The clinical signification of high-intensity zone in lumbar disc annulus fibrosus on MRI

Abstract

Objective To explore the possible pathological essence of HIZ in lumbar intervertebral disc by means of CT,MRI and histomorphology analysis.Methods All of 41 patients of low back pain with the HIZ in the lumbar disc on MRI were identified.There is 23 males and 18 females with mean age of 38 years (range 33-50 years).All the patients were divided into 2 groups according to the characteristics of HIZ on MRI:group A,29 patients with high intensity on MRI T2WI and low intensity on MRI T1WI; group B,12 patients with high intensity both on T2WI and T1WI.All these patients underwent X-rays and CT scan on the targeted level.26 patients in group A were performed discography and pain provocative test.15 patients in group A and 7 patients in group B underwent operation and those samples of HIZ region were excised for HE staining and immunohistochemical analysis.Results All the patients in group A were proved intervertebral disc degeneration on CT and MRI.21 patients in 26 who underwent discography and pain provocative test were proved positive and 15 of them underwent operation(Transforaminal lumbar interbody fusion or posterior lumbar interbody fusion).Histomorphology examination showed annular tear combined with granulation tissue in the samples of HIZ region which were excised in operation.Neoformative blood capillary could be seen through CD34 staining.Macrophage could be found in CD68 staining,but the regions off the HIZ were less stained.In group B,all those targeted discs showed calcified or ossified lesion on the posterior annular on CT scan,HE staining showed calcification or ossification of the posterior annulus fibrosus with frontier line.Conclusion The HIZ on MRI T2WI with low intensity zone on T1WI possibly refers to annular tear combined with granulation in-growth.But the HIZ both on MRI T2WI and T1WI might be calcification or ossification.The conventional concept of HIZ might be modified as HIZ on MRI T2WI,but low intensity zone on MRI T1WI.In addition,CT scan might be helpful in the distinguished diagnosis. Key words: Lumbar vertebrae; Intervertebral disc; Magnetic resonance imaging; Tomography, X-ray computed