Espetroscopia (1H) por ressonância magnética do disco intervertebral lombar no adulto e sua aplicação na rotina imagiológica

Abstract

Aims – To assess the potential of magnetic resonance spectroscopy (1H‑MRS) in the diagnostic of degenerative disease of the lumbar disc and to advocate the adding of this technique in the classification of the invertebral disc involution vs degeneration (L4‑L5 and L5‑S1) in the clinical routine of lumbar pain status, not related with mechanic causes. Material and method – We studied 102 out of 123 lumbar intervertebral discs. The distribution among spaces was 61 discs at L4‑L5, 41 at L5‑S1 level and 34 at D12‑L1 level. The magnetic resonance studies were performed using a 1.5 T scan-ner. A single‑voxel Point Resolved Spectra Selection (PRESS) technique was used. The ratios [Lac/Nacetyl], [Nacetyl/(Lac+Lip)] and additionally the resonance of lipids were applied to evaluate the biochemistry of the discs, its involution, disc disruption and eventual susceptibility to initiate degeneration process. The ratios and the lipidic value of L4‑L5‑S1 discs were ascertained with the different behavior of D12‑L1. Furthermore, the comparison between L4‑L5, L5‑S1 and D12‑L1 discs was performed according with rating in T2 weighted (adjusted scale 1‑4 from Pfirrmann1 criteria). Results – Related to D12‑L1, the ratios and the lipids of L4‑L5‑S1 discs are statistically different. When used as a complementary of conventional T2 weighted, they have a good discrimination in the all degrees of disc involution vs degeneration. The ratio [Lac/Nacetyl] at L4‑L5‑S1 level was increased when compared to D12‑L1 (p=0.033 for disks with [1+2] score of involution and p=0.004 for disks with score [3+4]). These results suggest that disc degeneration vs involution in higher degrees defines a decrease in the lactate’s peak. The ratio [Nacetyl/(Lac+Lip)] provides a good discrimination of involution between scores [1+2] and [3+4] at L4‑L5 level, presenting the values of the ratios (mean 0.65 and 0.5 with p=0.04). The mean ratio of [Nacetyl/(Lac+Lip)] in the L4‑L5 disc was 1.8 times higher than that of L1‑D12. The lipid spectrum at L4‑L5‑S1 in the higher scores showed no constant prevalence in the resonance frequencies. Conclusion – The (1H) spectroscopy of intervertebral discs may contribute with a supplementary semiology to the conventional MRI. The resonances of L4‑L5 and L5‑S1 discs, involuted or degenerated, must be related with D12‑L1, which are more stable and have lower likelihood of disc degeneration.