Absent nerve reflexes can be a symptom of an acute injury or the result of fatigue. The fatigue does not usually show up on the first or second try. It usually take 12 or more attempts to fatigue the nerve channels.

I have never had absent deep tendon reflexes but do have a positive Babinski response. When the bottom of the foot is stimulated/tickled, the toes should curl down. In a positive Babinski, the toes retract upward. The Babinski's sign can indicate upper motor neuron lesion constituting damage to the corticospinal tract. I have had this positive reflex since a youth.

Your MRI results will be interesting. My doctor tried a variety of imaging to find causes but all my images were normal. Maybe a functional MRI (fMRI) will be prescribed to look deeper. Sometimes, it will show an area that is not being activated as it normally would.