Novel classification of lumbar high-intensity zones and their association with other spinal magnetic resonance imaging phenotypes

Abstract

INTRODUCTION: The clinical relevance of high-intensity zones (HIZ) has been debated. Traditionally, T2-weighted (T2W) magnetic resonance imaging (MRI) has been utilised to identify HIZ of lumbar discs but the use of additional imaging like T1-weighted (T1W) MRI has not been addressed. Furthermore, controversy exists with regard to HIZ morphology, topography, and association with other MRI spinal phenotypes. METHODS: A cross-sectional study of 814 subjects with a mean age of 63.6 years from a homogenous cohort was performed. Both T2W and T1W sagittal 1.5-Tesla MRI was obtained on all subjects to assess HIZ from L1-S1. A novel morphological and topographical HIZ classification based on disc level, shape type (round, fissure, vertical, rim, and enlarged), location within the disc (posterior, anterior), and signal type on T1W MRI (low, high, and iso intensity) in comparison with the typical high intensity on T2W MRI was created. RESULTS: High-intensity zones was noted in 38.0% of subjects. Posterior HIZ was most common at L4/5 (32.5%) and L5/S1 (47.0%), whereas anterior HIZ was most common at L3/4 (41.8%). Of all discs, round types were most prevalent (anterior: 3.6%, posterior: 3.7%) followed by vertical type (posterior: 1.6%). At all affected levels, there was significant association between HIZ and disc degeneration, disc bulge / protrusion, and Modic type II (p<0.01). CONCLUSION: This is the first large-scale study reporting a novel classification scheme of lumbar HIZ. This study is the first to utilise T2W and T1W MRIs in differentiating HIZ sub-phenotypes. Specific HIZ sub-phenotypes were found to be more associated with specific MRI degenerative changes.