Becky,
I am glad you are feeling calmer.

ALS is a very serious diagnosis and a physician should not just suggest it as a possibilty without substantial evidence and numerous tests .

I feel kind of embarrassed that I lost my composure earlier

But all I could think is what ? --a MRI for a migrane led a doctor to suggest ALS, with a normal physical exam. How is this possible ?
As an MRI is just used to rule out other conditions -- in ALS MRi's are normal.
Migranes have nothing to do with ALS and are certainly not a symptom.

Still , even if this physician saw abnormal findings in a physical exam , he should be refering you to an ALS specialist for futher testing.As many things can mimic the early stages of the disease.
.
I have to tow a thin line ,as I am not a physician or even a nurse.So ,I certainly can not make diagnosis over the internet.

But ,I do feel quite confident in telling you , if what he has said has upset you , ask him for a referral to an ALS specialist. As only they are qualified to make a diagnosis of ALS.

If you have absolutely no physical symptoms whatsoever of this disease , try not to worry in the meantime . Lisa