4 - Cerebrovascular Disease

4.1About cerebrovascular disease

Cerebrovascular disease is disease involving the blood vessels supplying the brain.

Transient ischemic attack (TIA)

A transient ischemic attack (TIA) is a brief episode of neurological dysfunction caused by a temporary state of reduced blood flow to the brain.  The symptoms of a TIA are similar to a CVA (described below) but are temporary, typically lasting less than one hour and no more than 24 hours.  The most common cause of a TIA is a blood clot. A TIA is considered to be a warning sign that a CVA may be imminent. The risk of having a CVA is 10% in the first 90 days following a TIA, with a cumulative 3 year risk of 25%.

Cerebrovascular accident (CVA)

A cerebrovascular accident (CVA) or stroke is defined as rapidly developing clinical signs of focal or global disturbance of cerebral function, with symptoms lasting 24 hours or longer, or leading to death, with no apparent cause other than of vascular origin. A CVA can be classified as either ischemic or hemorrhagic.  Ischemic CVA refers to a CVA caused by thrombosis or embolism, and accounts for 85% of all CVAs.

Hemorrhagic CVAs are caused by an intracerebral hemorrhage (bleeding within the brain) or subarachnoid hemorrhage (bleeding between the inner and outer layers of the tissue covering the brain).

The symptoms of a CVA vary depending on what part of the brain is affected. The most common symptom is weakness or paralysis of one side of the body with partial or complete loss of voluntary movement or sensation in a leg or arm.  There can be speech problems and weak face muscles.  Numbness or tingling is very common.  A CVA can affect:

  • balance
  • vision
  • swallowing
  • breathing, and
  • level of consciousness.

Visual or spatial neglect is a common consequence of a CVA. With neglect, damage to the brain causes an individual to ignore one side of their visual field or their body, even if they retain sensation and function. Neglect is usually a result of a stroke affecting the right hemisphere of the brain, therefore causing neglect of the left side.  Visual neglect occurs in 33% to 85% of all strokes affecting the right hemisphere.

The prognosis for recovery following a CVA is related to the severity of the CVA and how much of the brain has been damaged. Most functional recovery occurs within the first two months following a CVA.

The risk of a subsequent CVA is approximately 4% per year, with a 10 year cumulative risk of 43%.  In the first six months following a CVA, the risk of a subsequent CVA is approximately 9%.

Cerebral aneurysm

A cerebral aneurysm is the localized dilation or ballooning of a cerebral artery or vein resulting from weakness in the wall of the affected vessel.  Most cerebral aneurysms have no associated symptoms until they become large or rupture. The majority (50% to 80%) remain small and do not rupture.

Symptoms associated with larger aneurysms include:

  • sudden severe headache
  • nausea and vomiting
  • visual impairment, and
  • loss of consciousness.

The risk of rupture increases with the size of the aneurysm. A rupture results in subarachnoid or intracerebral hemorrhage, leading to alterations in consciousness including:

  • syncope
  • seizures
  • visual impairment, and
  • respiratory or cardiovascular instability.

Treatment of unruptured cerebral aneurysms is controversial.  Treatment options include observation and surgical procedures to prevent blood from flowing into the aneurysm.

Risks of surgery include possible damage to other blood vessels, potential for aneurysm recurrence and rebleeding, and post-operative CVA.  Successful surgery reduces the risk of rupture.

4.2Prevalence

Transient ischemic attack

The results of a survey published in 2000 by the National Stroke Association found that half a million adults (18 years of age and older) in Canada had been diagnosed with a TIA.  A population-based study in Alberta found the age-adjusted incidence of TIA to be between .04% and .07% (44 and 68 per 100,000) annually.

The risk factors for a TIA are similar to those for a CVA (see below).

Cerebrovascular accident

CVAs are the 4th leading cause of death in Canada and account for 7% of all deaths in Canada. Of the 40,000 to 50,000 Canadians who have a CVA each year, 14,000 will die.

The risk factors for a CVA include:

  • high blood pressure
  • cigarette smoking
  • heart disease
  • carotid artery disease
  • diabetes, and
  • heavy use of alcohol.

The risk for males is three times greater than for females. Risk also increases with age, with those in their 70s and 80s at the greatest risk.

Cerebral aneurysm

Prevalence rates for cerebral aneurysm are unclear because they are often asymptomatic. Autopsy studies indicate a prevalence rate in the adult population between 1% and 5%, with 5% being a widely cited figure.

Under age 40, cerebral aneurysms affect equal numbers of males and females, but are rarely seen in infants and children. Over age 40, more women than men are affected. The peak age for clinical manifestation of cerebral aneurysm is between 55 and 60.

