Circadian rhythms in severely brain-injured patients: A clue to consciousness?

Blume C, Lechinger J, Santhi N, Giudice RD, Gnjezda MT, Pichler G, Scarpatetti M, Donis J, Michitsch G, Schabus M. Significance of circadian rhythms in severely brain-injured patients: A clue to consciousness? Neurology. 2017 May 16;88(20):1933-1941.

Abstract

OBJECTIVE:

To investigate the relationship between the presence of a circadian body temperature rhythm and behaviorally assessed consciousness levels in patients with disorders of consciousness (DOC; i.e., vegetative state/unresponsive wakefulness syndrome or minimally conscious state).

METHODS:

In a cross-sectional study, we investigated the presence of circadian temperature rhythms across 6 to 7 days using external skin temperature sensors in 18 patients with DOC. Beyond this, we examined the relationship between behaviorally assessed consciousness levels and circadian rhythmicity.

RESULTS:

Analyses with Lomb-Scargle periodograms revealed significant circadian rhythmicity in all patients (range 23.5-26.3 hours). We found that especially scores on the arousal subscale of the Coma Recovery Scale-Revised 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 2 out of 8 patients.

CONCLUSION:

The study provides evidence for an association between circadian body temperature rhythms and arousal as a necessary precondition for consciousness. Our findings also make a case for circadian rhythms as a target for treatment as well as the application of diagnostic and therapeutic means at times when cognitive performance is expected to peak.