Cataplexy

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Not to be confused with Catalepsy.
Cataplexy
Classification and external resources
Specialty Neurology
ICD-10 G47.4
ICD-9-CM 347
DiseasesDB 16311
Patient UK Cataplexy
MeSH D002385

Cataplexy is a sudden and transient episode of muscle weakness accompanied by full conscious awareness, typically triggered by emotions such as laughing, crying, terror, etc.[1] It is the cardinal symptom of narcolepsy with cataplexy affecting roughly 70% of people who have narcolepsy,[2] and is caused by an autoimmune destruction of the neurotransmitter hypocretin, which regulates arousal and wakefulness. Cataplexy without narcolepsy is rare and the cause is unknown.

The term cataplexy originates from the Greek κατά (kata, meaning "down"), and πλῆξις (plēxis, meaning "stroke").

Signs and symptoms[edit]

Cataplexy manifests itself as muscular weakness which may range from a barely perceptible slackening of the facial muscles to complete muscle paralysis with postural collapse.[3] Attacks are brief, most lasting from a few seconds to a couple of minutes, and typically involve dropping of the jaw, neck weakness, and/or buckling of the knees. Even in a full-blown collapse, people are usually able to avoid injury because they learn to notice the feeling of the cataplectic attack approaching and the fall is usually slow and progressive.[4] Speech may be slurred and vision may be impaired (double vision, inability to focus), but hearing and awareness remain normal.

Cataplexy attacks are self-limiting and resolve without the need for medical intervention. If the person is reclining comfortably, he or she may transition into sleepiness, hypnagogic hallucinations, or a sleep-onset REM period. While cataplexy worsens with fatigue, it is different from narcoleptic sleep attacks and is usually, but not always, triggered by strong emotional reactions such as laughter, anger, surprise, awe, and embarrassment, or by sudden physical effort, especially if the person is caught off guard.[5] One well known example of this was the reaction of 1968 Olympic long jump medalist Bob Beamon on understanding that he had broken the previous world record by over 0.5 meters (2 feet).[6] Cataplectic attacks may also occur spontaneously with no identifiable emotional trigger.[7]

Mechanism[edit]

In this simplified brain circuit, damage to orexin-secreting neurons in the hypothalamus can lead to inhibition of motor neurons, thus lowering muscle tone.

Cataplexy is considered secondary when it is due to specific lesions in the brain that cause a depletion of the hypocretin neurotransmitter. Secondary cataplexy is associated with specific lesions located primarily in the lateral and posterior hypothalamus. Cataplexy due to brainstem lesions is uncommon particularly when seen in isolation. The lesions include tumors of the brain or brainstem and arterio-venous malformations. Some of the tumors include astrocytoma, glioblastoma, glioma, and subependynoma. These lesions can be visualized with brain imaging, however in their early stages they can be missed. Other conditions in which cataplexy can be seen include ischemic events, multiple sclerosis, head injury, paraneoplastic syndromes, and infections such as encephalitis. Cataplexy may also occur transiently or permanently due to lesions of the hypothalamus that were caused by surgery, especially in difficult tumor resections. These lesions or generalized processes disrupt the hypocretin neurons and their pathways. The neurological process behind the lesion impairs pathways controlling the normal inhibition of muscle tone drop, consequently resulting in muscle atonia.[8]

Theories for episodes[edit]

A phenomenon of REM sleep, muscular paralysis, occurs at an inappropriate time. This loss of tonus is caused by massive inhibition of motor neurons in the spinal cord. When this happens during waking, the victim of a cataplectic attack loses control of his or her muscles. As in REM sleep, the person continues to breathe and is able to control eye movements.[5]

Hypocretin[edit]

The hypothalamus region of the brain regulates basic functions of hormone release, emotional expression and sleep. A study in 2006 in "Tohoku Journal of Experimental Medicine" concluded that the neurochemical hypocretin, which is regulated by the hypothalamus, was significantly reduced in study participants with symptoms of cataplexy. Orexin, also known as Hypocretin, is a primary chemical important in regulating sleep as well as states of arousal. Hypocretin deficiency is further associated with decreased levels of histamine and epinephrine, which are chemicals important in promoting wakefulness, arousal and alertness.[9]

Treatment[edit]

