Soft cervical disc herniation - Influence of cervical spinal canal measurements on development of neurologic symptoms

Study Design. In 100 consecutive patients who underwent surgery because of soft cervical disc herniation, the sagittal and transverse diameters, the a rea of the bony cervical spinal canal, the sagittal diameter of the hernia, and the minimal bony intervertebral foramen diameter were measured by comp uted tomography. The data were compared with measurements from a control gr oup of 35 matched healthy individuals. Objectives. To evaluate the relation between the severity of concurrent neu rologic symptoms and the sagittal and transverse diameters, the cross-secti onal area of the bony spinal canal, the sagittal diameter of the hernia, an d diameter of the minimal bony intervertebral foramen in patients with soft cervical disc herniation. Summary of Background Data. Traumatic injury and spondylotic changes have a far greater impact on the spinal cord and nerve roots if the sagittal diam eter of the bony cervical spinal canal is small. However, in the case of so ft cervical disc herniation, no computer tomographic measurements are avail able for sagittal and transverse diameters, cross-sectional area of the bon y spinal canal, sagittal diameter of the hernia, and diameter of the minima l bony intervertebral foramen in relation to the severity of concurrent neu rologic symptoms. Methods. Computed tomography was used to measure sagittal and transverse di ameters, cross-sectional area of the bony cervical spinal canal, sagittal d iameter of the hernia, and diameter of the minimal bony intervertebral fora men in 100 patients with symptomatic monosegmental cervical soft disc herni ation. All patients had undergone an anterior discectomy with removal of th e hernia and subsequent interbody fusion using an autologous bone graft tak en from the iliac crest. Results. A mean sagittal diameter of the bony cervical spinal canal of 12.9 mm was found, indicating a certain degree of developmental stenosis. Patie nts with motor disturbances had a significantly smaller sagittal diameter o f the bony spinal canal than did patients without motor disturbances. There was a linear correlation between the sagittal diameter of the bony cervica l spinal canal and that of the hernia. The sagittal diameter, the area of t he bony spinal canal, and diameter of the minimal bony intervertebral foram en were significantly smaller in patients with soft cervical disc herniatio n than in the control group. Conclusions. Results from this study strongly suggest that the degree and s everity of neurologic symptoms accompanying cervical soft disc herniation a re inversely related to the sagittal diameter and the area of the bony cerv ical spinal canal. The latter area is reduced in cases of developmental ste nosis or because of soft disc herniation. Moreover, patients with soft cerv ical disc herniation have a significantly smaller sagittal diameter of the bony spinal canal, a significantly smaller minimal bony intervertebral fora men diameter, and a significantly smaller cross-sectional area of the bony cervical canal than do healthy matched individuals.