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Biomedical subjects

D H Marshall

Publications and source records attributed to D H Marshall.

At least 19 recordsLinked to original sources
PubMed1995

Air guns: the main cause of enucleation secondary to trauma in children and young adults in the greater Ottawa area in 1974-93.

OBJECTIVES: To determine the proportion of enucleation procedures attributable to injuries from air guns in people aged 18 years or less and to identify the associated pathological findings. DESIGN: Case series. SETTING: Ophthalmic Pathology Registry, University of Ottawa, and affiliated Children's Hospital of Eastern Ontario (Ottawa), Ottawa General Hospital and Ottawa Civic Hospital. In addition, information on air gun injuries from April 1990 to December 1993 was obtained from the Canadian Hospitals Injury Reporting and Prevention Program (CHIRPP) database, with data from 10 pediatric and 5 general hospitals across Canada. PATIENTS: All patients aged 18 years or less who underwent enucleation between Jan. 1, 1974, and Dec. 31, 1993. RESULTS: Eighty-five patients were identified as having undergone enucleation. Trauma accounted for 51 cases (60%), of which 13 (25%) were caused by air guns, the largest single cause of enucleation secondary to trauma. Overall, air gun injuries accounted for 15% of enucleation procedures, whereas retinoblastoma accounted for 21%. All air gun injuries were in boys (median age 14 years, range 9 to 16 years). Of the 13 eyes with air gun injuries 7 had ocular perforation and 6 had ocular penetration. In all cases the intraocular structures were severely disrupted. The CHIRPP database included 165 air gun injuries; 32 were to the eye or ocular adnexa, resulting in 26 hospital admissions. CONCLUSIONS: Air guns were the largest single cause of enucleation secondary to trauma in our study. These guns are widely available in Canada and are unrestricted at muzzle velocities capable of causing death or serious injury, especially to the eye. We feel that air guns should be licensed only to people aged 16 to 18 years or older and that education in their use should be mandatory.

Adolescent↗
PubMed1995

Categories of Auditory Performance.

Categories of Auditory Performance (CAP) is an index consisting of eight performance categories arranged in order of increasing difficulty. It has been used to categorize 53 children who had been deafened below the age of 3. The children were assessed by means of the CAP before implantation, and over the following 3 years. Before implantation, only 2 of the children showed awareness of environmental sounds; immediately after initial tuning, all children showed awareness of environmental sounds, and 50% showed awareness of speech sounds. Their auditory receptive abilities gradually developed over the 3-year period, and by the 3-year assessment interval, 80% were understanding phrases without lipreading, and 40% were understanding conversation. Using these data, we predict that 90% of such children will understand conversation without lipreading 5 years after initial tuning.

Auditory Perception↗
PubMed1994

Clinical evaluation and test-retest reliability of the IHR-McCormick Automated Toy Discrimination Test.

The IHR-McCormick Automated Toy Discrimination Test (ATT) measures the minimum sound level at which a child can identify words presented in quiet in the sound field. This 'word-discrimination threshold' provides a direct measure of the ease with which a child can identify speech and a surrogate measure of auditory sensitivity. This paper describes steps taken to maximize the test-retest reliability of the ATT and to enable it to measure word-discrimination thresholds in noise as well as in quiet. It then describes the results of a clinical evaluation of the ATT in which paediatric audiologists measured word-discrimination thresholds in quiet from 215 successive attendees (in the age range 2 to 13 years) at a paediatric audiology clinic presenting over a 2-month period. When children with atypical cognition or delayed development of language were excluded, 72% of the children provided two word-discrimination thresholds and 83% provided at least one word-discrimination threshold. Children who failed to provide word-discrimination thresholds were generally younger than four years of age. Although a few children who could not perform pure-tone or warble-tone audiometry managed to provide word-discrimination thresholds, most children who could perform the ATT could also perform pure-tone audiometry. The average pure-tone threshold in the better-hearing ear could be predicted from the word-discrimination threshold with a 95% confidence interval of +/- 13 dB. The test-retest reliability of the ATT was measured in two ways. First, to enable comparison with published results, the within-subjects standard deviation of word-discrimination thresholds was calculated. It varied as a function of age and degree of impairment, but was never worse than 3.3 dB. Children of four years of age and older displayed the adult reliability of 2.3 dB. Second, the variability of absolute differences between word-discrimination thresholds was calculated. It was such that a change of 7 dB between two runs of the test (e.g. aided and unaided) would be expected to occur by change less than one time in 20. These results extend previous evaluations of the ATT to a clinically representative population and confirm that word-discrimination thresholds provide a useful complement to warble-tone and pure-tone audiometry.

