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A Gass

Publications and source records attributed to A Gass.

70 records · Page 4Linked to original sources
PubMed1996

[Functional magnetic resonance tomography during the activation of working memory].

AIMS: Functional magnetic resonance imaging was used in conjunction with a letter detection task for the study of working memory in 16 normal subjects. Because of movement artifacts, data from only 9 subjects were analysed. METHODS: In the activation task, subjects responded by pressing a button whenever any presented letter was the same as the second last in the sequence. In the control condition, the subjects had to respond to a fixed letter. Hence, the activation condition and the control condition differed only subjectively, i.e., regarding the task demand, whereas the stimuli and the type and frequency of response were identical. RESULTS: The activation condition produced significant activation in the dorsolateral prefrontal cortex (Brodmann's areas 10, 46, and 9). CONCLUSIONS: In contrast to experimental tasks previously used rather extensively to study the prefrontal cortex, the present paradigm is characterized by its simplicity, interpretability, and its ties to known neurophysiology of the frontal cortex.

Adult↗
PubMed1996

Abnormalities of torsional fast phase eye movements in unilateral rostral midbrain disease.

In a patient with a unilateral rostral midbrain lesion, three-dimensional scleral search coil eye movement recordings demonstrated slowing of ipsidirectional torsional fast phase eye movements without any abnormalities of torsional slow phases. On high-resolution MRI, the brainstem lesion localized to the area of the efferent pathways from the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF). This supports the experimental finding that unilateral inactivation of the riMLF results in a loss of ipsidirectional torsional fast phase eye movements and the hypothesis that there is lateralization of function throughout the torsional fast eye movement generating system.

Adult↗
PubMed1995

Cranial MRI in idiopathic retinal vasculitis.

Ten patients with clinically isolated idiopathic retinal vasculitis who had a positive family history for multiple sclerosis (MS) or positive typing for HLA B7 underwent magnetic resonance imaging (MRI) of brain and optic nerves in order to establish the frequency of clinically silent lesions. Brain MRI was normal in seven and abnormal in three: one had a single small white matter lesion, two had extensive white matter abnormalities resembling those seen in MS. In two patients a lesion was shown in the optic nerve. These findings suggest that a minority of patients with idiopathic retinal vasculitis have disseminated central nervous system lesions characteristic of MS, the frequency of such changes being less than in patients with isolated optic neuritis.

Adolescent↗
PubMed1995

High resolution magnetic resonance imaging of the anterior visual pathway in patients with optic neuropathies using fast spin echo and phased array local coils.

High resolution MRI of the anterior visual pathways was evaluated using frequency selective fat suppressed fast spin echo (FSE) sequences in conjunction with phased array local coils in patients with optic neuropathies. Fifteen normal controls and 57 patients were examined. Coronal T2 weighted fat suppressed FSE images were obtained in 11 minutes with an in plane resolution of 0.39 x 0.39 mm. The optic nerve and its sheath containing CSF were clearly differentiated. Central retinal vessels were often visible. In demyelinating optic neuritis and in anterior ischaemic optic neuropathy high signal within the nerve was readily delineated. Meningiomas and gliomas involving the optic nerve were precisely visualised both in the orbit and intracranially. Extrinsic compression of the optic nerves was readily visualised in carotid artery ectasia and dysthyroid eye disease. Enlarged subarachnoid spaces around the optic nerves were demonstrated in benign intracranial hypertension. High resolution MRI of the anterior visual pathway represents an advance in the diagnosis and management of patients presenting with optic neuropathy.

Adult↗
PubMed1994

Correlation of magnetization transfer ratio with clinical disability in multiple sclerosis.

We performed spin echo magnetic resonance imaging with and without application of an off-resonance saturation pulse in 43 patients with multiple sclerosis (MS), 10 age-matched controls, and 4 elderly asymptomatic patients with the radiological diagnosis of small-vessel disease. Magnetization transfer (MT) ratio images were obtained from these. All MS subgroups (primary progressive, secondary progressive, benign, early relapsing-remitting) showed significantly lower average lesion MT ratios than small-vessel disease patients. Secondary progressive MS patients showed significantly lower lesion MT ratios than those with benign disease, and there was an inverse correlation of disability with average lesion MT ratio. The degree of reduction of MT ratios is an indicator of the extent of tissue destruction. Thus, reduced MT ratios in MS may provide an indication of the degree of demyelination and axonal loss, both of which are likely to cause functional deficits in MS. We conclude that MT measurement is (1) a robust quantitative method that may increase the pathological specificity of magnetic resonance imaging, (2) has the potential to differentiate demyelination in MS from less destructive pathological changes, and (3) may be useful in monitoring modifications in tissue structure brought about by treatment.

Adult↗
PubMed1994

A method for visualization of MRI partial volume regions--PAIR (PArtial volume sensitised Inversion Recovery imaging).

The partial volume effect has a crucial influence on MRI in terms of the choice of slice thickness and slice orientation for diagnostic purposes, volume measurement, and quantification of tissue characteristics such as relaxation times, proton density, and magnetisation transfer contrast. It is, therefore, important to be able to assess the distribution and magnitude of partial volume voxels for an arbitrary slice thickness, slice orientation, and region of anatomy or pathology. There is currently no easy means of achieving this. We propose a novel inversion recovery based method for visualising regions of anatomy or pathology suffering from the partial volume effect, which we have termed PAIR (PArtial volume sensitised Inversion Recovery imaging). This method allows an informed trade off to be made between the partial volume effect and signal-to-noise ratio or imaging time. It also allows appropriate choice of imaging plane to reduce the partial volume effect, and facilitates choice of regions of interest for quantification purposes.

