A J McLean

Stalning af amyloid percursor protein to study axonal damage in mild head Injury

The most common definition of cerebral concussion is that of a transient loss of neurological function without macroscopic or microscopic abnormality in the brain. However, some patients have persistent symptoms and subtle neuropsychological deficits, particularly affecting memory. We have studied five patients aged 59-89 years who sustained mild concussive head injury and died of other causes (2-99 days post-injury). Immunostaining with an antibody to amyloid precursor protein, a marker of fast axonal transport, showed multifocal axonal injury in all five. All had axonal damage in the fornices, which are important in memory function.

Vehicle travel speeds and the incidence of fatal pedestrian crashes

The aim of this study was to estimate the likely effect of reduced travel speeds on the incidence of pedestrian fatalities in Adelaide, Australia. The study was based on the results of detailed investigations of 176 fatal pedestrian crashes in the Adelaide area between 1983 and 1991. The method developed to estimate the effect of reduced travelling speed is described and supported by references to the published literature. A reduction in the speed limit from 60 to 50 km/h was one of four speed reduction scenarios considered. The smallest estimated reduction in fatal pedestrian collisions in the selection presented was 13%, for a scenario in which all drivers obeyed the existing speed limit. The largest estimated reduction was 48% for a scenario in which all drivers were travelling 10 km/h slower. The estimated reductions in fatalities obtained in this study are compared with those observed in places where the urban area speed limit has been lowered.

Pontomedullary tears and other gross brainstem injuries after vehicular accidents

In a series of 988 autopsied victims of road crashes, there were 36 (3.6%) cases of gross primary brainstem injury. These fell into three groups. The first comprised eight cases of pontomedullary tearing without other gross brain injury: in seven of these, there were associated atlanto-occipital dislocations and/or high cervical fracture-dislocations. The usual cause appeared to be facial impact inducing acute hyperextension. Second, there were 17 cases of pontomedullary tearing associated with other brainstem lacerations and/or major damage elsewhere in the brain: in all, there were fractures of the skull base, typically transverse middle fossa fractures. Most of these injuries appeared to be due to facial impacts transmitting force to the anterior skull base, although hyperextension was also a factor in some. There was a third heterogeneous group of 11 cases with brainstem lacerations in sites other than the pontomedullary junction: in some of these it appeared that the impacts had caused skull base fractures by inducing calvarial torsion. In this series, the proportion of motorcyclists (41.7%) was double the expected figure. The use of a helmet modifies the mechanisms of impact head injury; the overall benefits of helmet use are well established, but there is need for more research on helmet design.

Extradural haemorrhage: strategies for management in remote places

A study of 109 cases of extradural haemorrhage (EDH) treated in South Australia over a period of 7 years showed that 35 cases (32.1 per cent) presented in country areas at considerable distances from a neurosurgical service: the mortality in these country cases was 22.9 per cent, comparing unfavourably with a mortality of 12.2 per cent in metropolitan cases. The country series contained a disproportionately large number of cases with multiple intracranial haemorrhages, which are known to have a poorer outcome; when these cases were excluded, the rural mortality (12.5 per cent) was only a little over the metropolitan mortality (9.7 per cent). These data suggest that it is possible to manage extradural haemorrhages successfully even in places remote from a neurosurgical centre, if communications and air transport are used effectively. However, it was found that emergency operations carried out in country hospitals were sometimes inadequate or done too late. Medical retrieval teams based on city hospitals were sent out on 15 occasions, either to assist a general surgeon to complete an emergency operation, or to provide intensive care during transfer to a neurosurgical unit. Osmotherapy (mannitol and/or frusemide) has been useful in gaining time for transfer; the choice between immediate operation and transfer may be difficult, and decisions should take transfer time, clinical state and rate of deterioration into account.

Mechanisms of brain injury related to mathematical modelling and epidemiological data

Measurements of the frequency response of head impact points on the exterior and the interior of a car were used to characterize the dynamic behavior of the object that was struck. These points were then arranged in a hierarchy of increasing stiffness. Thirty-two cases in which the distribution of injury to the brain had been recorded were grouped according to the stiffness of the object struck and by the location of the impact on the head. The distribution of the brain lesions were determined for each class of stiffness and location of impact. Three probable mechanisms of brain injury were distinguished: relative motion between the brain and the skull, local bone deformation, and intracerebral stresses. Each mechanism was related to a range of stiffness and natural frequency of the structure impacted. These theories of brain injury mechanisms are consistent with observed epidemiological data and with conclusions drawn from mathematical modelling.

