How to differentiate between Psychogenic Non-Epileptic Seizures (PNES) and epileptic seizures in a patient with a history of psychological trauma, anxiety, or depression?

Differentiating PNES from Epileptic Seizures

Video-EEG monitoring is the gold standard for diagnosis, but specific clinical features can reliably distinguish PNES from epileptic seizures at the bedside, with eyes closed during unconsciousness, prolonged duration (>5 minutes), asynchronous thrashing movements, and pelvic thrusting being the most characteristic features of PNES. 1

Key Distinguishing Clinical Features

Features Strongly Suggesting PNES

Duration and consciousness patterns:

• Episodes lasting longer than 5 minutes strongly suggest PNES over epileptic seizures 1
• Eyes closed during unconsciousness is highly characteristic of PNES, whereas eyes remain open in epileptic seizures 1, 2
• Patients may have memory recall of the event, unlike true seizures 3

Movement characteristics:

• Asynchronous, side-to-side thrashing movements with many movements that cannot be counted 1, 2
• 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, 3
• Eye fluttering is more likely in PNES 1

Episode characteristics:

• Fluctuating course throughout the episode 3
• Ictal crying during the event 3
• Episodes occurring from apparent sleep with EEG-verified wakefulness 3
• Absence of postictal confusion (unlike epilepsy where prolonged confusion is characteristic) 1, 3

Features Strongly Suggesting True Epileptic Seizures

Onset characteristics:

• Aura including rising epigastric sensation, unusual unpleasant smell or taste, déjà vu/jamais vu 1
• Ictal cry or shout at onset 1
• Stiff "keeling over" during tonic phase 1

Movement patterns:

• Movements begin at onset of unconsciousness or before the fall 1
• Symmetrical and synchronous bilateral movements 1, 2
• Hemilateral clonic movements 1
• Oral automatisms including chewing, smacking, blinking, and frothing at the mouth 1, 2

Specific signs:

• Lateral tongue biting is highly specific for epilepsy and uncommon in PNES 1, 2, 3
• Eyes typically remain open during unconsciousness 1, 2
• Duration of unconsciousness typically 74-90 seconds 1

Post-ictal features:

• Prolonged confusion after the event 1
• Postictal stertorous (snoring) breathing distinguishes generalized tonic-clonic seizures from convulsive PNES 3
• Aching muscles, headache, and sleepiness 1

Features That Do NOT Differentiate

Common pitfalls to avoid:

• Tongue biting (non-lateral) does not differentiate PNES from epilepsy 1
• Urinary incontinence does not differentiate PNES from epileptic seizures 1
• Biomarkers (neuron-specific enolase, prolactin, creatine kinase) are unreliable for differentiation and should not be relied upon 1, 2, 4
• Do not diagnose based on any single clinical feature alone, as no single feature is pathognomonic for PNES 5, 3

Diagnostic Algorithm

Step 1: Assess episode duration and eye position

• Duration >5 minutes + eyes closed → strongly suggests PNES 1
• Duration 74-90 seconds + eyes open → suggests epilepsy 1

Step 2: Evaluate movement patterns

• Asynchronous, side-to-side thrashing with pelvic thrusting → PNES 1, 3
• Symmetrical, synchronous movements with oral automatisms → epilepsy 1

Step 3: Check for specific signs

• Lateral tongue biting → epilepsy 1, 2
• Ictal crying + memory recall → PNES 3

Step 4: Assess post-event state

• Immediate clearheadedness → PNES 1, 3
• Prolonged confusion + postictal stertorous breathing → epilepsy 1, 3

Step 5: Confirm with video-EEG monitoring

• Video-EEG is the gold standard, showing normal EEG during PNES episodes versus epileptiform discharges during true seizures 1
• This is essential when clinical diagnosis remains uncertain 1

Special Considerations in Patients with Psychological Trauma

Psychiatric comorbidities are extremely common in PNES:

• PNES patients have high rates of depression, anxiety, somatoform symptoms, dissociative disorders, and PTSD 1, 4
• History of childhood trauma and abuse correlates strongly with PNES diagnosis 4
• Psychiatric evaluation is indicated for all patients diagnosed with PNES 1

Critical diagnostic challenge:

• 10-30% of patients with PNES have concurrent epileptic seizures or previous epilepsy ("dual diagnosis") 5, 4, 6
• This comorbidity can lead to misdiagnosis of pseudo-refractory epilepsy 6
• One in four to five patients admitted to video-EEG units with presumed drug-resistant epilepsy actually have PNES 6