Systems model of cortical organization: positron emission tomography and neuropsychological test performance.

Positron Emission Tomography (PET) has allowed researchers to examine in vivo brain-behavior relationships. Correlations of metabolic increases measured by PET with simple sensory tasks involving hearing, vision, and tactile/motor responses have generally produced metabolic changes in agreement with known neuronal pathways. However, complex neuropsychological tests such as Raven's Matrices and Verbal Fluency have resulted in cortical activation of unexpected areas as well as some negative correlations between test performance and metabolism. These observations provide the first demonstration of complex relationships between neuropsychological functioning and activation of the normal brain. Since PET technology offers a means of computing the simultaneous proportional contribution of multiple brain regions, the issue of "localization" of neuropsychological test performance might appropriately be considered for redefinition in terms of a "systems" approach. In spite of the advances brought about by PET, methodological problems still remain for researchers. Future studies will need to take into account the subtle regional effects of neuropsychological paradigms.     

18Fluorodeoxyglucose positron emission tomography studies in presumed Alzheimer cases, including 13 serial scans

Positron emission tomographic (PET) data on local cerebral metabolic rates for glucose (LCMR) are reported for 32 regions of interest (ROI)s in cross-sectional studies on 57 patients with clinically diagnosed Alzheimer's disease (AD) and 20 neurologically normal controls, and in serial studies on 13 of the AD cases, including a familial, young-onset case where the diagnosis has been confirmed at autopsy. Extensive psychological testing was done on all the AD cases. Almost all cortical regions showed a significant decline in LCMR with age in the control subjects. There were the expected cortical metabolic deficits in AD and the serial studies showed a general increase in such deficits over time in 12 of the 13 cases. The regions showing the greatest declines with time in serial studies are the same as those showing the most severe deficiencies in cross-sectional studies. The young-onset case did not show a greater rate of metabolic decline than many of the older cases studied. Results on individual psychological tests tended to correlate with metabolic rates in multiple, rather than single, cortical regions, suggesting intact neuronal networks are required for good performance. The correlations with cortical metabolic activity found were of a sign indicating that the higher the metabolic rates and the better the left:right asymmetry index, the better was the performance.     

Comparison of surgical bypass and percutaneous balloon dilatation with primary stent placement in the treatment of central venous obstruction in the dialysis patient: One-year follow-up

Central venous stenosis and occlusion are complications that are being observed with increasing frequency as a result of the use of long-term central venous catheters. These complications are especially problematic in patients with end-stage renal disease and functioning ipsilateral arteriovenous (AV) grafts or fistulas (AV grafts). We have previously demonstrated that the 1-year patency rate for simple balloon angioplasty in these patients is less than 10%. To compare the results of surgical treatment vs. percutaneous dilatation with stent placement, we undertook this retrospective study. All patients underwent multiple central venous catheter placements and had functioning ipsilateral AV grafts. Twenty-six patients were divided into two groups. The surgical treatment group included 13 patients: 10 with subclavian vein thrombosis and three with innominate vein thrombosis. All patients in the surgical group had arm swelling and edema. Surgical bypass procedures were performed in these patients using either polytetrafluoroethylene or saphenous vein. The stent group also included 13 patients; all of them had a diagnosis of subclavian or innominate vein obstruction and were treated with percutaneous transluminal angioplasty and placement of either a self-expanding rigid stent (n=6) or a balloon-expandable flexible stent (n=7). Two patients required multiple stent placements. No significant complications occurred in either group. The 1-year mortality rate in both groups was 31%. The percentages of patients who were symptom free at 6 and 12 months were also similar in the two groups. We conclude that surgical bypass and percutaneous transluminal angioplasty with stent placement are both efficacious in the treatment of central venous obstruction.     

Corticosteroid management of airway hemangiomas: Long-term follow-up

Nine children with airway obstructing hemangiomas were managed with corticosteroid therapy for durations of 6 weeks to 17 months. One patient required a tracheotomy. Steroid therapy improved the airways of the other 8 patients. Therapy was continued for 8 months or longer in 6 patients, none of whom developed life-threatening infections. Examinations 1½ to 7½ years after therapy revealed all of the patients to be within normal range for height and weight, but 3 of the 6 patients treated for 8 months or longer were in the lower range of normal. Steroid therapy is an effective method of protecting the airway in some patients with hemangiomas. Its disadvantage is that therapy may be necessary for several months. The risk of infections and growth suppression is minimized by using small maintenance dosage and alternate day therapy.