[Tumors of the oropharynx and oral cavity: MR, CT, PET-CT imaging]. / Imagerie des tumeurs de l'oropharynx et de la cavité orale: IRM, TDM, TEP-scan.

Pretherapeutic imaging plays a central role in the management of tumors of the oropharynx and oral cavity. MR and, to a lesser extent, CT and F-18 FDG PET-CT are the imaging modalities of choice for pretherapeutic work-up of these lesions. Imaging protocols should be simple and reproducible, and should provide the key elements for treatment planning.

[Imaging of the post-irradiation larynx for laryngeal and hypopharyngeal carcinomas]. / L'imagerie dans le suivi post-thérapeutique des cancers pharyngo-laryngés.

Imaging has a key role in the follow-up of patients treated for laryngeal or hypopharyngeal carcinoma. Imaging is complementary to clinical evaluation and has three goals: evaluation of chemo and radiation therapy; differentiation between complications and tumour recurrence; early detection of tumour recurrence, prior to clinical manifestations. Imaging may allow early detection of recurrences, when salvage treatment may still be less radical.

[Sonography of the eye and orbit with a multipurpose ultrasound unit]. / Echographie de l'oeil et de l'orbite avec un échographe polyvalent.

Our goal is to help echographists and radiologists become familiar with the various possibilities indications, technique and results of ophtalmic ultrasonography. We used a multipurpose ultrasound unit. The frequency of the transducer has to be equal or superior to 7.5 MHz. Color Doppler allowing the study of low flows is useful. The study must be standardized: the first step is to obtain measurements of both eyes. Then the entire globe is systematically evaluated. Finally, the orbital structures and vessels of the eye and orbit are analized. After a review of the anatomy and the normal sonographic features, the main indications are described as well as the main pathologies. Special attention is paid to intravitreal hemorrhage, retinal and choroidal detachments, intraocular tumors and orbital space occupying lesions.

[Inflammatory presentation of a cavernous dural fistula: diagnosis with color and pulse Doppler imaging]. / Fistule durale caverneuse d'allure inflammatoire: diagnostic avec écho-Doppler couleur et pulsé.

We report a case of a cavernous dural fistula in a 54-year-old man the source of inflammatory ocular symptoms. Poorly adapted treatment with corticosteroids led to iatrogenic complications. We will attempt to show the advantage of color Doppler imaging for the diagnosis of this infrequent lesion. The only indication of digitalized angiography is for endovascular treatment.

[Vascular tumours and malformation of the orbit]. / Les lésions vasculaires de l'orbite.

Vascular diseases are an important part of orbital pathology. We describe vascular tumours of the orbit and vascular diseases with repercussion on the orbit, from intra or extra orbital origin. The classification of these abnormalities is difficult and several terms are used to describe the same histological entity. The objective of this work is, using the current classification, to illustrate the different imaging aspects of the most frequent vascular diseases of the orbit.

[Imaging of postoperative failures and complications in stapes surgery for otosclerosis]. / Imagerie des échecs et complications post-opératoires de la chirurgie de l'otospongiose.

Otosclerosis (OS) is a dysplasia of the otic capsule located in most cases on the anterior margin of the oval window or fissula ante fenestrum. Progressive conductive hearing loss is the major clinical symptom, due to stapedovestibular ankylosis. Stapes surgery is the only effective treatment of OS, with excellent functional results in more than 90% of cases. However, failures and complications of the surgery may be observed. In theses cases, the etiologic work-up includes imaging evaluation (CT and MRI). Imaging findings are extremely useful in the therapeutic decision. Surgical failure represents 80% of the causes for surgical revision. The main causes of failure are: displacement of the prosthesis, fibrosis of the oval window, erosion of the long process of the incus, incudo-mallear dislocation, obliterative otosclerosis. CT is essential for diagnosis. MR imaging is rarely indicated in the work-up of surgical failures. Labyrinthine complications account for less than 20% of surgical revisions. Etiologies of labyrinthine complications are: intravestibular penetration of the prosthesis, perilymphatic fistula, intra-vestibular granuloma, labyrinthitis and intravestibular bleeding. CT and MRI are complementary for the work up of these complications.

[Imaging of neuro-ophthalmological emergencies]. / Imagerie des urgences en neuro-ophtalmologie.

MRI often is mandatory in the diagnostic work-up of visual loss, visual field alterations and oculomotor problems. It is performed emergently in patients with painful diplopia associated to mydriasis, to exclude aneurysm, or in patients with painful Horner syndrome to exclude dissection of the internal carotid artery. CT scan in emergency remains useful in case of acute lateral hemianopsia or acute post traumatic visual loss. Progressive neuro-ophthalmological symptoms may require imaging examination in a short delay to define the therapeutic strategy: monocular transient blindness (dissection or carotid stenosis), progressive visual loss (optic nerve compression), bitemporal hemianopsia (optic chiasm lesion), painful visual loss (optic neuritis). A very precise clinical indication is helpful for the choice of imaging protocol and to improve its diagnosis value.

[How to investigate a patient with exophthalmos?]. / Comment explorer une exophtalmie?

