Biomedical subjects
Publications and source records attributed to D Doyon.
Confusion developed in a 44-year-old man, who had diarrhoea and weight loss for three months. Jejunal biopsy showed infiltration by PAS-positive macrophages, indicating Whipple's disease. Cranial MRI disclosed multiple lesions mainly in the white matter and grey-white matter junction better demonstrated after gadolinium injection.
Two cases of central nervous system Behçet's disease, studied by gadolinium-enhanced MRI, are presented. In one patient, whose clinical picture was dominated by a brain syndrome, the gadolinium enhancement resolved with clinical improvement, although the hyperintense areas in the mesencephalon on T2-weighted images persisted. In the second, who had a pseudobulbar palsy and a mild right hemiparesis, there were many abnormal areas, but an enhancing focus in the posterior limb of the left internal capsule was probably the lesion responsible for the hemiparesis.
Lumbar subdural abscesses have rarely been reported in the literature, and the complications of epidural infiltrations predominantly include arachnoiditis, meningitis and epidural abscesses. We report a case of lumbar subdural abscess confirmed by surgery, which appeared following epidural infiltration for lumbar sciatica and was examined with computed tomography and MRI. Only the latter technique alone showed the abscess, after gadolinium injection, and established its intradural site.
Routine volume measurement techniques most often produce a rough approximate with poor accuracy for smaller structures. The results are generally improved by increasing the examination time, so that the technique then becomes unusable in daily practice. We propose a semiautomated volume calculation method with MRI, and its application to the surveillance of non-operated acoustic neuromas. This calculation technique, based on a threshold-setting method, allows accurately delineating the contours of the structures to be measured on each section and quickly calculating the total volume. After testing its reliability on control volumes, this techniques has been used to assess the evolutive nature of 16 acoustic neuromas with mild symptoms in 15 patients rejected for surgery. The radiological examinations were 428 days apart in average. On the basis of the obtained results, a theoretic tumor doubling time was calculated, thus allowing comparison between all patients. All controlled neuromas had a theoretic doubling time ranging from 427 to 4,884 days, corresponding to little- or non-evolutive lesions, which may be explained by the series selection bias excluding evolutive tumors referred to surgery. Owing to its rapidity and easy use, this semiautomated volume calculation technique for MRI seems to be very interesting as it allows reliably quantifying a volume variation that is usually estimated approximately.
MRI has transformed the diagnosis of cavernous hemangioma, a hamartoma that is most often located in the central nervous system. The appearance of this lesion is fairly characteristic with MRI. This technique has allowed distinguishing multiple forms. Encephalic sites are most frequent, with rare medullary sites, and double brain and cord locations are exceptional. Many cases of single or multiple brain involvement have now been reported. Series of medullary involvement are much less frequent and include few cases. Double sites in the brain and cord are exceptional. The authors present a case of cavernous hemangiomas of the central nervous system with multiple encephalic sites associated with a single medullary site confirmed by surgery.
Owing to computer programs, computed tomography allows obtaining sections of the facial structures in all spatial planes and to "pile up" all sections to reconstruct the structural unit studied. In addition, these images can be reconstructed by selecting a density threshold, for example that of dentin or of enamel, isolating those from their bony environment, and thus the patient's dental arch can be visualized as if one was manipulating a pair of dental models. The first results obtained with this technique are presented, and they seem to be highly promising.
Spinal subdural hematomas are rare. They should be considered in the diagnosis of spinal cord compression. Prompt surgical treatment, if it is performed, may lead to complete recovery of the neurological deficit. But such treatment is not always necessary because of possible spontaneous recovery. MRI appears to be the method of choice to reveal hematomas even of small size and to follow up patients after treatment.
The authors report about their experience with the merits of the normal systematization of epidural fat with MRI. On sagittal sections, this fat has a variable appearance, but its location along the spinal canal is constant. On axial sections, its morphology is suggestive of the level of section: cervical, upper or lower thoracic, lumbar. Some changes in this fat are precious data to explain local hypertrophy (scoliosis) or to locate an intra- or extradural process.
The authors perform a retrospective study of 65 spines examined with MRI. They specify the distribution of normal posterior epidural fat and establish the relationship between the anteroposterior thickness of epidural fat and the sagittal diameter of the spine on axial sections. On sagittal sections, the fat has a variable appearance, but a constant location along the spinal canal.
The authors report their experience and method for computed tomography of maxilla and mandible before endosseous implant surgery. CT defines indications of implant surgery, avoiding useless operations and sometimes allowing implant surgery that seemed impossible on standard X-rays. It provides good preoperative assessment, precising diameter and length of implant, exact location and state of anatomic structures to be avoided, quality of bone and ideal implant axis.
