Invasion of the mandible by squamous carcinomas of the oral cavity and oropharynx

The radiologic and histologic features of mandibular invasion, and its clinical implications, are considered in a retrospective series of 111 patients with squamous carcinomas of the oral cavity and oropharynx treated by composite resection. Eighty percent of the entire group had either recurrent or advanced (T3, T4) local disease, and 33 patients (30%) had histologic evidence of mandibular invasion by tumor. Preoperative radiologic assessment was unreliable in cases in which infiltrating tumor was confined to the periosteum and superficial cortex-44% false negatives. The extent of bone invasion was found to correlate with the size of the tumor, but not with its histologic grade. The mandibular periosteum was not seen as a morphologically discrete "barrier" and infiltration occurred at various points along the mandibular body, mainly related to the course of the inferior dental canal. The gross and microscopic patterns of bone invasion appeared to be similar in irradiated and nonirradiated resections. The incidence and pattern of recurrent disease following composite resection was the same in the groups with and without mandibular invasion: in each group half the patients were dead from disease and one third alive and free of disease at 2 years. Mandibular invasion alone did not appear to influence prognosis in this series.     

The learning experiences of dyslexic medical students during the COVID-19 pandemic: a phenomenological study

Advances in Health Sciences Education - Dyslexia is a Specific Learning Difficulty that impacts on reading and writing abilities. During the COVID-19 pandemic, medical schools have been forced to...     

Facilitators and Barriers in Cross-Country Transport of Evidence-based Preventive Interventions: a Case Study Using the Family Check-Up

Prevention Science - This study is a qualitative analysis of facilitators and barriers in the dissemination of Family Check-Up (FCU), a U.S.-developed preventive intervention in Sweden. The FCU is...     

Use of past care markers in risk-adjustment: accounting for systematic differences across providers

The European Journal of Health Economics - Risk-adjustment models are used to predict the cost of care for patients based on their observable characteristics, and to derive efficient and equitable...     

Comparison of 99Tcm dimercaptosuccinic acid scans and intravenous urography in children

A retrospective comparison of 99Tcm dimercaptosuccinic acid (DMSA) scans and intravenous urograms (IVUs) was performed on a large, unselected paediatric population to assess critically the relative merits of these two techniques. A total of 205 children were studied, providing 388 kidneys for comparison. The studies agreed in 81%, both being normal in 39%, and both abnormal in 42%. In 28 kidneys (7%), the IVU was abnormal when the 99Tcm DMSA was normal. There was a collecting system abnormality in 27 kidneys, but 10 kidneys also showed a parenchymal abnormality. In all these the parenchymal abnormality was global thinning on the IVU, and the contralateral kidney was small. In 40 kidneys (10%) the 99Tcm DMSA was abnormal when the IVU was normal: the abnormalities demonstrated were predominantly focal defects. After excluding IVUs of poor diagnostic quality, only 14 kidneys (3.6%) showed this disparity. The important clinical subgroups are infection, with or without reflux (27 kidneys), hypertension (4) and neonates with poor renal function (2). The one false positive 99Tcm DMSA was a result of an anatomical variant. Global thinning in a "normal" kidney on a 99Tcm DMSA scan may be overlooked when the contralateral kidney is poorly functioning and small.     

Experimental cutaneous leishmaniasis. III. Histopathological aspects of the developmental behavior of the cutaneous lesion induced in Cebus apella (Primates: Cebidae) by Leishmania (Viannia) lainsoni, L. (V.) braziliensis and L. (Leishmania) amazonensis

We have studied the histopathological aspects related to the evolution of cutaneous lesions experimentally produced in the monkey Cebus apella (Primates: Cebidae) by Leishmania (V.) lainsoni, L. (V.) braziliensis and L. (L.) amazonensis. Microscopical examination of a series of biopsies obtained from these animals showed the kinetics of the cutaneous lesions regarding three species of Leishmania inoculated, as follows: 1) an initial non-specific chronic inflammatory infiltrate; 2) macrophagic nodules; 3) necrosis of parasitized phagocytic cells; 4) epitheliode granuloma; 5) absorption of the necrotic area (sometimes forming "foreign-body granuloma"); 6) a non-specific residual inflammatory infiltration; and 7) cicatrization. These pathological processes are, of course, responsible for both development and resolution of the leishmaniotic lesion. We also discuss some immunopathological mechanisms probably related with the sequential events, and that could be also responsible for the different clinical aspects found in man.     

Learning by Selection in the Trion Model of Cortical Organization

The basic issue of whether mammalian learning in cortex proceedsvia a selection principle, as stressed by Edelman, versus aninstructional one is of major importance. We present here arealization of selection learning in the trion model, whichis based on the Mountcastle columnar organizational principleof cortex. We suggest that mammalian cortex starts out withan a priori connectivity between minicolumns that is highlystructured in time and in space, competing between excitationand inhibition. This provides a "naive" repertoire of spatial-temporalfiring patterns that stimuli and internal pro-cessing map onto.These patterns can be learned with small modifications to theconnectivity strengths determined by a Hobbian learning rule.As various patterns are learned, the repertoire changes somewhatin order to respond property to various stimuli, but the majorityof all possible stimuli still map onto spatial-temporal firingpatterns of the original repertoire. In order to show that theexample presented here is showing true selectivity and is notan artifact of more stimuli evolving into the learned pattern,we develop a selectivity measure. We suggest that some formof instructional learning (in which connectivities are finelytuned) is present for difficult tasks requiring many trials,whereas very rapid learning involves selectional learning. Bothtypes of learning must be considered to understand behavior.     

Epidemiologic research using existing databases of environmental measures

When detailed information on individuals is not available, databases of environmental measures are sometimes used in epidemiologic studies to provide data on human exposure. The use of such databases is based on the assumption that the data are representative of individual human exposure and are applicable to the study. Twenty-six databases that contained data on the environment pertaining to California were summarized and evaluated by categorical criteria of spatial and temporal precision, availability, amount of quantitative information, "machine-readability," and type of environmental measure.     

Prediction of temperature rise in layered media from measured ultrasonic intensity data

It is now widely recognized that under some circumstances exposure to ultrasound at current diagnostic levels may result in undesirable heating in tissue. The National Council on Radiation Protection and Measurements (NCRP) and the American Institute of Ultrasound in Medicine (AIUM) in conjunction with the National Electrical Manufacturers Association (NEMA) have suggested relatively simple methods for estimating the in situ temperature rise based on simplified ultrasonic intensity profiles. In this paper, the measured spatial intensity distribution from three unscanned ultrasonic transducers is used in an integral solution to the bioheat equation to calculate the temperature increase in layered media, and these calculations are compared with the simple predictions under similar conditions. The transducers included weak and strong focusing devices and one device with a non-cylindrical beam. The ratio between the NCRP and AIUM/NEMA predictions varied from 0.5 to 2.3 in equivalent situations. The ratio between the simple predictions and the more detailed calculations varied from 0.7 to 3.2 for NCRP, and from 0.3 and 3.5 for AIUM/NEMA. These results highlight the need, firstly, to establish simple 'standard' methods for estimating likely temperature increase during clinical examination, and secondly to be clear about whether these methods are intended to give 'worst case' or 'typical' estimates.