Exophthalmos is the main symptom revealing orbital masses. This sign needs to be imaged mainly by MRI and/or CT. As Graves disease is the main etiology of exophthalmos, CT scan should be performed as the initial imaging modality. Indications for US and Doppler are mostly limited to the study of ocular masses, and eventually may help the characterization of extra-ocular lesions. In all cases, imaging is useful to characterize: the precise location of the lesion which can be the intra-conal space (including muscles), the extra-conal space (associated or not to an extra-orbital lesion), or the eyeball; the features of the lesion (density, signal, enhancement.). These findings are used to generate a differential diagnosis. Imaging is also useful to precise the extension of the mass, and in some cases to select the appropriate surgical approach, and for follow-up.

[Transcranial Doppler imaging: state of the art]. / Echo-Doppler transcrânien: Mise au point.

Initially introduced in the early 1980's, transcranial Doppler followed by transcranial Doppler sonography were used in neurosurgical units for management and follow-up of intracranial vasospasm in patients with subarachnoid hemorrhage. This imaging technique, more sensitive and less invasive than catheter angiography, also proved to be of value for diagnosis of intracranial atherosclerosis, management of patients with head trauma, and evaluation of collateral flow through the circle of Willis. Doppler US would also allow prediction of the risk of symptomatic embolic events through monitoring of HITS. Evaluation of the middle cerebral arteries during carotid occlusion testing is useful for evaluating the need for particular revascularization techniques. Finally, Doppler imaging is useful to assess patients with possible brain death. A recent advance in Doppler imaging is the ability to provide a three-dimensional projection (3D Doppler) of the intracranial arteries enabling improved detection and evaluation of stenoses involving the circle of Willis and improved characterization of intracranial aneurysms. These new applications benefit from the use of US contrast agents and harmonic US imaging.

Pilocytic astrocytoma: unusual feature.

Juvenile pilocytic astrocytoma is a well-defined brain tumor. It most often occurs in children and young adults. It is located in the posterior fossa and has typical imaging features, associating cystic and strongly contrast enhancing mural nodule. After complete surgical removal, its prognosis is excellent. Adult cases are seldom observed. They develop almost exclusively within the cerebral hemispheres and share the same imaging and prognostic characteristics as the pediatric forms. We describe the case of a 42-years-old man presenting with a huge heterogenous posterior fossa lesion. Histopathological analysis of the lesion after surgical resection diagnosed a juvenile pilocytic astrocytoma. These peculiar location and imaging features in an adult patient may be misdiagnosed for infectious lesions and must be recognized.

Hemodynamic effect of iodinated high-viscosity contrast medium in the rat kidney: a diffusion-weighted MRI feasibility study.

RATIONALE AND OBJECTIVES: To assess the abilities of dynamic diffusion-weighted MRI to demonstrate the effects in vivo of a high-viscosity iodinated contrast agent on medullary and cortical blood flow in the rat kidney. METHODS: Dynamic diffusion-weighted, echoplanar MR images obtained from five b-value single-shot acquisitions and their isotropic apparent diffusion coefficient maps were obtained from nine rats anesthetized by pentobarbital sedation, before and after intravenous injection of a high-viscosity, dimeric iso-osmolar iodinated contrast medium (iodixanol), and compared with those obtained from four control rats that received saline. RESULTS: The mean baseline apparent diffusion coefficient values were 1.64 +/- 0.05 x 10(-3) mm2/s for the cortex and 1.75 +/- 0.06 x 10(-3) mm2/s for the medulla. In the iodixanol group, a significant decrease in renal diffusion was observed at 12 minutes and lasted at least until 24 minutes. The decrease in diffusion occurred earlier for the cortex and lasted less than for the medulla. There was no significant modification in diffusion over time in the control group. CONCLUSIONS: This preliminary experience in rats shows that dynamic diffusion-weighted MRI can be used to study noninvasively the in vivo renal hemodynamic response after injection of iodinated contrast.

[Value of MRI and computerized tomography scanner in oro-buccopharyngeal cancers with bone invasion]. / Apport de l'IRM et du scanner dans les cancers oro-buccopharyngés avec envahissement osseux.

The purpose of this prospective study was to assess the impact of Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) in the surgical management of carcinomas with mandibular bone invasion. Thirty-five patients with squamous cell carcinoma of oral cavity or oropharynx, with mandibular spread, were studied with both imaging methods before surgical treatment. We compared the radiographic findings with histologic examination. Sensitivity of CTScan and MRI was respectively 25% and 80% to identify bone invasion. CTScan was found less effective in the assessment of bone invasion before mandibular resection and was considered more radiologist dependent. MRI is becoming the imaging method of choice for these cancers, despite inherent disadvantages including limited availability and increased cost over CTScan. MRI is accurate in large oropharyngeal tumors with extension of base of tongue and pterygoid muscle, and to study bone invasion before surgery in oral cavity tumors.

Dysgenesis of the internal carotid artery associated with transsphenoidal encephalocele: a neural crest syndrome?

We describe two original cases of internal carotid artery dysgenesis associated with a malformative spectrum, which includes transsphenoidal encephalocele, optic nerve coloboma, hypopituitarism, and hypertelorism. Cephalic neural crest cells migrate to various regions in the head and neck where they contribute to the development of structures as diverse as the anterior skull base, the walls of the craniofacial arteries, the forebrain, and the face. Data suggest that the link between these rare malformations is abnormal neural crest development.