The issue that my infrared light therapy addressed was immense pain in my wrist and basal thumb joint. Since April I have not been able to use that hand. I tried any device (i.e. splints etc) to immobilize my hand as to give it the opportunity to heal. No luck until I decided to try this therapy. Once or twice daily for 2-3 weeks and my hand is good. I can open jars, lift groceries etc. So that is my amazing success story. I have no idea as to neck/back/sacrum pain so I am very tentative about translating my success to your journey.
As for the neuropathy, I am not sure if there is improvement. My neuropathy has been slowly progressing which makes it difficult to gauge success. I will continue to use this therapy on my feet and post my findings. I am a natural skeptic ... so I don't recommend an idea until I feel sure that it works. So for neuropathy, the jury is still out.