Glymphatic Clearance and Restorative Mechanisms

During sleep, the brain cleans up harmful metabolic byproducts as well as proteins that are neurotoxic. Xie et al93 showed that deep sleep leads to an increase in the rate of diffusion of cerebrospinal fluid for the elimination of neurotoxic metabolites. It is one of the most important reasons for why sleep is beneficial to the brain. The consolidation of memory happens during sleep due to the strengthening of neuronal connections needed for learning.94 As established by Rasch and Born94, memories are actively reactivated and reprocessed during the slow wave sleep period to become incorporated into long-term memory. 

Sleep is essential for rehabilitation since it allows the brain to flush and function properly. Sleep also controls the hormones that facilitate tissue repair and reduce inflammation. Besedovsky et al95 demonstrated that sleep promotes inflammatory homeostasis while aiding with immune functioning. In the same study Besedovsky et al95 also noted that sleep deprivation leads to chronic systemic inflammation. Chronic inflammation can lead to prolonged symptomatology and recovery.

For healthy rehabilitation, clinicians can help patients set up a consistent sleep schedule, including on weekends. This will regulate their circadian rhythm and reduce their daily mental fatigue. As Vasey et al96 explained, when a typical sleep wake cycle is altered, the natural release of melatonin becomes desynchronized with external cues, leading to a reduction in cognitive functioning and interfering with physiological recovery. 

Using melatonin around an hour before sleeping can support patients in calming the mind and promoting  restorative sleep on a predictable schedule. A randomized controlled trial conducted by Grima et al97 demonstrated that targeted administration of melatonin is effective at improving sleep quality and improving daytime fatigue, specifically in patients recovering from TBIs. As evidenced by Shekleton et al98, patients with a traumatic brain injury suffer from reduced melatonin production in the evening, which disrupts circadian rhythms. Nightly use of melatonin is a simple step that clinicians can suggest for their patients whose normal production of melatonin has been altered by TBI. 

An neurocompromised brain requires an improved sleep environment from pre-injury sleep conditions to get an adequate amount of sleep for rehabilitation. Okamoto-Mizuno and Mizuno99 found that maintaining a cool ambient temperature was also necessary for thermoregulation associated with sleep and helped the body transition into deep restorative sleep stages. The use of blackout curtains, in addition to removing or covering electronic devices that emit blue light or sounds, are useful signals to the brain that it is time to go to sleep and helps the patient get a full night of restorative sleep.100 Chang et al100 showed that short wavelength enriched light from electronic devices can lead to the suppression of melatonin, disruption of the circadian clock, and decrease in alertness in the morning and throughout the day.

The organization and arrangement of a patient's sleep environment can assist them in claiming their mind by removing excessive stimuli from their visual field. McMains and Kastner101 utilized MRI to prove that multiple competing stimuli in a cluttered visual field compete for neuronal representation, which causes an inability process information. A healthy sleep routine will calm the patient's mind as it goes to a state of rest. Irish et al102 found that maintaining a healthy sleep routine, like journaling and gentle stretching, as well as eliminating caffeine and alcohol, is beneficial for nocturnal sleep quality and reaching the deep sleep cycle necessary for restoration.

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