Adolescent↗
PubMed1993

Lip-reading the BKB sentence lists: corrections for list and practice effects.

Two groups of 21 adult subjects with normal hearing viewed the video recordings of the Bamford-Kowal-Bench standard sentence lists issued by the EPI Group in 1986. Each subject viewed all of the 21 lists and attempted to write down the words contained in each sentence. One group lip-read the lists with no sound (the LR:alone condition). The other group also heard a sequence of acoustic pulses which were synchronized to the moments when the talker's vocal folds closed (the LR&Lx condition). Performance was assessed both by loose (KW(L)) and by tight (KW(T)) keyword scoring methods. Both scoring methods produced the same pattern of results: performance was better in the LR&Lx condition; performance in both conditions improved linearly with the logarithm of the list presentation order number; subjects who produced higher overall scores also improved more with experience of the lists. The data were described well by a logistic regression model which provided a formula which can be used to compensate for practice effects and for differences in difficulty between lists. Two simpler, but less accurate, methods for compensating for variation in inter-list difficulty are also described. A figure is provided which can be used to assess the significance of the difference between a pair of scores obtained from a single subject in any pair of presentation conditions.

Adolescent↗
PubMed1992

Bisphosphonate space measurement in Paget's disease of bone treated with APD.

The bisphosphonate space (BPS) is a quantitative measurement of skeletal uptake of 99mTc-HMDP. We measured BPS in 36 patients with Paget's disease of bone, both before and 6 months after treatment with intravenous APD (disodium pamidronate) infusions. BPS fell after treatment, but proportionally less than serum alkaline phosphatase (ALP) and fasting urinary hydroxyproline/creatinine (HYPRO). There was no dose-response relationship between the dose of APD given and the percentage reduction in ALP and HYPRO at 6 months. Log dose of APD/pretreatment BPS, however, predicted the percentage reduction in ALP and HYPRO very well, and from the respective regression equations it was possible to predict the dose of APD needed to achieve normal values of ALP and HYPRO. In the 10 patients who achieved a normal ALP and 9 patients a normal HYPRO after more than 6 months treatment with APD (range 7-18 months), the predicted dose of APD agreed closely with the actual dose. In conclusion, our data support the idea that log dose APD/pretreatment BPS is a valid predictor of biochemical response in Paget's disease.

Alkaline Phosphatase↗
PubMed1992

Comparison of low-dose intramuscular and intravenous salcatonin in the treatment of primary hyperparathyroidism.

The treatment of hypercalcaemia with low-dose salcatonin (100 U/d), administered either as a single intramuscular bolus or as a continuous intravenous infusion for five days, was examined in two groups of 10 patients with primary hyperparathyroidism, in a randomized open parallel study. Both the peak (0.31 +/- 0.035 mmol/L v 0.13 +/- 0.034 mmol/L) and overall (0.073 +/- 0.016 mmol/L v 0.018 +/- 0.016 mmol/L) hypocalcaemic responses were greater in the infusion group. The peak reduction in serum calcium occurred on day 2 of treatment after which there was a progressive attenuation of response. All the differences between the two methods of administration wer due to renal rather than bony effects of salcatonin. Possible causes of progressive resistance to treatment included reductions in sodium excretion and serum phosphate. It is concluded that low-dose salcatonin administered as a continuous infusion was more effective than the same dose given as a bolus. The kidney played a pivotal role both in the cause of the hypercalcaemia and in the response to treatment, including the rapid development of resistance which limits the use of salmon calcitonin in primary hyperparathyroidism to short-term reduction of serum calcium.

Alkaline Phosphatase↗
PubMed1991

Early detection of hearing impairment: what role is there for behavioural methods in the neonatal period?

