There is not a large amount of unbiased information about Dr Sarno's methods that I could find quickly, but from what is available TMS appears to be a form of alternative medicine that has no basis in science, and instead relies on pseudoscience and the placebo effect.
Rather than the pain relief being due to TMS, there is probably a more likely cause behind the result. Perhaps stretching exercises or pain medicine was involved. Or perhaps even just the placebo effect itself.
Please read this article for more information. It even contains a brief mention of Dr. Sarno.
http://www.sciencebasedmedicine.org/why-do-people-turn-to-al...