[Early cerebral lesions in HIV infection. Postmortem radio-pathologic correlations in non-AIDS asymptomatic seropositive patients]. / Lésions cérébrales précoces au cours de l'infection par le VIH. Corrélations radiopathologiques post mortem chez des séropositifs asymptomatiques non SIDA.

In order to evaluate the diagnostic and prognostic value of MRI in the very early stages of HIV infection, we have compared the results of postmortem brain MRI and neuropathological studies in 7 asymptomatic HIV seropositive individuals, 8 seronegative controls with similar cause of death and 6 patients who died of AIDS in the absence of focal cerebral changes (opportunistic infection or tumour). Cerebral atrophy was consistently evaluated by both techniques. Seropositive asymptomatic cases were significantly more atrophic than the seronegative controls and significantly less atrophic than AIDS patients. Small high signal intensity areas in the white matter and basal ganglia were not significantly more frequent in seropositives than in seronegatives. No corresponding lesion was found at neuropathological examination. Diffuse myelin pallor of the cerebral white matter on myelin preparation was somewhat more severe in seropositive asymptomatic cases than in seronegative controls and less than in AIDS cases. However, these differences were not statistically significant. No significant correlation could be found between neuropathological myelin pallor and diffuse signal abnormalities of the white matter on MRI. We conclude that brain abnormalities are present at the early asymptomatic stage of HIV infection. These include vasculitis with opening of the blood brain barrier and consequent myelin pallor and gliosis of the white matter, and moderate brain atrophy. However MRI correlates are discrete or non specific on post mortem examination, and some probably correspond to scars of transient vascular inflammation. It is very unlikely that MRI examination has any diagnostic or prognostic value at the early stages of the disease.

[CMV and VZV encephalitis in AIDS]. / Encéphalites a CMV et VZV au cours du SIDA.

MATERIAL AND METHODS: Eighty patients were followed up prospectively. Histological correlation was obtained in 25 cases. All MRI examinations were performed on at 0.5 Tesla in T1-weighted sequences with and without gadolinium injection, and in axial or frontal T2-weighted spin echo sequences. Histological confirmation was obtained 30 days on average after the last MRI examination. Immunohistochemical stainings were performed in search of CMV, VZV, toxoplasma, HIV antigen and lymphoma. RESULTS: CMV meningoencephalitis was found in 6 cases. In 3 of these it was manifested by atrophy, either isolated or associated with high signal intensity punctiform areas. Histology detected cortical or subcortical microglial nodules. In 2 cases MRI displayed abnormalities of subependymal nodular signals without enhancement, associated with punctiform abnormalities of subcortical signals. Histology showed subependymal foci of necrosis and abnormalities of white matter. In one case, MRI showed a ventriculitis confirmed by histology. VZV meningoencephalitis was diagnosed in 2 cases. MRI displayed abnormal basal ganglia related to meningitis (n = 1). All abnormalities were confirmed at histology. CONCLUSION: Some images (ventriculitis, infarction in basal ganglia, abnormal subependymal signal) would suggest VZV and CMV encephalitis. Other images (abnormalities of punctiform signals or atrophy) are not specific.

Kinetics of elimination and acute consequences of cerebral air embolism.

The pathophysiology of arterial air embolism inducing brain injuries remains unclear. Previous experiments demonstrated the usefulness of computed tomography (CT) in the detection of air emboli in canine brain. This canine study investigates CT's ability to detect small air bubbles and to determine the kinetics of air elimination from cerebral arteries and its relationship with clinical, electroencephalographic (EEG), and histological manifestations. CT detects small air embolism, and intracerebral air volume strongly correlates with injected air dose (r2 = 0.86, p = 2 x 10(-3)). Air clearance time significantly depends on intracerebral air volume (r2 = 0.86, p = 0.04) and on the number of bubbles (r2 = 0.71, p = 0.03), whereas half-life of air elimination does not. No relationship was found between injected air dose, air clearance time, intracerebral volume of air, and clinical, EEG, and histological findings. The data indicate that CT accurately detects small air bubbles in the early course of cerebral air embolism, that air elimination from cerebral arteries follows a first-order compartment model, and that early CT findings do not correlate with clinical, EEG, and histological manifestations.

[Computed tomography in thoracic pathology]. / Le scanner en pathologie thoracique.

The fundamental principles of computed tomography (CT), its clinical applications and costs are presented followed by the indications and results in diseases of the mediastinum, the oesophagus, heart and great vessels, and the lung and pleura. The CT scan can give the precise localization and density of mediastinal tumours and be used to distinguish thymomas, goiters, lymph nodes, lymphomas, neurinomas and different bronchogenic and pleuropericardial cystic formations. The operability of oesophageal cancer can also be determined. In cardiovascular diseases, the CT scan is particularly useful to identify inborn anomalies, aneurysms, aortic dissection or caval compression or thrombus formation. In lung diseases, the indications for a CT scan are particularly important in bronchopulmonary cancer, tuberculosis, bronchopathies and chronic lung diseases. In bronchogenic cancer, for example, the CT scan is not only a major diagnostic tool but is also particularly useful in determining the prognosis and for following the effectiveness of treatment. The CT scan can be used to identify both effusions of liquid and gas as well as pleural reactions producing thick membranes of importance for both aetiology and later follow-up. Bronchectasis can be identified on serial sections where the degree of extension can be measured. CT scan is also indicated in patients with emphysema, both for evaluating extension and follow-up. Finally the indications and contraindications for interventional computed tomography, particularly in guiding needle biopsies, is presented.

Varicella-zoster virus infection of the central nervous system in the acquired immune deficiency syndrome.

