Study design: A prospective observational study of patients with low back pain and those without was performed.
Objective: To investigate the prevalence and significance of a high-intensity zone in a group of patients asymptomatic for low back pain, but who had known risk factors for lumbar disc degeneration. This asymptomatic group was compared with a symptomatic group of patients with respect to the presence of anular high-intensity zone and the pain response with discography.
Summary of background data: Some authors have estimated the prevalence of a high-intensity zone in a group of symptomatic patients to be 86%. They have reported a strong correlation between a high-intensity zone and positive discography in patients with low back pain. Other investigators have reported evidence either supporting or discounting these findings.
Methods: Patients with low back pain and those without underwent physical examination, psychometric testing, plain radiograph, magnetic resonance imaging, and discography. The presence of a high-intensity zone, anular disruption, and positive discographic pain then were compared between the two groups. There were strict inclusion criteria for both groups. A total of 109 discs in 42 patients were evaluated in the symptomatic group and compared with 143 discs in 54 patients in the asymptomatic group. The presence of a high-intensity zone was determined by a standardized criteria on T2-weighted magnetic resonance images. Psychometric testing also was administered to each patient before discography. Standard discography was performed on all the patients, and the pain response was recorded using a visual analog scale according to the Walsh et al criteria.
Results: The prevalence of a high-intensity zone in the patient populations was 59% in the symptomatic group and 24% in the asymptomatic group. In the symptomatic group, 33 (30.2%) of 109 discs were found to have a high-intensity zone. In the asymptomatic group, 13 of 143 discs were found to have a high-intensity zone. In the symptomatic group, 72.7% of the discs with a high-intensity zone were positive on discography, whereas 38.2% of the discs without a high-intensity zone were positive. In the asymptomatic group, 69.2% of the discs with a high-intensity zone were positive on discography, whereas 10% of the discs without a high-intensity zone were positive. In the patients with normal psychometric testing, 50% of the discs with a high-intensity zone were positive on discography, as compared with 100% positive discography results in patients with abnormal psychometric testing or chronic pain.
Conclusions: The presence of a high-intensity zone does not reliably indicate the presence of symptomatic internal disc disruption. Although higher in symptomatic patients, the prevalence of a high-intensity zone in asymptomatic individuals with degenerative disc disease (25%) is too high for meaningful clinical use. When injected during discography, the same percentage of asymptomatic and symptomatic discs with a high-intensity zone were shown to be painful.