The upper cervical canal stenosis is relatively rare compared to other cervical regions. We report a rare case of upper cervical canal stenosis caused by osteoma of C1 lamina related to dynamic factor of cervical rotation. A 43-year-old woman had a 2-year history of numbness and pain in the right hand. Because of aggravation of the numbness and loss of the fine movement and strength in the right hand, she visited our outpatient clinic. Computed tomographic (CT) scan revealed an ovoid bony lesion at the right side of the C1 lamina. And magnetic resonance (MR) imagings of the cervical spine showed intramedullary high intensity signals in T2-weighted imaging at a site slightly distant from the bony lesion. Rotational dynamic myelo-CT scan was performed because aggravation of the radiating pain was observed with neck rotation to the right. Dynamic CT scan of the craniocervical junction with neck rotation to the right revealed that the bony lesion was moved to the dorsal side and posteriorly compressed the spinal cord. The symptoms were relieved following surgical removal of this bony lesion. The histopathological examination was compatible for osteoma. The dynamic rotational factor for cervical canal stenosis should be taken in consideration, especially in dealing with upper cervical lesions.