The effects of beam shape on the ability to predict changes in vessel size from Doppler signal power

Theory suggests that, under certain ideal circumstances, the power of a Doppler signal is proportional to the size of the vessel from which it is recorded and can, therefore, be used to assess the scale of any changes in vessel size that occur during clinical recordings of cerebral blood flow. However, the relationship between signal power and vessel size depends on the intensity of the incident beam being uniform across the vessel. This is unlikely to be the case for cerebral vessels insonated by commercial transducers. A model was used to estimate the signal power received from vessels insonated by a beam passing through a homogeneous medium, and also by beams passing through each of five samples of temporal bone. In each case, the effects of initial vessel size and various changes in cross-sectional area were investigated for different vessel positions in the beam. The results for the beam paths through bone predict that the power change arising from a change in vessel cross-sectional area is between 5% and 75% smaller than that occurring in a uniform beam. If these results are representative of those arising for an in vivo change in middle cerebral artery size, then the potential magnitude of the error illustrates the caution that may need to be applied when interpreting changes in Doppler signal power.     

Hemorrhagic lymphadenopathy as a presenting feature of primary al amyloidosis

Lymphadenopathy associated with hemorrhage as a presenting feature of primary (AL) amyloidosis has not previously been described. We report two such cases one of whom had an acquired factor X and IX deficiency. The clinical presentations were characterized by sudden spontaneous enlargement of lymph nodes followed by partial regression. In both cases significant delay in diagnosis, and hence treatment, occurred due to the mode of presentation. One patient died with rapidly progressive disease but the other has had an excellent response to therapy with high-dose melphalan (HDM, 200 mg/m2) and peripheral blood stem cell rescue. AL amyloid should be considered in all patients presenting with hemorrhagic lymphadenopathy.     

Diversity of responses of renal cortical and medullary blood flow to vasoconstrictors in conscious rabbits

The medullary microcirculation receives only about 10% of total renal blood flow, but plays a critical role in long-term arterial pressure regulation, so we need to better understand its regulation. Although there is evidence that circulating and locally acting hormones can differentially affect cortical and medullary blood flow in anaesthetized animals, there is little information from studies in conscious animals. This study is aimed (i) to develop a method for chronic measurement of cortical and medullary blood flow in conscious rabbits, and (ii) to test whether renal cortical and medullary blood flow can be differentially affected by intravenous (i.v.) infusions of various vasoconstrictor hormones in conscious rabbits. At preliminary operations, rabbits were equipped with single-fibre laser-Doppler flowprobes in the (left) renal cortex and medulla, and Transonic flowprobes for measuring cardiac output and renal blood flow. Intravenous angiotensin II (300 ng kg(-1) min(-1)), [Phe2,Ile3,Orn8]-vasopressin (30 ng kg(-1) min(-1)), noradrenaline (300 ng kg(-1) min(-1)), endothelin-1 (20 ng kg(-1) min(-1)) and N G-nitro-L-arginine (10 mg kg(-1)) increased mean arterial pressure (by 10-45% of baseline) and reduced heart rate (by 16-35%) and cardiac output (by 16-45%). Consistent with previous observations in anaesthetized rabbits, all treatments except [Phe2,Ile3, Orn8]-vasopressin reduced renal blood flow (13-63%) and cortical blood flow (16-47%), but medullary blood flow was significantly reduced only by [Phe2,Ile3,Orn8]-vasopressin (41%) and N G-nitro-L-arginine (42%). The diversity of these responses of cortical and medullary blood flow to i.v. infusions of vasoconstrictors provides further evidence for physiological roles of circulating and local hormones in the differential regulation of regional kidney blood flow.     

Combined pleomorphic xanthoastrocytoma-ganglioglioma of the cerebellum

Combined pleomorphic xanthoastrocytoma-ganglioma is a rare neoplasm, occurring in patients younger than 30 years. The clinical course of these tumors is difficult to predict because of their rarity. We report a case of combined pleomorphic xanthoastrocytoma-ganglioma that, in addition to the patient's age, is unusual in several respects. The lesion was located in the cerebellar vermis of a 60-year-old man and was radiographically solid. Histologically, there was an admixture of markedly pleomorphic astrocytic cells and neoplastic ganglion cells, with permeation of the overlying leptomeninges and surrounding cerebellum. In addition, there was focal capillary endothelial proliferation. There was no necrosis, and mitotic activity was rare at 1 mitotic figure per 40 high-power fields. The patient underwent a near gross total resection and postoperative radiotherapy and remains well through 16 months of follow-up.     

