Non-syncopal conditions presenting with collapse
| Condition | Features that distinguish from syncope |
| Cardiac arrest | No spontaneous recovery from TLoC |
| Cataplexy | Loss of muscular tone and responsive, usually associated with narcolepsy |
| Coma | Longer duration of LoC without spontaneous recovery |
| Complex partial seizures, absence epilepsy | Unresponsiveness and amnesia without falls, with associated neurological features |
| Falls without TLoC | Absence of amnesia and unresponsiveness, clear cause for fall |
| Generalized seizures | Aura, flashing lights may trigger, longer duration of LoC, symmetrical rhythmic muscle movements, confusion after LoC lasting minutes (shorter with syncope) |
| Intoxication | Longer duration of LoC, consciousness often impaired rather than lost |
| Intracerebral or subarachnoid hemorrhage | Severe headache, neurological signs, and progressive LoC |
| Metabolic disorders (hypoglycaemia, hypoxia, hyperventilation with hypocapnia) | Longer duration of LoC, consciousness often impaired rather than lost |
| Psychogenic pseudosyncope | Increased frequency and longer duration of apparent syncope without true LoC, maintained hemodynamics, normal electroencephalogram |
| Subclavian steal syndrome | Upper extremity activity associated with focal neurological signs |
| Transient ischemic attack | Focal neurological features usually without TLoC. If LoC occurs, there is a longer duration of TLoC. |
Conditions that may be incorrectly diagnosed as syncope are listed, modified from the American College of Cardiology and European Society of Cardiology and syncope guidelines.12 32
LoC, loss of consciousness; TLoC, transient loss of consciousness.