What are the typical onsets and treatments of seizure mimics, including syncope and psychogenic non-epileptic seizures (PNES)?

Seizure Mimics: Typical Onset and Clinical Features

Syncope

Syncope typically presents with a flaccid collapse preceded by nausea, sweating, and pallor, with loss of consciousness lasting less than 30 seconds and any movements beginning after the onset of unconsciousness. 1

Prodromal Features

• Autonomic symptoms: Nausea, vomiting, abdominal discomfort, cold sweating, lightheadedness, and blurred vision characteristically precede syncopal episodes 1
• Cerebral hypoperfusion symptoms: Dark spots in vision, loss of color vision, sounds coming from a distance, buzzing or ringing in ears 1
• Pallor and sweating are common in syncope but uncommon in epilepsy 1

During the Event

• Flaccid collapse is the hallmark presentation, contrasting with the stiff "keeling over" seen in tonic seizures 1
• Movement characteristics are critical for differentiation:
  • Movements begin after the fall and after onset of loss of consciousness (mean 20 seconds delay) 1
  • Movements are asymmetrical and asynchronous 1
  • Few movements (approximately 10 or so), not countless 1
  • Duration typically <15 seconds 1
• Duration of unconsciousness <30 seconds strongly favors syncope over seizure 1
• Eyes are typically open except in shallow, short-lasting syncope 1

Post-Event Recovery

• Immediate clearheadedness is typical, with confusion usually of short duration 1
• Nausea, vomiting, and pallor may persist after neurally-mediated syncope 1

Common Triggers

• Fear, pain, instrumentation (classical vasovagal syncope) 1
• Prolonged standing, warm environments, hot baths 1
• Post-exercise in middle-aged and elderly (post-exercise hypotension) 1
• Postprandial (15 minutes after eating, particularly in elderly with autonomic failure) 1

Psychogenic Non-Epileptic Seizures (PNES)

PNES typically present with prolonged episodes (>5 minutes), eyes closed during unconsciousness, asynchronous thrashing movements, and pelvic thrusting, affecting 20-30% of patients in epilepsy centers. 1, 2

Key Distinguishing Features

• Duration of loss of consciousness >5 minutes strongly suggests PNES over epileptic seizures 1
• Eyes closed during unconsciousness is highly characteristic of PNES, whereas eyes remain open in epileptic seizures 1, 3, 2
• Movement patterns:
  • Asynchronous, side-to-side thrashing movements 2
  • Many movements that cannot be counted ("100", "cannot count") 1
  • Repeated waxing and waning in intensity with changes in movement nature 1
  • Pelvic thrusting is characteristic of PNES (though rarely seen in frontal lobe seizures) 1
• Eye fluttering is more likely in PNES than epileptic seizures 1

Clinical Presentation

• Episodes affecting 20-30% of patients attending epilepsy centers and over 10% of seizure emergencies 2
• May be as disabling as epileptic seizures and often occur on a subconscious level 4
• Incidence estimated at 1.4-4.9/100,000/year 5

Important Diagnostic Pitfalls

• Tongue biting does NOT differentiate PNES from epilepsy 1
• Urinary incontinence does NOT differentiate PNES from epileptic seizures or syncope 1
• Biomarkers are unreliable: Neuron-specific enolase, prolactin, and creatine kinase should not be relied upon for differentiation 2
• Comorbidity between epilepsy and PNES ("dual diagnosis") occurs and creates significant diagnostic challenges 5
• One in four to five patients with presumed refractory epilepsy actually have PNES (pseudo-refractory epilepsy) 5

True Epileptic Seizures: Distinguishing Features

Onset Characteristics

• Aura: Rising epigastric sensation, unusual unpleasant smell or taste, déjà vu/jamais vu 1
• Ictal cry (shout at onset) suggests epilepsy 1
• Triggers include flashing lights, sleep deprivation 1

During the Event

• Stiff "keeling over" during tonic phase 1
• Movements begin at onset of unconsciousness or before the fall 1
• Symmetrical, synchronous movements 1, 3
• Duration of unconsciousness >1 minute (mean 74-90 seconds) strongly favors epilepsy 1, 3
• Hemilateral clonic movements 1
• Oral automatisms: Chewing, smacking, blinking, frothing at mouth 1, 3, 2
• Lateral tongue biting (uni- or bilateral) is highly specific for epilepsy 1, 3
• Eyes typically remain open during unconsciousness 1, 3
• Cyanotic face may occur 1
• Stertorous (snoring) breathing suggests epilepsy over PNES 1

Post-Ictal Phase

• Prolonged confusion is characteristic 1
• Aching muscles, headache, sleepiness 1
• Elevation of creatinine kinase and prolactin more frequent (though not reliable for PNES differentiation) 1, 2

Other Seizure Mimics

Cataplexy

• Paresis or paralysis triggered by emotions, usually laughter 1
• Patients remain conscious with no amnesia 1
• Associated with daytime sleepiness in narcolepsy 1

Drop Attacks

• Sudden falls in middle-aged women (rarely men) 1
• Patients remember hitting the floor 1
• No loss of consciousness 1

Vertebrobasilar TIA

• Paresis, ataxia, brainstem signs 1