Brain↗
PubMed1994

Optic disc cupping in arteritic anterior ischemic optic neuropathy.

Patients with anterior ischemic optic neuropathy due to giant cell arteritis are thought to develop optic disc cupping, resembling that seen in glaucomatous eyes, while such cupping does not seem to occur in nonarteritic anterior ischemic optic neuropathy. However, this remains controversial. We describe a patient with arteritic anterior ischemic optic neuropathy (the clinical diagnosis was confirmed with a biopsy from the temporal artery) who developed disc cupping within 4 months after acute episode. This patient never had elevated intraocular pressure, and prior to the acute event the optic nerve heads had had a normal appearance with a physiologic cup.

Aged↗
PubMed1992

[Orbitocranial plasmacytoma: a case report].

A female patient aged 79 years suffered from a unilateral, slowly progressive and painless exophthalmus. The investigations lead to the diagnosis of a voluminous plasma cell tumor involving the fossa infratemporalis, a part of the lateral orbit, as well as the middle and anterior cerebral fossae. This rare case is described and placed in its clinico-pathological context.

Aged↗
PubMedDate not supplied

The role of echocardiography in heart transplantation.

Echocardiography has gained increasing importance as an imaging modality in the care of the cardiac transplant recipient. Its utility in detecting the complications of transplantation, with special reference to the diagnosis of rejection and graft arteriosclerosis, is discussed. On the basis of a review of the current literature, an outline for serial echocardiographic studies is proposed.

Coronary Artery Disease↗
PubMedDate not supplied

Correction of nonuniformity in images of the spine and optic nerve from fixed receive-only surface coils at 1.5 T.

OBJECTIVE: Our goal was to analyze the sources of nonuniform image intensity of two surface coil configurations used on a General Electric 1.5 T Signa scanner and to correct the major source. MATERIALS AND METHODS: Correction of receive coil nonuniform sensitivity is achieved using division by images of a uniform phantom. Patient images are transferred to a network of Sun workstations for routine correction by technologists. Spinal cord images, originally 512 x 512, are truncated to 128 x 512 to allow four slices to be copied onto one X-ray film. RESULTS: Images of the spinal cord, collected using a four coil multiarray, show marked coil-to-coil nonuniformity and a high signal level from subcutaneous tissue near the coils. After correction the cord has uniform intensity, with improved visualization in the posterior fossa and upper thoracic region, enabling more reliable detection of small intrinsic lesions as occur in multiple sclerosis. Images of the optic nerves, collected using a two coil array, show bright signal in the brain and subcutaneous tissue. After correction the images are more uniform. CONCLUSION: Nonuniformity in images of the spine can be corrected using division by a phantom image. Water phantoms must be restricted in size to avoid standing wave effects; for the optic nerves a cylindrical oil phantom 20 cm in diameter was used.

Artifacts↗
PubMedDate not supplied

Marchiafava-Bignami disease: reversibility of neuroimaging abnormality.

Marchiafava-Bignami disease (MBD) was diagnosed in a malnourished 43-year-old patient with chronic alcoholism, severe generalized extrapyramidal rigid syndrome, and severe dyspraxia. Cranial CT and MRI demonstrated isolated lesions in the geno and splenium of the corpus callosum (CC) characteristic for MBD. On thiamine therapy, a slow but steady recovery of clinical symptoms occurred, and serial CT and MRI studies demonstrated marked reversibility of abnormalities in the CC. Besides clinical improvement with a good functional outcome, reversal of CT and MRI abnormalities may occur in MBD.

Adult↗
PubMedDate not supplied

Fatal hyperthyroidism after amiodarone treatment and total lymphoid irradiation in a heart transplant recipient.

Recurrent severe allograft rejection is an uncommon but difficult management problem in heart transplantation. Total lymphoid irradiation is now a recognized treatment modality when conventional therapy has failed. We describe an unusual complication of total lymphoid irradiation in a patient who had been treated with amiodarone for malignant arrhythmias before transplantation.

Amiodarone↗
PubMedDate not supplied

Safety and efficacy of beta blockade in patients with chronic congestive heart failure awaiting transplantation.

BACKGROUND: Donor availability remains a limiting factor for heart transplantation while transplant waiting time entails significant morbidity and mortality. This study was designed to assess the efficacy and safety of long-term beta blockade as optimization of therapy in patients with severe congestive heart failure already receiving digoxin, diuretics, and converting enzyme inhibitors awaiting transplantation. METHODS: The beta-1 antagonist metoprolol was given to 19 patients with moderate to severe congestive heart failure. Hemodynamic, clinical, and neurohormonal measurements were obtained before drug therapy and after 3 months of treatment. Patients initially received 6.25 mg of metoprolol orally twice daily which was increased to a target dose of 50 mg twice daily over several weeks. RESULTS: Metoprolol produced significant clinical, exercise, and hemodynamic benefits. Long-term therapy was associated with improvements in New York Heart Association class, ejection fraction, 6-minute walk, and peak maximal oxygen consumption. There were significant decreases in heart rate, pulmonary arterial systolic pressure, and left ventricular filling pressure with significant increases in stroke volume index and stroke work index. Four patients were removed from the transplant list after improving to New York Heart Association I. Only one patient required hospitalization during the first 6 months of therapy. There were no deaths caused by progressive heart failure; however, one patient died suddenly. CONCLUSIONS: Beta blockade with metoprolol can be safely administered to patients awaiting heart transplantation producing clinical, exercise, and hemodynamic improvements. Thus, beta blockade may prove to be a safe and cost-effective bridge to transplantation.

Adrenergic beta-Antagonists↗