95886 is an add-on code so it shouldn't need a modifier, but several places online say some carriers want you to use a 59.
I do have a couple of questions. Are both codes being denied? Are you billing with multiple units on anything, or just 95909, 95886? Can you give an example of a reason for the services are being performed (eg, carpel tunnel, myopathy, pain, etc)? Are you billing with a "problem" DX?
There are a number of guidelines about these codes, aside from all sorts of LCDs, which is why I'm asking for more info.
95909 Nerve conduction studies; 5-6 studies
95886 Needle electromyography, each extremity, with related paraspinal areas, when performed, done with nerve conduction, amplitude and latency/velocity study; complete, five or more muscles studied, innervated by three or more nerves or four or more spinal levels (List separately in addition to code for primary procedure)
For 95909, it's 5-6 nerve studies; the guidelines state "Count each type of nerve conduction study only once when multiple sites on the same nerve are stimulated or recorded."
For 95886, it's 5 or more muscles... additionally, you have to indicate the number of extremities involved (up to 4 obviously).