Transient loss of consciousness ('blackouts') - or lost/altered awareness
Transient loss of consciousness (TLoC) or 'blackout' is very common - it affects up to half the population in the UK at some point in their lives.
An estimated 3% of A&E presentations and 1% of hospital admissions are due to TLoC.
Road traffic collisions resulting from blackouts are two or three times more common than those resulting from seizures. Recurrent TLoC (more than one isolated event), not including syncope, is uncommon - but always requires detailed medical assessment.
In relation to TLoC, three features are of note to medical practitioners:
In relation to road safety, however, the two most important features are:
A prodrome must allow time for a driver to find a safe place to stop before losing consciousness. A prodrome is reliable if the signs are clear, consistent across all events and provide sufficient duration to find a safe stop, or unreliable if these are absent.
Licence holders or applicants should be informed that they must notify the DVLA when TLoC occurs while sitting
For syncope occurring while standing or sitting, the following factors indicate high risk:
Further investigations such as 48-hour ambulatory ECG, echocardiography and exercise testing may be indicated after specialist opinion has been sought.
Transient loss of consciousness - solitary episode
Typical vasovagal syncope
Syncope with avoidable trigger or otherwise reversible cause
Transient loss of consciousness- recurring episodes
Recurrent episodes of TLoC are less common than isolated episodes but the relevance to increased risk in driving cannot be overemphasised.
Recurrent TLoC is most commonly due to recurrent syncope, occurring in around 20% to 30% of patients.
Recurrence of syncope is usually within three years of the first episode, and in over 80% of these cases there has been at least one additional episode within two years of the first episode.
In relation to road safety however, the two most important features of temporary loss of consciousness are:
A prodrome must allow time for a driver to find a safe place to stop before losing consciousness. A prodrome is reliable if the signs are clear, consistent across all events and provide sufficient duration to find a safe stop, or unreliable if these are absent.
Recurrent pre-syncopal events should be treated (from a licensing point of view) in the same way as recurrent syncope, and should therefore be categorised according to the standards for recurrent syncope.
Licence holders or applicants should be informed that they must notify the DVLA when transient loss of consciousness occurs while sitting
Recurrent typical vasovagal syncope with identifiable consistent prodrome
Recurrent syncope with avoidable trigger or otherwise reversible cause
For syncope occurring while standing or sitting, the following factors indicate high risk:
Further investigations such as 48-hour ambulatory ECG, echocardiography and exercise testing may be indicated after specialist opinion has been sought.
For more details and most up to date guidance then this must be obtained from the publication "At a Glance Guide to the Current Medical Standards of Fitness to Drive" and the website www.dvla.gov.uk.
Reference:
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