Another common pitfall is to assume seizure when there are any number of limb-jerking movements witnessed. A few limb jerks during a syncopal event are present in approximately 90 percent of witnessed syncopal episodes, as lack of blood perfusion to the brain causes anoxic neuronal irritation.⁷ One rule of thumb and clinical pearl to help

distinguish seizure from syncope is the 10:20 Rule. It states that patients with less than 10 witnessed myoclonic jerks after sudden loss of consciousness are more likely to have syncope as the cause, versus more than 20 myoclonic jerks witnessed makes the cause more likely to be seizure.⁹

Step 2: Consider Vascular Catastrophes Leading the Syncope

Acute vascular catastrophes such as subarachnoid hemorrhage, massive gastrointestinal bleeding, pulmonary embolism, and ruptured ectopic pregnancy may present as syncope, however additional clinical features make these diagnoses more apparent compared to syncope that presents in isolation.

Step 3: Distinguish Cardiac Syncope from Non-Cardiac Syncope

After considering syncope caused by vascular catastrophes, the priority in the ED should be distinguishing cardiac syncope from noncardiac syncope, as cardiac syncope carries significant morbidity and mortality and usually requires hospital admission. All other categories of syncope (such as reflex syncope and orthostatic syncope) are generally more benign. One exception is Eagle’s Syndrome, a rare cause of reflex syncope that involves a calcified, elongated stylohyoid ligament that presses on the carotid during neck extension that can lead to syncope. In patients who present with recurrent syncope after activities that involve neck extension (e.g., car mechanic, yoga, stargazing, etc.) with associated tinnitus or throat pain, consider a CT of the neck to rule out this rare syndrome.¹⁰

Clinical clues that should heighten one’s suspicion of cardiac syncope include the presence of multiple cardiovascular risk factors, history of structural heart disease, such as aortic stenosis or hypertrophic cardiomyopathy, pacemaker, syncope in the supine position, absence of prodrome prior to the syncopal event or prodrome that includes chest pain, shortness of breath, or palpitations, and syncope during exertion.^11,12,13,14

One lesser-known clinical clue for cardiac syncope is associated facial injury (including dental injury, eyeglasses damage, or tip of tongue bite), which is less likely to occur with reflex or orthostatic syncope.^15,16 While many emergency physicians appropriately ask about a family history of unexplained sudden death as a risk factor for cardiac syncope, the astute clinician will ask specifically about unexplained drowning and single motor vehicle crash in young first-degree relatives, which may uncover a positive family history of unexplained sudden cardiac death and prompt a referral to a cardiac electrophysiologist to rule out a hereditary life-threatening cardiac dysrhythmia as the cause of syncope.¹⁷ One physical examination finding suggestive of cardiac syncope is a new aortic stenosis murmur. Uncovering critical aortic stenosis in a patient with syncope may be lifesaving, as this combination portends a high short-term mortality rate that can be prevented if they undergo timely aortic valve replacement.¹⁸