Intracranial abnormalities in infants treated with extracorporeal membrane oxygenation: imaging with US and CT

Findings at neuroimaging in 100 consecutive infants treated with extracorporeal membrane oxygenation (ECMO) are presented. Imaging in these infants consisted of pretreatment cranial ultrasonography (US), daily US studies while on ECMO, and follow-up cranial computed tomography (CT) after treatment. There were findings of abnormalities in 43 patients. Thirty had intracranial bleeding, often of unusual extent and distribution. Thirteen additional infants had nonhemorrhagic abnormalities alone. Bleeding considered to be major was seen in 12% of infants. Large parenchymal hemorrhages and infarcts, cerebellar hemorrhages, and diffuse edema were the most significant abnormalities, with a 50% mortality (eight of 16 patients). No lateralization was noted with respect to distribution of bleeding sites or areas of nonhemorrhagic abnormalities. US was a sensitive but imperfect screening tool for intracranial abnormalities. Abnormalities missed with US included peripheral and small parenchymal lesions, subarachnoid hemorrhage, cerebral atrophy, and sagittal sinus thrombosis.     

Behavioral evolution and biocultural games: vertical cultural transmission.

We consider an evolutionary game model in which strategies are transmitted culturally from parents to offspring rather than inherited biologically. Our analysis yields two noteworthy results. First, biocultural games show a greater diversity of dynamical behaviors than their purely biological counterparts, including multiple fully polymorphic equilibria. Second, biocultural games on average exhibit greater equilibrium strategy diversity because of the countervailing influences of cultural transmission and natural selection. Therefore, knowledge of a strategy's influence on Darwinian fitness is not sufficient to infer the evolutionary consequences of biocultural games. Further, our results suggest that cultural transmission in the presence of natural selection may be an important mechanism maintaining behavioral diversity in natural populations.     

Mediastinal tumors: biopsy under US guidance

Percutaneous biopsies of mediastinal tumors were successfully performed under sonographic guidance in 14 of 21 patients. In 10 of 11 malignant lesions, malignancy was determined by means of cytologic and histologic examination of the specimens obtained. A histologic diagnosis was reached in seven patients with malignant mediastinal tumors, including all four cases of Hodgkin lymphoma. Mediastinal biopsy under sonographic guidance is a technically simple, rapid, and accurate procedure, but its application is limited to tumors of the anterior mediastinum.     

Breakage incidence with direct-bonded lingual retainers.

This study examined the effects of a number of patient and clinical variables on the breakage of bonded retainers, and consisted of a retrospective review of the survival of 200 bonded retainers. Data was collected from two clinical centres between November 1996 and February 1997. The subjects comprised 198 patients of both sexes divided into three age groups. Retainers at both centres were made in 018-inch co-axial wire with Relyabond and Helioprogress adhesives used at each respective centre. The effects on time to first breakage of adhesive, patient sex, and arch (upper/lower) were considered using Kaplan Meier survival graphs and in Log Rank Tests. Finally, a Cox Proportional Hazard Model was used to examine the joint effects of these factors and the patients' ages. Breakage over a 5-year period with Relyabond was 38.8 per cent upper, 22.1 per cent lower, and with Helioprogress 75 per cent upper and 23.2 per cent lower. Breakage appears to be unrelated to the materials used or to the age and sex of the patients. Upper retainers break more often than lowers (P = 0.016) and early breakage is more likely to occur at an adhesive pad than at a wire (9.6 versus 2.5 per cent within 6 months).     

Occult cerebral vascular malformations: high-field MR imaging

Occult cerebral vascular malformations (OCVMs) have characteristic appearances on high-field magnetic resonance (MR) images. These consist of circumscribed regions of low intensity, most prominent on T2-weighted images and representing hemosiderin deposits. Interspersed within most of these lesions are multiple areas of various signal intensity patterns, which correspond to hematomas in different stages of evolution and to fibrous regions containing calcium as well as hemosiderin. Forty-six lesions were found in 19 patients (34 supratentorial and 12 infratentorial). The supratentorial lesions tended to be subcortical or periventricular. Computed tomography depicted 24 of the 46 lesions demonstrated by high-field MR. Comparison of images obtained with both low-field MR (0.12 T and 0.35 T) and high-field MR (1.5 T) revealed that high-field MR imaging was superior in depicting OCVMs. High-field MR appears to be both sensitive and specific for OCVMs and may obviate the need for possible biopsy of these lesions.