[Development of immunizing agents against dengue]

The four serotypes of dengue flaviviruses are transmitted mainly by the Aedes aegypti mosquito, and some epidemics have been attributed to Ae. albopictus, Ae. polynesiensis, and various species of the Ae. scutellaris complex. The risk factors involved in dengue mortality and morbidity are related to the human host (genetic characteristics of infected persons; lifestyles, immune status, and health conditions of people; basic sanitation of dwellings; and water supply) and to the virus (genetic variability between and among serotypes, different pathogenicities, and geographic distribution). Notwithstanding the lack of knowledge of the immunopathobiology of dengue fever, important advances have been made in terms of a protective immune response, using attenuated dengue viruses or antigens produced by means of recombinant technologies. Efforts have been made since the 1940s to develop dengue vaccines. Immunity acquired from natural infection is specific for each serotype, and as many as three different serotype infections have been reported in one individual. For this reason, a tetravalent vaccine may likely be needed. Candidate vaccines against the four serotypes have been tested in volunteers and have proven to be immunogenic and safe. Although attenuated live virus vaccines are promising, more study is needed regarding their effectiveness and safety. Currently, several studies are ongoing to develop dengue vaccines using antigens from structural proteins (particularly E glycoprotein) and nonstructural proteins, with recombinant DNA technology and other biomolecular technologies. With the same goal, various expression vectors are being used, including Escherichia coli, baculovirus, vaccinia virus, and yellow fever virus. Unfortunately, no satisfactory results have been obtained in humans. The need for effective dengue vaccines is great, given the serious worldwide problem of the transmission of the four serotypes. Effective immunization against dengue would contribute to its prevention, with a positive cost-benefit relationship. Endemic dengue affects young children, and they should be immunized through the Expanded Program on Immunization.

Superior labrum anterior-posterior lesions: diagnosis with MR arthrography of the shoulder

PURPOSE

To determine the accuracy of magnetic resonance (MR) arthrography in the diagnosis of superior labrum anterior-posterior (SLAP) lesions of the shoulder.

MATERIALS AND METHODS

From January 1995 to June 1998, MR arthrography of the shoulder was performed in 159 patients with a history of chronic shoulder pain or instability. Fifty-two patients underwent arthroscopy or open surgery 12 days to 5 months after MR arthrography. Diagnostic criteria for SLAP lesion included marked fraying of the articular aspect of the labrum, biceps anchor avulsion, inferiorly displaced bucket handle fragment, and extension of the tear into the biceps tendon fibers. Surgical findings were correlated with those from MR arthrography.

RESULTS

SLAP injuries were diagnosed at surgery in 19 of the 52 patients (37%). Six of the 19 lesions (32%) were classified as type I, nine (47%) as type II, one (5%) as type III, and three (16%) as type IV. MR arthrography had a sensitivity of 89% (17 of 19 patients), a specificity of 91% (30 of 33 patients), and an accuracy of 90% (47 of 52 patients). The MR arthrographic classification showed correlation with the arthroscopic or surgical classification in 13 of 17 patients (76%) in whom SLAP lesions were diagnosed at MR arthrography.

CONCLUSION

MR arthrography is a useful and accurate technique in the diagnosis of SLAP lesions of the shoulder. MR arthrography provides pertinent preoperative information with regard to the exact location of tears and grade of involvement of the biceps tendon.

Systemic mastocytosis: MRI of bone marrow involvement

Systemic mastocytosis (SM) is an abnormal proliferation of mast cells, located in different structures: skin, bone marrow, spleen, liver and lymph nodes. Magnetic resonance imaging was prospectively performed in ten patients diagnosed by bone marrow biopsy in order to describe the different patterns of bone marrow involvement. Coronal T1-weighted spin-echo images were obtained in vertebral, pelvic, humeral and femoral bones. Depending on the extension of the cell infiltration, three patterns of bone marrow involvement were used: normal/no involvement (N), non-homogeneous (NH) and homogeneous (H). All ten patients presented bone infiltration. The patterns observed were: spine (50 % NH, 50 % H), pelvis (70 % NH), humerus 100(NH) and femur 40 % (NH). T1-weighted MR imaging is a sensitive technique for detecting marrow abnormalities in patients with systemic mastocytosis. There is no correlation between percentage of mast cells in bone marrow biopsy and extent or pattern of bone marrow involvement.

Magnetic resonance imaging of the peroneal tendons

Injuries of the peroneal tendons include tendinosis, tenosynovitis, tears, and dislocation. These injuries are being detected with greater frequency since the advent of MRI. After a review of the normal MRI anatomy of the peroneal tendons, this article will focus on the MR features of peroneal tendon disorders in the foot and ankle.