A method of estimating linear and angular accelerations in head impacts to pedestrians

In order to investigate the relationship between impact to the head and brain injury, we have developed a method, using information obtained from reconstruction of the collisions, of estimating the peak linear and angular accelerations of the head for pedestrian impacts on a vehicle. This information includes the location of the impact on the head, the impact velocity of the head, and the stiffness of the struck surface. In developing the method we assumed that the velocity of the head on striking the vehicle was the same as the velocity of the vehicle itself, that the force vector was normal to the surface of the skull, that the force-deflection curve characterising the combined response of the impacted surfaces was linear, and that the kinetic energy of the head immediately prior to impact was converted into strain energy in deforming the head and the vehicle structure. Only the loading phase of the impact was considered, there was no assumption of an elastic unloading phase. Using cadavers, the validity of these assumptions and hence the usefulness of the method were tested by comparing the estimates of peak linear acceleration with the results of 18 pedestrian-vehicle impact reconstructions. On average, the method underestimated the experimental values by about 15%, with a range of +/- 35%. The results from the application of this method are currently being used to study the relationship between the magnitude and direction of the impact to the head and the distribution and severity of the brain injury resulting from actual collisions.

Extradural haemorrhage in infancy and childhood

One hundred and two paediatric cases of extradural haemorrhage (EDH) were treated in Adelaide, South Australia, during the period 1954–1988; 10 were infants (0–2 years) and 92 were children (2–14 years). There were 9 deaths (mortality 8.8%). Long-term disabilities severe enough to interfere with school and/or employment were seen in 8 (7.8%) survivors. This relatively low number of adverse outcomes is partly an expression of a low incidence (5.9%) of associated intradural haematomas and few high-velocity impacts due to vehicular accidents. There is reason to believe that the results of treatment have improved in the decade 1977–1988. We attribute this in part to early diagnosis by computed tomography (CT), but a contributory factor may be earlier referrals from country centres to a paediatric trauma centre and rapid transfer, by air or road, by medical retrieval teams.

INVESTIGATION OF HEAD INJURY MECHANISMS IN MOTOR VEHICLE ACCIDENTS--A MULTIDISCIPLINARY APPROACH

This paper describes an on-going investigation of the mechanisms of head injury in motor vehicle accidents. The multidisciplinary approach combines detailed accident investigation with a neuropathological analysis of the injury to the brain. A pedestrian accident model using the MADYMO crash victim simulation package is being developed to be used as an aid in classifying the type and severity of the head impact. Two pedestrian cases are presented with details of the simulation and the neuropathology procedures. The direction of further development of the model is described.

Do Full-Face Helmets Offer Greater Protection Against Cervical Spinal Cord Injury than Open-Face Helmets?

In 1979, Yeo (1979a,b) reported a lower likelihood of damage to the cord of the cervical spine (cervical spinal cord injury, or cervical SCI) for wearers of full-face helmets compared with open-face helmets among motorcyclists that had sustained a head impact. However, it appears that the study suffered from factors biasing the results away from the null hypothesis. The present study suggests that there may be no added benefit or harm of the full-face helmet relative to the open-face helmet on cervical SCI.

PEDESTRIAN ACCIDENTS IN SOUTH AUSTRALIA OVER TWO DECADES

The paper reviews changes in the pattern of pedestrian accidents and pedestrian injuries in South Australia during the two decades from 1960. The data are drawn from two in-depth accident studies, each based on a representative sample of road accidents to which an ambulance was called, conducted in 1963-64 and 1976-77, and the road accident records of the South Australian Police Force. The paper examines the changes which have occurred in the frequency and nature of pedestrian accidents in conjunction with the more widespread use of controlled pedestrian road crossings, and also the marked liberalization of State licensing laws regarding hotel opening hours. Changes in the causes and distribution of injuries to pedestrians are also noted.