In the late 1930s, the American osteopath William Sutherland challenged traditional medical thinking with a new theory: that the bones that make up the skull (cranial bones) move and flex in response to the pulsing of fluid in the brain. Doctors and scientists dismissed Sutherland's theory, certain that the skull was a hard and inflexible housing for the brain. But in the 1970s, osteopath John Upledger and a group of scientists at the University of Michigan were able to prove that Sutherland's theory was correct. Moreover, Upledger found that manipulating the cranial bones could improve physical well-being. This inspired chiropractors, physical therapists, and massage therapists to take up this technique, called craniosacral therapy. 

The craniosacral system is made up of the fluid and membranes that surround and support the spinal cord and brain. It extends from the cranial bones down to the base of the spine (sacrum). The continuous filling and draining of the fluid within the membranes produces a rhythmic expansion and contraction that can be felt anywhere in the body. These movements occur at a rate of roughly six to 12 cycles per minute and are known as the craniosacral rhythm. Craniosacral therapy aims to clear up the blockages of these fluids caused by injury or stress and thereby restore the body to health. 

Practitioners first "listen" to the skull and spine with their hands to detect imbalances in the craniosacral system. Then they manipulate the soft tissues and bones of the head, the spine, and pelvis with a touch so gentle that many patients don't even feel it. Patients often report feeling deeply relaxed following a treatment session. This technique has been used to treat migraines, sinusitis, TMJ (temporomandibular joint dysfunction), chronic pain, and asthma. Some have claimed that craniosacral therapy also can help relieve depression and anxiety, as well as assist in the physical and emotional recovery of victims of severe trauma. 

However, a 1999 review of medical literature found there was insufficient reliable research to validate claims made for craniosacral therapy--it may be that a good head-neck massage can provide an equally relaxing, mood-lifting experience.