A 35-year-old man with neurofibromatosis type I presented with right arm weakness and gait disturbance that had developed gradually. MR imaging revealed bilateral intra-and extradural tumors at the C1-2 level. Although the adjacent spinal cord was narrowed, there was no evident contact between the tumors and the spinal cord. Computed tomography myelography revealed that the tumors compressed the cord only during neck rotation. The tumors were resected to make an abundant subdural space around the affected cord. The patient's neurological symptoms improved postoperatively. Because contact between the masses and spinal cord only occurred upon neck rotation, we believe it is important to consider the possibility of intermittent compression, termed dynamic rotational canal stenosis, in patients with masses at the C1-2 level, even when such masses are not seen to be in contact with the cervical cord on routine radiological examination.