Most MRI's are only 1 or 1.5 Tesla. That is not strong enough to see nerves. Even the 3 Tesla MRI's will not show nerves. It takes about 6 Tesla to start to see the finer details. A DTI MRI can be beneficial to a head injury but they are not commonly used.

The cervical MRI will likely be most revealing. Hopefully, the radiologist is a specialist in reading cervical MRI's The subtle cervical injuries common to concussion can be easily ignored by the untrained eye.