A systematic review including 116 studies (171 cases of injury) was abstracted in DARE. The most frequently reported injuries involved arterial dissection or spasm, lesions of the brain stem and Wallenberg syndrome. Death occurred in 18% of the cases (32 cases). The majority of injuries were attributed to manipulation by chiropractors. In the 12 RCTs evaluating the effectiveness of cervical spine manipulation the effect sizes ranged from 0.42 to 0.60 (small to medium effect sizes).