[Nontraumatic spondylolysis of the axis vertebra].

A case of nontraumatic spondylolysis of the axis vertebra is presented. A 55-year-old man suddenly experienced nausea and dizziness on January 15, 1984 when he rotated his neck toward the left. Since this episode, he experienced the same attacks twice. On examination, the patient was afraid of moving his neck abruptly and on gradual hyperextension of his neck, he started to complain of slight dizziness. But otherwise no abnormalities of motor, sensory and cerebellar functions were noticed. Lateral view of plain films of the cervical spine revealed a bilateral bony defect in the lamina of the axis vertebra. The surface of the bony margin around the defect seemed to be well corticated and smooth. There was no spondylolisthesis between the second and the third cervical vertebra. CT scan of the axis vertebra also showed bilateral true bony defect, not in the pars interarticularis but in the inferior articular process of the axis vertebra. Spondylolysis with or without spondylolisthesis of the cervical vertebrae is relatively rare and about 48 cases of the cervical spondylolysis have been reported in the previously published literature.