Ex vivo porcine model for eye, eyelid, and orbit movement analysis of 4-mm ferromagnetic foreign bodies in MRI.

PURPOSE: Ferromagnetic foreign bodies (FFB) present during magnetic resonance imaging (MRI) explorations can lead to tissue injury due to movement, especially in and around the eyes. Ferromagnetic foreign bodies located in the intraocular area, eyelids, and orbit are thus prohibited from undergoing MRI. The aim of the study was to analyze movement of 4-mm ferromagnetic foreign bodies in MRI in the eye, eyelid, and orbit using computed tomography (CT) scan. METHOD: We developed a porcine model using 12 quarters of fresh porcine heads. Each porcine head included one whole orbit with the ocular globe, orbital fat, muscles, and eyelids. Four-millimeter FFB were implanted in the eye within 2 days post-slaughter, and images were acquired within 5 days post-slaughter. Four-millimeter FFB movement was analyzed after 1.5-Tesla (T) MRI. Four locations were tested: intravitreous, suprachoroidal, intraorbital fat, and intrapalpebral. Movement analysis was assessed using computed tomography (CT) scan. RESULTS: The intravitreous ferromagnetic ball moved 14.0 ± 8.8 mm (p < 0.01), the suprachoroidal ball moved 16.8 ± 5.4 mm (p < 0.01), the intraorbital fat ball moved 5.8 ± 0.9 mm (p > 0.05), and the intrapalpebral ball moved 2.0 ± 0.4 mm (p > 0.05). CONCLUSION: The ex vivo porcine model was able to study FFB movement. The 4-mm ferromagnetic balls moved in intravitreous and in suprachoroidal locations after MRI.

Arterial spin labeling (ASL) perfusion: techniques and clinical use.

Arterial spin labeling (ASL) perfusion is a MRI technique to quantify tissue blood flow. ASL is a non-invasive technique that labels the protons in the arterial blood by radiofrequency pulses, without the exogenous injection of contrast media. This article has three goals: 1) present the principles of ASL perfusion, the types of labeling and the ways to obtain the mapping; 2) specify and the quality criteria for the mapping obtained, while emphasizing the artifacts; and 3) describe the main encephalic and renal applications.

Carotid rete mirabile and pseudoxanthoma elasticum: an accidental association?

We report the case of a young female patient with a transient amaurosis due to a carotid rete mirabile (CRM), a rare congenital carotid malformation, and pseudoxanthoma elasticum (PXE), an inherited autosomal recessive systemic metabolic disorder characterised by fragmentation and mineralisation of elastic fibres in connective tissues (skin, eyes) and the vascular system. CRM is a rare form of intracranial carotid malformation whose association with PXE (6 cases at present) would appear not to be accidental. This observation suggests a new link between congenital arterial remodelling and the PXE.

Quality-evaluation scheme for cerebral time-resolved 3D contrast-enhanced MR angiography techniques.

BACKGROUND AND PURPOSE: No practical tool has been reported in the literature to evaluate the quality of cerebral TR-3D-CE-MRA techniques. Our study assessed a large list of parameters used to propose a quality-evaluation scheme for TR-3D-CE-MRA. MATERIALS AND METHODS: A large list of visual and quantitative parameters used to study the quality of images was collected from the literature and evaluated in 19 healthy patients and 11 patients with arteriovenous shunts who had undergone both CENTRA keyhole TR-3D-CE-MRA at 3T and CCA. Several observers evaluated the visual parameters, such as the diagnostic confidence index, artifacts, maximum vascular signal intensity, arterial-to-venous separation, and visibility of 17 arteries and 7 veins; and quantitative parameters, such as maximum arterial SI, arteriovenous transit time, arteriovenous contrast curve, and ADW. A statistical analysis was used to determine interobserver reproducibility of the visual parameters, to calculate the sensitivity of TR-3D-CE-MRA for detecting each vessel (with CCA as standard of reference), and to compare the results of the visual and quantitative evaluations. RESULTS: Diagnostic confidence index, artifacts, arterial-to-venous separation, and 4 vessels-the PICA, ophthalmic and occipital arteries, and the ISS-demonstrated high reproducibility and sensitivity. The ADW was the most reliable dynamic quantitative parameter and was correlated with arterial-to-venous separation. CONCLUSIONS: The image quality of TR-3D-CE-MRA can be effectively evaluated with a scheme of 1 quantitative and 7 visual parameters.

Anatomic variants of the anterior part of the cerebral arterial circle at multidetector computed tomography angiography.

