Narcolepsy

Disease modifying treatment available:
Time critical diagnosis and management:
Lateralising:

Definition

None



Aetiology

In other mammals, narcolepsy is associated with mutations within the orexin gene. In humans though, there is a strong HLA association and the condition is thought to be autoimmune. Antibodies to Trib2 have been associated with the condition.

Narcolepsy can rarely be associated with structural lesions of the hypothalamus or third ventricle. These cases are almost always associated with other brainstem signs.



Associated Disorders




Clinical features


None

Narcolepsy may cause the following:




Investigations


The key initial investigations are polysomnography (PSG) and a multiple sleep latency test (MSLT). PSG may demonstrate early onset sleep (<10 minutes) and early onset REM (< 20 minutes). Low CSF orexin levels have been described in people with narcolepsy with cataplexy. The value of this test is less clear in those without cataplexy. This test is rarely done as narcolepsy with cataplexy is generally not a diagnostic challenge.

None


Laboratory Investigation Result

Treatment


Sleep hygiene and planned naps are the cornerstones of non-pharmacological management. Modafinil can be used to treat excessive daytime sleepiness. Amphetamines can be used but have the potential for tolerance and peripheral side effects. Amphetamines also have a role in the treatment of concomitant cataplexy.

Better sleep can improve cataplexy and this may also get better with age. Antidepressant drugs can be helpful with the management of cataplexy as well as other REM-related conditions.




Research


Open questions

None