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K M Johnston

Publications and source records attributed to K M Johnston.

At least 19 recordsLinked to original sources
PubMed2004

Functional abnormalities in symptomatic concussed athletes: an fMRI study.

Our aim was to quantify with functional magnetic resonance imaging (fMRI) changes in brain activity in concussed athletes and compare the results with those of normal control subjects. Regional brain activations associated with a working memory task were obtained from a group of concussed athletes (15 symptomatic, 1 asymptomatic) and eight matched control subjects, using blood oxygen level dependent (BOLD) fMRI. The average percent signal change from baseline to working memory condition in each region of interest was computed. Symptomatic concussed athletes demonstrated task-related activations in some but not all the regions of interest, even when they performed as well as the control subjects. Furthermore, several concussed athletes had additional increases in activity outside the regions of interest, not seen in the control group. Quantitative analysis of BOLD signals within regions of interest revealed that, in general, concussed athletes had different BOLD responses compared to the control subjects. The task-related activation pattern of the one symptom-free athlete was comparable to that of the control group. We also repeated the study in one athlete whose symptoms had resolved. On the first study, when he was still symptomatic, less task-related activations were observed. On follow-up, once his symptoms had disappeared, the task-related activations became comparable to those of the control group. These results demonstrate the potential of fMRI, in conjunction with the working memory task, to identify an underlying pathology in symptomatic concussed individuals with normal structural imaging results.

Adult↗
PubMed2003

Snowblading injuries in Eastern Canada.

OBJECTIVES: To evaluate injury patterns of snowbladers and compare them with those of skiers and snowboarders. To determine possible effects of helmet use in these sports on injury to the head and neck. METHODS: This prospective case series observational study was conducted by collecting the injury reports from the ski patrol during the 1999-2000 season at Mont Tremblant ski resort, Quebec. All participants in downhill winter sports who presented themselves to the ski patrol with traumatic injury related to their sport were included. A concussion was defined as any loss of consciousness, amnesia, confusion, disorientation, vertigo, or headache that resulted from injury. The ski patroller reported helmet use on the accident report at the time of injury. RESULTS: Snowbladers present with a unique pattern of injury compared with skiers and snowboarders. The incidence of leg, knee, and ankle/foot injuries were 20.5%, 25.6%, and 10.3% respectively. Concussions represented 11% of all injuries. There was no increase in other injury, including neck injury, related to helmet use. CONCLUSIONS: Unique injury patterns in snowbladers warrant reconsideration of equipment design. Concussion is a common injury on the ski slope. Although the effects of helmet use on concussion rate are inconclusive based on this study, helmet use did not increase the rate of neck injury, even when adjusted for age.

Adolescent↗
PubMed2001

Fate and transport of copper-based crop protectants in plasticulture runoff and the impact of sedimentation as a best management practice.

The fate and distribution of copper-based crop protectants, applied to plasticulture tomato fields to protect against disease, were investigated in a greenhouse-scale simulation of farming conditions in a coastal environment. Following rainfall, 99% of the applied copper was found to remain on the fields sorbed to the soil and plants; most of the soil-bound copper was found sorbed to the top 2.5 cm of soil between the plasticulture rows. Of the copper leaving the agricultural fields, 82% was found in the runoff with the majority, 74%. sorbed to the suspended solids. The remaining copper, 18%, leached through the soil and entered the groundwater with 10% in the dissolved phase and 8% sorbed to suspended solids. Although only 1% copper was found to leave the field, this was sufficient to cause high copper concentrations (average 2102+/-433 microg/L total copper and 189+/-139 microg/L dissolved copper) in the runoff. Copper concentrations in groundwater samples were also high (average 312+/-198 microg/L total copper and 216+/-99 microg/L dissolved copper). Sedimentation, a best management practice for reducing copper loadings. was found to reduce the total copper concentrations in runoff by 90% to a concentration of 245+/-127 microg/L; however, dissolved copper concentrations remained stable, averaging 139+/-55 microg/L. Total copper concentrations were significantly reduced by the effective removal of suspended solids with sorbed copper.

Adsorption↗
PubMed2001

Evidence-Based review of sport-related concussion: clinical science.

The clinical nature of sport-related concussion is discussed in this paper. Particularly highlighted are the difficulties with definition, injury severity grading, classification, and understanding of clinical symptoms. In addition, the well-recognized sequelae of concussion including the motor and convulsive manifestations are discussed in detail. Where possible, an evidence-based approach is adopted to assist the understanding of the literature in this complex area.

Athletic Injuries↗
PubMed2001

Evidence-based review of sport-related concussion: basic science.