4.3Cerebrovascular disease and adverse driving outcomes

Transient ischemic attack

There has been little research on the relationship between TIAs and adverse driving outcomes.

Cerebrovascular accident

There has been little research on episodic impairment (sudden incapacitation) of driving ability due to a CVA.

In studies that considered the effects of persistent impairments from CVAs as measured by fitness to drive assessments, 50% or more of the subjects who had a CVA were assessed as unfit to drive.  Surveys of drivers who had a CVA indicate that more than half did not resume driving after their CVA.

Cerebral aneurysm

No studies were found that considered the relationship between cerebral aneurysm and adverse driving outcomes.

4.4Effect on functional ability to drive

Condition Type of driving impairment and assessment approach Primary functional ability affected Assessment tools
Transient ischemic attack (TIA) Episodic impairment (risk for stroke): Medical assessment – likelihood of impairment Variable – sudden cognitive, motor or sensory impairment Medical assessments
Cerebrovascular accident (CVA) Persistent impairment: Functional assessment Variable – cognitive, motor or sensory

Medical assessments

Functional assessment

Cerebral aneurysm Episodic impairment (risk of rupture): Medical assessment – likelihood of impairment All – sudden impairment Medical assessments
Persistent impairment (where symptomatic): Functional assessment Variable – cognitive, motor or sensory

Medical assessments

Functional assessment

Transient ischemic attack

The primary concern for licensing is the potential for a subsequent CVA.  The greatest risk is within the 3 months following the TIA.

Cerebrovascular accident

The primary concern for licensing is the potential for a persistent impairment of functional ability following a CVA.  Depending on what part of the brain is affected, cognitive, motor or sensory functions may be impaired.

Cerebral aneurysm

The primary concern for licensing is the risk of an episodic impairment caused by rupture of the aneurysm.  Generally, this risk is not considered significant for licensing purposes unless the aneurysm is symptomatic or has been identified as requiring surgical intervention.

A large or leaking cerebral aneurysm could result in a persistent impairment of cognitive, motor or sensory functions depending on its size and location.

4.5Compensation

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. The effectiveness of individual vehicle modifications may be determined through a road test.

Some examples of compensatory mechanisms are shown in the following table.

Motor impairment Sensory (vision) impairment
  • Steering wheel spinner knob
  • Left-foot accelerator pedal
  • Restriction to automatic transmission or power-assisted brakes
  • Downgrade from commercial to non- commercial driving
  • Scanning horizon more frequently
  • Turning head 90◦ to maximize area scanned
  • Large left and right side mirrors

4.6Guidelines for assessment

4.6.1 Transient ischemic attack (TIA)

National Standard

All drivers eligible for a license if:

  • complete medical assessment shows no residual effects
  • any underlying cause has been addressed with appropriate treatment
  • conditions for maintaining a license are met
BC Guidelines RoadSafetyBC will not generally request further information
Conditions for maintaining licence
  • Remain under regular medical supervision and follow any prescribed diagnostic or treatment regime
  • Report any further TIAs to the authority
Reassessment If there are no residual effects and any underlying cause has been addressed with appropriate treatment; RoadSafetyBC will re-assess in accordance with commercial or age-related re-assessment unless a shorter reassessment interval is recommended by the treating physician.
Information from health care providers
  • Date of the TIA
  • Whether the driver remains under regular medical supervision
  • Opinion of treating physician whether the driver follows any prescribed diagnostic or treatment regime
Rationale The primary driver concern with a TIA is the risk for a CVA after a TIA. By definition, there are no persistent impairments associated with a TIA. The risk for a CVA is greatest immediately after the TIA and decreases significantly over time.  Subject matter experts recommended a minimum no-driving period of two weeks, with appropriate follow-up and treatment

4.6.2 Cerebrovascular accident (CVA)

National Standard

All drivers eligible for a licence if

  • Complete medical assessment shows no residual effects
  • any underlying cause has been addressed with appropriate treatment
  • a post CVA seizure has not occurred (if a post CVA seizure has occurred, see the guidelines under 17.6.1),
  • the functional abilities necessary for driving are not impaired, and
  • the conditions for maintaining a licence are met
BC Guidelines

If further information regarding an individual’s medical condition is required, RoadSafetyBC may request