Cataplexy is treated with medications. There are no behavioral treatments. People with narcolepsy will often try to avoid thoughts and situations that they know are likely to evoke strong emotions because they know that these emotions are likely to trigger cataplectic attacks.[5]

Gamma-hydroxybutyrate[edit]

Sodium oxybate and gamma-hydroxybutyrate has been found to be effective at reducing the number of cataplexy episodes.[10][11] Sodium oxybate is generally safe.[11] Sodium oxybate is typically the recommended treatment.[12]

Antidepressants[edit]

If the above treatment is not possible venlafaxine is recommended.[12] Evidence for benefit is not as good.[12]

Previous treatments include tricyclic antidepressants such as imipramine, clomipramine or protriptyline.[4] Monoamine oxidase inhibitors may be used to manage both cataplexy and the REM sleep-onset symptoms of sleep paralysis and hypnagogic hallucinations.[13]

Research[edit]

Research includes into hypocretin gene therapy and hypocretin cell transplantation for narcolepsy-cataplexy.[14][15]

See also[edit]

References[edit]

  1. ^ Seigal, Jerome (January 2001). "Narcolepsy". Scientific American: 77. 
  2. ^ "Narcolepsy Fact Sheet". Retrieved 2011-06-23. 
  3. ^ Bourgoin, Jean-Maxime. "Il s’endort au volant de sa voiture" (in French). Sun Media. Le Journal de Montréal. Retrieved 11 May 2015. 
  4. ^ a b Michelle Cao and Christian Guilleminault. "Cataplexy". Retrieved April 27, 2012. 
  5. ^ a b c Carlson, Neil R. (2012). Physiology of Behavior. Boston, MA: Pearson Education, Inc. ISBN 978-0-205-66627-0. 
  6. ^ Great Olympic Moments - Sir Steve Redgrave, 2011
  7. ^ The clinical features of cataplexy: A questionnaire study in narcolepsy patients with and without hypocretin-1 deficiency Sebastiaan Overeem, Sofie J. van Nues, Wendy L. van der Zande, Claire E. Donjacour, Petra van Mierlo, Gert Jan Lammers |title=The clinical features of cataplexy: A questionnaire study in narcolepsy patients with and without hypocretin-1 deficiency|url=http://www.sciencedirect.com/science/article/pii/S1389945710003011
  8. ^ Dauvilliers, Yves; Isabelle Arnulf; Emmanuel Mignot (10 February 2007). "Narcolepsy with Cataplexy". The Lancet 39 (9560): 499–511. doi:10.1016/S0140-6736(07)60237-2. Retrieved April 30, 2012. 
  9. ^ Walding, Aureau. "Causes of Cataplexy". Demand Media, Inc. Retrieved April 30, 2012. 
  10. ^ Boscolo-Berto, R; Viel, G; Montagnese, S; Raduazzo, DI; Ferrara, SD; Dauvilliers, Y (October 2012). "Narcolepsy and effectiveness of gamma-hydroxybutyrate (GHB): a systematic review and meta-analysis of randomized controlled trials.". Sleep medicine reviews 16 (5): 431–43. PMID 22055895. 
  11. ^ a b Alshaikh, MK; Tricco, AC; Tashkandi, M; Mamdani, M; Straus, SE; BaHammam, AS (15 August 2012). "Sodium oxybate for narcolepsy with cataplexy: systematic review and meta-analysis.". Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine 8 (4): 451–8. PMID 22893778. 
  12. ^ a b c Lopez, R; Dauvilliers, Y (May 2013). "Pharmacotherapy options for cataplexy.". Expert opinion on pharmacotherapy 14 (7): 895–903. PMID 23521426. 
  13. ^ Thomas F. Anders, MD (2006). "Narcolepsy". Childhood Sleep Disorders. Armenian Medical Network. Retrieved 2007-09-19. 
  14. ^ "Emerging Therapies in Narcolepsy-Cataplexy" (PDF). Retrieved 2011-06-23. 
  15. ^ Weidong, W.; Fang, W.; Yang, Z.; Menghan, L.; Xueyu, L. (2009). "Two patients with narcolepsy treated by hypnotic psychotherapy". Sleep Medicine 10 (10): 1167–1167. doi:10.1016/j.sleep.2009.07.011. PMID 19766057.  edit

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