A survey of the use of behavioural methods for neonatal hearing screening in 1985 (1) concluded that the future for automated methods was quite promising. Since then several studies have assessed the two main automated behavioural tests: the Auditory Response Cradle (ARC) and the Crib-o-Gram (COG). As a screen targeted at neonatal intensive care unit (NICU) babies and other high risk groups (at present the most cost-effective form of neonatal hearing screening), the ARC is shown to have low sensitivity, even for severe hearing impairments, and the COG has an unacceptably low specificity. Any future for behavioural testing during this period must therefore rely on new implementations flowing out of a fundamental understanding of (a) the way in which neonates respond to sound and (b) the ways in which a behavioural test might complement screening with Auditory Brainstem Responses (ABR) or Evoked Oto-acoustic Emissions (EOAE). A clearer understanding of the relative benefits of detecting different degrees of hearing impairment at birth in both the NICU population and the unrestricted population is urgently needed. To determine what role should be played by specific screening programmes such benefits need to be balanced against the total costs of screening assessment and rehabilitation, in which false positives (low specificity) play a large part.

Acoustic Stimulation↗
PubMed1991

Prediction of hearing thresholds in children using an automated toy discrimination test.

A previous paper described the development of the prototype of a semi-automated, sensitive and accurate version of the McCormick Toy Discrimination Test. In this report we describe a further development of the hardware, and demonstrate that results obtained from the automated test provide a basis for estimating the mean elevation of pure-tone threshold in the child's better ear. The correlation between speech and pure-tone results is high. The average of the better ear pure-tone thresholds at 0.5, 1 and 4 kHz can be predicted from the word-discrimination threshold obtained with the toy test, with a 95% confidence interval of +/- 11 dB.

Adolescent↗
PubMed1990

The evolution of acute renal failure, 1956-1988.

A total of 1347 patients with severe acute renal failure, treated at a single centre between 1956 and 1988, are reviewed. Only patients with an acute uraemic episode requiring dialysis and/or with serum creatinine levels above 600 mumols/l were included. The age of patients increased from median 41.25 years in the 1950s to 60.5 years in the period 1980 to 1988. The case-mix also altered with a decline in obstetric and traumatic disease, both of which carried an excellent prognosis, and an increase in the number of elderly patients with complicated medical and surgical conditions. Survival significantly decreased with increasing age and in the presence of complicating factors such as sepsis or malignancy. Despite these changes, there has been a progressive improvement in survival from 48.8 per cent in 1956-1959 to 57.9 per cent in 1985-1988. Survival for medical and surgical cases has improved from 38.5 per cent in 1956-1959 to 57.9 per cent in 1985-1988 (overall survival for non-obstetric cases was 44.2 per cent), due to improved prognosis for acute renal failure in general and acute renal failure due to intrinsic renal disease in particular.

Acute Kidney Injury↗
PubMed1989

Spinal osteoporosis in men.

In 94 men with crush fracture, 40 were found to have primary osteoporosis. Cross-sectional measurements of a number of variables related to bone in these 40 patients were compared to the values in various groups of healthy men aged 20-96. In healthy men, metacarpal and femoral cortical area/total area, bone volume, osteoid surfaces, seam and trabecular width, plasma dihydroepiandrosterone and estrone, and radiocalcium absorption fell with age, whereas eroded surfaces, trabecular number, urine hydroxyproline and calcium/creatinine ratios, plasma alkaline phosphatase, estradiol, androstenedione, cortisol and testosterone remained constant with age. As compared with healthy men, men with primary osteoporosis had reduced femoral cortical area/total area (P less than 0.05), and Singh grade (P less than 0.001) and in seven there was a history of forearm or femoral fracture. On iliac crest biopsy, bone volume (P less than 0.001) and trabecular number (P less than 0.01) were decreased. Plasma alkaline phosphatase (P less than 0.02) was increased but urine hydroxyproline and calcium excretion were not significantly raised. Calcium balance was negative due to failure of absorption to match urinary calcium loss and radiocalcium absorption (P less than 0.01) and plasma 1,25-dihydroxyvitamin D (P less than 0.05) were reduced.

Adult↗
PubMed1986

Osteoporosis in hypogonadal men: role of decreased plasma 1,25-dihydroxyvitamin D, calcium malabsorption, and low bone formation.

