Traumatic brain injury

Traumatic brain injury (TBI) occurs when external force strikes the head causing physical damage to the brain leading to an altered brain structure of function.¹ Altered brain structure and function can lead to problems with cognitive ability, movement and communication. TBI is categorised as primary and secondary. With primary the damage is immediate, and in secondary injury damage occurs more gradually appearing hours or days later. Secondary brain injuries are a result of reactive modalities from the brain such as swelling or inflammation that occur after the initial trauma to the head.¹

Causes of TBI

The main causes of TBI include:²

• Falls - falls are the most common cause of TBI happening most frequently in the youngest and oldest age groups
• Blunt trauma accidents - being struck with an object, particularly sports-related injuries 
• Vehicle-related accidents - Accidents involving bicycles and motor vehicles are the third most common cause of TBIs
• Assaults/ Violent Attacks - Abuse-related TBIs resulting from unsafe primary environments such as domestic abuse or shaken baby syndrome
• Explosions/ Blasts - Explosion and blast trauma is a common injury to members of the military

Diagnostic criteria for TBI

TBI severity is most widely categorised using the Glasgow coma scale (GCS) shown in Figure 1 below.¹ This is a standard 15-point test which measures the patient's consciousness after the injury. The patient's ability to open their eyes, and respond to physical cues and spoken questions is assessed. Severe TBI has a GCS of 3-8. Moderate 9-12 and mild 13-15. In a 2022 report by Lancet, it was documented that over 90% of TBI cases presenting to the hospital are mild, but around 50% of adult patients with mild TBI do not recover to pre-TBI levels of health by 6 months after their injury.³ In most cases, a mild TBI is a concussion, with either full neurological recovery or residual effects of short-term memory problems or concentration difficulties. When TMI is moderate, the patient is usually lethargic or in a stupor and in severe TMI, the patient is comatose and unable to follow commands. 

Importance of sleep In recovery

Sleep is a crucial part of the brain and body’s recovery system, especially following a TBI. It plays a number of key roles in optimising brain function which can be impacted post-TBI.

Detoxification

During sleep, the brain’s Glymphatic System is more active and clears metabolic waste products from the brain. The interstitial space in our brains, which is where fluid is found surrounding the cells, increases by 60% during natural sleep or anaesthesia. This allows for a big increase in the exchange of cerebrospinal fluid which speeds up the clearance of waste products in the brain. These metabolic waste products include beta-amyloid which is linked to neurodegenerative conditions. Adequate and high-quality sleep allows for effective detoxification which prevents further neural damage after a TBI.³

Repair and regenerate

As we sleep, the brain produces more growth hormones. Growth hormone is essential for repairing and restoring tissue. This is important following TBI, where tissues may be damaged.⁴

Cognitive ability and mood regulation

In the deep stages of sleep and REM (rapid eye movement) sleep, the brain organises and consolidates information from the day which is important for learning and memory. Proper sleep is also essential for regulating our moods and emotions. 

Neuroplasticity

Neuroplasticity is the body’s ability to build new neural connections and reorganise existing neural pathways. Sleep promotes neuroplasticity by helping the growth of new synapses and strengthening existing ones, supporting the ability of the brain to adapt.

Reducing inflammation

Long-term sleep disturbances are linked to higher levels of inflammatory markers which are harmful to brain health. When recovering from a TBI, high inflammation levels can slow down the healing process. Getting enough sleep helps regulate the immune system and reduce inflammation.

Pathophysiology of sleep disturbances following TBI

Direct Factors

Diffuse axonal injury

Diffuse axonal injury (DAI) is when the brain's nerve fibres known as axons shear as a result of brain injury. This shearing disrupts signals from nerve fibres and their function which causes waste products to build up in the brain. The metabolic cascade of cell injury and release of neurotransmitter glutamate cause swelling of the brain DAI in arousal and sleep regulation areas of the brain may be a cause of sleep disturbance effects of TBI.⁵

Hormone disruption

Patient groups with TBI are found to have reduced levels of hypocretin and histamine in their cerebrospinal fluid (CSF). Both these neurotransmitters promote wakefulness and so low levels are associated with hypersomnia (excessive sleepiness). In studies with mild TBI patients, 95% of patients had low CSF hypocretin (less than 320 pg/mL). In autopsies of individuals who died from severe TBI, a 41% reduction of histaminergic neurons was found in the hypothalamus.⁵ Melatonin levels have also been shown to be reduced in TBI, reduced melatonin levels are associated with decreased REM sleep.

Damage to key brain regions regulating sleep

The brain stem, hypothalamus and reticular activating system regulate sleep pathways. The retina-hypothalamic tract is involved in regulating the circadian pacemaker with the light-dark cycle⁵. Damage to this region can lead to abnormal circadian cycles and trouble sleeping.

Indirect factors

Following a TBI, secondary factors such as fatigue and depression may lead to sleep disturbances. For example, generalised anxiety disorder within 3 months of TBI is correlated with the onset of insomnia.⁵ People with TBI tend to be on more medications than the general population which may contribute to sleep irregularities. such as antidepressants, sedatives and analgesics.

Management strategies for sleep-disturbances post-TBI

Non-pharmacological interventions

Cognitive behavioural therapy for insomnia (CBT).

CBT for insomnia is designed to help the individual change their thoughts, perceptions and behaviours around insomnia. This is a highly effective tool and is usually the recommended first line of treatment. CBT techniques help the individual set cues for sleep, limit time spent in the bed or bedroom not sleeping, and reprogram negative beliefs about sleep to promote a relaxed state conducive to good sleep.

Sleep hygiene

Educating patients on habits and factors conducive to good quality sleep such as avoiding stimulants like caffeine or blue light.

Morning sunlight exposure

Exposure to daylight and sunlight within the first 30 minutes of waking can aid the circadian rhythm, promoting wakefulness in the day and sleepiness at night time.

Mindfulness and relaxation

Relaxation techniques help to reduce cortisol levels and promote better sleep. By calming the mind and muscle relaxation techniques, individuals have significantly improved sleep quality.

Pharmacological interventions

• Melatonin - melatonin can be prescribed to regulate the sleep-wake cycle by improving the onset of sleep in TBI patients⁵
• Sedative-hypnotics - Zolpidem can be used as a short-term treatment for insomnia⁵
• Stimulants - Modafinil can be used to manage hypersomnia⁵

Medications to manage sleep disturbances must be carefully monitored and regulated to balance their risk-benefit profile. Due to the risk of dependency and interactions with other medications, pharmacological interventions should only be consulted when non-pharmacological interventions have not been able to provide significant relief. A coordinated care plan tailored to the patient’s specific needs should be made to optimise treatment outcomes.⁶

Summary

Sleep is crucial for optimal brain health and performance and for recovery from TBI. During sleep, our brain repairs damage removes waste and promotes growth. When a patient experiences TBI, sleep disturbances are a common and challenging consequence. Disturbance of sleep significantly impacts recovery from TBI and can often persist for many years following the primary injury. Management of sleep disturbances as well as intubation in severe cases of TBI can significantly improve outcomes and integration back into life. By taking a comprehensive approach of non-pharmacological interventions and medication overall recovery and sleep quality can be improved.

• Following TBI, sleep disturbances are common. These include insomnia, hypersomnia and sleep apnea. Sustained sleep disturbances are distressing due to their impact on overall recovery to pre-TBI levels, mental health and cognition
• Post-TBI sleep disturbances are caused by neurological disruptions, hormonal changes and psychological factors
• Healthcare providers are encouraged to consider all non-pharmacological interventions as first-line treatment, monitoring the patient over time