What is cataplexy?

What is Cataplexy

Cataplexy is a sudden, brief episode of bilateral muscle weakness or paralysis triggered by strong emotions (particularly laughter), during which the patient remains fully conscious and can recall the entire event. 1

Core Defining Features

Cataplexy is pathognomonic for narcolepsy, meaning its presence essentially establishes the diagnosis of narcolepsy when combined with daytime sleepiness. 1, 2, 3

The three cardinal characteristics that define cataplexy are:

• Emotional triggering: Episodes are provoked by strong emotions, most commonly laughter, but also anger, excitement, or surprise 1, 3
• Preserved consciousness: Patients remain awake and aware throughout the entire episode, with complete memory of what occurred 1
• Bilateral muscle tone loss: Sudden weakness or paralysis of voluntary muscles, typically lasting less than 2 minutes 2, 3

Clinical Presentation Spectrum

In Adults

The severity ranges widely from partial to complete episodes:

• Partial attacks: May involve only neck muscles (head drop), facial sagging, jaw weakness, or knee buckling 4
• Complete attacks: Generalized flaccidity leading to falls, though consciousness remains intact 1, 4
• Duration: Episodes typically last seconds to less than 2 minutes 2

In Children (Atypical Presentation)

Childhood cataplexy differs dramatically from adult presentation and is frequently misdiagnosed as seizures or movement disorders. 1, 5 Key pediatric features include:

• Profound baseline facial hypotonia ("cataplectic facies") present even between attacks 1, 5
• Active motor phenomena: Tongue protrusion, complex perioral muscle movements that can resemble chorea 1, 4
• Episodes without clear emotional triggers, making diagnosis more challenging 1, 5
• Resemblance to seizures: May mimic clonic, atonic, or myoclonic seizures, but consciousness is preserved 1

Underlying Pathophysiology

Cataplexy results from degeneration of hypothalamic neurons that produce hypocretin/orexin, with Type 1 narcolepsy showing very low or undetectable CSF orexin levels. 1, 6, 2

The mechanism involves:

• Activation during wakefulness of brainstem circuitry that normally suppresses muscle tone during REM sleep 3
• Decreased excitation of noradrenergic neurons and increased inhibition of skeletal motor neurons by GABA-releasing or glycinergic neurons 3
• Emotional pathways through the amygdala and medial prefrontal cortex trigger the attacks 3

Critical Differential Diagnosis

Distinguishing from Epilepsy

• Epileptic seizures: Altered or lost consciousness, post-ictal confusion, episodes last ~1 minute, patients remain upright during absence or complex partial seizures 1
• Cataplexy: Consciousness preserved, no amnesia, no post-ictal state, may cause falls 1

Distinguishing from Syncope

• Syncope: True loss of consciousness from cerebral hypoperfusion, preceded by prodromal symptoms (lightheadedness, visual blurring), complete flaccidity during unconsciousness 1
• Cataplexy: No loss of consciousness, no prodrome, emotionally triggered 1

Distinguishing from Drop Attacks

• Drop attacks: Sudden falls without loss of consciousness, typically in middle-aged women, but lack emotional triggers and narcolepsy symptoms 1

Secondary Causes Beyond Narcolepsy

While cataplexy is pathognomonic for narcolepsy, it can rarely result from:

• Niemann-Pick type C disease 5, 4
• Prader-Willi syndrome 5, 4
• Hypothalamic or pontomedullary lesions 5, 4

Diagnostic Approach

The diagnosis is made clinically through history and observation, ideally supplemented with home video recordings. 4 Key diagnostic elements include:

• Emotional triggers (especially laughter) 1
• Preserved consciousness during episodes 1
• Associated narcolepsy symptoms: Excessive daytime sleepiness, hypnagogic hallucinations, sleep paralysis 1
• Absence of post-ictal confusion (distinguishes from epilepsy) 1

For confirmation of Type 1 narcolepsy, polysomnography followed by Multiple Sleep Latency Test (MSLT) showing mean sleep latency ≤8 minutes and ≥2 sleep-onset REM periods supports the diagnosis. 6 CSF hypocretin-1 levels are very low or undetectable in Type 1 narcolepsy. 1, 6

Common Diagnostic Pitfalls

• Childhood cataplexy misdiagnosed as seizures due to active motor phenomena and facial hypotonia 1, 4
• Childhood cataplexy confused with neuromuscular disorders due to profound facial weakness 4
• Missing the diagnosis when emotional triggers are subtle (excitement, surprise) rather than obvious laughter 1
• Overlooking isolated cataplexy as an early warning sign before full narcolepsy develops 7