A Traumatic Brain Injury (TBI) may result in neurological deficit, neurocognitive impairment, psychological/mood changes, and an elevated risk of post traumatic epilepsy. Thus a history of TBI may affect the safe operation of an aircraft.
All injuries need to be carefully evaluated by the ME. A very detailed history must be obtained of the accident event together with a copy of medical records, including those from the ambulance/paramedic service, the emergency department, and inpatient hospital records. This is to more accurately determine the severity of the head injury, duration of any neurological impairments such as LOC, amnesia or confusion, or persistent effects of the head injury. A careful evaluation of alcohol use is important if it was a factor contributing to the accident.
ACC is likely to have provided services in the event of head injury. ACC records, inclusive of fitness for work certificates, concussion services, neurology and neuropsychological reports should also be obtained. CT/MRI head scan reports and electronic images are very helpful.
A ME who is aware of a recent head injury should attempt to obtain a CT head scan evaluation within the first three days following the injury, while the presence of intracranial bleeding and new cerebral contusions can be detected.
Traumatic brain injury (TBI) is defined as an alteration in brain function, or evidence of other brain pathology, caused by external force (Carroll, Cassidy, Holm, Kraus, and Coronado, 2004).
The presence of a skull fracture should be considered to have a TBI associated with it.
Traumatic brain injuries can range from mild concussion (a brief change in mental status or consciousness) to severe (an extended period of unconsciousness and/or memory loss after the injury). The effects can be temporary or permanent.
Depressed fracture is one where the inner table of the skull is depressed more than the thickness of the skull.
Concussive convulsion is a seizure at the instant of the head injury, is not usually epileptic and does not raise the risk of post-traumatic epilepsy. However in the case of a concussive convulsion one must also ensure that an epileptic seizure was not the cause of the head injury.
Early post traumatic seizure occurs within one week of a head injury.
Post traumatic epilepsy (PTE) is the occurrence of one or more epileptic seizures one week or later after the head injury.
The severity of traumatic brain injuries (TBI) was previously based on clinical observations. Similar injuries by clinical criteria may have different anatomical substrates as demonstrated by modern brain imaging. The risk of PTE has now been showed to depend principally on the presence of intracranial blood.
Blood is readily detectable with early CT brain imaging and may be intracerebral, extracerebral, or both. Subdural bleeding may be acute or chronic. If acute it is generally accompanied by intracerebral bleeding.
Contusion is a form of superficially located intracerebral bleeding and bruising. The terms contusion and intracerebral bleeding may be used interchangeably.
The severity of head injuries can be classified as follows (adapted from Annegers et al, by Bill Wallis):
Results in loss of consciousness or post-traumatic amnesia for no more than 30 minutes in the absence of skull fracture or any persistent neurological symptoms or signs. CT scan shows no evidence of intracranial bleeding.
Results in loss of consciousness or post-traumatic amnesia for more than 30 minutes, but less than 24 hours. There may be other symptoms and/or a non-depressed skull fracture. There are no persistent central nervous system symptoms or signs. CT scan shows no evidence of intracranial bleeding.
Results in one or more of the following: Loss of consciousness or post-traumatic amnesia of more than 24 hours, structural brain injury (intracerebral or extracerebral haematoma, laceration, or contusion) as demonstrated by CT scan or surgical exploration, any persistent focal neurological deficits or symptoms indicative of cerebral hemisphere damage, an epileptic seizure occurring one week later or more following the TBI, a depressed fracture.
Clinical risk factors for PTE include post-traumatic amnesia > 24 hrs, focal neurological signs, loss of consciousness at the time of the injury, early seizures, the need for mechanical ventilation, and a history of alcohol abuse. Neuroimaging risk factors include focal cerebral injury/cerebral contusion, subdural haemorrhage, intracranial haemorrhage, midline shift and skull fracture. For the purpose of aeromedical certification the following estimates of likelihood of PTE can be obtained from the literature (adapted by Bill Wallis):
| TBI severity | Estimated initial risk of PTE | Estimated time to near the risk of the general population |
|---|---|---|
| Severe Combined extra and intracerebral bleeding |
Up to 40 % | Well over 10 years |
| Severe Intracerebral bleeding only |
25 % | 10 years and over |
| Severe No intracerebral bleeding; but may have extracerebral haematoma, early epilepsy, depressed skull fracture or more than 24 hours of post-traumatic amnesia |
3 – 4 % | 2 years if only one risk factor, 3 years if the risk factors occur in combination |
| Moderate Post-traumatic amnesia or loss of consciousness for greater than 30 minutes but less than 24 hours, may have a linear fracture with or without other signs or symptoms, no persistent signs or symptoms, CT scan shows no intracranial bleeding |
Close to that of the normal population | N/A |
| Mild Post-traumatic amnesia or loss of consciousness for less than 30 minutes, no skull fracture, no persistent signs or symptoms, CT scan shows no intracranial bleeding |
Same as normal population | N/A |
An applicant with a history of mild head injury (simple concussion) may be considered as having a condition that is not of aeromedical significance if:
An applicant with a history of moderate head injury should be considered as having a condition that is of aeromedical significance if unless:
For clarification a moderate head injury occurring within the past two years should generally be considered as being of aeromedical significance and handled via the flexibility process. This is to ensure correct classification of the head injury and resulting risk.
An applicant with a history of severe head injury should be considered as having a condition that is of aeromedical significance unless:
Applicants with documented structural brain injury, or evidence of intracerebral bleeding will generally not be considered for a return to flying until 5 to 10 years, or possibly more time has elapsed.
