nerve conduction study

what does decreased motor unit potentials in EDB mean on a nerve conduction test?

[COBOB]

EDB is normally an anatomical abbreviation for Extensor digitorum brevis, a muscle in the foot.  Motor unit potential might be more correctly called Motor Unit Action Potential (MUAP).
I think what they are getting to is that there is a decreases amplitude and shorter action duration in the MUAP going to the Extensor digitorum brevis muscle.

Decreased MUAP is considered an indication of peripheral nervous system damage, but these peripheral changes are sometimes seen in MS patients.   http://www.ncbi.nlm.nih.gov/pmc/articles/PMC490751/

Bob