Effects of contralateral extremity manipulation on brain function

Background : Manipulation of joints is associated with a variety of claimed outcomes, but without representative controlled studies. Physiological effects of electroacupuncture and manipulation of the cervical spine depend on the side of the body that treatment is applied to. Both treatments can change the size of the visual blind spot associated with the optic disc of the eye. Methods : We randomly allocated 62 healthy adults to either real or sham manipulative therapy, applied to the upper extremity on the side of an enlarged blind spot. Pre- and post-treatment blind spots were measured. Results : There was a highly statistically significant decrease in blind spot size following manipulation to the upper extremity in the intervention group when compared to the sham group. Left-sided manipulation was shown to result in a significantly greater change in the blind spot size than right-sided manipulation. Conclusions : Manipulation of an upper extremity on one side has a similar effect on the size of the blind spot as manipulation of the cervical spine and acupuncture treatment to the same side. The consequences of manipulation are greater than sham and promote questions to many of the currently held theories relating to change in brain function or visual perception following manipulation. It is recommended that further studies of blind spot phenomena specific to a variety of clinical disorders, treatments, and outcomes be contemplated.