Syncope Versus Seizures

When faced with a patient presenting with an episode of Transient Loss of Consciousness the clinical question may arise as to whether the patient has been syncopal or had a seizure.

This question is particularly valid if witnessess have commented that the patient 'definitely had a seizure'. It is not commonly understood that patients experiencing syncope due to cerebral hypoperfusion commonly have brief seizure like movements lasting up to one minute. This misconception can lead to a misdiagnosis and drug treatment for epilepsy if events are recurrent.

The history - in particular the circumstances leading up to and following the episode- can be fundemental in establishing whether an episode was syncopal or seizure related.

The disorders most commonly misdiagnosed as epilepsy. are:

• Neurally mediated syncope
• Carotid sinus hypersensitivity and
• Syncope due to postprandial hypotension

If the history of the event is suggestive of one of these disorders and brief seizure like movements occured then the event is still consistent with hypotensive syncope.

Various algorithms have been developed to try to differentiate syncope from seizures based on patient history and eye witness accounts.

In general:

Features suggesting epilepsy:

• Waking with a cut tongue
• Déjà vu/ jamais vu prodrome
• Events occuring with emotional stress
• Head turning during loss of consciousness
• Unusual posturing
• Episodes of unresponsiveness without loss of postural tone
• Post-ictal confusion
• No memory of event

Features suggesting syncope:

• Long history of events
• Episodes of presyncope
• Event occured with
  • Prolonged sitting or standing
  • Crowded environment
  • Postprandial period
• Precipitated by head turning
• Hot or cold before event
• Diaphoresis
• Abdominal discomfort
• Nausea/vomiting
• Pallor
• Rapid recovery
• Recollection of event
• Post event lethargy

Post event recovery and recollection for the event are areas that need careful consideration. The above differentiation does not always hold true.

• Elderly patients often do not have recollection of the event on recovery, despite on occasion commenting that 'they don't feel well' before the event.
  • This is particularly true for episodes of postprandial hypotension where there is a slow decline in blood pressure.
• Episodes of syncope due to carotid sinus hypersensitivity often occur without prodrome.
• Patients with arrhythmic syncope usually have a very rapid recovery, however patients with neurally mediated syncope and postprandial hypotension can have a more prolonged recovery on occasion - particularly if they are kept upright during the episode.
  • the mechanism of delayed recovery in some patients with neurally mediated syncope may relate to cerebral vasoconstriction which has been documented during episodes.

If most features of the history are suggestive of syncope then investigations should be initially directed towards cardiovascular causes of the episode of loss of consciousness.

• An electrocardiogram (ECG) must be performed no matter what the suspected cause of loss of consciousness.

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