What is cataplexy?

Cataplexy: Definition, Clinical Features, and Management

Cataplexy is a sudden loss of muscle tone triggered by strong emotions, while consciousness remains fully preserved. 1 It is most commonly associated with narcolepsy and is considered the pathognomonic symptom of narcolepsy type 1.

Clinical Presentation

Cataplexy presents as episodes of sudden muscle weakness with the following characteristics:

• Duration: Episodes typically last less than 2 minutes 2
• Consciousness: Patients remain fully conscious during attacks 1
• Triggers: Strong emotions, particularly positive ones like laughter, are the most common triggers 3
• Muscle involvement: Can be partial (affecting only certain muscle groups) or complete (causing falls) 4

Adult vs. Pediatric Presentation

Adult presentation:

• Often partial attacks affecting facial muscles, neck, or knees
• Clear emotional triggers (laughter, surprise, excitement)
• No confusion after the event

Pediatric presentation:

• More prominent facial involvement with hypotonia
• Active movements of tongue and perioral muscles
• May occur without clear emotional triggers ("cataplectic facies")
• Can be confused with neuromuscular disorders 4

Diagnostic Considerations

Distinguishing Cataplexy from Similar Conditions

Cataplexy must be differentiated from other conditions causing sudden loss of muscle tone:

1. Seizures: Unlike epileptic events, consciousness is preserved in cataplexy 1
2. Syncope: Cataplexy lacks the prodromal symptoms (lightheadedness, visual changes) common in syncope 1
3. Atonic seizures: These are rare and typically occur in children with pre-existing neurological problems 1
4. Drop attacks: These typically occur in middle-aged women who suddenly fall without warning 1

Key Diagnostic Features

• Preservation of consciousness during attacks
• Emotional triggers (particularly laughter)
• Brief duration (seconds to minutes)
• No post-event confusion
• Often associated with other narcolepsy symptoms (excessive daytime sleepiness)

Pathophysiology

Cataplexy is strongly associated with the loss of hypothalamic neurons that produce hypocretin/orexin. This neurochemical deficiency is believed to be the key mechanism underlying both narcolepsy and cataplexy 2. The muscle weakness during cataplexy results from:

• Decreased excitation of noradrenergic neurons
• Increased inhibition of skeletal motor neurons by GABA-releasing or glycinergic neurons 3

The amygdala and medial prefrontal cortex contain neural pathways through which positive emotions likely trigger cataplectic attacks 3.

Management

First-line treatment for cataplexy in narcolepsy is sodium oxybate (gamma-hydroxybutyrate), which is FDA-approved specifically for this indication 5, 2. Its therapeutic effects likely occur through GABA-B receptor-mediated actions on noradrenergic, dopaminergic, and thalamocortical neurons 2.

Antidepressants are commonly used off-label for cataplexy management, though systematic research evidence supporting their use is limited 2.

Special Considerations

• Cataplexy can occasionally occur in isolation without other narcolepsy symptoms, though this is rare 6
• In some cases, cataplexy may be associated with other conditions such as Prader-Willi Syndrome, where it affects approximately 18-25% of patients 1
• Diagnosis is primarily clinical, based on thorough history and, when possible, video documentation of attacks 4

Pitfalls to Avoid

1. Misdiagnosis as seizures: The preservation of consciousness during cataplexy is a key distinguishing feature
2. Overlooking pediatric presentation: Children may present with different features than adults
3. Failing to recognize cataplexy as a symptom of narcolepsy: Identifying cataplexy should prompt evaluation for narcolepsy
4. Confusing cataplexy with syncope: Cataplexy lacks the autonomic prodrome (nausea, sweating) typical of syncope 1

Early recognition and appropriate management of cataplexy are essential to improve quality of life and reduce the risk of injury from falls during attacks.