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Biomedical subjects

J Pearn

Publications and source records attributed to J Pearn.

At least 145 records · Page 8Linked to original sources
PubMed1978

Autosomal dominant spinal muscular atrophy: a clinical and genetic study.

A clinical and genetic study of 6 kindreds (13 patients) with autosomal dominant spinal muscular atrophy is presented. Evidence is presented to indicate that two separate autosomal dominant genes are involved. One of these causes clinical disease with onset in early childhood (birth--8 years), which is relatively benign and in which proximal selectively of muscle involvement is not marked. A separate autosomal dominant gene causes a disease with onset in adult life (median age 37 years), showing marked initial proximal selectively; this disease may be more rapid in its clinical progression. Penetrance of both genes approaches 100%. Incidence figures are presented; less than 2% of all cases of childhood onset spinal muscular atrophy, but 30% of adult onset cases, are due to an autosomal dominant gene transmitted from an affected parent. Implications for prognosis, diagnosis and genetic counselling are discussed. A review of 11 kindreds of dominant spinal muscular atrophy in the literature is presented.

Adolescent↗
PubMed1978

A genetic study of subacute and chronic spinal muscular atrophy in childhood. A nosological analysis of 124 index patients.

A genetic study of the subacute spinal muscular atrophies (SMA) of late infancy and early childhood has been undertaken. All such patients with chronic disease (with ages at onset up to 14 years, and excluding SMA Type I) known to 2 large Neurological Centres were reassessed clinically and genetically. There were 124 index patients (67 females and 57 males) and 17 secondary cases, which formed two consecutive unselected series. To investigate the genetic composition of this group, 4 nosological approaches were used; cluster analysis of clinical features of the disease, Haldane's sib-sib analysis on familial cases, interpretation of frequency distribution histograms, and a segregation analysis. A single autosomal recessive gene accounts for over 90% of cases, causes a clinical syndrome which manifests its first clinical signs before 5 years of age and in almost all cases before two years of age, but which is compatible with life into the third decade. Moderate intrafamilial discordance for some clinical features may be observed, but no genetic heterogeneity within this group was demonstrated. A small group of cases is caused by (a) new dominant mutation(s), or (b) is composed of phenocopies, or both. This relatively uncommon form may comprise the majority of late-presenting cases, and may account for all cases which manifest the first signs after 5 years of age. The spectrum of age-at-onset of this group cannot be determined at present, but the disease may be manifest before the age of two years; it is clinically indistinguishable from SMA caused by an autosomal recessive gene. The literature has been reviewed in the light of these findings. Empirical risks for use in genetic counselling are presented.

Child, Preschool↗
PubMed1978

Two early dynamometers. An historical account of the earliest measurements to study human muscular strength.

An account of two of the earliest dynamometers is presented, together with results of the first experiments attained with them. The Graham--Desaguliers dynamometer was developed in London in 1763 to measure human muscular force, in such a way that synergistic muscles could not impart a false mechanical advantage to the test. The Regnier dynamometer was invented in Paris in 1798 to measure the traction properties of artillery-horses, but was desinged as an all-purpose instrument to measure specific human muscle groups as well. Dynamometers were developed to record human strength along a continuum, to remove the need for a dead-weight or biological standard, and to measure many different groups of muscles, not just those of lifting or pushing. The foundations of modern clinical dynamometry are described.

England↗
PubMed1978

A study of environmental factors in relation to fatal infantile spinal muscular atrophy (SMA type I). An analysis of birth order and parental age effects, social class, seasonal influence, and clustering in time and place.

Major studies of the childhood spinal muscular atrophies have suggested that environmentally-produced phenocopies might occur, and that environmental factors might be important in some clinical features of these diseases. A formal analysis of some possible intra-uterine and post-natal influences has been undertaken in 78 index cases (72 families) of acute infantile SMA (acute Werdnig-Hoffmann disease; SMA Type I). There is no evidence to suggest that social class, parental age, birth order, or season of birth influences this disease or that clustering in time and place occurs.

Acute Disease↗
PubMed1978

Survival rates after serious immersion accidents in childhood.

A study of childhood survival rates, after loss of consciousness in fresh water, has been undertaken. Age-specific, sex-specific and site-specific survival rates for childhood fresh water immersion accidents are reported for the first time. The overall survival rate, after loss of consciousness in the water was 0.49; swimming pool and domestic bath tub serious immersion accidents have a survival rate of 0.60 compared with a rate of 0.05 for similar immersion accidents in creeks and rivers. Young male schoolboys have the lowest potential survival (0.20 or less) of any group. Survival rates were significantly higher during the winter (0.86) than during the warmer months (survival rate of 0.49). This gives a quantitative expression to the protection from cerebral anoxia afforded by body chilling which is not extreme. Survival rates have increased significantly over the 5 year period 1971--1975; it is considered that this is due to public education campaigns of the potential danger of water to children. The use of survival rates to measure factors which modify the pathophysiology of human drowning and near-drowning is discussed.

