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Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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Transient loss of consicousness (TLoC), especially if there is little or no warning, is a dangerous and disabling condition.

TLoC is very common: it affects up to half the population in the UK at some point in their lives

  • TLoC may be defined as spontaneous loss of consciousness with complete recovery. In this context, complete recovery would involve full recovery of consciousness without any residual neurological deficit
  • an episode of TLoC is often described as a 'blackout' or a 'collapse'

The diagnosis of the underlying disorder is important because:

  • treatment is usually available
  • some causes are life-threatening

The commonest causes of transient loss of consciousness are cardiovascular and epileptic, although metabolic and psychiatric causes are important.

Blackouts in adults (2)

  • refer urgently adults with new-onset blackouts (transient loss of consciousness), accompanied by features that are strongly suggestive of epileptic seizures, for neurological assessment

  • do not routinely refer adults with blackouts if there are clear features of vasovagal syncope, even if associated with brief jerking of the limbs


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