Passing Out

This topic addresses a patient who says they โ€œpassed out,โ€ usually somewhat recently, but now they feel and look completely fine.  Exam is normal.  We have possible causes to sort through.

For the E.R. diagnostic work-up of a patient actively in coma, seizing, or highly confused, see the mnemonic “Vowel TIPS”.

Causes of Loss of Consciousness (LOC)

…………..Patient Fell to Floor  
โ€ข Faint (a.k.a. Syncope)
โ€ข Seizure (generalized)
โ€ข Transient Ischemic Attack (TIA)
โ€ข Concussion  (from Head Trauma)
โ€ข Conversion Reaction
โ€ข Hyperventilation
โ€ข Intoxication
……….Episode of Amnesia (without Fall)  
โ€ข Complex-Partial Seizure
โ€ข Dissociative State
โ€ข Transient Global Amnesia
โ€ข Intoxication


Brief Definitions of the Diseases (see links for more explanation)

Faint:ย  Sudden momentary drop of blood circulation to the brain.ย  Several kinds:
โ€ข Vasovagal (due to emotions, certain body functions, hot room, etc.; may feel nausea / woozy)
โ€ข Orthostatic (standing up too fast if dehydrated, on certain meds, have certain diseases)
โ€ข Cardiac Arrhythmia
โ€ข Other Heart Diseases (Coronary Artery Disease; Obstruction of Blood Flow out of Heart)
โ€ข Occurs with Turning Head (very rare)
Seizure (generalized):ย  Nerve transmission in brain goes haywire; massive short circuits
Transient Ischemic Attack (TIA):ย  Start of a stroke, that resolves quickly on its own
Conversion Reaction:ย  Psychological way for mind to escape intolerable situation
Hyperventilation:ย  Very fast breathing from Anxiety
Complex-Partial Seizure:ย  Unconscious weird behavior; short-circuit in one lobe of brain
Dissociative State:ย  Mind is so distracted (often traumatic memories), acts without awareness
Transient Global Amnesia:ย  Canโ€™t retain new memories, like where they are, what theyโ€™re doing
Intoxication:ย  Alcohol; any substances; poisoning

We make the diagnosis 100% by the medical history.  Witnesses give crucial clues; unwitnessed LOC is much harder.  Our most likely diagnoses for someone who has passed out or lost consciousness are:

KEY CLUES  (we query witnesses if any, or glean as best we can):

Fell to (or Awoke on) the Floor

Duration of LOC on Floor:

  • <20 secs:  Faint
  • >1 min:  Seizure
  • >5 min:  Conversion Reaction


  • Rapid:  Faint; Conversion Reaction
  • Gradual transition from confused to aware (10-30 min):  Seizure

Patient Can Recall What Others Around Did During the Episode:   Conversion Reaction

Movements of Arms & Legs:

  • Stiff & Shaking:  Seizure (can occasionally occur briefly with simple Faint)
  • Flailing (random):  Conversion Reaction


  • Rolled back:  Seizure; Faint
  • Rapidly shake in one direction (aka โ€œnystagmusโ€):  Seizure
  • Glazed:  Faint; Seizure
  • Clenched Shut:  Conversion Reaction


  • Sides of Tongue:  Seizure; maybe Faint
  • Tip of Tongue, Lips, hands, etc.:  Conversion Reaction

Triggers That Provoked the Event:

  • Environmental (ugly sight, smell, etc); Straining; Emotions:  Faint
  • Exertion:  Faint from Heart Disease
  • Confrontational or Situational Stress:  Conversion Reaction
  • Neck Movement (rare):  Faint; TIA (very rare)

Atherosclerosis (Heart Risks: old age, smoking, hypertension, diabetes, etc; see link)

Symptoms Just Before Collapse:

  • Aura (vague sensations like smell, flashing lights, etc.):  Seizure
  • Vertigo, Double Vision, Slurred Speech, Swallowing difficulty:  TIA

Face Turned Blue / Foamed at Mouth / IncontinenceSeizure

No Fall, but Loss of Awareness (Witnessed)

Strange Movements or ActionsComplex-Partial Seizure

  • grimace, lip-smack, chew, teeth clench, drool, swallow, blink
  • twitch shake, foot stomp, hand wave, tremor
  • stare, stiffen up
  • randomly walks around / runs / undresses
  • utters meaningless sounds

Patient Recall

  • Total amnesia of the episode:  Complex-Partial Seizure
  • Total loss of awareness during the episode:  Complex-Partial Seizure
  • Knew his/her name during the episode:  Transient Global Amnesia
  • Retained past memories during the episode:  Transient Global Amnesia

No Fall, episode of Amnesia  (Unwitnessed):  

We do tests to distinguish Complex-Partial Seizure vs. Dissociative State

  • Total Global Amnesia possible (if lasted 1-10 hours)
  • Intoxication possible
  • Can be impossible to distinguish


Tests we order depend on the reason we think a person passed out:

1.  If we suspect Faint (a.k.a. Syncope):

  • History suggests Vasovagal or Orthostatic Syncope  โ†’   no tests
  • Faint during Exertion  โ†’  EKG, Echocardiogram, maybe Stress Tests
  • Simply Faints  โ†’  EKG
    • Cardiac Referral if EKG abnormal
  • Faints repeatedly when turns head a certain way (very rare)
    • Angiogram by MRI or CT; then Refer to Vascular Specialist
  • We send to ER if:
    • Same-day Faint with exertion
    • Same-day Faint + abnormal EKG or risks for Heart Disease

2.  If we suspect Seizure (any kind):

3.  If we suspect basilar artery Transient Ischemic Attack (TIA) [rare)]

4.  If we suspect a Conversion Reaction  โ†’  no tests

  • We reassure patient it is a common psychological defense mechanism
  • If patient / family insist on โ€œtestsโ€   โ†’  Refer to Neurology to decide

5.  If unwitnessed episode of Amnesia without a Fall

See Passing Out โ€” Full Text for more in-depth explanations and discussions.

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