20 - Traumatic brain injury - CCMTA Medical Standards
Traumatic brain injury and medical fitness to drive.
20.1 About traumatic brain injury
Traumatic brain injury (TBI) is a nondegenerative, noncongenital insult to the brain from an external mechanical force, possibly leading to permanent or temporary impairment of cognitive, physical and psychosocial functions, with an associated diminished or altered state of consciousness. The leading causes of TBI are falls and motor vehicle crashes.
Descriptions of the severity of a TBI reflect the length of time a person is unconscious or lacks awareness of their environment. Mild TBI indicates only a brief change in mental status or consciousness, while severe TBI describes an extended period of unconsciousness or amnesia after the injury.
TBI can result in a wide range of impairments, which will vary depending on the severity and location of the injury, and the age and general health of the injured person. Possible sensory impairments include:
- Visual field deficits
- Visual neglect
- Diplopia, and
- Loss of sensation or hearing
Possible motor impairments include paralysis, paresis (partial loss of movement or impaired movement) and slowed reaction times. Possible cognitive impairments include deficits in:
- Executive functioning
- Processing speed, and
- Visuo-spatial abilities, including visual memory
Behavioural impairments are common, including disorders affecting mood and impulse control. Sleep disturbances, sleep apnea and fatigue are also commonly reported. TBI is also associated with epilepsy.
Anosognosia (unawareness of impairment) is common in individuals with TBI, particularly in those with moderate to severe TBI, and is of particular concern for driving. Research suggests that anosognosia is more frequently associated with cognitive and behavioural impairments than with physical deficits.
Rates of incidence and prevalence of TBI are difficult to determine due to a lack of uniformity in definitions and reporting methods. Canadian data suggest that the overall prevalence of TBI is 62.3 per 100,000 adults. Rates were highest in the 45 to 64 year old age range, three times the rate of those in the 15 to 24 year old range.
20.3 Traumatic brain injury and adverse driving outcomes
Numerous studies have examined the relationship between TBI and driving outcomes. Although few studies have examined crash rates, the existing research indicates higher rates of crashes and traffic violations for those who have experienced a TBI. Notably, studies indicate that approximately 50% of those experiencing a TBI will not resume driving after the TBI. Research examining road test results indicates that approximately 30% of individuals who have experienced a TBI will fail a subsequent road test.
20.4 Effect on functional ability to drive
|Condition||Type of driving impairment and assessment approach||Primary functional ability affected||Assessment tools|
|Traumatic brain injury||Persistent impairment: Functional assessment||Variable – cognitive, motor or sensory||
|Episodic impairment: Medical assessment – likelihood of impairment||Variable – sudden impairment (epilepsy)||Medical assessments|
Traumatic brain injury may result in a persistent cognitive, motor or sensory impairment, or an episodic impairment (epilepsy), or both.
Drivers who have experienced a persistent impairment of motor or sensory function may be able to compensate. An occupational therapist, driver rehabilitation specialist, driver examiner or other medical professional may recommend specific compensatory vehicle modifications or restrictions based on an individual functional assessment.
Some examples of compensatory mechanisms are shown in the following table.
|Motor impairment||Sensory (vision) impairment|
20.6 Guidelines for assessment
If a driver has epilepsy as a result of a TBI, also see the standards in Chapter 17.
All drivers eligible for a licence if:
|Conditions for maintaining licence||No conditions are required|
RoadSafetyBC will restrict an individual’s licence so that they only drive with any permitted vehicle modifications and devices required to compensate for their functional impairment. This may include one or more of the following restrictions
|Reassessment||No re-assessment is required, other than routine commercial or age-related re-assessment|
|Information from health care providers||
|Rationale||The potential functional impairments associated with traumatic brain injury are variable|