Original communicationThe occurrence of acute subdural haematoma and diffuse axonal injury as two typical acceleration injuries
Introduction
In the last 20 years, there has been a new classification of closed head injuries in two main categories: focal and diffuse,1 and with regard to the biomechanism of their occurrence they are grouped as contact and inertial (acceleration–deceleration) injuries.2 Contact injuries occur as a result of the direct impact to the head, and acceleration–deceleration injuries are caused by a sudden movement of the head, and the direct impact is not necessary for their occurrence as it was experimentally shown.3 Acute subdural haematoma (ASDH) and diffuse axonal injury (DAI) are two typical acceleration–deceleration injuries which occur as a result of the acceleration to the head, with a special contribution of the rotational acceleration,4 but differ in the duration of acceleration forces to the head.
It has been shown experimentally that ASDH is caused by relatively short duration (5–10 min) angular acceleration loading at high rates of acceleration, whereas DAI occurs most readily when the head moves coronally and it occurs when the acceleration duration is longer (20–25 min) and the rate of acceleration lower than conditions that produce ASDH.5, 6 In real life, circumstances for ASDH mostly occur during falls when the head rapidly decelerates against a firm surface, whereas the conditions for producing DAI occur in vehicle traffic accidents where impact to deformable and padded surfaces lengthens the deceleration and decreases its rate.
Nowadays, there are reported cases of DAI in the events such as falls from a considerable height,7 falls from a simple height,8, 9 and blow,10, 11 but caution is needed for two things: first, these cases were reported prior to the widespread recognition of other causes of axonal damage, particularly ischaemia, and second the diversity of the yielded results in great part depends on the different criteria for diagnosing DAI. Also, there are studies which report almost a constant association of ASDH and DAI in traffic accident victims.12 Here lies the necessity of revising and revitalising the discussion about which traumatic events are more typical for the occurrence of ASDH and which are more likely to result in DAI.
For this purpose, we analysed the occurrence of ASDH and DAI in three different types of traumatic events: traffic accidents, falls and assaults (blow). A hypothesis has been established that the occurrence of ASDH is more characteristic of cases of simple fall, blow and those types of traffic accidents associated with a rapid fall on a firm surface (cyclists), whereas DAI is more characteristic of vehicle traffic accidents and falls from a considerable height.
Section snippets
Materials and method
Eighty cases with fatal closed head injuries have been investigated with a post mortal period up to 24 h and time of survival between immediate death and 1.5 months (age ranged from 5 to 94 years, 57 males and 23 females). The information about the traumatic event in which injury occurred is given in Tables 1 and 3. All 80 cases have been analysed for the occurrence of ASDH (Table 1), and for the occurrence of DAI, only cases with time of survival of at least 2 h have been analysed (Table 3), a
Results
The occurrence of ASDH in different types of traumatic events is presented in Table 1. Evidently, ASDH is mostly found in cyclists, simple falls and cases of assault.
Statistical evaluation was made to explore the interdependence between the occurrence of ASDH and a particular category of traumatic events. One category comprises those events where the injury mechanism is closely related with a rapid deceleration on a firm surface: cyclists, simple falls and cases of blow associated with fall.
Discussion
Results show that ASDH was most frequently found in cases of simple fall – 67%, assault cases, where blow was often associated with fall on a firm surface – 67%, and in those kinds of traffic accidents where a great part of the injury mechanism has been attributed to fall on a firm surface, represented by cyclists – 80%. On the other side, ASDH was least frequently found in drivers – 14%, and was not found at all in passengers, which makes it an injury not so typical of vehicle traffic
Ethical approval
None declared.
Funding
None declared.
Conflict of interest
None declared.
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