A second opinion is wise. I just wanted to let you know that I have MS and my mother had ALS. With her ALS, she never experienced numbness and tingling. She had weakness, muscle fasciculations and muscle atrophy. With MS, numbness and tingling are common. There are MANY neurological disorders. MS may not show on a MRI right away. You should have a cervical spine MRI in addition to a brain MRI. Make sure they do the test with and without contrast. A second opinion would be helpful and a follow up MRI in the future. Good luck with answers and don't stop until your comfortable with the answers you receive.