Sensory symptoms although rare can occur in ALS but to the extent that you desribe, I am not sure I can attribute this to ALS
In that case, there may be alternative explanations. Sometimes an area of sensitivity in that area of the back can be from a pinched nerve root off the thoracic spine - an MRI can evaluate for this. You may be describing Lhermitte's phenomenom - where a stretching of the neck causes an electric shock like sensation down the spine - it is usually due to a spinal lesion for instance an area of demyelination in MS, a compression of the spinal cord etc and is a sign that the spinal cord is irritated by something. This does not tyopically happen in ALS so other causes should be looked for also by MRI, blood test (B12, HTLV, and other causes of a MYELOPATHY)
Good luck