Cervical stenosis (narrowing of the central canal which compresses the spinal cord) causes a condition called myelopathy. Myelopathy does not include neck pain as a symptom by itself as the spinal cord does not have any pain nerve ending in its substance.
Neck pain is normally generated by the discs, facets and nerves but not by compression of the cord. You report “head pain” which I think you mean back of the skull headaches. If that is the case, this type of pain is typically generated by the facets at C2-3 and C3-4 (rarely by the C1-2 facets). If you have had a fusion of the C3-4 level and it is solid (lack of fusion can also cause these symptoms), then the base of skull pain could be from C2-3. Facet blocks (see website) can help to diagnose this condition.
Shoulder pain radiating into the left arm sound to be a radiculopathy (see website- compression of a nerve root). If the pain radiates down below your elbow, that could originate from the C6 or C7 nerves. If the pain does not radiate below the elbow, then the C5 nerve could be involved as well as C6 or C7.
Torticollis, I assume you to mean that you have neck pain that stiffens your neck. If this is the case, this neck pain can originate from degenerative disc disease or facet disease in the lower portion of your neck (assuming that your fusion of C3-5 is solid). A new MRI and physical examination can go a long way to help sort out your disorder.
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.