EMG Test - Pinched Nerve

Can a doctor tell how long the nerve has been pinch by doing a EMG?  I had a car accident 2 months ago and that's when I started having symptoms and was given an MRI and was told I had a slipped disc at c-5 & c-6 with nerve encroachment at c-5 and that a spasm has straightened the curve in my neck.  When I got the results from my EMG test, the PA left a phone message (couldn't ask her this question) saying I had pinched nerves in both my arms from the slipped disc and that it had been pinched for 3 or more months.  Can they tell that from an EMG?  I never had a problem with this pain until the car accident.