21 Apr Considering Circadian Rhythms May Aide in Diagnosis of Consciousness Disorders
MedicalResearch.com Interview with:
Dr. Christine Blume PhD
University of Salzburg
Centre for Cognitive Neuroscience (CCNS)
Laboratory for Sleep, Cognition & Consciousness Research
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: We are governed by rhythmic processes. Many of these processes follow a circadian pattern, that is, they have a period length of approximately 24 hours and are under tight control of a biological master clock located in the suprachiasmatic nucleus of the hypothalamus. Given the circadian variation in global states like alertness, it is not surprising that consciousness also varies rhythmically in healthy individuals, it follows the sleep-wake cycle.
From a clinical perspective, misalignment of circadian rhythms, which occurs when the sleep-wake schedule is at odds with the light-dark cycle as in the case of night shifts, can cause considerable stress, have detrimental effects on the immune system and impair cognitive abilities. Despite the knowledge that entrained circadian rhythms are important for healthy body and brain functioning, very little is known about circadian rhythms in patients diagnosed with a disorder of consciousness (DOC) following severe brain injuries. We argue that studying circadian rhythms in DOC patients may be especially interesting and important for two reasons.
First, the presence or absence of circadian rhythms as well as anomalies in them could be informative about the state of the patient as well as their potential for recovery.
Second, this could provide information about time points that best capture remaining cognitive functions thereby minimising the risk of misdiagnoses.
Beyond this, examining circadian processes may also provide targets for therapeutic interventions such as light stimulation, which has proven successful in individuals with e.g. circadian sleep disorders. Interestingly, analyses with Lomb-Scargle periodograms revealed significant circadian rhythmicity in all patients (range 23.5-26.3h).
We found that especially scores on the arousal subscale of the Coma Recovery Scale-Revised (CRS-R) were closely linked to the integrity of circadian variations in body temperature.
Finally, we piloted whether bright light stimulation could boost circadian rhythmicity and found positive evidence in two out of eight patients.
MedicalResearch.com: What should readers take away from your report?
Response: Clinicians should consider circadian rhythms in the diagnostic process, i.e. by selecting times when patients can be expected to be maximally responsive from a circadian point of view.
Moreover, they should aim at creating an environment that mimics the diurnal light-dark cycle.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: We suggest carrying out a proof of principle study to further investigate the usefulness of stimulation with bright light, which we found to have positive effects in two out of eight patients. Moreover, the synchronisation between different body rhythms should be investigated.
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Christine Blume, Julia Lechinger, Nayantara Santhi, Renata del Giudice, Maria-Teresa Gnjezda, Gerald Pichler, Monika Scarpatetti, Johann Donis, Gabriele Michitsch, Manuel Schabus. Significance of circadian rhythms in severely brain-injured patients. Neurology, 2017;
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