Apart from 'restless leg syndrome' (internal itching) I have had a creeping sensation rather like a small mouse, very very slow, typically moving downwards from approx between shoulder blades to above waist either side like a foot distance in 20 mins.
I thought it might be some terrible disease, however, osteo/massage treatment does relieve it for a day or two, so I asume it is a muscular --skeletal thing.
BTW I found a product that helps with the restless legs, its called Restless Legs Relief by Martin and Pleasance.
Its made in Australia, they do have a web site, www.martinandpleasance.com, but there maybe an equivalent elsewhere.
Its homeoepathic and taken orally. This is NOT and advert, I just found it helps a lot, even if its phsyosematic!
Be interested to hear any info from 'back crawling' sufferers.
Cheers Good Luck
Steve