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J Alger

Publications and source records attributed to J Alger.

8 recordsLinked to original sources
PubMed2005

Analysis of the brain-stem white-matter tracts with diffusion tensor imaging.

The authors have reviewed the diffusion tensor imaging (DTI) of the brain stem in 19 subjects, consisting of 15 normal volunteers and four multi-system atrophy patients. The study was performed with 1.5 T MRI scanners. DTI was correlated with an automated program allowing superposition of the structural anatomy. Axial, sagittal, and coronal images demonstrated major white-matter fibers within the brain stem, including cortico-spinal tracts, transverse pontine fibers, and medial lemniscus. Smaller fibers, such as medial longitudinal fascicles and central tegmental tracts are difficult to visualize. To identify the anatomical orientation of the brain stem, white-matter fibers will help us understand the different functional disease processes, and DTI will play an important role for the evaluation of the different white matter fibers in the brain stem.

Adult↗
PubMed2000

Impact on stroke subtype diagnosis of early diffusion-weighted magnetic resonance imaging and magnetic resonance angiography.

BACKGROUND AND PURPOSE: The purpose of the present study was to assess the diagnostic usefulness of early diffusion-weighted MRI (DWI) and MR angiography (MRA) in patients with ischemic stroke. Past approaches to stroke diagnosis required a series of diagnostic tests over several days of hospitalization. New magnetic resonance methodologies that include DWI and MRA may allow more rapid characterization of stroke pathophysiology. However, no previous study has assessed the impact on formal stroke subtype diagnosis of early imaging with DWI/MRA. METHODS: We analyzed 46 consecutive patients with acute ischemic stroke who underwent DWI/MRA within 24 hours of admission. Initial diagnoses were rendered with use of the 2 most widely used formal stroke subtype classification schemes, the TOAST and the Oxfordshire methods, which were applied to patients after CT/conventional MRI but before DWI/MRA. Modified TOAST and Oxfordshire diagnoses were then rendered based on the results of day 1 DWI, MRA, and DWI plus MRA. Final TOAST/Oxfordshire diagnoses at discharge were taken as the gold standard. RESULTS: Compared with final diagnoses, pre-MRI TOAST diagnoses matched final diagnoses in 48%, improving to 83% after DWI alone, 56% after MRA alone, and 94% after DWI plus MRA. For the TOAST diagnostic subtypes of large-vessel atherothromboembolism and small-vessel disease, pre-MRI diagnoses matched final diagnoses in 56% and 35% of patients, respectively, improving to 89% and 100% after DWI/MRA. Pre-MRI Oxfordshire diagnoses matched final diagnoses in 67% of patients, improving to 100% after DWI. CONCLUSIONS: The use of DWI/MRA within 24 hours of hospitalization substantially improves the accuracy of the diagnosis of early ischemic stroke subtype. When initial management and clinical trial eligibility decisions are influenced by stroke subtype, day 1 multimodal MRI is advantageous as a guide to therapy.

Female↗
PubMed1999

Variation of post-treatment H-MRSI choline intensity in pediatric gliomas.

Pediatric brain gliomas are not always amenable for complete surgical excision, therefore adjuvant treatment for a large tumor mass is often required. As tumor volume shrinkage may not be a reliable method for assessing response to treatment, information about the tumor growth potential is desirable for an adequate follow-up of the patients. Choline (Cho) signal intensity, determined by proton magnetic resonance spectroscopy imaging (H-MRSI), has proved to be a reliable indicator of the metabolic activity and of tumor progression in various intracranial tumors. In this study we have sought to determine if H-MRSI can be of use in monitoring the response of pediatric gliomas to different forms of therapy. We performed pretreatment and post-treatment H-MRSI in 10 children with biopsed or partially excised brain gliomas. The follow-up period ranged between 6 and 40 months. A total of 38 H-MRSI were performed. All the patients had chemotherapy or radiotherapy. As an indicator of tumor activity we utilized the ratio between tumor/brain Cho signal intensity. Treatment response was evaluated as a function of tumor volume and clinical outcome. In 6 patients whose tumor volume decreased or remained stable we observed that the Cho ratio decreased (p < 0.01) after treatment and remained low during longitudinal follow-up. In the 4 patients whose tumors progressed the Cho ratio increased after treatment. These observations suggest that serial H-MRSI can provide valuable information regarding the response to therapy in pediatric gliomas and therefore be of use in the follow-up of these neoplasms of childhood.

Astrocytoma↗
PubMed1998

Regional brain activation in humans during respiratory and blood pressure challenges.

1. The aim of the present study was to determine the brain sites mediating aspects of respiratory and cardiovascular control in adult humans using non-invasive functional magnetic resonance (fMRI) procedures, thereby avoiding the spatial and temporal sampling limitations associated with classic neural assessment techniques. 2. We examined activity changes across the entire brain following application of respiratory loads and upon induction of blood pressure and heart rate alterations. Magnetic resonance signals were visualized with a 1.5 Tesla scanner in healthy volunteers (22-52 years of age) using procedures that optimally assess changes in brain tissue microcirculation. Images were collected during a Valsalva manoeuvre, inspiratory loading, hypercapnia, cold pressor challenges to the hand and forehead and during intervening baseline states. 3. Image values from experimental conditions were compared with corresponding baseline values on a pixel-by-pixel basis to identify brain regions in which the experimental conditions produced physiological activation. 4. Ventilatory and pressor challenges elicited significant changes in regional image signal intensity in areas within the orbital cortex, amygdala, hypothalamus and hippocampus. Cerebellar, medullary and pontine areas were also recruited. However, while particular brain regions were only activated during specific stimuli, other regional signal changes occurred with multiple experimental manipulations. 5. The findings indicate that respiratory and cardiac challenges elicit discrete activity changes over multiple brain sites. Activated regions include structures not often related to respiratory or cardiovascular regulation, such as the cerebellum; a prominent role for limbic forebrain structures in mediating the response is also suggested. The fMRI visualization procedures may greatly assist in the determination of neural structures that mediate respiratory and cardiovascular control in humans.

Adult↗
PubMed1997

Subcutaneous dirofilariasis: single inoculum, multiple worms.

The present report describes an unusual case of subcutaneous dirofilariasis attributed to Dirofilaria repens. The patient, a 42-year-old caucasian male, who acquired the infection in Africa, presented on two different occasions, 10 months apart, with a sudden onset of symptoms and a living worm moving about in the periorbital tissues. Both worms were mature nongravid females. Based on the maturation of the respective reproductive systems and the volume and distribution of eggs in the reproductive tracts, it was concluded that both worms were in the same infecting inoculum. The first worm was at least two years old and the second was therefore 10 months older than the first. These observations indicate that the worms developed and resided in the tissues without eliciting any host response for two and three years.

Adult↗