Risk factors for syncope in a community-based sample (the Framingham Heart Study)

The epidemiology of syncope has not been well described. Prior studies have examined risk factors for syncope in hospital-based or other acute or long-term care settings. To determine risk factors for syncope in a community-based sample, we performed a nested case-control study. We examined reports of syncope in Framingham Heart Study participants who underwent routine clinic visits from 1971 to 1990. For each syncope case (n = 543) 2 controls were matched for age, sex, and examination period. Mean age of subjects was 67 years (range 25 to 95); 59% were women. History of stroke or transient ischemic attack, history of myocardial infarction, high blood pressure, use of antihypertensive medication, use of other cardiac medication, smoking, alcohol intake, body mass index, systolic blood pressure, diastolic blood pressure, heart rate, atrial fibrillation, PR interval prolongation, interventricular block, and diabetes or elevated glucose level were examined as potential predictors. Using conditional logistic regression analysis, the predictors of syncope included a history of stroke or transient ischemic attack (odds ratio [OR] 2.56, 95% confidence interval [CI] 1.62 to 4.04), use of cardiac medication (OR 1.67, 95% CI 1.21 to 2. 30), and high blood pressure (OR 1.46, 95% CI 1.14 to 1.88). Lower body mass index was marginally associated with syncope (OR per 4 kg/m(2) decrement 1.10, 95% CI 0.99 to 1.22), as were increased alcohol intake (OR per 5 oz/week 1.11, 95% CI 0.99 to 1.26), and diabetes or an elevated glucose level (OR 1.29, 95% CI 0.96 to 1.75). To our knowledge, this study represents the first community-based study of risk factors for syncope.     

Diagnostic dilemma

In those issues in which our regular Case of the Month does not appear, The Green Journal will present a Diagnostic Dilemma-an electrocardiogram or radiograph, or both, with a brief case history-as a challenge for our readers to solve. The correct answer appears on page 742. If you would like to contribute a Diagnostic Dilemma, please submit a high-quality copy of the ECG or radiograph with a brief synopsis (<250 words) of the case to editorial office of the American Journal of Medicine.     

Traumatic lumbar puncture at diagnosis adversely affects outcome in childhood acute lymphoblastic leukemia

The effect of traumatic lumbar puncture at the time of initial diagnostic workup on treatment outcome in children with newly diagnosed acute lymphoblastic leukemia (ALL) was investigated. The findings of the first 2 lumbar punctures performed on 546 patients with newly diagnosed ALL treated on 2 consecutive front-line studies (1984-1991) at St Jude Children's Research Hospital were retrospectively reviewed. Lumbar punctures were performed at the time of diagnosis and again for the instillation of first intrathecal chemotherapy. The event-free survival (EFS) experience for patients with 1 cerebrospinal fluid (CSF) sample contaminated with blast cells was worse than that for patients with no contaminated CSF samples (P =.026); that of patients with 2 consecutive contaminated CSF samples was particularly poor (5-year EFS = 46 +/- 9%). In a Cox multiple regression analysis, the strongest prognostic indicator was 2 consecutive contaminated CSF samples, with a hazard ratio of 2.39 (95% confidence interval, 1. 36-4.20). These data indicate that contamination of CSF with circulating leukemic blast cells during diagnostic lumbar puncture can adversely affect the treatment outcome of children with ALL and is an indication to intensify intrathecal therapy.     

Factors influencing the efficacy of light cured materials for earmoulds.

This work was undertaken to investigate two systems for producing light-cured earmoulds, in order to evaluate the factors which influence the efficacy of such procedures. It was shown that there were variations in light intensity in the light boxes, and that the depth and age of gel in which curing takes place was important. Degree of cure of the materials was assessed by hardness measurements for hard materials and resistance to tearing for hard materials. Light-cured technology has great potential for the rapid production of earmoulds.     

Lead abatement training for underserved populations: lessons learned

An environmental-justice (equity) grant program was used to make accessible an existing lead-training program to minority persons and residents of low-income communities. The purpose of the program was to enhance the knowledge base within the communities concerning lead hazards and intervention strategies and expand possibilities for employment in the lead abatement industry. Barriers to attendance were anticipated and addressed, and included transportation, meals, license application fees, reminders of course date and location, and day care. The program was evaluated through measures of recruitment rates, pre- and post-testing scores, and change in perception of confidence at pre-test, post-test, and at four-month follow-up. Fee-paying registrants over the same time period were used as a comparison group. First day attendance rates for individuals recruited into the equity-grant was 59 percent, of these 94 percent completed all days. Equity and fee-paying groups had similar scores on the pre-test (p = .209), while mean scores on the final exam differed significantly (p < .001) between the groups and were 77 percent and 85 percent, respectively. After adjusting for demographic and course type attended, perceptions of self-efficacy (benefit) and outcome-effectiveness (confidence) increased significantly from pre- to post-tests for both groups and remained at post-course levels at four months follow-up. Lessons learned include: (1) Lead abatement and other related activities can be successfully taught through traditional training methods; (2) A necessary element for delivery of educational services to minority groups is forming workable ties with local community groups, but eligibility requirements must be maintained; (3) Once barriers to first-day attendance are overcome, the information necessary to perform specific work skills can be taught; (4) Positive changes in belief are not dependent on minority status, income, or education levels; (5) Training and education increased confidence in ability to perform learned skills, and belief that there will be a beneficial outcome when performed for themselves, their families, and communities; and, (6) A consensus regarding applicability of regulations must be achieved among federal, state, and local communities.