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Biomedical subjects

D Doyon

Publications and source records attributed to D Doyon.

At least 199 records · Page 11Linked to original sources
PubMedDate not supplied

Magnetic resonance findings in 92 acoustic neuromas.

A retrospective analysis of the MR findings in 92 cases of acoustic neuromas is presented. The method of examination included in all cases intravenous injection of Gadolinium (Gd-DTPA or DOTA) with realization of sections in the axial and coronal planes. In 21 cases native MR studies were performed in the axial plane, before Gadolinium injection, with T1WI (n = 21), and T2WI (n = 6) images. Tumors were strictly intracanalar in 19 cases (20.7%), only localized in the cerebellopontine angle (CPA) in 5 cases (5.4%), and in 68 cases (73.9%) the tumors had intra- and extracanalar components. In this last group of lesions, 63.2% completely filled the internal auditory canal (IAC), and 36.8% occupied the internal portion of the IAC. In most cases (85.3%) the mean diameter of the CPA component was less than or equal to 2.5 cm. Lesions were more frequently homogeneous (58.8%) after Gd i.v.-enhancement. Heterogeneity was noted mainly in large lesions (greater than 2.5 cm: 100%). In all cases but one, the tumors were round, or oval-shaped, well-delineated, and did not present significant contact with the petrous bone. In 80.9% of CPA lesions, the center of the tumor was posteriorly excentered in relation to the internal auditory canal, whereas it was centered in 16.2% of cases. Widening of the IAC was observed in 51.1% of cases. In 45.2% of tumors of the CPA, smoothing of the posterior edge of the porus was visible.

Adolescent↗
PubMedDate not supplied

Post-traumatic diabetes insipidus: MR demonstration of pituitary stalk rupture.

We report the magnetic resonance findings in a case of post-traumatic diabetes insipidus (DI). They consisted of pituitary stalk rupture shown on both coronal and sagittal planes with associated disappearance of the normal high signal intensity of the posterior lobe on T1 images. This last sign, previously described in nontraumatic DI, appears to represent a finding indicating nonfunctioning neurohypophysis.

Adult↗
PubMedDate not supplied

MRI in chronic progressive radiation myelopathy.

OBJECTIVE: Our goal was to assess medullary lesions in patients suffering from chronic progressive radiation myelopathy (CPRM) using MRI. MATERIALS AND METHODS: In a group of 10 patients suffering from CPRM, MRI findings (11 examinations), radiation protocols, and patient prognoses were reviewed. RESULTS: A cord enlargement was demonstrated in five cases, whereas four cases presented with medullary atrophy. As demonstrated by MRI, radiation-induced medullary lesions progressed toward cord atrophy in one patient. When MRI and/or comparison myelogram were performed within 8 months following the onset of the myelopathy, a cord enlargement was usually encountered. When the patient was evaluated > 8 months after the first neurological symptoms, a cord atrophy was always demonstrated. Medullary lesions extended beyond the boundaries of the radiation field in 67% of the cases. However, with the exception of one case, the main focus of the cord damage was included within an irradiated cord segment. An enlarged cord was often associated with a neurologic deterioration and a fatal outcome. In patients with cord atrophy, the neurologic deficit was often static and survival rates were better. CONCLUSION: These results suggest a revision of classic criteria used for the diagnosis of CPRM. By demonstrating cord lesions, MRI helps to establish disease prognosis.

Adolescent↗
PubMedDate not supplied

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.

Cerebellar Neoplasms↗
PubMedDate not supplied

Ventriculus terminalis of the conus medullaris: MR imaging in four patients with congenital dilatation.

MR findings in four patients with MR evidence of congenital cystic dilatation of the ventriculus terminalis were reviewed retrospectively. The ventriculus terminalis is a small cavity of the conus medullaris that forms during embryonic development as result of canalization and retrogressive differentiation. The dilated ventriculus terminalis appears on MR images as a small ovoid cavity with regular margination; intralesional fluid resembles cerebrospinal fluid on all MR sequences. After injection of contrast material, MR imaging shows no enhancement of the cyst or its wall, and thus differentiates congenital dilatation of the ventriculus terminalis from cystic tumors, which occur more frequently in this region.

Adult↗
PubMedDate not supplied

[Ante- and posthypophyseal insufficiency with infundibulum abnormalities].

The hypopituitarism and the diabetes insipidus are often idiopathic. A retrospective study of 6 cases of diabetes insipidus and 8 cases of partial or total idiopathic antehypophyseal insufficiency has shown the value of MRI to demonstrate anomalies of the infundibulum or hypothalamic-hypophysis "stages". MRI allows to bring together some cases of idiopathic hypopituitarism in a new entity which is the hypopituitarism due to a newborn section of the infundibulum.

Adult↗
PubMedDate not supplied

[Very severe haemorrhages of the lower digestive tract. The value of emergency arteriography (author's transl)].

The authors report six cases of massive lower gastro-intestinal tract haemorrhage, diagnosed by angiography. They emphasize the value of angiography performed on an emergency basis. It is the most reliable diagnostic modality to know before surgery the precise localization of the bleeding point and sometimes its aetiology. The interest and the problems of therapeutic angiography are discussed.

Adult↗
PubMedDate not supplied

[Comparative study of Hexabrix and Lipiodol UF in sialography].

Many new lipid- and water-soluble contrast media can be used in sialography, the three main criteria of choice being the cost, the quality of filling, particularly of the parenchyma, and its evacuation and clinical tolerance. Duroliopaque possesses very similar physicochemical properties to those of Lipiodol UF, but a sufficiently satisfactory filling of the parenchyma is not obtained. Comparison of Lipiodol UF and Hexabrix in parotid and submaxillary contrast imaging showed good clinical tolerance for both products, but improved parenchymatous filling with Lipiodol UF. However, the more effective glandular evacuation with Hexabrix makes this the product most suitable at the present time for morphologic exploration of salivary glands.

Contrast Media↗
PubMedDate not supplied

[Developmental x-ray computed tomographic and magnetic resonance studies of swinging frontal cerebral radionecrosis].

Changes in CT scan and NMR imaging findings are reported in a patient with cerebral radiation lesions affecting first the left and then the right frontal cerebral cortex. This case is exceptional since voluntarily and by necessity the radiation dose for an inextirpable frontal sinus tumor had been very high. As a result of this radiotherapy, a survival of about 10 years was obtained under good conditions, with cerebral lesions provoking relatively moderate functional consequences.

Brain↗