Imaging of the cerebral arterial circle (CAC) is essential in neurovascular diseases such as ischemic stroke for detecting arterial occlusions and evaluating arterial supply, and in subarachnoid or intralobar hemorrhage for detecting intracranial malformations. Multidetector computed tomography angiography (MD-CTA) is increasingly being used for the detection and treatment planning of intracranial aneurysm. For optimal interpretation and treatment planning, this method requires suitable post-processing equipment, and extensive knowledge of the relevant anatomy and anatomical variants. Anatomical variants of the CAC are common, particularly in the anterior CAC, the most common site of intracranial aneurysm. The aim of this review is to illustrate the normal anatomy and most common anatomical variants of the anterior CAC detected by MD-CTA, and to discuss the relevant embryological and technical considerations.

[Magnetic resonance imaging in patients with pacemakers and implantable cardioverter-defibrillators: a systematic review]. / Imagerie par résonance magnétique chez les patients porteurs de stimulateurs cardiaques et de défibrillateurs automatiques implantables: revue de la littérature.

The presence of a pacemaker or an implantable cardioverter-defibrillator was historically considered a contraindication to magnetic resonance imaging (MRI), due to the risks for both patient and device: reed-switch closure responsible for asynchronous pacing, inhibition of pacing, rapid ventricular pacing, heating on the lead tip or even device displacement... However, many recent studies demonstrate that if MRI is crucial for the management of the patient, it can be performed under specific monitoring and scanning conditions and after device reprogramming. The growing implication of device constructors in constructing a MRI safety device will perhaps extend in the future the indications of this imaging modality in implanted patients.

Optimized time-resolved 3D contrast-enhanced MRA at 3T: appreciating the feasibility of assessing cervical paragangliomas.

OBJECTIVES: To describe an optimized 3D time-resolved contrast-enhanced MR angiography (3D TR-CE-MRA) at 3T in diagnosing head and neck paragangliomas and assessing their morphology and relation to neighboring vessels. METHODS: In a prospective study, eight consecutive patients presenting cranial cervical masses suspected to be 10 paragangliomas were examined with 3D TR-CE-MRA at 3T. Two neuroradiologists evaluated the overall image quality, the presence of a paraganglioma, the maximum diameter, as well as the vessel invasion. RESULTS: In all of the cases, the overall image quality was scored as good. The tumors (n=10) were all visualized and localized. The mean maximum diameter was 32.7mm [range 7-80]. Vessel invasion was assessed as uncertain in one case and improbable in nine cases. CONCLUSION: 3D TR-CE-MRA at 3T associated with conventional sequences facilitates a comprehensive investigation of paragangliomas, thus providing the anatomical and functional information.

[Imaging of subarachnoid hemorrhage]. / Imagerie de l'hémorragie sous-arachnoïdienne.

Even if acute subarachnoid hemorrhage (SAH) accounts for only 5% of strokes, its diagnosis is very important because its clinical consequences can be tragic. Recent technological advances in medical imaging have improved diagnostic and therapeutic management of patients with SAH. Nonenhanced CT of the head is the initial imaging modality in suspected SAH for the detection of ruptured intracranial aneurysms. Digital subtraction angiography (DSA) remains the reference exam. Multidetector row CT angiography may potentially replace DSA in the emergency setting, as it provides image data that allows evaluating aneurysmal morphology, the neck size or the visualization of vessels in the vicinity of the aneurysm. For SAH unrelated to aneurysm rupture (15% of cases), MRI and MRA can be added to the diagnostic work-up in order to exclude other differential diagnoses such as venous thrombosis or angiitis. Finally, transcranial color-coded duplex sonography, CT, or MRI are used in clinical practice in order to detect aggravating factors of SAH like hydrocephalus or vasospasm.

Transtemporal-transchoroidal approach and its transamygdala extension to the posterior chiasmatic cistern and diencephalo-mesencephalic lesions.

The aim of this report is to illustrate the successful surgical management of five patients with suprasellar retrochiasmatic and diencephalo-mesencephalic tumours, using a trans-amygdala extension of the trans-temporal/trans-choroidal fissure approach. The procedure is described for five surgically treated patients with such lesions that includes three retrochiasmatic craniopharyngiomas, one hypothalamic hamartoma, and one pilocytic astrocytoma in the left crus cerebri. The management procedure included computed tomography scan (CT scan) and magnetic resonance imaging (MRI). The trans-temporal/trans-choroidal fissure approach enabled us to perform total tumour resection in four patients and a subtotal resection in one. Some technical aspects and pitfalls of the procedure are discussed. This method creates optimum conditions for a radical excision of various suprasellar retrochiasmatic and diencephalo-mesencephalic tumours without mortality and only minimum morbidity. However, no single surgical approach can provide access to the entire variety of tumours located in the suprasellar retrochiasmatic and diencephalo-mesencepalic region. Surgical approaches must be tailored to the site, type of lesion, and its extensions. This method is only another surgical option. Its successful use requires a familiarity with the anatomy of these regions and an understanding of its specificity for a radical excision of some selected tumours, as well as its limitations to access others types of lesions. Although, it seems effective, this approach needs to be evaluated by further experience, owing to the small number of patients reported in this series.

