PubMed Health⌕ Search

Biomedical subjects

M McCaffrey

Publications and source records attributed to M McCaffrey.

30 records · Page 2Linked to original sources
PubMed1987

Motor evoked potential as a predictor of recovery in chronic spinal cord injury.

In injury to the spinal cord, motor function is the most critical system affected. The introduction of motor evoked potential (MEP) monitoring techniques over the past 5 years has opened new possibilities for the assessment of motor function. We examined the MEP change in 30 cats that received weight drop injuries to the thoracic spinal cord and correlated it with function. The MEPs were recorded above and below the injury and in the sciatic nerves. In these animals, we found that the peripheral nerve response to the MEP was the most sensitive to injury, disappearing immediately upon weight drop. The MEP at the spinal cord level was somewhat more sensitive to injury than the SSEP at the cord level, and the SSEP at the cortex was the least sensitive to injury. The MEP spinal cord signal below the lesion showed both a latency increase and a substantial amplitude decrease after impact. The latency increase, however, was of relatively small absolute magnitude making the amplitude change easier to monitor. The animals were followed chronically, and 17 of the 30 regained ambulation. In all animals (followed up to 2 months), the peripheral nerve signals returned at or immediately before the time of ambulation. In none of the animals who failed to regain a peripheral nerve response was ambulation attained. This supports a strong correlation of the peripheral nerve response with walking. However, the peripheral nerve response was only a short term predictor. Examination of the spinal cord signal showed that the MEP spinal cord signal below the lesion as a percentage above the lesion was a significant correlate of current ambulation recovery, with a correlation coefficient of 0.55. This suggests that evaluation of the SSEP and MEP spinal cord signals may be able to predict longer term recovery in animals and perhaps humans.

Animals↗
PubMed1986

Evolution of the atmosphere and oceans.

The residence times of most constituents of the atmosphere and oceans are small fractions of the age of the Earth and, in general, their rate of output has been nearly equal to their rate of input. We are disturbing a number of these dynamic equilibria quite severely. The mineralogy of marine evaporites rules out drastic changes in the composition of sea water during the last 900 Myr. The chemistry of soils formed more than 1,000 Myr ago suggests that the atmosphere then contained significantly more CO2 and less O2 than at present. Hydrogen peroxide may well have been the principal oxidant and formaldehyde the main reductant in rain water between 3,000 and 1,000 Myr ago. Major changes in atmospheric chemistry since that time are almost certainly related to the evolution of the biosphere.

Atmosphere↗
PubMed1986

Motor evoked potential in cats with acute spinal cord injury.

We have previously reported that a motor evoked potential (MEP) can be produced by transcranial stimulation of the motor cortex in cats and humans. This signal travels in both dorsolateral and ventral spinal cord. We report here the evaluation of this evoked potential in comparison to the somatosensory evoked potential (SEP) in an acute spinal cord weight drop model. In all animals, the peripheral nerve signal was the component of the MEP most sensitive to injury. Often, it was significantly reduced in amplitude by incidental manipulation of the spinal cord during a careful laminectomy and then returned. It was lost first in animals with weight drop spinal cord injury and was abolished with as little as 50 to 75 g/cm of force. The spinal cord signal of the MEP was consistently more sensitive to injury than the SEP and was abolished at about 100 to 150 g/cm of impact. The cortical SEP was abolished at about 200 to 250 g/cm, and the spinal cord SEP was abolished at similar levels. The SEP returned earlier after injury than the MEP. Anesthetic agents had an effect on the MEP in the spinal cord and substantially changed the peripheral nerve signal, in both wave form shape and optimal stimulation frequency. Marginal cord injury and abnormal metabolic conditions caused the peripheral nerve signal to decrement in amplitude with increasing trial numbers during a run and become unstable. These latter effects need further characterization and are critical guides to investigative and clinical use of this test. This study indicates that the MEP is more sensitive than the SEP in detecting spinal cord injury.

Animals↗
PubMed1986

Nonpyramidal motor activation produced by stimulation of the cerebellum, direct or transcranial: a cerebellar evoked potential.