Adolescent↗
PubMed1978

Predisposing factors leading to child trauma. An analysis of specific versus non-specific causes in motor vehicle and drowning fatalities.

In many Western countries, trauma is the chief cause of death in children aged one to 14 years. A large number of these deaths are the result of motor vehicle accidents or drowning. It is postulated that the causes of such trauma can be classified into (a) non-specific, predetermining social factors; (b) specific social factors; and (c) acute triggers. Prevention strategies vary considerably for these three groups. Prevention is most cost-effective when directed against specific social factors. In this paper, data for childhood motor vehicle and drowning fatalities in Australia have been analysed and scored for non-specific social influences on childhood accidents such as overcrowding or poverty. This approach allows the ranking of different communities by risk. Motor vehicle accident ratios have been calculated, and these are sufficiently specific, by age and sex, to enable comparisons to be made in future with other communities.

Accidents, Traffic↗
PubMed1978

Incidence, prevalence, and gene frequency studies of chronic childhood spinal muscular atrophy.

A total population study of chronic childhood spinal muscular atrophy (arrested Werdnig-Hoffmann disease, Kugelberg-Welander disease, SMA type II and III) was undertaken in north-east England to establish gene and carrier frequencies, incidence, and prevalence. The incidence of this disease was 1 in 24 100 live births. Prevalence was 1.20 per 100,000 of the general population. A technique for estimating an autosomal recessive gene frequency in the known presence of dominant new mutations (or phenocopies), using data from a segregation analysis, is described. Gene frequency was in the range (0.00451 to 0.00659 (95% confidence limits), with a working estimate of 0.0055. Carrier rates for the autosomal recessive gene concerned were 1 in 76 to 1 in 111 (95%) confidence limits), with a working estimate of 1 in 90 for genetic counselling purposes.

Child, Preschool↗
PubMed1978

Genetic studies of acute infantile spinal muscular atrophy (SMA type I). An analysis of sex ratios, segregation ratios, and sex influence.

An analysis of segregation and sex ratios, and of sex influence, was undertaken in a series of 78 index patients with acute infantile spinal muscular atrophy (SMA type I). The sex ratio of index patients was 2.0, and the excess of males was shown to occur principally among sporadic cases. The sex ratio of familial cases did not differ significantly from 1.0. The implications of this are discussed. No sex influence on age at onset, or on life expectancy, was present. The segregation ratio (Weinberg Proband method) was 0.29 for all index cases, and 0.26 for all cases excluding those referred specifically to a genetic counselling clinic. Autosomal recessivity is confirmed for this disease, with the probable inclusion of unrecognised male phenocopies in clinical series.

Acute Disease↗
PubMed1978

Segregation analysis of chronic childhood spinal muscular atrophy.

A formal segregation analysis for the disease 'chronic childhood spinal muscular atrophy' is presented. This disease is also known as 'Kugelberg-Welander disease', 'arrested Werdnig-Hoffmann disease', and 'chronic proximal or generalised spinal muscular atrophy'. There were 124 index cases occurring in 115 families. Ascertainment of index patients was by incomplete multiple selection. Three types of segregation analysis were performed: Weinberg Proband, an improved Weinberg Proband with a variance corrected formula for differences both in family size and ascertainment probability and a backeting technique assuming the extremes of both single and of truncate selection. All three methods gave similar results. The improved Weinberg Proband method with corrections for differences in ascertainment and in family size gave a segregation ratio of 0.18 and a 95% confidence range of 0.11 to 0.25. The mid-point of the bracketing method assuming extremes of truncate and of single selection was 0.19. The segregation ratio of that group of children with clinical onset before 9 months of age was 0.21, which does not differ significantly from the 0.25 predicted on the basis of autosomal recessivity. Evidence is presented to indicate that 25% of index patients may be due to new dominant mutations, or phenocopies, or both, and that these occur particularly among sporadic cases with clinical onset over 2 years of age. Empirical risk figures for use in genetic counselling are presented, and the literature of the subject is reviewed.

Child, Preschool↗
PubMed1977

Drowning in Australia: a national appraisal with particular reference to children.

National statistics of drowning (accidental and submersion) for Australia, by State, age and sex have been compiled. The national rate is 3.29 per 100 000 which compares well with that from other countries of similar latitude. The national childhood drowning rate (age group of 0 to 14 years) is 5.19 per 100 000; the rate for the 0 to four years age group ranges from almost zero in the Australian Capital Territory to 15.69 in Queensland. In all States, a drowning rate for preschool children is at least four times that of school children. Preschool versus total drowning ratios have been calculated, by State; the rank order of this data (those of Victoria are highest at 4.65) is further evidence that climatic factors alone are not necessarily major predisposing causes leading to high drowning statistics of preschool children observed in other series.