132 cases of malformative syringomyelia have been studied at the C.I.E.R.M. (Interdepartmental Magnetic Resonance Center) of Bicêtre Hospital. The authors describe their technique for the exploration on the cord in case of suspected intramedullary cavitation, and emphasize the morphological and evolutive aspects of these abnormalities, whether they have been operated or not.
Hypopituitarism and diabetes insipidus are often idiopathic conditions. A retrospective study of 6 cases of diabetes insipidus and 8 cases of partial or global idiopathic anterior hypopituitarism has shown that MRI is of considerable value to detect abnormalities of the pituitary stalk or hypothalamo-pituitary "relay". On the basis of MRI findings, some cases of idiopathic hypopituitarism can now be grouped together in a new entity which may be called hypopituitarism due to neonatal transection of the pituitary stalk.
In order to assess the value of MR in the depiction of intracranial nerves, we retrospectively reviewed 60 patients investigated over a period of 2 years. The aim of this study was: 1) to assess the score of MR in the detection of cranial nerves III to XII; 2) to determine accurate landmarks allowing for easy detection of those cranial nerves. Cranial nerves III, V, VII, VIII are well seen (70 to 100%), very often in both axial, sagittal and coronal sections. Nerves IX to XII are correctly studied only on axial planes [81 and 83%), but it is difficult to distinguish between the vagal nerve and the glossopharyngeal and spinal nerves. Due to their oblique direction and small size, fourth and sixth nerves are rarely visualized. The more important landmarks are the chiasma, the colliculi, the Meckel's cave, the internal auditory canal, the jugular foramen, the hypoglossal canal and the different brainstem structures. We suggest the following scanning protocol: short spin echo sequences (TR = 600 ms, TE = 20 msec), 3 to 5 continuous sections, 16 to 20 cm field of vue with respectively 4 or 2 excitations, 256 x 256 matrix, with at least one acquisition plane (axial), but preferably two or three planes. Thus MR is sensitive exam in the recognition of cranial nerves, and it must be the first step exam in patients presenting with cranial nerve disease.
The clinical and magnetic resonance (MR) imaging findings in 20 patients with MR evidence of occult cerebrovascular malformations (OCVMs) were retrospectively analyzed. Of 27 lesions followed up throughout a mean period of 18 months, eight showed obvious evolution on MR images (four cases of regression and four cases of new bleeding). Three new independent lesions were disclosed. Clinical evolution was discordant with MR findings in five patients. In the other patients, topography of the lesion, mass effect, and location of the hemorrhage could explain clinical data. The dynamic nature of OCVMs must be considered in decisions on therapeutic management.
In order to assess the value of MRI in the depiction of intracranial nerves, we retrospectively reviewed 60 patients investigated over a 2-year period. The purposes of this study were: 1) to determine the score of MRI in detecting cranial nerves III to XII, and 2) to establish accurate landmarks for easy detection of these nerves. Cranial nerves III, V, VII and VIII are well seen (70 to 100%), very often on axial, sagittal and coronal sections. Nerves IX to XII are correctly studied only on axial planes (81 and 83%), but it is difficult to distinguish between the vagus nerve and the glossopharyngeal and spinal nerves. Due to their oblique direction and small size, nerves IV and VI are seldom visualized. The most important landmarks are the chiasma, the colliculi, Meckel's cavity, the internal auditory canal, the jugular foramen, the hypoglossal canal and the brainstem structures. We suggest the following scanning technique: short spin-echo sequences (TR 600 ms, TE 20 ms), 3 to 5 mm thick contiguous sections, 16 to 20 cm field of view with 4 or 2 excitations respectively, 256 x 256 matrix, and at least one acquisition plane (axial plane), but preferably two or three planes. MRI is a sensitive examination in the recognition of cranial nerves. It should be the first-step exploratory procedure in patients with cranial nerve pathology.
The epidural hematoma of the spine is a seldom disease and a neurosurgical emergency. MRI allows an early diagnosis. Only surgery can provide a good anatomical and functional prognosis.
The neurilemmoma of the pterygoid fossa are very rare. The authors reports one case of a 32 years old man, with such a neoplasm, exteriorized on the lateral facial region (area of the glandula parotis) clinical and radiological data could not differentiate benign neurilemmoma or slow evolutive sarcoma and have justified a conservative latero facial approach of the neoplasm. The final diagnosis of ancient neurilemmoma was based on both light and electron microscopy morphology.
Intradural lipoma is a rare and slow growing tumor which represents 1% of all intra-spinal tumors. This tumor is often associated with dysraphism. It can be isolated without any associated vertebral or cutaneous malformations. Its clinical evolution is extremely slow and progressive. The fatty composition of this type of tumor allows easy detection by CT as well as by MRI. MRI permits: Reliable and direct assessment (in 3 different plans) of the extension of the lesion. An excellent post operative control.