The emphasis on this study is to review the use of PBMT as a potential treatment modality to improve both sleep symptoms and consequent neuropsychological functions affected by sleep disturbances in a cohort of post-mTBI patients with sleep issues not secondary to sleep apnea.

Concussion or mild traumatic brain injury (mTBI) is an acute neurophysiological event related to blunt impact applied to the head and/or neck due to sudden acceleration, deceleration or rotational forces. It can happen due to motor vehicle accidents, sport or recreational injury, falls, workplace injury or assault. mTBI can be differentiated from moderate and severe traumatic brain injuries by having negative imaging or laboratory results and a Glasgow Coma Scale (GCS) score of 13-15. Current treatment modalities for the various symptoms associated with mTBI are mostly supportive: pain medication, antidepressants, psychotherapy, physiotherapy, vision therapy and referral to sleep clinics.

mTBI symptoms are usually divided into four groups: cognitive symptoms, physical symptoms, emotional symptoms and sleep symptoms. Although most of these symptoms resolve or improve with or without treatment within 3 months following injury there is a significant population of post-mTBI patients who continue to suffer from symptoms 3 months to years after their injury. Previously called Post-Concussive Syndrome (PCS) most groups now classify PCS as a neurological disorder with persistent post-concussive symptoms. Insufficient and disturbed sleep are reported by half of all patients and are among the most common complaints following mTBI, and can develop during the early to chronic post-mTBI phases. Various sleep abnormalities, including post-TBI insomnia, hypersomnia, and sleep apnea are frequently observed. Most cases of sleep symptoms associated with mTBI that are diagnosed during sleep studies tend to be apnea related, although the cause of this is still unknown. Sleep apnea can be obstructive or central sleep apnea, but both types tend to respond well to Continuous Positive Airway Pressure. For other types of non-apneic sleep related symptoms post mTBI though, treatment can vary from Cognitive Behavioural Therapy (CBT) to various sleep medications. However, it is noted that despite an improvement in objective sleep symptoms with conventional approaches to patients with mTBI, there continues to be a lack of improvement in terms of subjective sleepiness or neuropsychological functions.

Photobiomodulation therapy (PBMT) is an innovative modality for the stimulation of neural activity in order to improve brain function and is currently under investigation as a treatment for several diverse neurological disorders, including concussions. Noted among the effects of PBMT among post-mTBI patients in our clinic is a subjective improvement in sleep, sometimes described by patients as "the best sleep they've ever had." Our emphasis on this study is to review the use of PBMT as a potential treatment modality to improve both sleep symptoms and consequent neuropsychological functions affected by their sleep disturbances in a cohort of post-mTBI patients with sleep issues not secondary to sleep apnea.

Inclusion Criteria:

• Patients between the ages of 18-70 years clinically diagnosed with a mTBI diagnosed between 3 to 24 months from presentation complaining of sleep disturbance.
• Underwent an overnight sleep study PSG within the previous year and diagnosed with a primary sleep disorder and in which there has been symptom development suggesting another co-morbid sleep disorder, or an established diagnosis of a sleep disorder other than a sleep related breathing disorder who have significant symptom progression or non-response to therapy.
• Documentation of a history of a qualifying mTBI within 3 to 24 months of traumatic incident and/or diagnosis with persistent symptomatology after 3 months. For reference, International Classification of Diseases, Tenth Revision (ICD-10) clinical criteria for Post Concussive Syndrome (PCS) require a history of TBI and the presence of three or more of the following eight symptoms: 1) headache, 2) dizziness, 3) fatigue, 4) irritability, 5) insomnia, 6) concentration or 7) memory difficulty, and 8) intolerance of stress, emotion, or alcohol4.

Exclusion Criteria:

• Any positive cranial findings on imaging studies
• A current diagnosis of neuropsychiatric co-morbidity including severe anxiety (or score of ≥15 on the GAD-7), severe depression (or score of ≥20 on the PHQ-9), schizophrenia or bipolar disorder.
• A family history of neuropsychiatric conditions
• Any additional diagnoses compounding the diagnosis of a mTBI.
• Currently undergoing CBT.
• Currently taking any medication for the purpose of improving sleep including medical and recreational cannabis, barbiturates, benzodiazepines, antidepressants, antihistamines, melatonin or other natural supplements.
• Currently undergoing any alternative or complementary medical procedure, i.e. acupuncture, hypnosis, homeopathy, etc.
• Pregnancy
• Malignant growth in the neck and cranium
• Taking any photosensitizing medication.