Definition reprinted with permission from Culebras, Antonio, Clinical Handbook of Sleep Disorders, Butterworth-Heinemann
One of the tetrad of symptoms of narcolepsy. A sudden decrement in muscle tone and loss of deep tendon reflexes, leading to muscle weakness, paralysis, or postural collapse. Cataplexy usually is precipitated by an outburst of emotional expression—notably laughter, anger, or startle. During cataplexy, respiration and voluntary eye movements are not compromised.