Adolescent↗
PubMed1977

Are swimming pools becoming more dangerous?

The rate of childhood drowning and near-drowning accidents in home swimming pools has doubled over the last five years. A study has been undertaken to determine whether this is due simply to an absolute increase in the number of home swimming pools, or whether pools themselves are becoming intrinsically more dangerous, or both. Direct measurement of pool-house ratios has been undertaken by means of aerial photography. Supportive data have been obtained from municipal records. Pool-home ratios for the cities of Canberra and Brisbane are compared (estimated 1: 10.7, and 1:13.3 respectively). It is suggested that swimming pools are not becoming intrinsically more dangerous to children; the data suggest that effective pool legislation will prevent childhood drownings in spite of increasing trends in home pool ownership.

Accidents, Home↗
PubMed1977

The clinical features of tick bite.

The clinical features of bites by the Australian scrub tick, Ixodes holocyclus, are reviewed. Eight cases of tick bite are summarized, including six new cases of tick paralysis in children. In almost all cases neuroparalysis became worse transiently, after the tick had been removed. One child with life-threatening respiratory and bulbar palsy received canine antitick antivenene, with rapid reversal of clinical signs. The differential diagnosis of tick bite includes all acute childhood diseases which can affect the motor units; the importance of including the possibility of tick envenomation in the differential diagnosis of acute weakness or paralysis in children is illustrated. The clinical features of neuromuscular paralysis are described, together with a review of the tick's local effects at the bite site.

Adult↗
PubMed1977

Prevention of childhood drowning accidents.

The data from the Brisban Drowning Study have been analysed in this article to provide guidelines for preventive strategies. The separate causal links comprising the drowning chain have been identified, and quantitative scores have been assigned to the three identifiable groups of causative factors--environmental, parent-related and victim-related. The identifiable causes of child drowning are absence of a safety barrier or fence around the water hazard, non-supervision of a child, a parental "vulnerable period", an inadequate safety barrier, and tempting objects in or on the water. Effective environmental control can be achieved only through legislation. The complementary role of a public educational thrust in discussed. Increasing the tempo of "drownproofing* and of teaching children to swim will help, but the expected reduction in deaths and near-deaths from this strategy alone cannot yet be assessed. Compulsory first aid training for pool owners is required. Costs of implementing a total drowning preventive programme are presented.

Age Factors↗
PubMed1977

Bathtub immersion accidents involving children.

A review of 19 consecutive serious bathtub immersion accidents (11 survivals, 8 fatalities) is presented. In all instances, consciousness was lost in the water. Unlike other childhood accidents which usually show a male predominance, the sexes are equally affected. The modal age is 11 months. Six separate causes of bath drownings and near-drownings have been identified, and in 14 of the 19 accidents, two or more causes were operating concurrently. Median estimated immersion time for survivals was four minutes, and five minutes for fatalities. The median depth of water was eight inches. An 'at risk' profile for home bathtub drownings is presented; this includes the youngest or second youngest child of a large family, a family of grade 4 to 7 sociooccupational status (congalton) and a family in which routine is temporarily broken.

Accidents, Home↗
PubMed1977

Neurological and phychometric studies in children surviving freshwater immersion accidents.

A study of the neurological and intellectual sequelae of childhood near-drowning is reported. Results are from a total population study, without selection, of all freshwater immersion accidents in which consciousness was lost in the water. Such accidents affected 56 children in the city of Brisbane and environs over the period 1971-75. 54 of these children have been re-examined medically and psychometrically. Over 95 per cent of children who survived such accidents were neurologically normal. The median i.q. of survivors was 110 (range 90-137), which is higher than that of the general population. There is a suggestion that visualmotor (performance)) skills are particularly vulnerable to freshwater immersion hypoxia. In 20 per cent of survivors subscale disparities between verbal and performance skills exceeded 15 i.q. points. No correlation between the post-immersion I.Q. and either estimated immersion-time or water temperature was demonstrated in this study. No long-term emotional or personality disorders were encountered. Uncommon gross clinical sequelae of prolonged immersion in fresh water included spastic quadriplegia and gross mental retardation. All children in this study were apparently dead at the moment of rescue; despite this, the prognosis of near-drowning in childhood is excellent

Child↗
PubMed1977

Neuromuscular paralysis caused by tick envenomation.

The Australian scrub-tick Ixodes holocyclus causes a series of significant toxic effects in its victims. The most important feature of tick envenomation is neuromuscular paralysis. Children poisoned by ticks may manifest only local motoneural effects, usually facial paralysis. Progressive ascending flaccid paralysis occurs if the removal of an embedded tick is delayed. The specific neurological features of tick-bite are discussed in the light of a series of 6 children who all showed signs of tick paralysis. Tick venom is known to slow nerve conduction, and may have a botulinum-like effect at the neuromuscular junction. The literature on the neurological effects of tick-envenomation is reviewed.

Australia↗