Seizure vs syncope differences
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syncope seizure differential diagnosis features guideline
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| Feature | Seizure | Syncope (fainting) |
|---|---|---|
| Mechanism | Abnormal electrical activity in the brain | Brief global reduction in brain blood flow |
| Typical trigger | May occur without a trigger; sleep deprivation, missed antiseizure medication, alcohol withdrawal can contribute | Prolonged standing, heat, pain, emotion, dehydration, standing up quickly; sometimes exertion or arrhythmia |
| Warning symptoms | Aura: unusual smell/taste, déjà vu, rising abdominal sensation, focal sensory symptoms | Lightheadedness, dimming vision, nausea, sweating, warmth, muffled hearing |
| Fall | Often sudden, may occur in any position | Usually while standing or sitting; can be prevented by lying down if warning occurs |
| Movements | Sustained tonic stiffening followed by rhythmic jerking is common in generalized convulsive seizure | Brief, irregular jerks can occur in “convulsive syncope,” usually after collapse |
| Duration of unconsciousness | Often 1-2 minutes or longer | Usually seconds, with rapid spontaneous recovery |
| Recovery | Confusion, headache, muscle soreness, sleepiness can last minutes to hours: postictal state | Rapid return to normal orientation, though brief fatigue or nausea may persist |
| Tongue bite | Supports seizure, especially a side-of-tongue bite | Uncommon |
| Urinary incontinence | Can occur | Can also occur, so it does not reliably distinguish the two |
| Skin color | May become bluish with prolonged convulsion | Often pale and sweaty |
| ECG/orthostatic BP | May be normal, but diagnosis depends on clinical history plus EEG when appropriate | ECG and orthostatic blood pressure are central parts of assessment |
Key point: jerking alone does not prove epilepsy. Brief tonic-clonic or myoclonic movements can accompany syncope. More suggestive of seizure are an epileptic aura, lateral tongue biting, and confusion lasting more than a few minutes afterward. Tintinalli's Emergency Medicine, lines 608-610.
Urgent assessment is needed after a first episode of loss of consciousness, especially if it happened during exercise, while lying down, without warning, or with chest pain, palpitations, shortness of breath, severe headache, persistent confusion, focal weakness, or injury. These can signal dangerous cardiac or neurologic causes. A history, witness account, examination, ECG, and orthostatic blood pressure commonly guide initial evaluation, as summarized in this syncope evaluation review.
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