An article in the Lancet Neurology (February 2015),"Treatment of progressive multiple sclerosis: What works, what does not, and what is needed," includes a chart listing treatments--Table 2, "Studies of symptomatic management in chronic progressive multiple sclerosis." Some symptoms are listed, including spasticity, and among the treatments shown to have a benefit (for PPMS) is Naltrexone.
The text reads:
A 6-month open-label study showed low-dose naltrexone effectively reduced spasticity in 40 patients with PPMS.
and the article in the references is:
Gironi, M, Martinelli-Boneschi, F, Sacerdote, P et al. A pilot trial of low-dose naltrexone in primary progressive multiple sclerosis. Mult Scler. 2008; 14: 1076–1083
The entire article can be seen
here.
I've heard that open-label studies are almost worthless and yet one of them has been cited in this article by one of the world's leading medical journals.
So many people have claimed to have found benefits in LDN that we have to pay some attention to it--and to any studies of it. (There haven't been many studies of it, apparently, or at least I haven't found them.)