Cataplexy

Cataplexy is defined as a sudden loss of voluntary muscle tone with preserved consciousness, triggered by emotion.¹ The emotional stimulus may be, for example, laughter, pleasure, anger or excitement. The attacks can last just a few seconds or many minutes.

Cataplexy occurs only as part of narcolepsy (see our dedicated record). Cataplexy is specific to narcolepsy and is the best diagnostic marker for narcolepsy.²

• Narcolepsy with cataplexy affects 0.02% of adults worldwide.²
• Onset of narcolepsy is usually in early adulthood.³
• Cataplexy affects about 75% of patients with narcolepsy.⁴

• Narcolepsy may be caused by the loss of a relatively few neurons that are responsible for producing the neuropeptide hypocretin in the CNS.³ Patients with narcolepsy and cataplexy have low concentrations of hypocretin in the CSF, compared to controls and those with other sleep disorders.²
• Narcolepsy-cataplexy is strongly associated with a specific HLA allele, DQB1*0602.²

• History: a sudden drop of muscle tone triggered by emotional factors, most often by positive emotions such as laughter, humour, or a pleasant surprise; or by anger. It is not usually triggered by stress, fear, or physical effort.
• Attacks vary considerably in severity, e.g. from a barely susceptible slackening of the facial muscles, dropping of the jaw or the entire head, to weakness at the knees or collapse on to the floor. In severe attacks, all voluntary muscles except the diaphragm may be affected.
• During attacks, speech may be slurred and eyesight impaired with blurring or double vision.
• Hearing, awareness and consciousness are intact.
• Frequency of attacks can vary, from several per day to less than one per year.¹

Note: Ask specifically about mild symptoms of cataplexy (such as slight facial weakness) which patients may not report.

• Epilepsy
• Syncope⁵
• Sleep apnoea is part of the differential diagnosis of narcolepsy.

This may involve investigations for narcolepsy, or to rule out other causes:

• Sleep studies
• EEG
• Brain MRI to exclude other causes, e.g. space-occupying lesions
• Measurement of CSF hypocretin levels may aid in the diagnosis

• Family members need to learn when the patient may need assistance.
• Full-blown cataplectic attacks can be frightening. Attention must be given to the emotional impact on both the patient and the rest of the family.
• There is no known cure for cataplexy and treatment focuses on controlling symptoms. Therefore drug treatment should be avoided if cataplexy is not causing a significant problem for the patient.
• Narcolepsy has implications for driving.

Drug treatment options

• Tricyclic antidepressants (clomipramine⁷ and imipramine) and SSRIs (fluoxetine⁸) have been widely used with beneficial effect, although they have not been studied in randomised placebo-controlled clinical trials.²
• More recently, sodium oxybate has been shown to be effective,^3,9,10 and its use in cataplexy is endorsed by European guidelines.¹ Concerns about sodium oxybate include its abuse potential and its danger in overdose.²

There are no studies directly comparing antidepressants and sodium oxybate for treatment of cataplexy."¹⁰

Psychological and social effects, e.g. patients with cataplexy may avoid social situations where attacks could occur, and may therefore become socially isolated. Patients may also need support around employment and the attitudes of employers and others towards their condition.⁴

There is little mention in the literature concerning the prognosis of cataplexy specifically. However, the associated narcolepsy is generally regarded as a lifelong condition.