Help with my 13 year old son

Hey - I have joined here as I turn over every stone to help with my 13 year old son who has suffered from migraine headaches since the age of 9.  His migraines have worsened over the years  - greater frequency and intensity as he ages.  we just came off series that included 10 straight school days and 1 weekend night.  We find barometric pressure and anxiety his major triggers (though he is really a low key kid whose anxiety rarely shows) He takes nasal imatrex  - which has helped him bounce back more quickly than maxalt, his previous medication.  His neurologist just put him on Propanolol (sp?), 2 10 mg doses per day.  We also had blood work done this morning and he will have a catscan next week - he hasn't had one since he was 9.  Can anyone tell me more about Propanolol - any side effect concerns.  I have his pediatrician and neurologist in the loop, want to make sure I am doing all I can.  Thanks!