We undertook a best-evidence synthesis on the incidence, risk factors and prevention of mild traumatic brain injury. Methods: Medline, Cinahl, PsycINFO and Embase were searched for relevant articles. After screening 38,806 abstracts, we critically reviewed 169 studies on incidence, risk and prevention, and accepted 121 (72%). Results: The accepted articles show that 70-90% of all treated brain injuries are mild, and the incidence of hospitaltreated patients with mild traumatic brain injury is about 100-300/100,000 population. However, much mild traumatic brain injury is not treated at hospitals, and the true population-based rate is probably above 600/100,000. Mild traumatic brain injury is more common in males and in teenagers and young adults. Falls and motor-vehicle collisions are common causes. Conclusion: Strong evidence supports helmet use to prevent mild traumatic brain injury in motorcyclists and bicyclists. The mild traumatic brain injury literature is of varying quality, and the studies are very heterogeneous. Nevertheless, there is evidence that mild traumatic brain injury is an important public health problem, but we need more highquality research into this area.

We searched the literature on the epidemiology, diagnosis, prognosis, treatment and costs of mild traumatic brain injury. Of 428 studies related to prognosis after mild traumatic brain injury, 120 (28%) were accepted after critical review. These comprise our best-evidence synthesis on prognosis after mild traumatic brain injury. There was consistent and methodologically sound evidence that children's prognosis after mild traumatic brain injury is good, with quick resolution of symptoms and little evidence of residual cognitive, behavioural or academic deficits. For adults, cognitive deficits and symptoms are common in the acute stage, and the majority of studies report recovery for most within 3-12 months. Where symptoms persist, compensation/litigation is a factor, but there is little consistent evidence for other predictors. The literature on this area is of varying quality and causal inferences are often mistakenly drawn from cross-sectional studies.Descriptive: 98.65% made good recovery, 0.25% died. All with LOC <15 minutes had good outcome. 5.9% developed seizures

There is 'gold' level evidence (www.cochranemsk.org) that supervised aerobic exercise training has beneficial effects on physical capacity and FMS symptoms. Strength training may also have benefits on some FMS symptoms. Further studies on muscle strengthening and flexibility are needed. Research on the long-term benefit of exercise for FMS is needed.

We examined diagnostic procedures in mild traumatic brain injury by a systematic literature search. After screening 38,806 abstracts, we critically reviewed 228 diagnostic studies and accepted 73 (32%). The estimated prevalence of intracranial CT scan abnormalities is 5% in patients presenting to hospital with a Glasgow Coma Scale score of 15 and 30% or higher in patients presenting with a score of 13. About 1% of all treated patients with mild traumatic brain injury require neurosurgical intervention. There is strong evidence that clinical factors can predict computerized tomography scan abnormalities and the need for intervention in adults, but no such evidence for mild traumatic brain injury in children. We found evidence that skull fracture is a risk factor for intracranial lesions, but the diagnostic accuracy of radiologically diagnosed skull fracture as an indication of intracranial lesions is poor. There is only a little evidence for the diagnostic validity of cognitive testing and other diagnostic tools for mild traumatic brain injury.

Neck pain is common. Nonmodifiable risk factors for neck pain included age, gender, and genetics. Modifiable factors included smoking, exposure to tobacco, and psychological health. Disc degeneration was not identified as a risk factor. Future research should concentrate on longitudinal designs exploring preventive strategies and modifiable risk factors for neck pain.