Dynamic foraminal disc herniation revealed by functional MRI (fmri®) of the spine

Abstract

This case study demonstrates the possibilities oVered by upright, weight bearing, multi-position, i.e. functional MRI of the spine (fmri). This particular, top-front open MRI (0.6 T) system allows imaging in various, especially in symptomatic positions. This 40-year-old patient has been complaining of position and motion-dependent pain along the left L4 dermatoma for several weeks, associated with a moderate quadriceps weakness. A Wrst recumbent MRI (Figs. 1, 2) showed only a slight disc degeneration with a minimal left lateral to foraminal bulging. These pictures could not explain the patient’s signs and symptoms. After further worsening under conservative treatment, he was sent to the fmri center for further investigations in symptomatic positions: sitting in extension and upright standing with lateral bending to the left. Both examinations showed a left annular tear with an intraforaminal L4/5 disc herniation extending cranially compressing the L4 nerve root (Figs. 3, 4). This evident fmri Wnding was correlated with the patient’s complaints and clinical signs. Most of the patients with comparable symptoms are traditionally investigated in recumbent MRI. The high-Weld technology is presently considered as gold standard. In a consecutive cohort of 25 patients investigated for low back pain, 13 surgically relevant pathologies were revealed by positional MRI under loading conditions, as reported by Smith et al. [10, 11] in 2005. In a second study [7], incuding 58 patients with signs and symptoms of spinal stenosis, disc protrusions were more prominent in 65% of these patients when investigated in the upright sitting position, allowing a better understanding of the condition of the spine, which resulted in an improved management. Another study from Aberdeen in 2007 Alexander et al. [1] analyzed the response of the nucleus pulposus to functionally loaded positions: the physiological biomechanical behavior of the disc could be visualized and veriWed by dynamic MRI. The most recent paper from 2008 by Zou et al. [12] points at “missed lumbar disc herniation” and conWrms the additive value of functional “positional” MRI studies in patients with symptomatic radiculopathy and no obvious anomaly on conventional MRI. These statements about the higher sensitivity and speciWcity of uprightTM, weight-bearing, dynamic-kinetic or multi-positionTM, i.e., “functional” MRI (fmri), conWrm the statements made by Jinkins et al. [6–8] in various papers and book chapters written since 2002, and our own experience in Zurich since [2–5]. Our case shows again that position and loading-dependent complaints of the patients should be investigated further by functional MRI. In many cases, however, such patients are suspected of aggravating their symptoms or having a pain syndrome of psychosomatic origin. The comparison of Figs. 1 and 2 (1.5 T MR) versus Figs. 3 and 4 (fmri) demonstrates that this 0.6 T open MR can provide valuable images of the spinal anatomy under weight bearing conditions, and in diVerent positions. This article will also be published in ArgoSpine News and Journal, Springer France, ISSN 1957–7729.