The intranuclear cleft of the intervertebral disk: magnetic resonance imaging.

Three cadaver spines, 40 patients who were symptomatic for lumbar disk disease, and ten healthy subjects were examined by MR. T2 weighted spin echo images were used to evaluate the character of an intranuclear cleft. This cleft appears identical to annular tissue both on T2 weighted images and histologically. A 120 msec TE, 3 sec TR image was used to delimit the normal nucleus pulposus from the annulus. The incidence and age distribution of the cleft were calculated. An intranuclear cleft was present in all normal disks in both control and symptomatic subjects who were 30 years of age and older. If present in one disk, it was also present in 94% of the other disks in the same subject. This cleft represents a normal anatomic structure and appears to be a constant feature in subjects 30 years of age or older. Its absence, in the presence of an increased signal intensity within the disk, suggests a pathological process with a long T2 value, such as inflammation.