  • a Driver’s Medical Examination Report; or
  • additional information from the treating physician
  • If the treating physician indicates significant residual loss of one or more of the functions necessary for driving, RoadSafetyBC will request functional assessment(s) as appropriate for the type(s) of impairment and class of licence
Conditions for maintaining licence
  • Remain under regular medical supervision and follow your physician’s advice regarding treatment
  • Report any further CVAs to the authority
(Note that additional conditions may be required, depending upon the nature of any functional impairment and the ability of the driver to compensate)
Reassessment If there are no residual effects and any underlying cause has been addressed with appropriate treatment, and no post-CVA seizure has occurred;  RoadSafetyBC will re-assess in accordance with commercial or age-related re-assessment unless a shorter reassessment interval is recommended by the treating physician.
Information from health care providers
  • Date of the CVA
  • Opinion of treating physician whether any underlying cause has been addressed with appropriate treatment
  • Whether the driver has experienced a post CVA seizure
  • Opinion of treating physician whether there may be significant residual loss of the functional abilities necessary for driving, and if yes, the results of any functional assessments the physician carried out, e.g. cognitive screen
  • Whether the driver remains under regular medical supervision
  • Opinion of treating physician whether the driver is compliant with the physician’s advice regarding treatment
Rationale The primary driver fitness concern with a CVA is the potential for a persistent impairment.  Subject matter experts recommended a minimum no-driving period of one month, with appropriate follow- up and treatment

4.6.3 Cerebral aneurysm that requires surgical repair

National Standard All drivers not eligible for a licence
BC Guidelines RoadSafetyBC will not generally request further information
Conditions for maintaining licence N/A
Reassessment N/A
Information from health care providers N/A
Rationale The primary concern with a cerebral aneurysm is the risk of rupture. Where the risk of rupture is such that surgery is recommended to repair the rupture, a driver is not eligible for a licence

4.6.4 Surgery to repair a cerebral aneurysm - Non-commercial drivers

National Standard

Non-commercial drivers eligible for a licence if

  • it has been at least 3 months since the surgery, and
  • the driver has no symptoms of the aneurysm, or
  • if the driver continues to have symptoms, the symptoms do not impair the functional abilities necessary for driving
BC Guidelines

If further information regarding an individual’s medical condition is required, RoadSafetyBC may request

  • A Driver’s Medical Examination Report
  • Additional information from the treating physician, or an
  • assessment from a neurosurgeon

If the treating physician indicates symptoms that impair one or more of the functions necessary for driving, RoadSafetyBC will request functional assessment(s) as appropriate for the type(s) of impairment and class of licence held

Conditions for maintaining licence None
Reassessment
  • If the individual does not have ongoing symptoms, no re-assessment, other than routine age-related re-assessment, is required
  • If the individual has ongoing symptoms, RoadSafetyBC will determine the appropriate re-assessment interval on an individual basis, depending upon the nature and severity of the symptoms
Information from health care providers
  • Date of the surgery
  • Whether the driver experiences any symptoms of the aneurysm, and if yes, a description of the symptoms
  • Opinion of treating physician if any symptoms impair the functional abilities necessary for driving, and if yes, the results of any functional assessments the physician carried out
Rationale

Successful surgical treatment for a cerebral aneurysm significantly reduces the risk of rupture. A waiting period of 3 months after surgery is imposed to allow for an assessment of the effectiveness of the surgery or any complications of surgery

The impact of any symptoms caused by the aneurysm or by complications from surgery should be assessed

4.6.5 Surgery to repair a cerebral aneurysm - Commercial drivers

National Standard

Commercial driver eligible for a licence if

  • it has been at least 6 months since the surgery, and
  • the driver has no symptoms of the aneurysm, or
  • if the driver continues to have symptoms, the symptoms do not impair the functional abilities necessary for driving
BC Guidelines

If further information regarding an individual’s medical condition is required, RoadSafetyBC may request

  • a Driver’s Medical Examination Report
  • additional information from the treating physician, or
  • an assessment from a neurosurgeon.  

If the treating physician indicates symptoms that impair one or more of the functions necessary for driving, RoadSafetyBC will request functional assessment(s) as appropriate for the type(s) of impairment and class of licence held

Conditions for maintaining licence None
Reassessment
  • If the individual is not having symptoms, no re-assessment, other than routine commercial re-assessment, is required
  • If the individual is experiencing symptoms, RoadSafetyBC will determine the appropriate re-assessment interval on an individual basis, depending upon the nature and severity of the symptoms
Information from health care providers
  • Date of the surgery
  • Whether the driver experiences any symptoms of the aneurysm, and if yes, a description of the symptoms
  • Opinion of treating physician whether any symptoms may impair the functional abilities necessary for driving, and if yes, the results of any functional assessments the physician carried out, e.g. cognitive screen
Rationale The waiting period for commercial drivers is longer than that for non-commercial drivers in order to provide more certainty about the success of surgery prior to a return to driving