Acute presentation of hydromyelia in a child.

The authors document a rapid development, within 3 weeks, of hydromyelia in a 12 year-old boy. The boy was admitted to a local hospital because of drowsiness and persistent severe neck pain. Neurological examination disclosed a lethargic boy with no neurological deficit other than Parinaud's sign. During his transfer to our department, he presented a cardio-respiratory arrest with coma and bilateral mydriasis. External ventricular drain and craniocervical decompression achieved excellent clinical and neuroradiological outcomes. The development of hydromyelia in this case is caused by obstruction to the natural cerebrospinal fluid pathway at the craniocervical junction and the cardio-respiratory arrest is provoked by a brain stem compression against the clivus and odontoid process. This report illustrates that hydromyelia may complicate acute obstructive hydrocephalus due to acquired Chiari malformation.

MR imaging features of idiopathic thoracic spinal cord herniations using combined 3D-fiesta and 2D-PC Cine techniques.

Idiopathic thoracic spinal cord herniation (TISCH) is a rare cause of surgically treatable progressive myelopathy. The authors report 3 cases of TISCH diagnosed based on conventional T1- and T2-weighted Spin-Echo (SE) MR images in one case, and T1- and T2-weighted SE images combined with 3D-FIESTA (Fast Imaging Employing Steady state Acquisition) and 2D-Phase-Contrast Cine MR imaging in 2 cases. Conventional MRI findings usually provided the diagnosis. 3D-FIESTA images confirmed it, showing the herniated cord in the ventral epidural space. Moreover, in combination with 2D-Phase Contrast cine technique, it was a sensitive method to for the detection of associated pre- or postoperative cerebrospinal fluid spaces abnormalities.

MR imaging features of spinal schwannomas and meningiomas.

Spinal schwannomas and meningiomas are mostly benign, intra-dural extramedullary tumours. We retrospectively reviewed the Magnetic Resonance Imaging (MRI) examinations of 52 spinal schwannomas and meningiomas operated on at our institution since 1998. The series included 28 schwannomas and 24 meningiomas. We compared MRI features of schwannomas and meningiomas and evaluated statistical features that would allow differentiation. Tumours with extraspinal extension were excluded. Concerning the cranio-caudal distribution, half of the cervical tumours were schwannomas, 72% of thoracic lesions were meningiomas and all lumbar tumours were schwannomas. Meningiomas were significantly located at the upper and mid thoracic levels and schwannomas in the lumbar area. On T1-weighted images, MRI signal intensity and heterogeneity were not statistically different between meningiomas and schwannomas. On T2-weighted images, the signal intensity appeared significantly hyperintense and heterogeneous for schwannomas. After Gd-DTPA, we observed a significant difference between meningiomas and schwannomas, the enhancement being intense and heterogeneous in cases of schwannomas, and moderate and homogeneous in cases of meningiomas. The last significant qualitative item was the "dural tail sign", a dural enhancement or thickening near the tumour. It was found in only 16 cases of meningiomas. A simple diagnostic test was built for schwannomas by processing a multiple agreement analysis with the 6 significant items: cranio-caudal location, T2 signal intensity, T2 signal heterogeneity, Gd-DTPA enhancement intensity and heterogeneity, and the "dural tail sign". This test allowed diagnosis of schwannomas with a sensitivity of 96.4%, a specificity of 83.3%, a positive predictive value of 87.1%, and a negative predictive value of 95.7%. In conclusion, we consider that a diagnosis of schwannoma should be made when a spinal intradural extramedullary tumour shows hyperintensity on T2W images or intense enhancement without dural tail sign; otherwise meningioma is more probable.

[Persistent primitive trigeminal artery associated with brain cavernoma. Case report]. / Artère trigéminale associée à un cavernome cérébral.

Among cases of embryonic carotid-basilar anastomosis which may persist after birth, persistent trigeminal artery is the most common. It has been associated with a wide variety of intracranial abnormalities. We are unaware of any other reported association with cavernoma. We report a young woman who experienced seizures following spontaneous abortion. A CT scan disclosed a right frontal hematoma. MRI revealed a cavernoma associated with a persistent trigeminal artery. The cavernoma was removed through a frontal approach. The aim of the present case is to report another type of lesion fortuitously associated with a persistent trigeminal artery.

