moderate sensori-neural loss --cause???

    My child's school nurse detected a hearing problem in the right ear.  After visilting with the pediatrician, audiologist, ENT this has been confirmed to be moderate sensori-neural loss rising to normal in right ear. . We had a CT scan and that is negative(normal).  I ordered blood work for Lyme Disease(western blot), a test for autoimmune inner ear disease, and allergens.  The only thing that shows is in the Western Blot, is P41.    
   When child was born, there is no record of a hearing test.  Although, She has bee receiving speech therapy for 3 years(Just before she turned 4), and working with a speech therapist, since then.  Speech is normal.  Diagnosed with ADD.   Peditrician did a in -office ear exam 2 years ago, and child passed at 25decibels.  Last year she passed, but could not detect the 500 hertz.  (Not clear about the 1000 hertz as the way the nurse recorded it- per doctor).   She is now, not passing the test at the 1000 hertz.  The right ear is only able to understand 40% of the words.  Left ear is normal.  ENT says in many cases you will never find a reason why.  Could have been viral.  This is suppose to be a "permanent hearing loss",I need a reason.  Can you suggest any possibe tests that We should be doing? Or any suggestion,besides having it monitored in 6 months.  There is no family history of hearing loss in childred.  Only in 60+ year olds. Grandfather has diabetes, aunt was diagnosed with MS 5 years ago.