Dengue virus in the brain of a fatal case of hemorrhagic dengue fever

Neurologic complications associated with dengue fever are in general unusual. However, recent reports evidence more frequent neurologic alterations. In Mexico, neurologic involvement has not been reported in dengue cases. This report demonstrates the detection of dengue virus in the brain of a fatal case of dengue hemorrhagic fever. Serotype 4 was detected by immunohistochemistry and by RT-PCR in the inferior olivary nucleus of medulla and in the granular layer of cerebellum. Immunoreactivity was observed in neurons, astrocytes, microglia and endothelial cells. Our results emphasize the importance of neurologic manifestations in patients with dengue fever.

Quantitative measurements of the spinal cord and canal by MR imaging and myelography

There is a large individual variation in human spinal cord and canal size, even in patients of different series studied by the same modality, and no authorized standard method has been established. A comparative study of sagittal diameters of the cervical spinal cord and canal using myelography and MRI is presented. The purposes of this paper are (a) to establish the correction factor (CF) needed for quantitative comparison of the two imaging modalities, and (b) to determine the different factors that may modify the measurement of these diameters. We studied 45 patients with clinical findings compatible with cervical spondilotic myelopathy. In our experience, the CF for accurate correlation of MRI and myelography measurements is 1.32 and depends almost entirely on the radiographic geometry of the myelographic procedure. In addition, there is a variability in the group of MRI results due to imprecision of the pressure-pad measuring/input device of the instrument itself and the sequence performed.

Spontaneous enterourachocutaneous fistula in Crohn's disease: sonographic diagnosis

Spontaneous abdominal wall fistulas are rare in Crohn's disease. We report a case of enterourachocutaneous fistula in a woman with Crohn's disease and present the sonographic, computed tomographic, and sinographic findings.

[Magnetic resonance in the diagnosis of extent and osseous complications of Gaucher's disease type 1]

OBJECTIVE

To evaluate the usefulness of magnetic resonance (MR) for investigating bone involvement in Gaucher disease type 1 (GD).

METHODS

Ten adult patients with the diagnosis of GD type 1 were studied. Weighted sequences were performed in spin-echo (SE) T1 and T2 of 4 body areas: spine, pelvis, hips, and femurs. The patterns of bone infiltration proposed for the study were: homogeneous infiltration (H), non-homogeneous infiltration (NH), and normality (N). Four patients were receiving enzyme replacement therapy.

RESULTS

All patients (100%) showed changes associated with infiltration with Gaucher cells. The distribution of patterns was as follows: the homogeneous pattern predominated (60 and 50%, respectively) in spine (6H/2NH/2N) and pelvis (5H/3NH/2N), whereas the non-homogeneous pattern predominated (60% and 80%, respectively) in hips (1H/6NH/3N) and femurs (1H/8NH/1N). As bone complications two cases of hip avascular necrosis were noted, one of them with bilateral involvement, one case with infarcts in femur diaphysis and other case with medullar edema in a bone crisis.

CONCLUSION

MR is an excellent technique for detecting medullar bone infiltration and complications in GD type 1.

[Magnetic resonance imaging usefulness in the diagnosis of intratumor bleeding in hypophyseal adenomas]

Hypophyseal adenomas are the most frequent intrasella tumours. They are classified as macroadenomas or as microadenomas depending on whether their size is greater or less than 1 cm. Hypophyseal tumours may undergo ischaemic necrosis and haemorrhage when the blood supply is reduced. Intratumoural bleeding is found in varying percentages, between 9.9% and 26%. We review our series of 122 patients with hypophyseal adenomas in whom MR was done. Signs of bleeding were found in 12 patients (9%). In five cases, bleeding had presented as hypophyseal apoplexy, in five cases with subacute symptoms and in two cases was asymptomatic and diagnosis fortuitous. Of the adenomas with intratumoural bleeding, 9 were functioning tumours (4 secreted PRL, 4 ACTH and 1 GH) and 3 non-functioning. The risk factors considered in the pathogenesis of intratumoural bleeding are numerous. The increased incidence of bleeding in large and in invasisve adenomas, especially when treated with bromocriptin, is well established. MR is the ideal technique to detect intratumoural bleeding, T2 weighted sequences being very useful in the diagnosis of bleeding in the acute phase. In the subacute phase, focal areas of hyperintensity are seen in T1 and of hypo/hyperintensity in T2. In the chronic phase, areas of hypodensity are seen both in T1 and in T2. In our study we analyze the clinico-radiological correlation in patients with signs of intratumoural bleeding.