[Electronic imaging with photo-realistic rendering for neuroanatomy teaching. Methods and preliminary results]. / Imagerie électronique en rendu photo-réaliste pour l'enseignement de la Neuro-anatomie. Méthodes et résultats.

Advances in software, networking, and imaging technology provide a unique opportunity for developing information systems in anatomy that can deliver relevant knowledge to the clinicians, researchers, educators, and students. Recent software tools initially produced for graphic imaging are now available in the medical graphic design field. The authors describe an original method they used to create electronic images of the central nervous system and its coverings with photo-realistic rendering. They present preliminary results and discuss the potential of this new technique as a teaching tool for neuroanatomy.

Intracerebral hemorrhage complicating cervical "hourglass" schwannoma removal. Case report.

The authors report a case of infra- and supratentorial intracerebral hemorrhage complicating the postoperative course of a patient who had undergone surgical removal of a cervical schwannoma with an hourglass configuration. To their knowledge, this is the first case in which this neurosurgical procedure was followed by such a complication. Possible mechanisms are discussed; however, pathological events leading to this complication are unclear. The development of new neurological deficits not attributable to the surgical procedure should suggest this possibility.

MRI of intramedullary spinal schwannomas: case report and review of the literature.

Intramedullary spinal schwannomas are uncommon. We report a solitary cervical intramedullary schwannoma shown by MRI and treated surgically, and review 12 previous cases with MRI. MRI findings and pathogenesis are discussed.

[Spontaneous disappearance of a thoracic disc hernia]. / Disparition spontanée d'une hernie discale thoracique.

We report a case of a 55-year-old man who experienced spontaneous resolution of a large herniated disc at T8-9. Spontaneous resolution of disc herniation is well known at the lumbar level. This case is a rare example of a large thoracic disc herniation diagnosed by CT and MRI which completely regressed six months after a medical treatment with complete disappearance of symptoms. The mechanism of resolution of a disc herniation is unclear and we discuss theoretical considerations. We emphasize the interest of conservative therapy in patients with thoracic disc herniation without neurological deficit.

Rathke's cleft cysts: surgical-MRI correlation in 16 symptomatic cases.

Rathke's cleft cysts (RCCs) are non neoplastic epithelial lesions of the sellar region that have been rarely reported as a clinical entity. We retrospectively reviewed the magnetic resonance imaging (MRI), intraoperative, and pathological findings of a series of 16 cases of RCCs operated at our institution since 1992. Concurrently, we discussed the different hypotheses about their embryological origin. The patients included 12 females and 4 males, 11 to 73 years of age. Endocrine disturbance was the most common presentation, followed by headaches and visual impairment. The location of the cyst was intrasellar in 7 cases, intrasellar and suprasellar in 6 cases, and suprasellar in 3 cases. The size of the cyst ranged from 8 to 26 mm (mean 12 mm). MRI signal intensity was quite variable on T1-weighted images. The cyst appeared hyperintense in 6 cases, hypointense in 6 cases, isointence in 3 cases, and heterogeneous in one case. On T2-weighted images (available in 13 cases), the signal intensity was more constant and appeared hyperintense in 11 cases and hypointense in 2 cases. After Gd-DTPA, we did not observe enhancement either of the cyst contents or of the cyst wall, but only of the pituitary gland in all patient. Most often, the pituitary gland was displaced inferiorly by the cyst located above showing a typical image of "an egg in a cup". Fifteen patients were operated upon via the transsphenoidal approach and one upon a frontal craniotomy. Intraoperatively, the cyst contents were gelatinous or thick, and dark colored. In 2 cases, it was cerebrospinal fluid-like corresponding to the signal observed on MRI. The position of the pituitary gland confirmed by surgery in 15 cases coincided with enhancement seen and MR imaging. In 13 cases where biopsy of the cyst wall was performed, it confirmed focally ciliated columnar or cuboid epithelium. A coexistent adenoma was found in one case. In conclusion, we consider that RCCs have varied MRI characteristics so that no pathognomonic sign may be observed. Except in few cases, there were no correlation between MRI and intraoperative findings. Therefore, even with MRI studies, differential diagnoses with others cystic lesions of the sellar region remains extremely difficult. The most interesting findings on MRI studies of RCCs were to locate the pituitary gland to help the surgeon to preserve pituitary tissue during surgery.

Intramedullary cavernous malformations.

Five cases of intramedullary cavernous malformations were retrospectively reviewed. There were 4 women and one man ranging in age from 30 to 67 years. Thoracic spinal cord was involved twice and cervical cord in three cases. Four of them underwent surgery: two improved, one remained stable and symptoms worsened in one. Clinical, radiological features and surgical management are discussed in the light of the follow-up and literature analysis. The role of T2* weighted sequence in MR diagnosis of intramedullary cavernomas is emphasised.