Herniation of intervertebral disc or stenosis rarely occurs at T1-2 level. This area is generally obscured by the shoulder in X-ray examination, and commonly located at the caudal end in computed tomography (CT) or MRI examination. Thus, it is difficult to observe this area carefully. Accordingly, when this area has a lesion, it is frequently misdiagnosed with medical diseases or other level herniation of intervertebral disc as shown in this case, and sometimes, it is identified during the treatment [11
]. In the case of T1-2 disc herniation, spinal cord or T1 root compression occurs. T1 root is a root comprising the brachial plexus, and constitutes the ulnar nerve along with C8 root. Thus, T1 radiculopathy may accompany numbness of the fourth and fifth fingers, or weakness of intrinsic muscle of hand as similar to C8 radiculopathy. As symptoms similar to the aforementioned symptoms may be observed if the entrapment of the peripheral nerve, such as cubital tunnel syndrome or Guyon's tunnel syndrome, it is important to correctly identify the lesion location. According to previous reports, radiating pain at medial aspects of the forearm and at fourth and fifth fingers, and axial pain at the neck and periscapular area were reported to occur with a frequency of 86% and 81%, respectively, for T1-2 disc herniation (). T1 radiculopathy may accompany Horner's syndrome. In this case, level of neural compression can be more easily predicted, but diseases such as pancoast tumor and intrathoracic neoplasm should be ruled out [10
]. Although upper thoracic disc herniation has been known to rarely occur, but relatively commonly occur at T1-2 level among the upper thoracic levels [17,19
]. The literature review showed that a majority of patients had only radiculopathy, and underwent laminectomy or foraminotomy via a posterior approach, and achieved a good outcome [3,10,17,19
]. Taken together, successful treatments were achieved using posterior laminotomy and/or foraminotomy in 17 (81%) out of 21 cases. Meanwhile, an anterior approach was applied in four cases (19%) showing myelopathy due to the compression of the spinal cord by central disc herniation. Some studies reported that successful treatments were achieved using Southwick-Robinson approach without sternotomy, but others reported that partial sternotomy was required [14,16,18
]. Therefore, when a surgical treatment using an anterior approach is planned, the relationship between the sternum and T1-2 level should be considered before surgery, and an appropriate procedure should be prepared if sternotomy is required.
Summary of the symptoms and signs (T1-2 HNP in literature review) (n = 21)
T1-2 level is a region that is not observed closely in cervical spinal radiographs or MRI. Of patients who show radiating pain or numbness at the medial aspect of the forearm, or weakness of the intrinsic muscle of the hand, those who have non-typical results in physical examination, or who had an effect less than expected after selective nerve root block on the lower cervical spine are suspected to have T1 radiculopathy. A delicate physical examination and a radiologic evaluation including this area and treatment plan are required for the aforementioned patients.