Efficacy of Diffusion-Weighted Magnetic Resonance Imaging in Diagnosing Spinal Root Disorders in Lumbar Disc Herniation

Study Design. Prospective study based on magnetic resonance imaging for lumbar disc herniation. Objective. In this study, we captured diffusion-weighted imaging (DWI) of dorsal root ganglion (DRG) of the affected nerve root in lumbar disc herniation and examined the relationship between apparent diffusion coeffi cient (ADC) and clinical symptoms to evaluate the effi cacy of DWI in the diagnosis of lumbar spinal disorders. Summary of Background Data. DWI captures diffusion of water molecules in intracellular or extracellular fl uid, allowing visualization of edematous changes, and is therefore used in diagnosis of hyper-acute cerebral infarction. In addition, it is possible to quantify the degree of diffusion using ADC calculated from the DWI data. Meanwhile in lumbar disc herniation, edematous changes occur in DRG of affected nerve root. If DWI enables visualization of these edematous changes, it will be possible to diagnose objectively the affected level. Methods. The subjects were 30 patients who underwent surgery of unilateral radiculopathy and a single level lumbar disc herniation. We analyzed the relationship between morbidity duration, visual analogue scale (VAS) score of leg symptoms, and ADC. In addition, we investigated any correlation between VAS recovery ratio (i.e., VAS preoperative -VAS postoperative)/VAS preoperative x 100) with ADC. Results. When compared with the contralateral side, ADC of the affected DRG was observed to increase in 18 and decrease in 12 subjects, and thus no defi nite trend was observed. The relationship between morbidity duration, VAS score, and ADC had no observed correlation. A positive correlation between ADC and VAS recovery ratio was statistically observed (P < 0.01, leg pain: r = 0.707, leg numbness: r = 0.738). Conclusion. This study showed that patients with decreased ADC tended to show poor improvement of leg symptoms, which may suggest the possibility that ADC of DRG is related to neuronal plasticity.