The intervertebral disc during growth: Signal intensity changes on magnetic resonance imaging and their relevance to low back pain

Abstract

Life-time prevalence of low back pain (LBP) in children and adolescents varies from 7% to 72%. Disc changes on magnetic resonance imaging (MRI) have been reported in up to 44% of children with earliest observations around pre-puberty. In this longitudinal cohort study, our objective was to determine the natural history of disc changes from childhood to early adulthood, and the possible association of these changes to LBP. Healthy 8-year-old schoolchildren were recruited for this longitudinal study consisting of a semi-structured interview, a clinical examination, and an MRI investigation at the age of 8-9 (Y8), 11-12 (Y12) and 18-19 (Y19) years. The interview inquired about LBP without trauma. T2-weighted sagittal MRI of the lumbar spine was acquired. Life-long prevalence of LBP was determined, and the disc signal intensity (SI) at the three lowest lumbar levels was assessed both visually using the Schneiderman classification (Bright-Speckled-Dark), and digitally using the disc to cerebrospinal fluid -SI ratio. Possible associations between SI changes and LBP were analyzed. Ninety-four of 208 eligible children were included at Y8 in 1994, 13 and 23 participants were lost to follow-up at Y12 and Y19, respectively. Prevalence of LBP increased after the pubertal growth spurt reaching 54% at Y19. On MRI, 18%, 10% and 38% of participants had disc SI changes at Y8, Y12 and Y19, respectively. No significant associations between self-reported LBP and either qualitative or quantitative disc SI changes were observed at any age. Life-time prevalence of LBP reached 54% by early adulthood. Disc SI changes on MRI traditionally labeled as degenerative were seen earlier than previously reported. Changes in disc SI were not associated with the presence of LBP in childhood, adolescence or early adulthood.

Fig 1. Flow diagram of the study.

Fig 2. The evolution of disc changes throughout the study period in one study participant.

The MRI images illustrate the visual assessment of the signal intensity (SI) of the intervertebral disc using the Schneiderman classification. At Y8, all lumbar discs presented with a Bright nucleus pulposus (a). At Y12, the L4/L5 disc was graded Speckled (b), and at Y19, both L4/L5 and L5/S1 discs were graded Dark (c).

Fig 3. Computerized measurement of the disc signal intensity (SI) to cerebrospinal fluid SI–ratio at 8, 12, and 19 years in subjects with or without LBP.

Means with whiskers representing 95 per cent confidence intervals.