To investigate the pathogenesis of osteoporosis in male hypogonadism we have investigated a heterogeneous group of 13 men with hypogonadism: 7 men (median age 60, range 31-79) with two or more vertebral crush fractures and 6 men (median age 61.5, range 28-76) without vertebral fractures. The group with crush fractures had trabecular and cortical osteoporosis as assessed by Singh grade, iliac crest trabecular bone volume, and metacarpal cortical area/total area. This was accompanied by an altered trabecular architecture with a reduction in number of trabeculae but no change in trabecular width, which contrasts with age-related bone loss in men where there is no reduction in trabecular number but thinning of trabeculae. The fracture group had significantly lower plasma 1,25-dihydroxyvitamin D [1,25(OH)2D] concentrations than the nonfracture group, and this was associated with malabsorption of calcium. Irrespective of the presence or absence of osteoporosis, treatment with testosterone led to a significant increase in total and free plasma 1,25(OH)2D and an improvement in calcium absorption measured with radiocalcium and by balance techniques. In addition, urine biochemistry, metabolic balance studies, and bone biopsy suggest that skeletal retention of calcium and bone formation are increased by testosterone treatment. We conclude that male hypogonadism causes both cortical and trabecular osteoporosis and altered trabecular architecture. A major risk factor for the development of osteoporosis is reduction in plasma 1,25(OH)2D, leading to malabsorption of calcium and reduced bone formation.

Adult↗
PubMed1986

Are scintigrams of the spine useful in vertebral osteoporosis?

To determine whether technetium diphosphonate scintigraphy could be used to date vertebral crush fractures, serial scintigrams and radiographs were obtained on two groups of 27 osteoporotic patients. Although radiologically crushed vertebrae were significantly associated with areas of increased isotope uptake on the scintigrams (p less than 0.001), this did not depend on the age of the crush fracture. Some radiologically uncrushed vertebrae, particularly in the lumbar spine, also showed increased isotope uptake.

Adult↗
PubMed1986

A comparison of the effect of sorbitol and glucose on calcium absorption in postmenopausal women.

It has been suggested that the oral administration of sorbitol promotes calcium absorption, while glucose has no effect. We have therefore compared the effect of oral sorbitol and glucose on the absorption of radiocalcium from low and high carrier loads in healthy postmenopausal women. In a control group of 20 women given neither sorbitol nor glucose, the mean +/- SEM fractional radiocalcium absorption rate from a low carrier load was 0.65 +/- 0.05 (fraction of dose/h). In a second group of 10 women the fractional absorption rate from the low carrier load was lower (p less than 0.05) with 10 g sorbitol (0.48 +/- 0.05) than with 10 g glucose (0.65 +/- 0.08). Fractional absorption of radiocalcium from a high carrier load measured in a third group of seven women using two isotopes (oral 45Ca, IV 47Ca) was also lower (p less than 0.001) with 10 g sorbitol (0.22 +/- 0.01, fraction/3 h) than with 10 g glucose (0.29 +/- 0.02). The results suggest that calcium absorption from a low carrier load is unaltered by glucose but that absorption of calcium from both low and high carrier loads is lower with sorbitol than with glucose.

Aged↗
PubMed1985

A stochastic model of age-related bone loss and fractures.

A stochastic model of age-related bone loss capable of predicting age-specific incidence of fractures has been implemented by Monte Carlo simulation. Each simulation involves aging a large cohort of individuals from 20 to 100 years. Every individual is randomly allocated a particular amount of bone as a young adult, an age of onset of bone loss, and parameter values that determine the subsequent bone loss. Fracture risk is assumed to be zero when the amount of bone is above a global threshold level, increasing progressively as the amount of bone falls below the threshold. From the individual fracture risks, a fracture subpopulation is identified and age-specific incidence evaluated numerically. By adjusting the model parameters, predicted and observed incidences of femoral neck fracture can be closely matched in both sexes by use of a linear function to describe age-related bone loss. For fracture of the distal radius, a close match can be achieved in women by use of an exponential function to describe the bone loss phase. In men, the incidence is independent of age; trauma, rather than the amount of bone in the forearm, appears to be the main determinant of fracture risk.

Adult↗