliosis, to have a correct morphological and functional evaluation. MRI gives an excellent study of the spinal cord with an excellent analysis of a primitive or foraminal syringomyelia, but also traumatic, infectious or post arachnoiditis syringomyelia. Spin echo T1 weighted images with injection of gadolinium can be used if an intra-medullary tumor is suspected. MRI is also useful for the post-operative follow up to evaluate the persistence of the medullary cyst and the enlargement of the foramen magnum.

[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.

[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.

[Neurocysticercosis]. / La neurocysticercose.

The neurocysticercosis is an infestation of the central nervous system by larvae of Taenia solium. The disease is endemic in a few countries of Latin America, Asia, and Africa and is becoming increasingly prevalent in the United States and Europe. The immigration of individuals from endemic areas and the tourism in these areas require a good knowledge of this disease. A retrospective study evaluating the neurocysticercosis lesions with MR and CT is proposed. Parenchymal, subarachnoid and intraventricular cysts are evaluated. We were able to recognise four CT and MR stages. MR was useful in detecting the cysts of neurocycticercosis in the first stage but was inferior in the detection of parenchymal calcifications.

Anomalous vessel in the middle ear: the role of CT and MR angiography.

An 8-year-old child was examined because of conductive hearing loss with a retrotympanic mass on otoscopy. CT and MR angiography showed a large inferior tympanic artery traversing the hypotympanum and joining a thin, irregular internal carotid artery with a normal middle meningeal artery. These investigations, coupled with knowledge of the embryological development allowed a diagnosis of a complex vascular anomaly in the middle ear and avoided potential surgical complications.

[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.

[Intracranial metal foreign bodies and contraindications of MRI. Apropos of a case]. / Corps étrangers métalliques intracrâniens et contre-indications de l'IRM. A propos d'une observation.

We report a firearm wound of the brain which could not be analyzed by computed tomography because of induced artifacts. MRI study was remarkably after verifying the non-ferromagnetic nature of the projectiles.

[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.

Osteoid osteoma of the petrous bone.

We present a case of osteoid osteoma of the petrous bone presenting with progressive sensorineural hearing loss. CT showed a dense homogeneous mass at the promontory surrounded by a thin bony border. On MRI this lesion gave intermediate signal intensity on T1- and T2-weighted spin-echo images and enhanced intensely with gadolinium. Surgical removal and pathological study proved the diagnosis.

[Osteoid osteoma of the middle ear. Review of the literature apropos of the first described case]. / Ostéome ostéoïde de la caisse du tympan. Revue de la littérature à propos du premier cas décrit.

The case of an osteoid osteoma of the middle ear in a 42 year old man is reported. No former case has now been reported in the literature for this localization. The suspected diagnosis of osteoid osteoma was based on the pain and the findings of bone computerize tomography. In our case, the osteoid osteoma was totally painless and the diagnosis was made after surgical findings by histological studies. Some clinical and imaging points, pathologic findings and differential diagnosis are also discussed.

[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.

[Hemangioma of the facial nerve]. / Hémangiomes du nerf facial.

In this retrospective study the respective values of MRI and CT in the location and nature diagnoses of facial nerve haemangiomas were evaluated. The four male patients examined were 31, 44, 56 and 62 years old; they presented with facial nerve pals and/or cochlear-vestibular dysfunction. The haemangiomas were located in the internal auditory canal, the geniculate ganglion, the tympanic segment of the facial nerve and the petrous bone apex. MRI revealed a tumoral process, while CT showed intratumoral calcifications and provided a diagnosis of mass nature in two cases. In the other cases the pre-operative diagnosis was neurinoma of the VIIIth or VIIth cranial nerve. Histology ascertained the diagnosis. MRI is the method of choice in cases of facial paralysis or cochlear-vestibular dysfunction if a tumoral cause is suspected. Haemangioma is an uncommon tumour without specific image, except for calcifications and neighbouring osseous reactions. It must also be considered on the basis of clinical and topographical findings revealed by CT and MRI imaging.