Can a right l5s1 tranforaminal epidural steroid injection creep to the left side and relieve pain on the l?

Possibly: Although not typical, these types of injection and other selective nerve root blocks are not necessarily "selective" to one side, especially . If more than 0.5 ml is injected. Have peek at this research summary: http://www.Ncbi.Nlm.Nih.Gov/pubmed/19057631.

Possible: However if you have pain on both sides, have doctor consider a bilateral L5 s1 injections to get better coverage.