First, a thoracic disc herniation is not too rare. I am curious as to why you had a thoracic MRI if you had no symptoms.
Old disc herniations can calcify. The herniation tears the annulus and “pushes it into the canal” This creates traction on the bone/annulus interface and this tractions causes new bone formation. The calcification is characteristic of a herniation that has been there for some time (at least 6 months to one year).
One of the factors in considering surgery is how significant the size of the herniation. Some can cause severe cord compression and signal change in the cord (a white signal on T2 scans) and probably need to be addressed surgically. Other herniations might be smaller and minimally cord compressive without generating signs and symptoms and can be watched without surgical intervention.
If you have no symptoms but do have signs of cord compression (called long tract signs), then the decision becomes somewhat more murky. If long tract signs are present, there is at least some cord dysfunction. These probably can be watched but there is more concern of continued compression and cord injury.
There is always the possibility of recurrent disc herniation (another disc herniation at the same level due to the annular tear) but I cannot remember seeing one of these in the thoracic spine (they do occur in the cervical and lumbar spines).
Symptoms from cord compression cannot be “treated” with exercise or manual therapy.
Dr. Corenman
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.