Tumors at the lateral portion of the C1-2 interlaminar space compressing the spinal cord by rotation of the atlantoaxial joint: New aspects of spinal cord compression - Report of 2 cases

The authors describe 2 patients with C-2 nerve root tumors in whom the lesions were located bilaterally in the lateral portions of the C1-2 interlaminar space and compressed the spinal cord when the atlantoaxial joint was rotated. The patients were adult men with neurofibromatosis. Each presented with clumsiness of both hands and motor weakness of the extremities accompanied by spastic gait. Magnetic resonance imaging of the cervical spine performed with the neck in the neutral position showed tumors at the bilateral lateral portion of the C1-2 interlaminar space without direct compression of the spinal cord. The spinal cord exhibited an I-shaped deformity at the same level as the tumors in one case and a trapezoidal deformity at the same level as the tumors in the other case. Computed tomography myelography and MRI on rotation of the cervical spine revealed bilateral intracanal protrusion of the tumors compressing the spinal cord from the lateral side. The tumors were successfully excised and occipitocervical fusion was performed. The tumors were pushed out into the spinal canal from the bilateral lateral portion of the interlaminar spaces due to rotation of the atlantoaxial joint. This was caused by a combination of posteromedial displacement of the lateral mass on the rotational side of the atlas and narrowing of the lateral portion of the interlaminar space on the contralateral side due to the coupling motion of the lateral bending and extension of the atlas. The spinal cord underwent compression from both lateral sides in a one-way rotation. Without sustained spinal cord compression, intermittent long-term dynamic spinal cord compression from both lateral sides should induce a pathognomonic spinal cord deformity and the onset of paralysis. To the authors' knowledge, there have been no reports of the present conditions - that is, the bilateral protrusion of tumors from the bilateral lateral portion of the C1-2 interlaminar spaces into the spinal canal due to atlantoaxial rotation.