Objective: Understanding the role of circadian rhythm in movement disorder and associated sleep disturbances.

Background: Dopamine and other neurotransmitters(NTs) follow a circadian rhythm. NTs have a role in movement disorders, which are affected by circadian rhythm and in turn affect sleep. 

Method: A Pubmed search was done using keywords (circadian rhythm) AND (Restless leg syndrome), (circadian rhythm) AND (Parkinson’s Disease), (circadian rhythm) AND (Dystonia), (circadian rhythm) AND (Tourette disease) and (circadian rhythm) AND (Juvenile myoclonic epilepsy). Out of 238 articles published in the past five years, relevant ones were reviewed.

Results: Our body follows a 24 hr cycle called circadian rhythm. The master clock – suprachiasmatic nucleus, located in the hypothalamus, receives input about light and darkness from the retina and sends cues to local clocks in various parts of the brain that regulate the peripheral clocks. Every cell follows this cycle and NTs are no exception, for example, an increase in the secretion of dopamine in the morning while that of GABA in the night. This physiological process plays an important role in the sleep cycle, disturbance of which can lead to sleep disruptions.

Movement disorders have an impact on sleep. In Parkinson’s disease, there is degeneration of cells in the retina that affects input to SCN and disrupts sleep-wake cycle(1). In Restless Legs Syndrome (RLS ): the symptoms aggravate at nighttime, which correlates with dopamine levels (which are low at nighttime and have a role in the pathology of RLS) and leads to fragmented sleep (2). In dystonia, there is a disruption in sleep-dependent communication between cerebellum and cortical regions that regulate circadian rhythm.Many NTs that are involved in the pathophysiology of Tourette disorder are also involved in the sleep cycle and thus explain disruptions in sleep.In Juvenile myoclonic epilepsy (JME), jerks occur more in the morning. This is due to more cortical excitability in the early hours, explained through the GABA-mediated pathway involved in circadian rhythm. The patients of JME suffer from insomnia (3).

Conclusion: The 24-hour cycle followed by NTs has a role in movement disorder and associated sleep patterns. Understanding and implementation of chronobiology can mitigate some of the serious effects, if not all and can also be a helpful diagnostic tool.

References: 1.Gros P, Videnovic A. Overview of Sleep and Circadian Rhythm Disorders in Parkinson’s Disease. Clin Geriatr Med. 2020 Feb;36(1):119-130.
2.Vlasie A, Trifu SC, Lupuleac C, Kohn B, Cristea MB. Restless legs syndrome: An overview of pathophysiology, comorbidities and therapeutic approaches (Review). Exp Ther Med. 2022 Feb;23(2):185.
3.Xu L, Guo D, Liu YY, Qiao DD, Ye JY, Xue R. Juvenile myoclonic epilepsy and sleep. Epilepsy Behav. 2018 Mar;80:326-330.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/circadian-rhythms-role-in-movement-disorders-and-associated-sleep-disturbances/