There is a need to monitor the functional status of the motor pathways well enough to predict the state of that function during operations and in injured or diseased patients. We previously reported that a motor evoked potential (MEP) can be produced by direct or transcranial stimulation of the motor cortex in both cats and humans. This signal descends through both the dorsolateral and ventral spinal cord and is primarily localized in the pyramidal tracts, producing a peripheral nerve signal and an electromyogram (EMG) response. It is more sensitive to injury than the somatosensory evoked potential (SEP). We report here that one can stimulate the cerebellar cortex, either directly or transcranially, and produce a descending signal in the spinal cord that has different characteristics from the MEP. The cerebellar evoked potential (CEP), located in the dorsolateral and the ventral cord, has an earlier latency and a faster conduction velocity than the MEP. It is predominantly ipsilateral with some contralateral components and also produces EMG responses. In the peripheral nerves, the CEP often produces a pattern of several waves that is different from the one or two predominant contralateral waves of the MEP. The CEP is not diminished by pyramidotomy. It arises from two sites on the cerebellar cortex, medial and lateral. The pathways activated may be the vestibulospinal, rubrospinal, reticulospinal, and fastigiospinal systems. This test seems to offer a monitor of selected motor pathways in the spinal cord largely separate from and complementary to the MEP. The ventral pathways activated probably include those demonstrated to be most essential to basic ambulation after spinal cord injury in primates. Also of importance, one type of evoked potential can facilitate another, which provides additional diagnostic tests. The CEP should be of investigative and clinical value.

Animals↗
PubMed1984

Motor evoked potentials from transcranial stimulation of the motor cortex in cats.

Electrical testing of central nervous system pathways is assuming increasing importance in clinical medicine. However, there is no direct monitor of the motor system. We previously reported using a motor evoked potential created by direct excitation of the spinal cord, placing a stimulating electrode over the corticospinal tract area. To produce a less invasive test, we now use direct transcranial stimulation of the motor cortex through the scalp or direct stimulation of the motor cortex itself during operation. A descending signal can be recorded over the spinal cord and in the peripheral nerves where no retrograde sensory signals should be able to descend. This motor cortex stimulation produces contralateral limb movements and selective activation of the peripheral nerves of a limb. The characteristics of this signal are similar to those described in the neurophysiological literature for a descending motor signal. With a depth electrode, it was found that the signal was strongest in the spinal cord near the corticospinal tracts and in the anterior horn cell area. A set of lesioning studies showed that most of the signal travels in the area of the corticospinal tract, with some traveling in the ventral portion of the spinal cord, perhaps in the anterior corticospinal tract. Section of the pyramid essentially abolishes the signal, but lesioning of the red nucleus does not. This test offers an electrical assessment of the motor system that can be useful in experimental work on spinal cord and brain function. It has potential clinical applicability in humans.

Animals↗
PubMed1984

Motor evoked potentials from transcranial stimulation of the motor cortex in humans.

Electrical monitoring of the motor system offers the potential for the detection of injury, the diagnosis of disease, the evaluation of treatment, and the prediction of recovery from damage. Existing evoked potentials monitor one or another sensory modality, but no generally usable motor monitor exists. We have reported a motor evoked potential using direct stimulation of the spinal cord over the motor tracts in cats and in humans. To achieve a less invasive monitor, we used transcranial stimulation over the motor cortex in the cat, thus stimulating the motor cortex. We report here the initial application of this method to humans. A plate electrode over the motor cortex on the scalp and a second electrode on the palate direct a mild current through the motor cortex which will activate the motor pathways. This signal can be recorded over the spinal cord. It can elicit contralateral peripheral nerve and electromyographic signals in the limbs or movements when the appropriate stimulation parameters are used. In clinical use to date, this has been more reliable than the somatosensory evoked potential in predicting motor function in patients where the two tests differed. It offers a number of possibilities for the development of valuable brain and spinal cord monitoring techniques, but requires further animal studies and clinical experience. Studies to date have not demonstrated adverse effects, but evaluation is continuing.

Adult↗
PubMedDate not supplied

Smoking, occupancy and staffing levels in a selection of Dublin pubs pre and post a national smoking ban, lessons for all.

BACKGROUND: On the 29th March 2004 the Irish government introduced a comprehensive workplace smoking ban to protect the health of workers. This study evaluates the impact the ban had on staffing levels, customer numbers and smoking rates in a sample of 38 public houses in Dublin. METHODS: A total of 38 public houses were visited prior to the introduction of the ban, each visit lasted at least three hours, and the number of staff, customers and the number of people smoking was recorded each hour. Follow-up visits were conducted exactly one year later, on the same day of the week and at the same time of day, allowing controlling for seasonal and weekday effects. RESULTS: There was a decrease (8.82%) in average staff levels while customer numbers increased by 11% and there was a dramatic reduction in numbers smoking on a visit to a pub (77.8%). CONCLUSIONS: The hospitality industry predicted major job losses as a consequence of the introduction of the smoking ban; this work has shown that there was no significant decrease in the number of staff employed or in customer numbers. There was full compliance, with no customers smoking inside the public houses following the introduction of the ban. The ban has been good for the industry, staff, and customers.

