Exploratory Study of Melatonin Induced Sleep Regularization in Severe Brain Injury

Patients with severe brain injuries often have slow accumulating recoveries of function. Recently, the National Institute for Disability and Rehabilitation Research (NIDRR) published data on their long-term outcomes of over 9,000 patients, 400 of which suffered disorders of consciousness (Nakase-Richardson et al. 2012). Patients were followed for 1, 2, and 5 year outcomes and several important and unexpected results were obtained: a large majority of patients initially in minimally conscious state (MCS) continued to improve recovering consciousness within a year and recovery was demonstrated to continue at the 2 and 5 year timepoints for as many as 20% of patients. In these cases outcomes included vocational reentry. Other studies have confirmed that MCS recovery can occur over long-time periods and lead to good outcomes or significant recovery of meaningful cognitive function despite enduring convalesce in MCS (Luaute et al. 2010, Lammi et al. 2005).

In ongoing studies we have discovered that elements of electrical activity during sleep may correlate with the level of behavioral recovery observed in patients (Forgacs et al. 2014, Thengone et al. 2012). It is unknown, however, whether such changes are causally linked to behavioral recovery. Forgacs et al. 2014 showed a cross- sectional relationship between retention of key elements of sleep EEG architecture and behavioral level. Thengone et al. 2012 correlated longitudinal changes in sleep architecture and quantitative spectral measures with behavioral recovery in 4 patients with severe brain injuries. No studies, however, have used an instrumental causal design to address whether improvement in sleep architecture can be promoted in patients with severe brain injuries and if so, whether or not changes in wakeful behavioral level are causally linked to such instrumentally generated changes in sleep.

Sleep processes are associated with several critical processes supporting the cellular integrity of neurons and neuronal mechanisms associated with learning and synaptic modifications giving face validity to this approach. (Steriade, 1999; Tononi and Cirelli, 2012). For example, studies in healthy volunteers (Huber et al. 2004) have provided evidence that local spindle density changes are associated with learning of specific information over sleep periods and can be topographically related to cortical populations engaged by the wakeful learning process. Additional evidence indicates that recovery of spindles within the electrical architecture of sleep is more associated with recovery of motor function in stroke (Gottselig, 2002). Collectively, although only a limited number of studies exist there is a biological basis for improvement in sleep architecture to potentially drive recovery and reorganization of brain networks organizing wakeful behavior.

These known associations suggest the possibility that targeting the normalization of brain electrical activity during sleep may aid the recovery process. In fact, in one human subject studied here in our program, central thalamic deep brain stimulation (CT-DBS) applied beginning 20 years after severe traumatic brain injury (TBI) correlated with a normalization of sleep architecture beginning at the time after exposure to continuous DBS. These findings strongly suggest a link between increased driving of synaptic activity during the day and modification of sleep processes as this subject was only exposed to CT-DBS during daytime hours (Adams et al 2014). These findings improve the likelihood that there is a bi-directional causal relationship sleep dynamics and wakeful brain dynamics as linked to changes in behavior. Thus, the working hypothesis of the present study is that causal intervention to normalize sleep processes in patients with severe brain injuries may aid recovery of behavioral function.

A well-studied mechanism organizing the normal patterns of electrical activity that characterizes sleep is the body's release of the substance melatonin. Melatonin is produced in the brain and released at a precise time during the day (normally around 8-10PM) to signal the brain to initiate aspects of the sleep process each day (Dijk, 1997). It is possible to exogenously trigger and drive melatonin signaling of sleep processes and initiation of sleep via oral dosing of the agent (Lewy et al. 1992). Use of oral melatonin supplements is common for pre- treatment of expected travel delay sleep disturbances ("jet lag") and has been investigated in treatment of mood disorders (Lewy et al. 1996).