Absolutely! The only constraints for a flight review have to do with category and class. If the LSA is in the proper category and class (say, for example, ASEL), then a pilot completing a flight review in it is good to go for the next 24 calendar months in ASEL. There is nothing in the FARs that says the CFI needs to have a current medical.
_________________The opinions expressed in this post are those of one CFI, and do not necessarily represent the position of the FAA or its lawyers.
Prof. H. Paul Shuch, Ph.D., CFII, LSRM-A/GL/WS
AvSport of Lock Haven