The evidence base for sport-related concussive brain injury is reviewed in this paper. In the past, pathophysiological understanding of this common condition has been extrapolated from studies of severe brain trauma. More recent scientific study demonstrates that this approach is unsatisfactory, and the clinical features of concussion represent a predominantly functional brain injury rather than manifest by structural or neuropathological damage. Such understanding of this condition remains incomplete at this stage.

Athletic Injuries↗
PubMed2001

New frontiers in diagnostic imaging in concussive head injury.

Concussed athletes may have documented incapacitating postconcussive symptoms, neuropsychological deficits, and consequent important changes in their lives and sport, yet the majority of neuroimaging attempts reveal few findings to account for these signs and symptoms. In this paper, we explore new techniques in the neuroimaging of concussion including diffusion-weighted magnetic resonance imaging and functional brain imaging technology.

Athletic Injuries↗
PubMed2001

Recommendations for grading of concussion in athletes.

Mild sports-related concussions, in which there is no loss of consciousness, account for >75% of all sports-related brain injury. Universal agreement on concussion definition and severity grading does not exist. Grading systems represent expertise of clinicians and researchers yet scientific evidence is lacking. Most used loss of consciousness and post-traumatic amnesia as markers for grading concussion. Although in severe head injury these parameters may have been proven important for prognosis, no study has done the same for sport-related concussion. Post-concussion symptoms are often the main features to help in the diagnosis of concussion in sport. Neuropsychological testing is meant to help physicians and health professionals to have objective indices of some of the neurocognitive symptoms. It is the challenge of physicians, therapists and coaches involved in the care of athletes to know the symptoms of concussion, recognise them when they occur and apply basic neuropsychological testing to help detect this injury. It is, therefore, recommended to be familiar with one grading system and use it consistently, even though it may not be scientifically validated. Then good clinical judgement and the ability to recognise post-concussion signs and symptoms will assure that an athlete never returns to play while symptomatic.

Athletic Injuries↗
PubMed2001

Outbreak of Salmonella indiana associated with egg mayonnaise sandwiches at an acute NHS hospital.

An outbreak of Salmonella indiana infection in December 2000 affected 17 staff, relatives and patients at an acute NHS Hospital in Swansea. Epidemiological investigation identified egg mayonnaise sandwiches as the vehicle of infection. It was not possible to definitively determine the source of the infection or how the prepared sandwiches became contaminated. The most likely explanation was a pasteurisation failure of a batch of the egg roll used to make these sandwiches. Sandwiches are the most frequently identified vehicle of infection in foodborne outbreaks of salmonella infection in hospitals in England and Wales. The process of sandwich preparation has inherent risks because it involves considerable handling of food, which is consumed without further cooking. Care is required in all stages of preparation including the sourcing of materials used to produce the sandwiches. NHS Trusts should review their Hazard Analysis Critical Control Point plans for sandwich production.

Case-Control Studies↗
PubMed2000

Concussions in athletes produce brain dysfunction as revealed by event-related potentials.

We have used event-related potentials (ERP) to assess cerebral activity following mild traumatic brain injuries in 20 college athletes practising contact sports. Concussion victims showed a striking decrease in P300 amplitude, an effect presumed to reflect alterations in attentional-cognitive processes. Moreover, the degree of impairment was strongly related to the severity of post-concussion symptoms. Our data suggest that concussions cause objectively measurable changes in the electrophysiological markers of brain activity and hence in the functions of the structures from which they originate. ERPs may thus constitute a reliable method to accurately monitor the clinical course and recovery of head injuries in athletes.

Adult↗
PubMed2000

Concussions during the 1997 Canadian Football League season.

OBJECTIVE: To examine the incidence and characteristics of concussions for one season in the Canadian Football League (CFL). DESIGN: Retrospective survey. PARTICIPANTS: 289 players reporting to CFL training camp. Of these, 154 players had played in the CFL during the 1997 season. MAIN OUTCOME MEASURES: Based on self-reported symptoms, calculations were made to determine the number of concussions experienced during the previous season, the duration of symptoms, the time for return to play after concussion, and any associated risk factors for concussions. RESULTS: Of all the athletes who played during the 1997 season, 44.8% experienced symptoms of a concussion. Only 18.8% of these concussed players recognized they had suffered a concussion. 69.6% of all concussed players experienced more than one episode. Symptoms lasted at least 1 day in 25.8% of cases. The odds of experiencing a concussion increased 13% with each game played. A past history of a loss of consciousness while playing football and a recognized concussion while playing football were both associated with increased odds of experiencing a concussion during the 1997 season. CONCLUSION: Many players experienced a concussion during the 1997 CFL season, but the majority of these players may not have recognized that fact. Players need to be better informed about the symptoms and effects of concussions.

Adult↗