Passing Out / Amnesia

This topic addresses a patient who says they โ€œpassed out,โ€ or had amnesia for a period of time, usually somewhat recently, but now they feel and look completely fine.  Exam is normal.  We have possible causes to sort through (see table below). For patients with Memory Loss, see that topic.

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, “Grand Mal”)
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:  Sudden momentary drop of blood circulation to the brain.  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):  Nerve transmission in brain goes haywire; massive short circuits
Transient Ischemic Attack (TIA):  Start of a stroke, that resolves quickly on its own
Conversion Reaction:  Psychological way for mind to escape intolerable situation
Hyperventilation:  Very fast breathing from Anxiety
Complex-Partial Seizure:  Unconscious weird behavior; short-circuit in one lobe of brain
Dissociative State:  Mind is so distracted (often traumatic memories), acts without awareness
Transient Global Amnesia:  Canโ€™t retain new memories, like where they are, what theyโ€™re doing
Intoxication:  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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