The 10/20 Rule | Seizure vs Syncope

April 25, 2018

Written by Clay Smith. 

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Syncope and seizure may be differentiated in two key ways.  Ten or fewer jerks favor syncope; 20 or more jerks favor seizure.  Loss of tone favors syncope.

Why does this matter?
Sometimes bystanders think a patient has had a seizure, because they had rhythmic jerking movements after losing consciousness.  This can be very confusing for the bystander and the physician when trying to figure out what happened.  It is common to have some myoclonic jerking with syncope.  But is there a way to tell this from true seizure activity causing loss of consciousness?

I’m just gonna shake, shake, shake, shake, shake…
This was an awesome study of 65 patients over age 15 on a tilt table with confirmed syncope who were then compared to 50 patients with confirmed convulsive seizures.  All cases were videotaped, and the abnormal movements with each noted.  Tonic posturing was common in syncope (65%) and jerking was present in 51%.  Loss of tone strongly favored syncope.  They coin the “10/20 rule.”  Ten jerks or less is syncope; 20 jerks or more is seizure.  Asynchronous jerks of both arms count as two jerks and argues against convulsive seizures (LR- 0.19).  The actual median number of jerks in syncope was 2 and was 48 in seizure.  So the Taylor Swift song would be syncope, as she’s just gonna shake 5 times.

Source
Differentiating motor phenomena in tilt-induced syncope and convulsive seizures.  Neurology. 2018 Mar 16. pii: 10.1212/WNL.0000000000005301. doi: 10.1212/WNL.0000000000005301. [Epub ahead of print]

Peer reviewed by Thomas Davis.