Circadian rhythms in the vegetative state

Objective: To evaluate whether vegetative state patients maintain circadian rhythms. Research design: An observational study of five single cases. Methods and procedures: Five chronic vegetative state patients underwent clinical and neurological evaluations and 2-week continuous temperature measurements. Main outcomes and results: The two patients with traumatic brain injury showed well-formed circadian temperature rhythms and had more reflexive behaviours and relatively low cortical and sub-cortical atrophy, whereas the three patients from anoxic-hypoxic origin demonstrated no cycles or rhythmic behaviour. Conclusions: The presence of periods of wakefulness does not imply preserved sleep-wake cycling capacity, nor preserved circadian rhythms and it should not be taken as a distinguishing feature for the definition of the vegetative state.