You can't see patients or do other clinical activities while monitoring.  All billing is based upon the idea that you are continuously monitoring a case.  It is hard to schedule patients at all on days that you are monitoring because you are essentially at the whim of the surgeons.  If it takes an extra hour to do a case, then you are there an extra hour.  If you get an add-on case, then you are occupied for whatever time that case takes as well.
This is from the AAN guide:
"1. IOM is a procedure that describes ongoing electrophysiologic testing, and 
monitoring performed during surgical procedures. It includes only the time 
spent during an ongoing, concurrent, real-time electrophysiologic monitoring. 
2. Time spent in clinical activities, other than those above, should not be billed 
under 95940 and/or 95941. The time spent performing or interpreting the 
baseline electrophysiologic studies must not be counted as intraoperative 
monitoring, but represents separately reportable procedures. "
https://www.aan.com/uploadedFiles/W...overage_Policies/Coverage Policies - IONM.pdf