Humans↗
PubMedDate not supplied

An analysis of an air-ambulance program for children.

Air-ambulance services are extremely expensive to operate and maintain. The value of their existence has been questioned in this era of rationalization and downsizing. We examined the cost, safety, flight crew composition, types of trauma, and effectiveness of our air-ambulance program at the Children's Hospital of Eastern Ontario (CHEO) over a 3-year period, 1994-1997. During this time, 392 children were aeroevacuated to CHEO, 113 surgical (29%), 136 medical (35%), and 143 neonates (36%). Of the surgical cases, 43% were transferred for orthopaedic trauma, the commonest being fractured femur, 23% for general surgical cases, most common being thoracoabdominal trauma, and 22% for neurosurgical reasons, most commonly basilar skull fractures. The average response time (time from which the call was received to the time when the helicopter reached the patient site) for all of the cases was 46 min. The average travel time (time from departure of patient site to arrival at CHEO) for these same cases was 25.59 min. The air-ambulance program for children in the Ottawa-Carleton Eastern Ontario areas, was found to be safe, effective, and allowed earlier specialized medical care to be provided.

Air Ambulances↗
PubMedDate not supplied

The adolescent pilon fracture: management and outcome.

Pilon fractures in the adolescent are complicated by the presence of the adjacent physis. These fractures usually result from high-energy trauma, frequently associated with soft-tissue trauma, further potentiating treatment difficulties. Although rare, such fractures are associated with a high complication rate, including physeal arrest. It was the objective of this review to increase awareness of this fracture pattern in the adolescent, to determine the types of complications in this difficult group, and to develop a treatment plan to improve the outcome of treatment. Seven children, with a total of eight pilon fractures were treated at a major pediatric tertiary referral center over the past 10 years. The average age of the children was 15 years 10 months (range, 13 years 6 months to 17 years 7 months). The average length of follow-up was 16 months (range, 3 months and 3 years 10 months). There were three Reudi type II equivalent fractures and two Reudi type III equivalent injuries. Three fractures did not fit the Reudi classification system as there was an associated ankle dislocation. All fractures were treated with open reduction and internal fixation. There were two cases of posttraumatic osteoarthritis and one physeal arrest. Results were good to excellent in 63% of cases. A new classification system for pediatric pilon fractures has been proposed.

Adolescent↗
PubMedDate not supplied

Spermatozoal DNA flow cytometry and recurrent miscarriage.

Clinical investigations of the male partner of couples with recurrent miscarriage involves investigation of abnormalities in paternal chromosomes. This route of investigation does not include analysis of semen parameters. This investigation was conducted to evaluate DNA flow cytometry profiles of spermatozoa following staining with propidium iodide of couples attending the Pregnancy Loss Clinic for recurrent miscarriage. Ejaculates of 21 men were included in this study. DNA fluorescence was measured on the Becton Dickinson Fac Star Plus. Data were correlated with spermiogram parameters. The neat semen median minus peak channel values were negatively correlated with motility (p < .05). Therefore, DNA flow cytometry can provide confirmatory evidence for conventional semen analysis and is useful as a preliminary screening procedure for clinical management of the couple. It could also be used in association with programs for the assessment of possible reproductive toxicity and infertility in couples with recurrent miscarriage.

Abortion, Habitual↗
PubMedDate not supplied

Air bags and children: a potentially lethal combination.

Air bags have been responsible for saving thousands of lives since their introduction in the early 1970s. Now, however, it has become apparent that under certain conditions, these restraint mechanisms designed to save lives have in fact been the cause of needless morbidity and mortality in children. We reviewed 13 children injured by air bags in Canada, where seat belt wear is mandatory for all occupants. Although 12 of the children sustained relatively minor air bag trauma, one child was killed by the air bag deployment, sustaining an occipital-C1 dislocation. The pediatric population is at particular risk as many parents continue to unwittingly place their children in the front seat and thus in jeopardy of sustaining air bag-induced injuries should a collision occur.

Accidents, Traffic↗