You may not necessarily experience any symptoms from this. There are many findings that are identified on MRI scans that are incidental, that is they just happen to be present. Believe it or not, that include herniated and/or bulging discs! Many studies have been done on people who have never had back or neck pain and MRIs have demonstrated that 50% of them have some type of disc bulge or herniation.
However, if there were to be clinically significant involvement at the C6-7 level, one might expect to experience local neck pain if there was no nerve root involvement. In the case of arthritis at that level there could be some referred pain to the upper back. If there was nerve root compression at the C6-7 level you could expect radiating pain, tingling and/or numbness into your arm into the middle finger of your hand.
Mild thecal sac effacement however, is not likely to be a symptom producer.
Help please
you may find this site useful, i used it myself a few years ago, if i remember correctly they show the symmetries on diagrams for all the point groups and state a crystal structure where these symmetries could be found http://www.phys.ncl.ac.uk/staff/njpg/symmetry/Categorisation.html