Productive varicella-zoster virus (VZV) infection of the central nervous system (CNS) was demonstrated in 11 acquired immune deficiency syndrome (AIDS) patients using immunocytochemistry and in situ hybridization. A characteristic zoster skin eruption was seen in only four cases. From our own series and 11 other cases in the literature, we identified five clinico-pathological patterns of VZV infection of the CNS in AIDS patients which could occur simultaneously. (i) Multifocal encephalitis predominantly involving the white matter, likely to be due to haematogenous spread of the infection was found in four cases. (ii) Ventriculitis was found in three cases. In two cases there was complete acute or chronic necrosis of the ventricular wall with marked vasculitis; in the third, the ependymal lining appeared irregular with foci of VZV-infected ependymal cells, some of which protruded into the ventricular lumen. (iii) Acute haemorrhagic meningo-myeloradiculitis with necrotizing vasculitis was observed in two cases. In one, this was associated with ventriculitis and was possibly due to shedding of infected ependymal cells into the ventricular lumen and secondary seeding of the CSF. (iv) Focal necrotizing myelitis was seen in one case. It followed cutaneous herpes zoster and was considered to result from neural spread from the diseased dorsal root ganglion similar to cases previously described of encephalitis limited to the visual system following VZV ophthalmicus, or bulbar encephalitis following a trigeminal zoster. (v) Vasculopathy involving leptomeningeal arteries and causing cerebral infarcts was seen in four cases, it was associated with meningitis in most cases. These findings are in keeping with the observation in non-AIDS patients that VZV spread to the CNS may follow different routes. Our study tends to show that VZV infection of the CNS occurs more frequently in AIDS than previously suspected and suggests that it must be considered as a diagnosis in cases of encephalitis, ventriculitis, focal myelitis, acute myeloradiculitis and cerebral infarcts in these patients.

MR imaging of posteromedial and posterolateral stabilisers of the knee: anatomic basis and patterns of lesions in knee injuries.

The angular points are the ligamentous and tendinous structures that reinforce the posteromedial and posterolateral capsule of the knee and share in fixation of the posterior horns of the menisci. They are often damaged in acute injuries and this is usually associated with ruptures of the cruciate and collateral ligaments and may add to the degree of laxity. We describe the normal appearance of these structures in terms of the sectional anatomy, correlated with the lesional appearances of complete and incomplete ruptures and associated meniscal detachments as shown by clinical testing and arthrotomy findings.

Periventricular leukomalacia: correlation between MR imaging and autopsy findings during the first 2 months of life.

PURPOSE: To correlate magnetic resonance (MR) imaging and pathologic findings in premature infants with periventricular leukomalacia (PVL). MATERIALS AND METHODS: Eight premature infants with PVL who died after 3-7 weeks of life were studied with in vivo T1-weighted MR imaging, and imaging patterns were compared with hypoxic-ischemic injuries at pathologic analysis. RESULTS: Cavities were seen as zones of absent or weak signal intensity. Translucent sparsely cellular zones appeared as areas of intermediate intensity, and cellular reactions were seen as limited linear or punctate zones of increased intensity, usually less intense than the cortex. MR imaging provided reliable depiction of these lesions, with adequate estimation of their volume and topography. However, the extent of periventricular cellular lesions was underestimated. In one case, blood seen as hyperintense or isointense zones masked portions of cystic lesions, and in three cases small thalamic lesions were overlooked. CONCLUSION: With the above limitations, T1-weighted MR imaging offers precise evaluation of PVL.

Temporal and spatial assessment of normal cerebrospinal fluid dynamics with MR imaging.

The purpose of this study was to measure normal cerebrospinal fluid (CSF) pulsations within the intracranial and upper cervical subarachnoid spaces and the ventricular system. Phase contrast cine MR sequences were performed in sagittal and axial planes on 13 volunteers with flow encoding in the craniocaudal direction. CSF pulsations displayed considerable variations in healthy subjects, depending both on measurements localization and subjects, with CSF peak velocities ranging from 0 to 7 cm/s. In the subarachnoid spaces, the highest velocities occurred in the anterior location and increased from the cerebellar pontine angle cisterns towards the lower cervical spaces. In the ventricular system, the highest velocities occurred through the aqueduct of Sylvius. CSF flow within the third ventricle seemed to reflect a circular motion. There was a caudal net CSF flow in the aqueduct whereas in the upper cervical spaces net CSF flow was caudal anteriorly and cranial laterally. Velocity profiles of CSF pulsations demonstrated arterial morphology. After the R wave, caudal systolic motion was first observed in the posterior subarachnoid spaces, soon after in the anterior subarachnoid spaces and later in the ventricular system. Considering the morphology of CSF pathways, three successively initiated phenomena may explain the temporal course of CSF motion: the systolic expansion of the main arteries at the base of the brain, the systolic expansion of the cerebrospinal axis and, finally, the systolic expansion of the choroid plexuses.

The meniscofemoral ligaments: magnetic resonance imaging and anatomic correlations.

Examination of the knee joint by magnetic resonance imaging (MRI) is a noninvasive technique of proven reliability as regards lesions of the menisci and ligaments. It provides good definition of the different anatomic structures. The meniscofemoral ligaments have been observed with varying frequency and may be responsible for false images. However, it is important to detect them in cases of hypermobile discoid menisci of the 'Wrisberg ligament type' in order to guide the surgeon in their excision during total meniscectomy. We have attempted to assess the ability of MRI to visualise the meniscofemoral ligaments in correlation with an anatomic study and to identify certain anatomic pitfalls. This study will allow better investigation of the hypermobile menisci associated with the meniscofemoral ligaments. A clinical case is reported to illustrate its practical importance.